Of Particular Significance

Matter and Energy: A False Dichotomy

Matt Strassler [April 12, 2012]

It is common that, when reading about the universe or about particle physics, one will come across a phrase that somehow refers to “matter and energy”, as though they are opposites, or partners, or two sides of a coin, or the two classes out of which everything is made. This comes up in many contexts. Sometimes one sees poetic language describing the Big Bang as the creation of all the “matter and energy” in the universe. One reads of “matter and anti-matter annihilating into `pure’ energy.” And of course two of the great mysteries of astronomy are “dark matter” and “dark energy”.

As a scientist and science writer, this phraseology makes me cringe a bit, not because it is deeply wrong, but because such loose talk is misleading to non-scientists. It doesn’t matter much for physicists; these poetic phrases are just referring to something sharply defined in the math or in experiments, and the ambiguous wording is shorthand for longer, unambiguous phrases. But it’s dreadfully confusing for the non-expert, because in each of these contexts a different definition for `matter’ is being used, and a different meaning — in some cases an archaic or even incorrect meaning of `energy’ — is employed. And each of these ways of speaking implies that either things are matter or they are energy — which is false.  In reality, matter and energy don’t even belong to the same categories; it is like referring to apples and orangutans, or to heaven and earthworms, or to birds and beach balls.

On this website I try to be more precise, in order to help the reader avoid the confusions that arise from this way of speaking.  Admittedly I’m only partly successful, as I’ll mention below.

Summing Up

This article is long, but I hope it is illuminating and informative for those of you who want details.  Let me give you a summary of the lessons it contains:

  • Matter and Energy really aren’t in the same class and shouldn’t be paired in one’s mind.
  • Matter, in fact, is an ambiguous term; there are several different definitions used in both scientific literature and in public discourse.  Each definition selects a certain subset of the particles of nature, for different reasons.  Consumer beware!  Matter is always some kind of stuff, but which stuff depends on context.
  • Energy is not ambiguous (not within physics, anyway).  But energy is not itself stuff; it is something that all stuff has.  
  • The term Dark Energy confuses the issue, since it isn’t (just) energy after all.  It also really isn’t stuff; certain kinds of stuff can be responsible for its presence, though we don’t know the details.
  • Photons should not be called `energy’, or `pure energy’, or anything similar.  All particles are ripples in fields and have energy; photons are not special in this regard. Photons are stuff; energy is not.
  • The stuff of the universe is all made from fields (the basic ingredients of the universe) and their particles.  At least this is the post-1973 viewpoint.

What’s the Matter (and the Energy)?

First, let’s define (or fail to define) our terms.

The word Matter. “Matter” as a term is terribly ambiguous; there isn’t a universal definition that is context-independent.  There are at least three possible definitions that are used in various places:

  • “Matter” can refer to atoms, the basic building blocks of what we think of as “material”: tables, air, rocks, skin, orange juice — and by extension, to the particles out of which atoms are made, including electrons and the protons and neutrons that make up the nucleus of an atom.
  • OR it can refer to what are sometimes called the elementary “matter particles” of nature: electrons, muons, taus, the three types of neutrinos, the six types of quarks — all of the types of particles which are not the force particles (the photon, gluons, graviton and the W and Z particles.)  Read here about the known apparently-elementary particles of nature.  [The Higgs particle, by the way, doesn’t neatly fit into the classification of particles as matter particles and force particles, which was somewhat artificial to start with; I have a whole section about this classification below.]
  • OR it can refer to classes of particles that are found out there, in the wider universe, and that on average move much more slowly than the speed of light.

With any of these definitions, electrons are matter (although with the third definition they were not matter very early in the universe’s history, when it was much hotter than it is today.) With the second definition, muons are matter too, and so are neutrinos, even though they aren’t constituents of ordinary material.  With the third definition, some neutrinos may or may not be matter, and dark matter is definitely matter, even if it turns out to be made from a new type of force particle.  I’m really sorry this is so confusing, but you’ve no choice but to be aware of these different usages if you want to know what “matter” means in different people’s books and articles.

Now, what about the word Energy. Fortunately, energy (as physicists use it) is a well-defined concept that everyone in physics agrees on.  Unfortunately, the word in English has so many meanings that it is very easy to become confused about what physicists mean by it. I’ve briefly describe the various forms of energy that arise in physics in more detail in an article on mass and energy. But for the moment, suffice it to say that energy is not itself an object.  An atom is an object; energy is not. Energy is something which objects can have, and groups of objects can have — a property of objects that characterizes their behavior and their relationships to one another.  [Though it should be noted that different observers will assign different amounts of energy to a given object — a tricky point that is illustrated carefully in the above-mentioned article on mass and energy.] And for this article, all we really need to know is that particles moving on their own through space can have two types of energy: mass-energy (i.e., E= mc2 type of energy, which does not depend on whether and how a particle moves) and motion-energy (energy that is zero if a particle is stationary and becomes larger as a particle moves faster).

Annihilation of Particles and Antiparticles Isn’t Matter Turning Into Energy

Let’s first examine the notion that “matter and anti-matter annihilate to pure energy.” This, simply put, isn’t true, for several reasons.

In the green paragraphs above, I gave you three different common definitions of “matter.”  In the context of annihilation of particles and anti-particles,  speakers may either be referring to the first definition or the second. Here I want to discuss the annihilation of electrons and anti-electrons (or “positrons”), or the annihilation of muons and anti-muons.  I’ve described this in detail in an article on Particle/Anti-Particle Annihilation. You’ll need it to understand what I say next, so I’m going to assume that you have read it.  Once you’ve done that, you’re ready to try to understand where the (false) notion that matter and antimatter annihilate into pure energy comes from.

What is meant by “pure energy”?  This is almost always used in reference to photons, commonly in the context of an electron and a positron (or some other massive particle and anti-particle) annihilating to make two photons (recall the antiparticle of a photon is also a photon.)  But it’s a terrible thing to do.  Energy is something that photons have; it is not what photons are.  [I have height and weight; that does not mean I am height and weight.]  

The term “pure energy” is a mix of poetry, shorthand and garbage.   Since photons have no mass, they have no mass-energy, and that means their energy is “purely motion-energy”.  But that does not mean the same thing, either in physics or intuitively to the non-expert, as saying photons are “pure energy”.   Photons are particles just as electrons are particles; they both are ripples in a corresponding field, and they both have energy.  The electron and positron that annihilated had energy too — the same amount of energy as the photons to which they annihilate, in fact, since energy is conserved (i.e. the total amount does not change during the annihilation process.) (See Figure 3 of the particle/anti-particle annihilation article.

Moreover (see Figures 1 and 2 of the particle/anti-particle annihilation article), the process muon + anti-muon → two photons  is on exactly the same footing and occurs with almost exactly the same probability as the process muon + anti-muon → electron + positron — which is matter and anti-matter annihilating into another type of matter and anti-matter.  So no matter how you want to express this, it is certainly not true that matter and anti-matter always annihilate into anything you might even loosely call `energy’; there are other possibilities.

For these reasons I don’t use the “matter and energy” language on this website when speaking about annihilation.  I just call this type of process what it is:

  • particle 1 + anti-particle 1 → particle 2 + anti-particle 2

With this plain-spoken terminology it is clear why a muon and anti-muon annihilating to two photons, or to an electron and a positron, or to a neutrino and an anti-neutrino, are all on the same footing. They are all the same class of process. And we need not make distinctions that don’t really exist and that obscure the universality of particle/anti-particle annihilation.

Not Everything is Matter or Energy, By a Long Shot

Why do people sometimes talk about “matter and energy” as though everything is either matter or energy?   I don’t know the context in which this expression was invented.  Maybe one of my readers knows?  Language reflects history, and often reacts slowly to new information.  Part of the problem is that enormous changes in physicists’ conception of the world and its ingredients occurred between 1900 and 1980. This has mostly stopped for now; it’s been remarkably stable throughout my career.

[String theorists might argue with what I’ve just said, pointing out that their great breakthroughs occurred during the 1980s and 1990s.  That’s true, but since string theory hasn’t yet established itself as reality through experimental verification, one cannot say that it has yet been incorporated into our conception of the world.]

Our current conception of the physical world is shaped by a wide variety of experiments and discoveries that occurred during the 1950s, 1960s and 1970s. But previous ways of thinking and talking about particle physics partially stuck around even as late as the 1980s and 1990s, while I was being trained as a young scientist. This isn’t surprising; it takes a while for people who grew up with an older vision to come around to a new prevailing point of view, and some never do. And it also takes a while for a newer version to come into sharp focus, and for little niggling problems with it to be resolved.

Today, if one wants to talk about the world in the context of our modern viewpoint, one can speak first and foremost of the “fields and their particles.” It is the fields that are the basic ingredients of the world, in today’s widely dominant paradigm.  We view fields as more fundamental than particles because you can’t have an elementary particle without a field, but you can have a field without any particles. [I still owe you a proper article about fields and particles; it’s high on the list of needed contributions to this website.]  However, it happens that every known field has a known particle, except possibly the Higgs field (whose particle is not yet certain to exist, though [as of the time of writing, spring 2012] there are significant experimental hints.)

What do “fields and particles” have to do with “matter and energy”? Not much. Some fields and particles are what you would call “matter”, but which ones are matter, and which ones aren’t, depends on which definition of “matter” you are using.  Meanwhile, all fields and particles can have energy; but none of them are energy.

Matter Particles and Force Particles — Well…

On this website, I’ve divided the known particles up into “matter particles” and “force particles”. I wasn’t entirely happy doing this, because it’s a bit arbitrary. This division works for now; the force particles and their anti-particles are associated with the four forces of nature that we know so far, and the matter particles and their anti-particles are all of the others. And there are many situations in which this division is convenient.  But at the Large Hadron Collider [LHC] we could easily discover particles that don’t fit into this categorization; even the Higgs particle poses a bit of a problem, because it arguably is in neither class.

There’s an alternate (but very different) division that makes sense: what I called matter particles all happen to be fermions, and what I called force particles all happen to be bosons. But this could change too with new discoveries.

What this really comes down to is that all the particles of nature are simply particles, some of which are each other’s anti-particles, and there isn’t a unique way to divide them up into classes . The reason I used “matter” and “force” is that this is a little less abstract-sounding than “fermions” and “bosons”  — but I may come to regret my choice, because we might discover particles at the LHC, or elsewhere, that break this distinction down.

Matter and Energy in the Universe

Another place we encounter words of this type is in the history and properties of the cosmos as a whole.   We read about matter, radiation, dark matter, and dark energy. The use of the words by cosmologists is quite different from what you might expect — and it actually involves two or three different meanings, and depends strongly on context.

Matter vs. Anti-Matter:  when you hear people talk this way, they’re talking about the first definition within the green paragraphs above.  They are typically referring to the imbalance of matter over anti-matter in our universe — the fact that the particles that make up ordinary material (electrons, protons and neutrons in particular) are much more abundant than any of their anti-particles.

Matter vs. Radiation: if you hear this distinction, you’re dealing with the third definition of `matter’.  The universe has a temperature; it was very hot early on and has been gradually cooling, now at 2.7 Celsius-degrees above absolute zero. If you have a gas (or plasma) of particles at a given temperature T, and you measure the energies of these particles, you will find that the average motion-energy per particle is given by k T, where k is Boltzmann‘s famous constant. Now matter, in this context, is any particle whose mass-energy mc2  is large compared to this average motion energy kT; such particles will have velocity much slower than the speed of light. And radiation is any particle whose mass-energy is small compared to kT, and is consequently moving close to the speed of light.

Notice what this means. In this context, what is matter, and what is not, is temperature-dependent and therefore time-dependent! Early in the universe, when the temperature was trillions of degrees and even hotter, the electron was what cosmologists consider radiation. Today, with the universe much cooler, the electron is in the category of matter.  In the present universe at least two of the three types of neutrinos are matter, and maybe all three, by this definition; but all the neutrinos were radiation early in the universe. Photons have always been and will always be radiation, since they are massless.

What is Dark Matter?  We can tell from studying the motions of stars and other techniques that most of the mass of a galaxy comes from something that doesn’t shine, and lots of hard work has been done to prove that known particles behaving in ordinary ways cannot be responsible. To explain this effect, various speculations have been proposed, and many have been shown (through observation of how  galaxies look and behave, typically) to be wrong. Of the survivors, one of the leading contenders is that dark matter is made from heavy particles of an unknown type.  But we don’t know much more than that as yet.  Experiments may soon bring us new insights, though this is not guaranteed.  [Note also there may be not be any meaning to dark anti-matter; the particles of dark matter, like photons and Z particles, may well be their own anti-particles.]

And Dark Energy? It was recently discovered that the universe is expanding faster and faster, not slower and slower as was the case when it was younger.  What is presumably responsible is called “dark energy”, but unfortunately, it’s actually not energy. As my colleague Sean Carroll is fond of saying, it is tension, not energy — a combination of pressure and energy density. So why do people call it “energy”? Part of it is public relations. Dark energy sounds cool; dark tension sounds weird, as does any other word you can think of that is vaguely appropriate. At some level this is harmless.  Scientists know exactly what is being referred to, so this terminology causes no problem on the technical side; most of the public doesn’t care exactly what is being referred to, so arguably there’s no big problem on the non-technical side. But if you really want to know what’s going on, it’s important to know that dark-energy isn’t a dark form of energy, but something more subtle. Moreover, like energy, dark-energy isn’t an object or set of objects, but a property that fields, or combinations of fields, or space-time itself can have.  We don’t yet know what is responsible for the dark-energy whose presence we infer from the accelerating universe.  And it may be quite a while before we do.

By the way, do you know what an astronomer means by “metals”?  It’s not what you think…

You might conclude from this article that modern physicists and their relatives have not been very inventive, creative, or careful with language.  Apparently it’s not our collective strong suit.  Big Bang?  Black Hole?  The world’s poets will never forgive us for choosing such dull names for such fantastic things….

310 Responses

  1. Humans require a lot of energy to collect matter 8n specific functions and that forms a mass, etc liver, heart with a function, to make something with a function in a human is almost unimaginable

  2. So glad so many are thinking.i a human is a particle. And it goes to the game, the stadium becomes a mass of particles, matter is what we see, we see it as 2 dimension image, we relate depth to it very fast to give us the feel of it

  3. I like this article… but I don’t agree with the thinking behind it. When the universe first forms the math says when it’s a billion degrees nothing is physical its all ENERGY. When the energy cools off, we start to get clumps of energy that formulate matter… You can’t have matter without the energy. The comparisons of trying to separate the two sound like chalk & cheese and don’t make a lot of sense. You may separate the two in common discussion but everything is made of energy so the pushback on them being similar just baffles me. It’s nonsensical to do so.

    1. I’m afraid that this is not true. Nothing is *made* of energy. Everything *has* energy, yes, but energy is not a substance from which anything is made. Even “dark energy” isn’t actually energy, if you look under the hood. That’s what the equations of physics say very clearly.

      1. After reading Waves in An Impossible Sea, I’ve formed a very sketchy view of how the Higgs Field interacts with other fields to confine “energy” & “matter” in the form of wavicles. If this is a reasonable assumption, then it would seem that pure energy and pure matter are abstractions that can’t be isolated outside of some field, i.e., they are higher order entities? My background is in chemistry, so in that context, it would seem that various fields act as substrates upon which matter & energy “condense” into the sensible world? Please excuse my near total ignorance of particle physics.

        1. Well, let me see what I can do to help you here. I’m afraid that your starting assumption isn’t right. One way to see that is by asking what would happen if the Higgs field were removed, or if it were switched off. The wavicles of the other fields would still exist, they just wouldn’t have rest mass. Wavicles exist without the Higgs field; the Higgs field just changes how they vibrate.

          Pure matter and pure energy simply don’t exist. There is no energy without something to carry it, and any form of matter has energy. I don’t know where the notions of “pure matter” or “pure energy” arise from; neither one ever appears in any physics class or physics book, from first year to advanced Ph.D. level.

          The Higgs field isn’t confining energy or matter, and isn’t creating wavicles. It is simply changing how the wavicles of other fields vibrate. And the fields don’t act as substrates; matter isn’t built *on* them. Instead, their vibrations are what matter is built *out of*.

          You and everything around you are made of vibrations, and the question to ask is how it is that vibrations can make up matter, without condensation, confinement or substrates. To form matter, what you need is objects with mass and attractive forces between them. The Higgs field assures that some types of wavicles have mass. Other fields, in particular the electromagnetic, gluon and gravitational fields, assure there are attractive forces. These then allow atoms and molecules to form, on up to planets.

          The last important ingredient is the Pauli Exclusion Principle to assure that large clumps of atoms and molecules don’t quickly collapse, and instead can form structures such as crystalline solids and condensed liquids.

        2. Dr. Strassler:

          Thank you for your reply, it helped considerably in my understanding of how the basic ingredients of everything fit together. The question then moves to how matter, energy, fields and relative motion are so precisely organized so as to produce the “same predictable” outcomes throughout the universe, with the possible exception of black holes. Please no details, but “precisely organized” implies mathematics could/do exist that define everything in a manner analogous to how the Schrodinger Equation defines orbitals surrounding nuclei of atoms of varying atomic number? Does this even remotely suggest the Universe, and chemistry, have a gameplan? Please excuse my veering off into the realm of kooky speculation/philosophy.

          Henry Becker

          1. The question of why the universe has laws of nature and is a predictable place, one that is well described by relatively simple mathematics, is a profound one. However, it is at heart a metascientific question, not a scientific one.

            When you ask if its predictability “remotely suggests … a gameplan”, all I can say is that “it does to some people.” Whether it does or not depends on one’s assumptions about the universe and how it might have come to be. Intelligent people differ on those assumptions about reality, purpose, ultimate causes, etc, none of which can be tested by scientific method.

            Science is the study of what can be inferred by assuming the universe is predictable and seeing what logically follows, under that assumption, from observational data. As always, you cannot use a method to test the assumptions that underlie the method; that’s logically impossible. The success of science does suggest that the universe is mostly predictable, most of the time, but that’s all it does. And there’s no way to go further and ask, well, if the assumption is strictly true, why is it true?

            Suppose someone were to suggest an experiment that would show that there is something that created a gameplan for the universe. That something would clearly not follow the laws of nature of our universe, so a key test of the idea is that the laws of nature are sometimes violated. But that would itself violate the premise of science, making the drawing of a scientific conclusion impossible. Intelligent people would simply end up arguing about the significance of the experiment, some arguing that something beyond the universe had been discovered, and others arguing that it simply means that what we thought were the complete laws of nature were not the full story, and more laws remained to be found.

            So I don’t want to tell you what to think; I have my biases and assumptions, and there is no reason you should adopt them in place of any that you might have. [My philosophy is that when a question’s answer depends on your assumptions, then the true answer to the question isn’t knowable and might not even exist or be meaningful. But others disagree.]

    1. Thoughts are *vastly* more complicated than simple particles and their mass and energy. Brain and consciousness research is a huge subject, but it is still in its infancy, and I am neither a brain researcher nor a consciousness researcher, so I can’t give you the most up-to-date viewpoint. But one thing that’s certain is that “thoughts” are not objects — some believe they emerge out of complex representations in the brain involving its pattern of electrical activity and its huge number of neurons. So your question, while extremely interesting and important, is far from having a scientific answer at this time. It’s not even clear it’s the right question; it may be that it has to be reformulated before it can be answered. The very idea of a “thought” may not entirely make sense (after all, exactly how many thoughts did you just have in the last minute? 93? 152,000? 4?)

  4. Matter and energy are both mass. They don’t possess mass. They are mass. Mass that moves at the speed of light is called energy. Mass that moves at less than the speed of light because of the Higgs field or because it is ensnared by some force is called mass.

  5. You lack proof. Photons are energy! We electrical engineers make radio waves (photons). Alternating currents fly off of antennae, continually swapping energy of electric and magnetic fields. It has been proven that light needs no ether medium.

  6. Bonsoir, cette article est fabuleux il m’acroche et me dit beaucoup sur le moment actuelle. IL ME dit où le courant cosmologique est .Bravo à vous tous. Moi aussi j’aimerais participer. Phil..

  7. Actually it is energy and *mass* that are closely related according to Einstein. Both are properties of matter, and the relation is mathematical. An analogy would be to confuse a person (matter) with his weight (mass). One is an entity, the other a property of that entity. Are they related? Sure. Are they in the same category? No.

    1. First let me say im a lay person.

      I didn’t realize that matter and mass are two different things. Im pretty sure that this is why I get confused alot regarding mass. Can you explain, in very simple terms, the difference between mass and matter?

      Thank you so much!


      1. Hi Cecil,

        Matter is the thing that Matt refers to as “stuff”. It’s not a concept that’s easy to rigorously define, but those things that you think of as matter certainly are examples of matter (i.e. a particle, a person, a coffee table, etc.).

        Mass is a property of matter. Think of the following example: You have a certain weight. You and your weight are not the same thing. Rather, weight is a property you have (e.g. like your eye color). You also have mass. The only difference between weight and mass is simply that your weight is a measure of your mass subject to gravitational forces, in other words, measurement of your weight will depend on where in the Universe that measurement is taken.


  8. On this link : profmattstrassler.com/articles-and-posts/particle-physics-basics/mass-energy-matter-etc/matter-and-energy-a-false-dichotomy/

    page you said:

    “In reality, matter and energy don’t even belong to the same categories; it is like referring to apples and orangutans, or to heaven and earthworms, or to birds and beach balls.”

    Einstein describe’s in his theory that energy an matter are closely related.

  9. Wow. Thank you for contributing in the efforts to hold back the flood of assumption and more assumption about one’s ability to comprehend PHYSICS.THANK YOU!
    I am currently acquiring some introductory level material so I may learn calculus. Words as you’ve pointed out will not come close to expressing Theoretical Physics. Many other fields as well.
    That being said, I do have a question:
    I’ve keep reading the claim “There is 0 net energy in the universe.” Gravity being “negative energy”.
    Is this something that Astrophysicists would use to describe a known quality of the universe or a hypothetical version?
    Electric charge, and curvature were also mentioned.

  10. If you can not clearly define your terms, you can not clearly define your topic. What fool would believe experiments performed on a poorly defined experiment can give well defined results? Physics and modern science and their institutions have been lying to us. They are completely lost, and rather than admit it and start over, they have decided to try and convince us we’re just not smart enough to understand. The examples are off the scale.. has anyone seen this Oort Cloud we’ve had around our system since it was discovered in 1950? No, because it never was discovered. Yet they say it was and our children are taught all about this non-existent fact… The blind are not being led here by the blind, but by criminals robbing taxpayers and teaching the next generation garbage so they can be thrown away. Pull it together people! You’ve got to say, “No more!”

  11. Whyte.
    I am not a scientist or physicist but your blog has been inspiring and has opened a lot of complex questions on the subjects of matter and energy. Perhaps the great number of unknowns in quantum mechanics and physics can be easily explained if we consider that all of this relates to a physical universe where time and space are relevant and must be part of the equations. As an esoteric and a Gnostic student, the physical universe only exists because our consciousness created it. Just as there is no place for consciousness, nonphysical dimensions and spirituality in physics and science, there is no place for time ,space and matter in the nonphysical world. So as Einstein himself postulated, “We can’t solve problems by using the same kind of thinking we used when we created them”. The observer in quantum mechanics has no calculable physical input on the result but still creates a conundrum that can only be explained by consciousness. The theory of everything will be discovered when an equation for consciousness is found.

  12. really, energy and matter are two mutual relatively working basic things but sure they both are total different. can we convert Energy to Mass as per M=E/C × C. Really, No. why ? if we broke particles in more smaller particles, why veri little decay in new separated particles total mass as per E =mc x c. it proven. some people says that particles are very very dence energy in very small space area. but how in reality it is possible to turn Energy into Mass ? no way. no one has never observed any how En ergy convert into Mass. Mass only can increase or decrease or steady. Energy can change Mass in static Mass or moving Mass. but Energy self can never convert itself into Mass. if E=mxcxc is true and proven in experiments. but why M=e/c x c can not done in practical. ?

  13. It is called matter to what exists and constitutes in a real and objective way the bodies that generate immeasurable space.
    What is observed is that everything is in motion (dynamic) and that in most of the matter that is perceived, there is the tendency to rest (static). This is the starting point of this analysis.
    This observation suggests the existence of matter with one of the two mentioned properties. Dynamic or static. This is a critical issue as it determines a drastic change in the concept of what exists.
    According to this notion, matter is not only mass, which weighs, if it is also, what generates movement and is dynamic in all its manifestations.
    It is proposed, then, that this that generates the movement, is something to or can legitimately be called matter, one of whose properties is the energy, which is now measured with the work done. Once it acts. To that matter with energy will be called DYNAMIC MATTER, from now on. It is conceived of as that which generates the dynamic and vital forces of nature and as responsible or cause of all the energetic and vital phenomena, and the constitution and behavior of living and dynamic living beings and evolutionary phenomenon.
    In the same way, mass is recognized with matter with inertia, so it opposes the change of motion and the movement itself. To this matter with inertia will be called STATIC MATERIA, from now on. It is conceived of as generating the static and opposing forces of life in nature and as responsible or cause of the totality of inert phenomena and contrary to life, and the construction and behavior of beings antagonistic to life, And the evolutionary phenomenon. It also possesses the property of being extensive.
    Dynamic matter and static matter are not created or destroyed.
    Electromagnetic radiation is considered to be predominantly dynamic matter, that is, it can be an aesthetic portion and radiation consisting of particles with mass, contains the static component that comes from the mass.
    The property of rest generation is exclusive of static matter. This generates the rest, putting itself at rest and preventing the movement of that which surrounds it and which it can retain.
    These latter two properties are contradictory to each other and constitute the causal root of universal contradiction. They do not coexist in the same atom.
    Each atom has as attribute or property one or the other of these two properties.
    This formulation of the properties of matter follows from the principles of conservation, inasmuch as matter has been uncreated, it has always been as it is today. That is, their fundamental properties must have the quality of immutable, or as it is mentioned in the language of the Physics, they are invariants against the time and with respect to transformations of all type, if they were described with respect to a frame reference. On the other hand, in its temporal temporal evolution, its manifestation changes according to the environment, the concrete circumstance in which the atoms are found, and the level of evolutionary integration that it has reached.
    Thus matter has two fundamental properties, spatial property and the property of general movement, the dynamic matter or the property of generating rest static matter. The minimum component of matter, the atom, not the atom of the chemical element, turns out to be an entity impenetrable at very short distances and penetrable at great distances, is able to exert forces outside itself, and to associate with other atoms under Certain conditions. The dynamic and static properties of generating movement or rest respectively are the causal root of the essence or nature of the corresponding atoms or corresponding matter.
    Vázquez-Reyna, Mario (1998). Reflexiones en torno la materia, la energía y la masa. Anexo B. Cd. de México. ISBN 970-91797-1-3

  14. I came across this discussion because I was looking up the word ‘thing’. To me a thing is something that I can either see, or hear, or touch/feel, or taste, or smell. So, aren’t matter and energy both things?

    Matter has the following fundamental properties:
    First. It is indestructible, and exists in infinite quantity. For which the nothing has not existed, does not exist, and will never exist, and the laws of conservation are generated. The universal order comes from the immutable character of the properties of the primordial components of matter.
    Second. Matter is impenetrable at very short distances. It is and has its own space. At great distances the spaces of atoms are penetrable, being fields and overlapping, generating ordinary space, which is, as it is said, property of matter, and can not be empty, since it is itself matter.
    Third. Matter is composed of atoms. The atomic components of Matter have energy or inertia, are heterogeneous with each other, and the character of heterogeneity is energetic or inertial, so they generate movement and opposition to it, the tendency to repose, universal, and Universal diversity.
    Fourth. By virtue of their energy or inertia, the atoms of matter with energy and the atoms of matter with inertia are contradictory among them; they apply forces out of themselves and therefore become ponderable. These atoms are components of the so-called chemical elements.
    Fifth. The atoms are associated with each other by their energy, or by their inertia, that is, they integrate with each other those of the same essence, and by their association, of those who move, those of the dynamic essence, generate universal movement, Life, the universal process of evolutionary integration and universal diversity, and those of the static essence, which oppose life, generate gravity and inertia and try to stop progress by tending to rest, without respite.
    Sixth. The existence and form of being of matter do not depend on whether any Being is observing it, that is, it exists by itself and is, and therefore has an objective character.
    Seventh. It is knowable by itself being an integrated being. And, it reiterates, it generates the knowledge of itself, by itself.
    Eighth. Its properties are immanent to it, that is, they constitute it, and were not created.
    Ninth. Life is the property of dynamic matter. This property manifests as organic life when a dynamic entity reaches a certain level of evolutionary integration, that of algae, for example, in which the phenomenon of individuation appears for the first time in the history of the process of evolutionary integration. And much later, in due time, consciousness appears in the beings who reached the last level of evolutionary integration, achieved to date.

    1/ The definition of atom that is used is: the atom as basic and indivisible block that composes the matter of the universe, that was postulated by the atomistic school in Ancient Greece, Century V A.C., being Democritus one of its exponents.

    Vázquez-Reyna, Mario (2008). Teoría general de la Materia. Borrador. Ciudad de México.

  16. Seventh. It is knowable by itself being an integrated being. And, it reiterates, it generates the knowledge of itself, by itself.
    Eighth. Its properties are immanent to it, that is, they constitute it, and were not created.
    Ninth. Life is the property of dynamic matter. This property manifests as organic life when a dynamic entity reaches a certain level of evolutionary integration, that of algae, for example, in which the phenomenon of individuation appears for the first time in the history of the process of evolutionary integration. And much later, in due time, consciousness appears in the beings who reached the last level of evolutionary integration, achieved to date.

    1/ The definition of atom that is used is: the atom as basic and indivisible block that composes the matter of the universe, that was postulated by the atomistic school in Ancient Greece, Century V A.C., being Democritus one of its exponents.

    Vázquez-Reyna, Mario (2008). Teoría general de la Materia. Borrador. Ciudad de México.

    1. It’d be interesting to see your results published in peer-reviewed journal

  17. Energy as in photons always moves at light speed. Matter cannot move at light speed. How can they be two different sides of the same coin? Sure matter has energy inherent in it, as in e=mc2, but I think if you release all that energy, the matter is still there. Dead matter, so to speak. Atomic dust if you will, with no motion and no charge so probably impossible to detect.

    Photons if anything are a wave. This always moving at light speed suggest they are not a sphere since no part is going to move faster or slower than light speed, whatever happens to it. It is not going to rotate.

    The photon has two speed components. It moves at light speed in the direction of travel, and moves from side to side, so giving us wavelength and frequency, which seems to work out at one third of light speed (one metre wavelength gives a frequency of 10^8 Hz, so one hundred million metres per second).

    The more energy a photon has, the smaller it’s wavelength, so the side to side movement in turn becomes faster. The constant here gives us that effect; that what it adds to the speed, the frequency, it must take from the width, the wavelength. I know what I mean but I am not good at explaining this.

    1. Isnt frequency simply the duration of the wave? And don’t photons have different frequency? As in visable light verses microwave?

      1. Frequency is the number of waves that pass through a fixed point over a given unit of time (so not a time measurement per se). Any yes, photons have different frequencies.

  18. “All particles are ripples in fields and have energy…” As it stands this statement is blather. A field of what? A ripple caused by what? One can substitute ‘strings’ for ‘fields’ in this statement and many a Ph.D. physicist might agree. Yet both versions are without any proof; see Lee Smolin ‘The Trouble with Physics’

  19. Can one describe energy as a measure of the matter which acts on a system to put it back to it’s balanced state…and if so, that without matter energy would be undetectable?

  20. energy is nonmatter, as matter possess energy and energy do not possess matter they are 2 different sides of a single coin , and do not get confused in terms of photons particle , as photon particles as photon particles are stuff of no mass and infinite energy…their mass converts into energy…..Thanx ….by Abhinav…a highschool student…..India ….u.p..alld….ghoorpur.

  21. energy is nonmatter, as matter possess energy and energy do not possess matter they are 2 different sides of a single coin , and do not get confused in terms of photons particle , as photon particles as photon particles are stuff of no mass and infinite energy…their mass converts into energy…..Thanx ….by Abhinav…a highschool student…..India ….u.p..alld….ghoorpur

  22. How does one explain to children the difference between solids, liquids, kinetic energy, potential energy…but oh by the way…everything we know about matter vs energy is bogus? How should one approach educating children about the distinction between matter and energy or the types of energy and matter if this is an incorrect dichotomy? For example, how would I describe the basic state of a car vs the sun or electricity or sound or motion…etc. now that doing so will only lead ultimately to misleading information – and that our basic knowledge regarding energy and matter is a false paradigm? Thanks

  23. One last question. Is it time or distance that dilates at velocity? All quantum weirdness should vanish if you get all the above right.

    The end result could be, not a big bang but the continuous bang of a “white hole” and not a big crunch but a continuous crunch of entering a zero dimension a “black hole”.

  24. start with least complexity space time. how energy might create it? it should answer why the speed of light is consonant whither traveling toward or away from the source in very simple terms. then understand the function of spin and you have it. so simple

  25. Try thinking of energy in an evolution way maybe something like. Energy starts with zero complexity then increases in complexities until it finds symmetry with entropy thus returning energy to zero complexity. Then you can map complexity on an evolutionary tree. It soon becomes clear that gravity is the least complex form of all energy and maybe the source of all energy, from a zero point singularity formed by the single characteristic of nothing. “You cannot separate objects without space time.” A zero point singularity is inevitable in a zero dimension.

  26. you might find this interesting to think about ” the universe being made by energy” instead of “being made of energy” this allows for the creation of non physical properties such as space time. Try to start by thinking of energy as a wave and a particle as the work being done, where the work being done is turning nothing into something.

  27. as a developer, I’d say that:
    – mass is an “excess” of position information (stuff moving in a stationary way)
    – energy is an “excess” of speed/momentum information (stuff moving “freely”)


  28. My Question is for Mr Matt Strassler –

    You say there are field without mass but no mass without field. What is the basic thing for which field obtain mass and also field obtain energy.

    Ultimately we can not ignore E=mc^2, which means mass and energy are convertible.

    Also could not understand proper relation between mc^2 and kT. How they are related if say the velocity of the particle (or field?) is v? Is there any mathematical formulae for the same.

    I also have a question on the concept of “Point of Singularity”.

    All the fundamental particles which form into “matter” have some basic dimension, however small it may be, which is why they have mass (leaving the particles with zero mass, as matter can not be formed with particles of zero mass alone). Therefore, even if we reduce particles to such a level a physical space would be available for the particle. Therefore, I conclude that there may not be any point of singularity at all – it would have some minimum space consideration which is what we may assume as “singularity” although it will not be same as mathematical singularity.
    So it may happen that our very assumption that big bang happened from a singularity may not be a valid assumption.
    However, supposing such a point of singularity to even exist, how does one visualize existence of energy in a concept of singularity.

  29. Hello ALL, I bumped into this article and Matter-Energy Blog just on this Thanksgiving Day. Happy Thanksgiving to all. I am searching for particles /energy that explain physical and spiritual dimensions. Is Higgs’ Filed/Bosons the fundamental physical particle representing the Cosmos and we are still after the Holy-Grail, Spritual/Atman Particle? I am convinced that Higgs’ Field explains the material construction.

  30. Matt,
    Stumbled onto the post searching for publications on this topic. Find much of your presentation w/r to matter and energy is agreeable to me. We have recently published a short article on this topic, and perhaps should have used the term “radiation”, as you did, rather than “radiant energy” as we wrote. Don’t hold your breathe expecting solid evidence for “dark energy” or “dark matter”.

  31. Hi,
    I’m in my late 50’s and have taken a fascination with science, and am thoroughly enjoying learning about it. I found your article certain helpful, although much was over my head. I have saved it and will re read when will understand more.
    Thank You,

  32. As a novice, in trying to make sense of matter vs. energy I have read several papers on the subject and concluded that the word “energy” is nothing more than a way of describing an action and reaction on mass/matter. An example is 2 iron balls, of 5# and 10# respectively, hung at equal heights in a vacuum. Dropped simultaneously, both will hit the ground at the same time with one exception, the heavier ball will dig a deeper hole. And why? Because of “ENERGY” generated by the weight of the mass.

  33. Let me begin by saying that every atom in the entire universe has one intrinsic characteristic and that is, Magnetism. No matter how thin we slice or dice it, the atom, even down to what we believe is its lowest common denominator, quarks, has one thing in common, spin, angular momentum or, magnetism. Is it possible that energy itself is derived from something below this level, or in the way atoms get bounced around?

  34. Thank you. But I had a question. Accordingto your article: what is energy in a field? Its amplitude or its wave velocity (I guess this would be C)?

  35. Very helpful. I landed here with a question . Assuming the properties of only a gravitational interaction, why not just call it like unbound gravity or something? I mean we won’t ever see anything else there.

  36. Hi, to relieve your mind of the contradiction and ambiguity 🙂 I can tell you this: First of all, this dichotomy clearly originates from before the early twentieth century, when the dual nature of light, and with that of all matter, was not yet apparent. I mean, from before the de-Broglie equation.

    This dichotomy of matter and energy, actually originates more from chemists than from physicists. In chemistry we use it primarily to define the traditional study of chemistry, as opposed to the study of physics. And we frequently say, chemistry is the study of matter – properties, changes… etc. and physics is the study of everything else (energy). when we say matter, we mean atomic matter. This is not accurate, and modern chemistry and physics overlap quite a lot, but what we mean when we say this is:

    properties of a substance -> properties of matter -> chemistry
    A reaction between two substances -> changes of matter -> chemistry
    energy changes during a reaction -> iffy, could be physics or chemistry, but chemists study it differently
    intermolecular and intramolecular forces -> same as above
    other forces -> physics
    the electromagnetic spectrum -> physics
    subatomic particles -> physics

  37. Dr. Strassler: As a novice and a much older high school dropout, any of the sciences leaves me in shambles. However I do ask many questions which usually get me in trouble. So here goes. Might there be an antithesis of energy at the very core of this universe growing exponentially as our material universe dies at an ever increasing speedy death of attrition? While modern science tells me our universe has no center, I have my doubts. I am hoping this may turn into a good and constructive discussion? Thanks, LeftyR

  38. Dear Matt, I’m glad that people like you explain things to people like me. Love you for it! 😉

  39. I believe we are missing an an equation to satisfy a problem. Matter to energy must have something quantifiable to keep a constant. Since energy can not be created nor destroyed we are left with doing the math to convert both in a dance of harmony. Dark matter is the gorilla in the room. Unless we can move past the speed of light, we can never know.

  40. what is the universe made up of energy or elementary particles .
    And how particles can be created from energy

  41. Hello Dr. Strassler,
    I love your site and the scintific facts and knowledge you share.
    I would like you to please explain a phenomenon I’m interested in for many years:
    what cause the matter to became a matter?
    In psychological language (Jungian and others), it is the anima (the feminine aspect), that sedused the masculin aspect to became a matter.
    Okay, I can understand this. But what is the equivalent scientific explanation, for lay people like me.
    very comlicated indeed.
    Would very much appreciate your reply.

  42. hello,
    I agree with the cringing feeling you mentioned: I wish there was a cleanly defined ontology for physics too, as there are many for other scientific fields (“http://www.cs.ox.ac.uk/isg/ontologies/lib/”).

    I also agree that the dichotomy matter/energy is inappropriate (a correct one would rather be mass/energy, as they can be tranformed into each other, right?), as matter is “stuff” and mass or energy are properties of that stuff.

    But then another dichotomy would be stuff/void or matter/spacetime, right?


    1. ok, no replies…
      Maybe ontologies are out of scope here!
      but that’s strange, since both “here” (the web) and ontologies are by Tim Barners Lee, a physician…

      Anyway, to strictly speak your language and tell about things you know/care…

      The below is what I wondered about, when I studied (as an hobby) Susskind’s “Special Relativity and Electrodynamics”:

      So, just take the SR’s invariant (a metric!): dTau^2 = dt^2 – dx^2 – dy^2 – dz^2, then divide it by dTau^2, as Susskind does in one of those lectures.

      You get an equation on the components of the four-velocity, but what does it say?

      It says that the square of time component of the 4-velocity, minus the sum of the squares of the spacial components of the 4-velocity is always equal to one.


      Now, what does this mean/imply?

      Let’s take “me”, or any “material thing”:
      I am always “at rest” in my own frame of reference, right?
      So the spatial components of my 4-velocity shall all be 0, right?
      That then means the time component shall be 1, right?


      I, in my own frame or reference, have “some kind of motion” in time, indeed I see it “passing by on my clock”, it’s “moving” with respect to me and vice-versa: the time component of my 4-velocity is 1!

      To me, that is basically equivalent to say “I ‘keep existing’ as time goes by”.

      But there’s not just things like “me”, not just (massive) “particles”, out there, right?

      There also are things for which “time does not pass by” and “all space is compressed in the direction of motion”, so that they cannot have a frame of reference of their own… pretty weird, right?

      If they could have a reference frame of their own, they would say about themselves that their time component of the 4-velocity is 0 and their space components squared sum up to -1, so if you take the motion along one single space component, their speed is i=sqrt(-1)… too weird, right?

      BTW: to me, this is pretty much the same thing that happens in EMF with the components of the 4-current:
      – take the time component: we call it charge density
      – take the space components: we call them currents
      why do we do so?

      To me, it’s us introducing this dichotomy, nature hasn’t (this one).


  43. Sorry everyone but you are over complicating ! Consider particles are constricted energy, energy seen is variation in dark matter energy field but what is energy?

  44. Polarity is required for thinking. So, for example, if you don’t know what up is, you don’t know what down is. If there is no up, there is no down.

    Energy has been a difficult concept to define because no one knows its polar opposite. Feynman has said that science has no idea about what energy is, and that makes sense, because there is no polar opposite to energy.

    I suggest science and philosophy will have the same problem with the objectivity and subjectivity. Like energy, science, by its own requirements, cannot define objectivity, because, there is no polar opposite. Subjectivity, and hence consciousness, can only be defined by science in objective terms. According to current science, as I understand it, subjectivity is only a kind of objectivity we do not understand yet.

    Hence, since there is no real polar opposite to objectivity, objectivity cannot be defined. You know, and like “consciousness,”like “energy”.

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  46. I knew someone who had exactly this problem, in fact I myself discovered the problem while searching the net for a particular literary piece he had written. I put several keywords into a search engine, and lo and behold, I was directed to another site. Worse still, the owner of this other site was passing off his intellectual property as her own. He had a lawyer draw up a cease and desist order (really just a letter), and the plagiarized material was gone within the next 48 hours. I’m not sure an actual lawyer is necessary, since you could probably draw up a convincing letter yourself and self-promote to “Esquire” 😉

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  48. Two words regarding the matter\energy equivalence debate, “conserved quantities”… energy and matter are interchangeable. There is no dichotomy. Matter is an observed point particle at a specific place and time within a collapsed wave function, just an observed probability. We know that where there is energy we can observe matter popping in and out of existence (for want of a better word)ad nauseam.

    In my mind the day will come where we realise that scale-symmetry will clarify unequivocally a fundamental view of “what stuff is”. we will drop the idea of super-symmetry and accept that matter having physical dimensions e.g the current zoo of point particles we observe is just a misleading by-product of fundamental symmetry breaking. last month at the International Conference of High-Energy Physics in Valencia, Spain, researchers analysing the largest data set yet from the LHC said and I quote “we have found no evidence of super symmetric particles”. Yes you can always say that at higher energies we can expect to see a super massive primordial particle beyond the combined 14GeV the LHC can pump out, now we have 5 sigma results on the Higgs what’s next? I will retract this when I see a 5 sigma result on a Electron\Selectron pair stopping the Higgs boson mass inflating exponentially being observed …

    To quote the matrix… “there is no spoon”, but again in my mind there is (at the scales we observe from the observable universe down to the Planck length) a bloody good 4D observable representation of that spoon gaining mass from our old friend Mr H Boson…or if your a M Theorist an 11/6D one bent Uri Geller like through an unobservable Calibi Yau Manifold ;o) Or to put it more accurately the energy that constitutes it appears on our narrow scale of observation to be a spoon, because the interaction it has with the Higgs field ascribes mass to it on our scale … please understand my tongue is placed firmly in my cheek here… ;o) thanks for the article I enjoyed it and the comments below it very much…

  49. recalling my highscholl physics where the teacher would tell us that the electrons quantum jumps between orbits ? Where does it go ?

  50. Do fields extend endlessly across or through the known universe? Can any distinction be made between fields and their particles on the one hand and the phenomenal world we actually experience by way of our sense modalities? When you suggest that “objects” have (energy), are you arguing for “entities” that have an independent, autonomous existence and an intrinsic identify? I haven’t encountered such as yet, at least not in the phenomenal sense, wherein a thing exists ONLY in relation to other things. – Cal

  51. Hello there, You’ve done a great job. I’ll certainly digg it and personally suggest to my friends.

    I am confident they’ll be benefited from this website.

  52. Is consciousness matter or energy, or some combination? Well, actually, you don’t know. So, I will tell you. Consciousness is aware-ized energy, and all energy is aware-ized, whether you believe me or not. : )

    That statement is scientific heresy. Subjectivity cannot be demonstrated within the context of current science. How do I know? I know by experiencing my own consciousness in many ways. Learn by doing.

  53. Incredible story and string – and I always thought it was only we economists who were all screwed up with ‘on the one hand, this’ but ‘on the other hand, that’, ‘but then again maybe it’s…….’ and so on and on. How refreshing.

  54. And now I can say, consciousness is aware-ized energy, and, all energy is aware-ized. Of course, only subjective experience can tell. I think Matt is missing out on that part. Science has bound up the minds of even its own even most original thinkers, like Matt, for they dare not stray from certain scientific principles.

    When his private experience of himself does not correlate with what he is told by science, then he may become familiarized with the roots of ego consciousness. This will be done under the direction of an enlightened and expanding egotistical awareness. Then, he could use his talents to organize the hereto neglected knowledge.

    Not a judgement, just an observation.

  55. not only “may be that energy is all there is” but energy is all there is, and its different forms (force fields and “matter”)

  56. def(matter)by Google “physical substance in general, (in physics) that which occupies space and possesses rest mass, especially as distinct from energy.”

    It all depends on your perspective. I meant matter in general, not A specific bit. I also meant that when matter takes a form, that form IS a result of energy. So, for example, the form of a balloon, and the material components of the balloon, are shaped by the forces acting on it and them.

    “…especially as distinct from energy.”

    Matter IS distinct from energy, but is not separate from energy, since no matter can exist without energy.

    Just to emphasize the ambiguity of language, your phrase, “matter is A form that energy CAN take”, implies that energy can take other forms. Of course, you can say that energy takes different forms, such as EM and gravitational, taking “form” in a different sense. When you experience matter, EM energy, and gravity, are you experiencing energy? What about mass? When you perceive mass are you perceiving energy? Aren’t mater and mass simply phantasms composed of energy?

    In fact, it may be that energy is all there is. : )

  57. Is it possible for energy (represented by a field) to act within and upon itself? What d’ya say?

  58. I should change that to ask if it is possible for a field to act within and upon itself?

  59. Is it possible for energy to act within and upon itself?

    Is it at least possible that consciousness is a form of energy? Or, are there reasons i tcannot be?

  60. thank you that was very informative and has given me a lot to think about , i just don’t understand how light speed or fster than light speed was achieved in the first few seconds of the start , in whatever state of energy or near mass everything was :_)

  61. Not sure if this will make sense to someone with knowledge, but when the big bang happened you had pure energy and massive temperatures, as the universe expanded it cooled and turned into (matter) could dark energy be the remaining energy and temperature in the universe wanting to turn into (matter)? Also when the universe started it was extremely hot its cooled so much why did it stop cooling? Why did it stop just above absolute zero in deep space? These are probably stupid questions just thought I’d try to better understand something that interests me.

  62. If energy is neither created nor destroyed than it is neither present nor absent in a particular space and time.Energy and matter are one and same.There is nothing called dark matter and dark energy.All divisions are like dreams.For mind time is understanding through thought/memory.Mind cannot differentiate between dream and reality because it functions by continuous reciprocal causation.One cannot prove in unreal{dream like} time and space.

  63. Hello Professor Strassler. In your post you say that energy is something that objects have, that energy is not an object itself. But I have heard string theorists like Brian Greene say on science tv shows that if string theory is true then everything is made of strings. And what are these strings? He says they are strings of energy. He says these strings are made of energy. But if strings can be made of energy, wouldn’t that mean energy is stuff? And wouldn’t that mean matter is energy at the fundamental level?

    To hear Brian Greene say this watch these short videos:


  64. sorry but I haven’t read the full website … can you succintly put everything in a simple short phrase ?? would it be fair to say that everything is energy and it manifests only in two ways: matter and force fields ??

  65. Well Sir, After reading all this “stuff” , off course not that stuff which you have been mentioning about, I’ve got a feeling that some of my doubts can be cleared by this well learned friend of mine namely Mr. Matt. The following are my doubts Sir, Please address to them:
    1. Is the light a form of energy as every one is thinking as on now?
    2. If it happens to be right, Is the energy incident on earth’s surface from sun is in form of sunlight?
    3. If it is only partially right, what are the other forms in which the energy is being conveyed to earth from the sun?
    Based on the answers for this queeries there may be further observations you have to answer Sir, Please reply.

  66. Also it is my opinion that dark energy is a result of entropy caused by the transfer of energy not being 100 % efficient during the energy transfer process. And as the universe has expanded and aged, the entropy has increased and that has caused an increase in dark energy that is in a chaotic state. This “dark energy’ then behaves as regular energy, but instead creates dark matter as a result of its chaotic state. energy in is greater then energy lost in most efficient energy systems, and this loss/entropy is the reason for the related increase and amount of dark energy in the universe, and the amount shall ever increase in relation to entropy due to inefficiency. just my opinion though…

  67. A Photon is an eternal carrier of information that can transfer and receive energy through contact and interaction upon various fields of mass. This ability can best be represented as you gaze upon a full moon at night, for you do see the moon light shining, and you do see the moon, but in reality you are seeing photons that came from the Sun, interacted upon the mass field of the moon, then imprint the information of this mass field upon the photon, then as it enters your optic nerves the information your neurons receive is that of the physical image of the moon shining from photons originating inside of the Sun. The eternal energy and motion of these photons is lost as each transfers its energy into the organic neural/electrical network becomes a particle transfers its energy ( information ), and ceases to exist in its previous form. Photons have been captured from telescopes that have traveled billions of lights years across space and time, yet they retain there speed only slightly influenced by gravitational fields of fields of mass, and they retain the information of there source of origin, and can attain constant updates to this information as it interacts upon various fields of mass, sometimes exchanging its energy, and sometimes transferring its energy to another medium. this vast universal communication system is recently being discovered as quantum mechanics and physics are relating it to the vary method used by the brain to communicate along vast and complicated neural networks, so, as above, then so below. Energy is eternal it can not be created nor destroyed, only transferred between fields of mass….

  68. Matt,
    You say “it happens that every known field has a known particle, except possibly the Higgs field (whose particle is not yet certain to exist, …”
    I had always thought that evidence for the existence of the Higgs field and that of the Higgs particle were more or less on equal footing, in fact, that acceptance of the Higgs field’s existence was predicated on detection of the Higgs particle. But your statement above suggests to me that even if a Higgs particle were not to be found (or somehow proved to not exist), then the prevailing point of view would be that the Higgs field exists nonetheless, only having no minimum eigenstate.
    Is this slight (and very respectful) criticism anywhere close to accurate?
    I feel blessed to have stumbled upon your site, and will be an ardent reader of your posts/articles. You have an extraordinary talent for expressing complex ideas in a clear, yet scientifically responsible, manner. This is very, very rare.
    – Doc

  69. Hi Matt,
    Below I quote two things that you have said about dark energy and ask for a bit more explanation:-
    “Dark energy is a property that fields, or combinations of fields, can have.”
    If there is one thing you’ve got into my head is the idea of “fields and ripples”.
    A field can have a ripple, an object (stuff) like an electron or a photon.
    “Dark energy isn’t an object or a set of objects.”
    Do you say this because the effect in the field is more subtle, like the distrubance in space-time that gives us the gravitational field (stuff, but not defined enough to be called an object)? And if gravity can be visualised as a heavy ball on a trampoline, could dark matter be visualised as something bending its field(s) to make a hill as opposed to gravity’s valley?

  70. Excellent article, thank you Matt!
    I think the abuse of terminology is common to layman description of all technical fields, and is not a prerogative of physics. Part of it comes from public relations (try explaining your discovery to a reporter, and, what is way more difficult, making sure it is published without inaccuracies!), and part of a linguistic inertia. I think as the boldest example of the latest we should recall the fact that in numerous languages (less in English, though) the word “ether” is used to indicate the broadcast of a radio or tv program. “In ether” is used in these languages as a synonym to “on air”. This archaic heritage of the long-obsolete luminiferous ether theory still remains in our terminology, and even modern network technology that has nothing to do with ether bears the name of “Ethernet”.

  71. Thank you for a solid blog on an important subject. I’m 65 and have a question based on the above mentioned “pre-1973” science era I grew up in.

    In today’s Physics, is the fundamental essence of the Universe still considered to be Space, Time, and Matter, or, as I gather from the above, something more akin to one of the following:

    A. Space, Time, Energy
    B. Space-Time, Matter-Energy
    C. Energy (when stretched out=Space, when condensed=Matter, and otherwise simply Energy)
    D. None of the above

  72. I know you use “mass” to mean rest mass, but aren’t there some cases where we really need to talk about the mass corresponding to the total energy of a system? Like the fact that a system as a whole is literally heavier (has greater mass, as one can measure by the inertia or gravitation of the system as a whole) when DeltaE of *any* type is added to it (without allowing any energy to escape of course): let in some light, add heat, set a top spinning that was at rest before, compress a spring, pull positive and negatively charged objects further away from one another within the system, etc. I’m assuming that we’re examining this system in a single inertial frame in which the system as a whole is at rest, with no external forces or fields, so we don’t have to think about the kinetic or potential energy of the system as a body itself within its environment. The extra mass we’ll measure will be given of course by DeltaE/c^2, but here the E and m both refer to the total energy of the system.

  73. Most people do not have a clue as to the things they speak, nor can they prove them. But they speak none the less, it is all theory, opinion, best guesses, until it is proven to be true. And anyone that claims to understand Quantum Mechanics and the Sub-Atomic plane, is the same person that claims to be \/\/ise, anyone can claim to be anything, but it is one thing to “understand” the “truth”, and one thing to guess about it.

    But it is fun to read other peoples opinions, but it be better to read the truths, but those are yet hidden. Even though much is understood, he that speaks as if understanding is a given, speaks in circles, because they do not understand the truth.

    It is ok professor, no one understands it completely, or has the truth. but your opinions do have merit.

    1. Are you trying to reassure me? 🙂 No reassurance needed; my knowledge is used to make cell phones, rocket ships and lasers. What are your alternatives used for?

      1. cell phones, rocket ships, and lasers, are great technologies for the advancement of understanding. But they are each only different manipulations of the same energy that is present in all. A photon of light travels at the speed of light throughout the universe carrying the information of its source for eternity, unless interaction upon another force disrupts or absorbs its energy, such as in vision, if not for this information your eye could not interpret the origins of said photon to turn that information into a “picture” for your neurons to process. In order to travel at the speed of light a photon needs to be a particle, a wave, or both at the same time, and is basically mass-less, but yet still has the ability to transfer information, as Darpa has shown transferring information upon photons. As soon as a Photon “interacts: upon the human eye for example, it has to assume the form of a particle in order for the information to be “read” and transported to neurons for interpretation, this biological process does not occur in non-living matter, also in order to travel at the speed of light, a photon needs to maintain the mass less form of energy in order to reach the speed of light threshold, as no particle of mass may reach this thresh hold, as I am sure you understand completely during experiments preformed using accelerated particles, none of them have achieved 100% equal to the speed of a photon, that reason is established. It has been observed in many recent experiments that light ( a photon ) can be any or all forms at once, or that a photon can change forms as needed in its travels. Decay being the key, for Photons have been collected from telescopes that collected them after they traveled billions of light years across space and time, there are no particles that can achieve this velocity unless they change into pure energy to achieve this speed. Experiments at Cern have even held this constant to be true.. so for you to say that light is not pure energy, is disputed by many recent experiments, and by many old experiments…

        1. Wow! ya why listen at all? Especially when you have everything figured out in your own head and can just vomit streams of metaphysics all over the comment section. No wonder the good professor stopped responding to you

  74. Everything you said about matter, stuff, energy, I agree with. A learner has to create separation between the two concepts in order to learn these. Its just like learning the language. A child will break up a long word into sylabils and memorize its pronunciation and meaning that way. And since its almost impossible to define either one of the terms (matter or, energy), why worry about it. Or, a layperson might reach a wrong conclusion that physicist in general are afraid of the word ‘spirit’ (pure energy). I meant spirits, like God for example. Physicists may cringe but the truth is this ‘stuff’ falls into category all on it own and being ethereal it can not be detected, tested or, experimented on in LHC. There is also a big likelihood that this ‘stuff’ disapproves of humans splitting the atom and destroying something he created for the benefit of all humans_ the blue planet, third rock from the Sun.

  75. Scientists have trouble expressing themselves coherently or agreeing on how to say things… noted.

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  76. Thank you for your excellent article, and website. I would like to ask how are ‘mass energy’ and ‘motion energy’ related? Can motion energy ever be converted into mass energy and/or vice versa? You seem to be saying in your replies to other posts that ‘E’ in Einstein’s equation E=MC2 doesn’t include motion energy. If not then why does science use the same word ‘energy’ for both concepts when to do so leads to confusion?

    1. The point about energy is that energy of one type can be converted to energy of another type, but all the while, in particle physics (and elsewhere, unless you’re trying to keep track of the universe as a while), the total amount of energy remains constant. That’s why we use the concept.

      So yes, motion-energy can indeed be converted to mass-energy and back again. Indeed, that is the principle reason that particle physicists use particle accelerators to make new particles. See for example http://profmattstrassler.com/articles-and-posts/particle-physics-basics/particleanti-particle-annihilation/ .

  77. You said in this article “Early in the universe, when the temperature was trillions of degrees and even hotter, the electron was what cosmologists consider radiation. Today, with the universe much cooler, the electron is in the category of matter.” Why does “high temperature” make the Higgs (and gluon?) field being “zero” on average early in the universe? Why/how does “temperature” affect these fields? Why does “high temperature” prevent these forces (gluon, Higgs, etc.) acting on particles? And why do these different forces start acting on particles at “different temperatures”?

  78. http://www.livescience.com/24509-light-wave-particle-duality-experiment.html Date: 05 November 2012 Time: 07:29 AM ET

    Now, for the first time, a new type of experiment has shown light behaving like both a particle and a wave simultaneously, providing a new dimension to the quandary that could help reveal the true nature of light,

    Depending on which type of experiment is used, light, or any other type of particle, will behave like a particle or like a wave. So far, both aspects of light’s nature haven’t been observed at the same time.

    But still, scientists have wondered, does light switch from being a particle to being a wave depending on the circumstance? Or is light always both a particle and a wave simultaneously?

  79. sorry, I just seen this quote from one the the links you gave me.

    your quote’s :
    light waves (and the waves of any relativistic field satisfying the relativistic Class 0 equation) move at the speed c.

    the energy stored in the wave is

    E = (n+1/2) h ν

    where h is Planck’s constant, which always appears when quantum mechanics is important. In other words, the energy associated with each quantum of oscillation depends only on the frequency of oscillation of the wave, and equals

    E = h ν (for each additional quantum of oscillation)

    This relation was first suggested, for light waves specifically, by Einstein, in 1905, in his proposed explanation of the photo-electric effect.

    Please explain how this does not agree with my statements.

  80. Another side note ( should of put this all on one message, I apologize ):
    .the initial energy for a Photon comes from its source ( for example a star )

    Energy may be stored in systems without being present as matter, or as kinetic or electromagnetic energy.

    Stored energy is created whenever a particle has been moved through a field it interacts with (requiring a force to do so), but the energy to accomplish this is stored as a new position of the particles in the field—a configuration that must be “held” or fixed by a different type of force (otherwise, the new configuration would resolve itself by the field pushing or pulling the particle back toward its previous position). This type of energy “stored” by force-fields and particles that have been forced into a new physical configuration in the field by doing work on them by another system, is referred to as potential energy

    Any form of energy may be transformed into another form. For example, all types of potential energy are converted into kinetic energy when the objects are given freedom to move to different position

    This mathematical entanglement of energy and time also results in the uncertainty principle – it is impossible to define the exact amount of energy during any definite time interval. The uncertainty principle should not be confused with energy conservation – rather it provides mathematical limits to which energy can in principle be defined and measured.

    It seems to me that as a wave of (electromagnetic) energy a photon travels at ‘C” then changes to a particle upon observation or interaction.

    Everything I read leads to this conclusion.

  81. as a side note : The total energy contained in an object is identified with its mass, and energy cannot be created or destroyed. When matter (ordinary material particles) is changed into energy (such as energy of motion, or into radiation), the mass of the system does not change through the transformation process.


    this does allow for a Photon to change from a wave of energy then into a particle, and so on. Maybe this is how it travels at “c” and never decay’s as a wave of energy it is basically eternal and there fore could travel at “c” for infinity, or for 1 Billion years for example, and then as interaction or observation dictates it changes into a particle, and interacts as dictated by the contact.

    your thoughts on this .

  82. Okay, I checked out the links you provided, very good information, any knowledge into this subject I welcome into my deposit of knowledge.

    I understand your phrase of “motion energy” in the context it was used now. As far as mass experiencing drag per se, I was using the word in context to a Photon moving in space at “C”, having no mass it experiences no loss of motion, maybe the word “drag” is not the best to use, maybe friction, or another one is more appropriate.

    As far as particle/wave duality, my understanding on a Photon is that it can either be a wave or a particle depending upon observation and/or.interaction as illustrated in the double slit experiment.

    As far as “mass” I see this the same as the emergence of consciousness, for example one neuron can not create consciousness, just as one particle can not create significant mass, but it is the number of neurons and the complexity of the neural networks that create consciousness, I see object mass in the same way, once a grouping of particles come together into a certain “level” of complexity, then “mass’ follows in the same way that consciousness follows, that is how I see the “Higgs” field, this field is the result of this complexity, the more complex the structure and the more mass it has, the more it is affected by Gravity, Hence the heavier elements are more dense, thereby they have more mass, gold or lead being a good example, but there are of course many exceptions.

    And as far as a Photon traveling at “c” as a wave of energy I use this observation as my basis, as one example.


    This link shows a cluster of stars 1 Billion light years away, which means that each Photon from this star had to travel for 1 Billion years in order to reach our solar system. (More amazing to me, is the fact that some of those stars probably do not even exist anymore, yet we still are able to see them as they did exist 1 Billion years ago).

    In order for the Photons to travel over space and time for 1 Billion years, it seems to me the probability that a particle could travel these distance and time frames at ‘c” for 1 Billion years and not decay is remote.

    I see a Photon as being a ‘timeless” carrier of information, and I do not see how a particle could travel at “c” for 1 Billion years, and not decay. It seems more probable that in order to do that, it would have to be a wave of energy to accomplish this amazing feat.

    Of course since no human being has ever “observed” a Photon traveling at “c” or observed one at “rest”, Ie. snapped a Photo of one in either state I think it is too early to come to any conclusions as to exactly how a Photon for example can travel through space and time for 1 Billion years all the time, maintaining “C”, and not decay.

    I appreciate you quick response to my inquiry, and realize that so many of these answers are not going to be available until the technology to settle some of these big issues comes into play. But I am always striving to improve my outlook and knowledge on these matters, and value any and all inputs I can gather..

    Thank You

  83. you say that a Photon’s energy is equal to it’s motion, every calculation I have seen, says it’s energy is dependent on it’s frequency, not it’s motion. You also say that A Photon is not pure energy, but that it is a particle made up out of stuff, since a resting photon has never been seen, are you sure that a photon is not a wave/particle potential of pure energy. It seems to me that the reason a Photon can travel at C is that it is mass less, hence it experiences no “drag”, per se, as it travels. If you are saying that a Photon is not energy but has energy, then it can not be mass less as a particle

    it seems that in a Photons wave/particle duality.
    As a particle it has mass and interacts, as a wave it is pure energy and has only momentum..
    A photon as pure energy explains how it can be mass less and yet still carry information as a wave.

    1. I need to fix last sentence. It said – A photon as pure energy explains how it can be mass less and yet still carry information as a wave.

      I meant to say. A photon as pure energy explains how it can be mass less and yet still carry information as a Particle.

      It travels at C as a wave of energy ( hence “pure energy ), then as it needs to interact it either changes to a particle ( to interact for example in Human Vision ) to interact, or remains a wave to interact in that form…

    2. I never said “a photon’s energy is equal to its motion.” I said a photon’s energy is pure motion-energy. It happens that this motion energy is proportional to the photon’s frequency, which is completely consistent with what you learned; I simply didn’t explain that here because I wasn’t addressing the relation between energy and frequency in this article. See
      where this issue IS addressed.

      You must avoid thinking of mass as a sort of drag. Drag only occurs for an object in motion relative to a medium. Mass is something that is present even in vacuum and even for stationary objects.

      Regarding wave/particle duality: you have some profoundly confused concepts here. You might want to read my introduction to particles and fields:

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  84. Bravo Matt, well explained. I am finding that it is easier to do background ‘research’ for an article I am writing by reading your articles than any others I have come across.

  85. I am a bit confused:
    I find your distinctions very insightful and helpful, but my understanding is not satisfied:
    1. What is an energy what is matter? I think you should mention positive definitions so one can refute them otherwise they are too vague.
    2. Nothing wrong with vagueness though, words as said are problematic, but when words have an intrinsic failure, I tend to attribute it to the failure of ‘way to observe the world as human’. I.e. when our senses cannot grab the world. EX: Time in SR as 4th dimension (or 11 dimensions in the strings theory, or particle-vague duality) – the 4th dimension is nothing but a poetic metaphor of the universe that help me to understand the meaning of it, knowing that I am condemn to observe my surrounding in 3 dimensions only and cannot really grab this dimension. Although in physics these concepts makes perfect sense, they are limited to mathematical language and cannot be translated into human one.
    YOU are doing a precious job in helping me and other to have a better understanding but if words fail it is because it just does not match our human perception. BTW, no problem for me, as after Copernicus I lost hope…

    3. A characteristic of an object is also an object UNLESS this characteristic in a a-physical attribute. Ex: A wooden table vs. nice table. As I can assume you refereed only to physical attributes, I cannot see how they are not part of the object itself.
    4. “…I have height and weight; that does not mean I am height and weight” – this is at best a problematic example. What is the I is a long philosophical question and unless you are a pure materialist the I to which you refer is not a physical object and therefore cannot be defined by these adjectives (if you are a materialist you should define what that ‘I’ is).

  86. I was reading through this and several comments, and all seem to agree that Z and W bosons of the weak force act as massive particles because of the Higgs field, but prior I was reading Fear of Physics by Lawrence M. Krauss, and came to the conclusion that these bosons act as massive particles because of virtual particles. As virtual particles pop into existence, it takes energy to do so, so pop back out to conserve energy and momentum, but if two virtual particles are attracted to each other, and instead of one pair, fill the entire system being observed, if these particles were to be adjusted in a way to have less energy than in a system with no such particles, due to the fact that two objects bound together have less energy than two separate objects, the system could fill with these particles, which could in turn affect the weak force bosons, causing them to act massive, for the same reason that photons act as massive particles in superconductors. Either I am entirely wrong (very likely) or is it possible that either these virtual particles are themselves the Higgs field, or that these virtual particles are waves in the Higgs field, rather than the specific weak force boson field? P.S. this is a great sight for the novice high school student of 16! Thank you for such a great resource professor!

    1. “I was reading Fear of Physics by Lawrence M. Krauss, and came to the conclusion that these bosons act as massive particles because of virtual particles”

      That conclusion is not correct.

      One thing you should know: `virtual particles’ are not particles (Krauss is not alone in not explaining this well); you should read http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/ at some point.

      Also, have you read the Higgs FAQ yet? If not you should. http://profmattstrassler.com/articles-and-posts/the-higgs-particle/360-2/

      Now — there are two separate questions:

      1) What does the Higgs field do?

      2) What is the Higgs field made from (if anything)?

      Answer to 1) The Higgs field gives masses to the W and Z particles; and a Higgs-like field (often called the Landau-Ginsburg field) gives mass to the photon inside a superconductor.

      Answer to 2) It could be a single fundamental scalar field, or several such fields, or it could be made as a bound state (simple or complicated) of other particles. The Landau-Ginsburg field turns out to be a field made from electron-electron bound states (Cooper pairs) bound together by phonons. That need not have been the case; it could have been a fundamental field of spin two, or a much more complex object that Krauss would have had even more trouble describing, and it would still have given mass to photons in a superconductor and given us all the phenomena of superconductivity. The Higgs field CANNOT be of a precisely similar form as the Landau-Ginsburg field; Cooper-pair-like objects would break Einstein’s relativity equations. There is something analogous (called `technicolor’) but then the binding between the virtual particles that make up the Higgs field must in such a case be much, much stronger, relatively speaking, than in a typical superconductor. (Incidentally, if there really is a Higgs particle with a mass around 125 GeV/c-squared, technicolor is significantly disfavored.)

      So you see that there is no contradiction between the two statements; they are simply operating a different levels. Question (1) is about what the Higgs field does, which we know, but knowing the answer does not answer question (2); question (2) is about the very nature of the Higgs field, which we do NOT know, and that’s why we have a Large Hadron Collider, to help us answer this question. Similarly, for superconductors, the answer to question (1) was known long before the answer to question (2).

  87. If Matt has trouble defining the rules of the game, perhaps we are just goldfish in a bowl. No. I refuse to give up on science.

  88. PS: “God” is something more fundamental that consciousness. I believe the door to God is understanding the fundamental nature of free energy, the source of temperature at the Big Bang.

  89. To aa.sh.: I was just trying to make the point that we have no idea how to build a robot that is conscious but a fertilised human egg will divide many times over the course of 9 months according to the laws of chemistry/nature etc and produce a baby that is conscious. And its done it countless times since the dawn of the human race. I agree that conscious experience appears to be something completely different from what we call the materlistic world (for a start is a private and subjective not objective ‘thing’) but where ever it appears (at least in this universe/reality) there is also this biological organ we call a brain present. Surley u see nature as GODs design – a nature that is able to support the emergence of consciouness experience. Perhaps that is a better way to say it.

    1. Sorry but consciousness is a manifestations derived from the billions of permutations of electrical / biologic signals. When we are awake we can control our thinking via negative biofeedback processing of billions of “digitized” thoughts.
      And when we sleep, because we have no conscious control, our dreams become more chaotic and random in nature, but we can remember those which are channeled in conscious thoughts, make sense to us because we created them during our awaken phase.

      If there is a universal consciousness, (and I believe there could be due to the striking similarity between the universe and our own brain structures. see a wonderful video below) it would not belong to God since the universal consciousness would be like our own, manifestations derived from the billions of permutations of particle interactions.


  90. TO LUP : Again you are trapped in the fallacy of deciding/decreeing a stand where no real scientific proof exists , and all logical / rational understanding converge…… you decreed that NATURE create consciousness , this is total void statement :
    What is nature ? laws ?fields? both have no power to implement any thing in reality.
    Nature is the material universe while consciousness is beyond m and E .
    What is your proof for your decree ?
    See what i mean ? this is exactly the stand 99% of scientists adopt …to claim the unproved as the ultimate fact, we need to be humble in front of the majestic creation of GOD seeing that human consciousness is the ultimate awe inspiring reality as it is the object of feeling and the feeling itself.
    You need to read lots of sources just to start to feel the awesome tremendous meaning of the reality of what made you understand and decide………..good luck my friend.

    1. Did you really have to bring god into this! Nature is what I would regard as the knowable reality what ever affects or had observable affects in our reality. Laws describe what we observe in reality and fields are what we call certain entities with certain apparent characteristics. The things we are describing to affect our reality but we can only name the properties they possess which is equivalent to saying this is how they affect our reality.

  91. Neurons and neuron networks can be reduced to the realm of forces and particles while sensations and feelings can never be reduced to any thing within material universe , as such all talks about machine consciousness are complete void ………beware of A.I. deception with completely material category claimed to represent completely non material category , but if science retreats , here comes logic and rationality …..a law ….a necessity : any non-material category can never in principle be reduced to material category ….sensations and feelings can never obtained from fields , particles and forces .
    This is a settled fact once all concerned be free of pre-conceptions , prejudice and materialistic naturalistic philosophy , for any individual , he is free in his stand , but once he addresses the public no personal world view is allowed to pollute the innocents .

  92. Most people are making a major category mistake w.r.t. N.N.W. , neuron networks are designed to achieve specific goals within the chemoelectrical medium of brain and body , N.N.W. are systems of equations designed so that with a system of input -output and pre-set goal it converge to accomodate similar goals.
    What is missed by most people is the fundamental category chasm between chemoelectrical output and sensations or feelings ……. you can never in principle get feeling as output while your input was electro-chemical impulses , only monists say that nonsense , for a very simple reason : this nonsense is the ONLY one within which materialism is possible.
    I was obliged to write this to clarify some mistaken comments written above.

    1. If I may concur with this in a simple way: one must distinguish between systems that appear to be conscious and systems that actually are conscious. I believe the rest of you experience consciousness because you are similar to me, and I know I experience it. But I don’t have any way to actually check experimentally that you are experiencing what, from the outside, you appear to be.

      That fundamental problem — the lack of an experimental test of the experience itself — will make it difficult to determine whether a machine which behaves as though conscious actually is conscious. And a question for which there is no experimental test, even in principle, lies outside the reach of science… so until someone invents a convincing test that establishes whether a particular creature, natural or artificial, experiences its apparent consciousness, I cannot easily be convinced that the issue is ever going to be understood scientifically.

      1. The thing that we are most familiar with is also the most difficult and puzzling of all known phenomena. but nature creates it effortlessly every day.

  93. Let us have a mental experiment , a static closed universe where only one electron at rest reside :
    What is the physical meaning then of its m ? E/ c^2 ? well , what is E ? mc^2 ? see what the problem is ? in all your posts E and m were never defind independent of each other , so , what is E ALONE ? and so for m …….
    here we have one electron really at rest , what is the physical reality of its E or of its m are both interconnected in a closed circle where they are in principle beyond our understanding? does E and m really have no independent physical essence that we can ever grasp ? then what is m that belongs to that single static electron ?is it a scale by which we measure the ” amount ” / ” quantity ” of ripples ?

  94. Back on the subject of photons losing energy in cosmic expansion. If we’re to view that as the result of the absence of any time-like Killing vector and hence no energy conservation, how are we to view gravitational redshift in a Schwarzschild geometry, where is time-translation innvariance?

    1. Agreed. But when you have substantial amounts of evidence of correlation, you’d better take the possibility of causation — or at least, interrelation — very seriously.

  95. Objection : NO images or feelings are IN the brain , for the first time in all your presentations you decreed/decided on something where no shred of evidence exists as to the ultimate reality of consciousness / feelings / concepts…..etc.
    David chalmers wrote an article titled ( consciousness and its place in NATURE ) , that was a prejudice , i sent to him

    asking : how can you decree that its place IS in nature while your article is searching for its place with no conclusion reached ? that is what i call pre-conception/prejudice where a scientist decide / decree a point of view as fact , i really hope that some day science can free itself from decrees based ONLY on relative time dependent observations far from final absolute knowledge.

    1. You are right, I did not phrase this well.

      Your statement is, I think, a little too strong — we do know that there are electrical phenomena occurring in the brain that are related in some way to the things we see and think, and we know that damage to areas of the brain (strokes, direct injury, disease) result in correlated damage to conscious experience. But how they are related, we do not know. So I would say that it’s not that there’s “no shred” of evidence — just that there’s no clear understanding of the meaning of the evidence.

      In any case, all I really wanted to say is that conscious experience does not in any sense involve a direct encounter with the physical objects of which we are conscious. What conscious experience itself arises from, I certainly don’t know.

      1. Neurons —> Bosons
        Synapse chemicals —> Fermions
        Eddy currents across the neuron membranes —> Field(s) (EMF)
        Transfer of chemicals across synapses —> Fields (Colors)
        Synapse firings —> Atoms (type)
        Sequence of synaptic firings —> Ensemble of atoms (hadrons)
        Thoughts —> Relativistic structures

        Hence, one can speculate that our consciousness is part of the universal consciousness and our body, including our wiring in our brain is just one more fiber and/or groups of fibers of the overall cosmic quilt.

        1. Um — You can speculate all you want, but there’s no math on the left-hand side of your correspondance, while there’s a huge amount of detailed, predictive mathematics on the right side. The reason we take the right-hand side seriously is that it goes along with mathematical equations which predict, correctly, the results of millions of experiments. If you can’t make the link from the right-hand side’s math to some corresponding math for the left-hand side, then we have no reason to believe any correspondance of the form you suggests exists.

          For example, fermions satisfy a Pauli Exclusion Principle. Are you suggesting synapse chemicals satisfy a similar principle? Do Neurons form condensates the way bosons do? Atoms can be bosons or fermions; are you suggesting that synapse firings can be neurons or synapse chemicals?

          I insist on precise statements. Because that’s what’s needed for science to get done.

      2. I am glad you brought up Pauli’s Exclusion Principle.

        Which is valid, matter is standing spherical waves oscillating at the Compton wavelength or is matter a Fermi sphere with such a radius so as to give a Fermi energy equivalent to the mass-energy of that particular particle?

        I can understand Pauli Exclusion Principle via the Fermi sphere definition but not with the standing wave theory. Are we missing some math?

        1. I think you are confusing some things.

          Atoms involve a nucleus surrounded by electrons which are standing spherical waves (or more complicated standing waves.) The Pauli Exclusion Principle simply says that no two electrons can be in the same standing wave if their spins have the same orientation.

          Metals involve matter in which the electrons in a given volume form a Fermi sphere. NOTE: this is not a sphere in physical space. It is a sphere in an abstract space (“momentum-space.”) [The standing waves that electrons in atoms occupy are spheres in physical space.]

          The vacuum does not have an associated Fermi sphere. The mass-energies of particles in empty space are not associated with a Fermi energy.

      3. Ok, thank you for clarifying. It’s been awhile since I done some of this math so I am quickly trying to catch up before diving into B-E and F-D statistics. So to help me visualize, Pauli Exclusion Principle says if the standing waves are in-phase they cannot interfere due to possible ‘beating” and hence tend to infinite resonance (infinite energy which is not allowed by conservation?) Conversely, a standing wave of 180 degree phase shift will cancel the electron’s wave and bring it down to the ground state, (Dirac’s antiparticle? What does he mean when he describes it, antiparticle, as a hole? Is not opposite phase the same thing?)

        The different fermions are basically standing waves of different amplitudes and frequencies? Why are the half lives different?

        So, the Fermi sphere is the “mechanism” of transferring momentum from one standing wave to another? How does that work, superposition?

        Final question, does the standing wave’s ripples propagate to infinity or do they reduce down to ground state at some radius? Is there any association between this radius and quantum entanglement?

        1. I’m afraid that’s not what the Pauli Exclusion Principle says. You have to first work out, for a particular physical system, what its one-electron states are; then the exclusion principle says that nature cannot put two electrons in the same state. This is not something that I know how to visualize, because it involves a quantum mechanical effect for which there is no visualizable analogue. Not all facts about quantum theory can be represented by a picture in the mind; this is part of what makes it hard.

      4. PS; I apologies for my hieroglyphics but my brain works better with images. i can sit a study a math page and get very quickly but the next day I would forget the details and only the images that were created remain, for a long long time, 🙂

      5. “… for a particular physical system, what its one-electron states are; then the exclusion principle says that nature cannot put two electrons in the same state.”

        Can one interpret this as saying the second “electron” wave cannot superimpose over the first “electron” wave because the “electric charge” imbalance will “push” the second wave to a different phase, higher state? So it is the combined nucleus-electron interaction that prevents the second “electron” wave from coming too close to the nucleus? What about two loose electrons, can they superimpose or is it that the probability of two electron waves coming close to each other is nil?

        Does the exclusion principle have any thing to do about the Z and W having mass or is it solely because of the variants of the spin states of these bosons?

        If I can speculate again, and I have seen the derivation of the equations for the Hiiggs field and I somewhat understand the definition of symmetry “breaking” to give the mass term. But physically specking, is it correct to say that it requires the interaction of two bosons to create a higher enough resonance in the composite wave to give it “mass”? But, again, why do different fermions have different half lives? In other other words why is the electron so stable of the other fermions decay so quickly?

      6. One physical object we do experience more directly is our own brain – or at least parts of it. i think that because certain brain activity appears to have SUBJECTIVE sensations associated with it, there is a certain aspect of the reality around us that is not accessable to our scientific instruments. what do u think?

      7. lup, you say ..

        “i think that because certain brain activity appears to have SUBJECTIVE sensations associated with it, there is a certain aspect of the reality around us that is not accessable to our scientific instruments.”

        I wonder. There are some very interesting ways of configuring “scientific instruments” to do a lot our own brains can achieve. Take a look at this very cool stuff:


  96. One of the great properties i like much in what Matt. write is his total freedom of any prejudice ane pre-conceptions , he gives us the state of the matter with true honest description , so let me state what — being non-physicist — i understand as the core of all what have been said :

    1- We only know that there are something /stuff which is the most – maybe- fundamental kind of physical existence which we call fields of which reality –the thing as it is- we know nothing.
    2- That stuff have properties we can observe we call m , E , p , interacting according to pre set codes we call theories , these theories are our POINT OF VIEW AS PER TODAY never to be confused with ultimate reality.
    Now the main essential difference is :
    Matt. never claimed that what he says is the final ultimate truth in contrast to 99% of articles and books where they claim that what they present is such……………thanks Matt. , this is the true , honest way of doing science.

    1. I think you are more or less stating my point of view, yes. I don’t know what ultimate reality is and I have no idea how I would come into contact with it. I just know that we have found ways of classifying the objects in the world such that we can predict in great detail how they behave. I can’t tell you that classification is unique or complete.

      Along these lines I think it is also important to keep in mind that we, as minds, never come in contact with anything physical at all. See the table across the room? What do you know about this table? The only thing you know is the image created somehow in your brain, formed on the basis of electrical impulses down your optic nerve from your eye, which in turn are based on photons impinging on your eye, some of which came down from the sun or from the light bulb in the room, and bounced off the table in just the right direction to enter your retina. There are many steps from your image of the table to the table itself.

      Even when you touch the table, what you feel is in your brain, created from nerve impulses sent down from your fingers, from nerves firing in response to the deformation of your skin by the inter-atomic forces between your skin and the table. Your brain is not in contact with the table. What you feel is in your brain, not in your fingers.

      Our senses are no different from the measuring equipment used by scientists, allowing us the ability to detect aspects of the world around us. What we know of the world, through our natural sense organs and through the artificial sense organs of scientific experiments, is always indirect.

  97. One thing has always puzzled me about dark energy. It is supposed to contribute 74% of the mass-energy density of the universe, but at least naively it doesn’t even seem like it should be commensurate with energy. Obviously that’s wrong. I’m dimly aware that there’s such a thing as the stress-energy tensor. But I would have thought “density” would be a component of the tensor, but it seems like the 74-22-4 decomposition must be based on some kind of norm? I guess my real question is, what does that 74-22-4 decomposition mean?

  98. At least I know what metals are.
    Even if I’m more a chemist than an astrophysicist.

  99. Let me be bold and see if I, an “outside observer”, can “cause” a “disturbance” and create some “fire” in this “medium”.

    I say, for the lack of a better theory, God caused the universe to ignite and hence the Big Bang.

    The boundary of our math only goes to the time-energy uncertainty principle was given in 1945 by L. I. Mandelshtam and I. E. Tamm, as follows. For a quantum system in a non-stationary state ψ and an observable B represented by a self-adjoint operator , the following formula holds:

    σE x (σB / | dB / dt | ) >= Planck’s reduced constant / 2

    where σE is the standard deviation of the energy operator in the state ψ, σB stands for the standard deviation of B. Although, the second factor in the left-hand side has dimension of time, it is different from the time parameter that enters Schrödinger equation. It is a lifetime of the state ψ with respect to the observable B. In other words, this is the time after which the expectation value changes appreciably.

    This principle says the quantum state ψ cannot stay the same forever since that means infinite energy, I hope I am right, 🙂 So, once an external disturbance ignites the charged initial state change will continue until all the useful work is spent.

  100. Now i really wonder , what is the source of the intrinsic movements / momentum in all sub-atomic entities , what “pushed ” the quarks or electrons to always be in motion , you said – nothing is at rest – well , what physical mechanism is the CAUSE of all that movements , i am beyond some equations equilibrium , i am at the CAUSE , THE URGE , THE DESIRE !!!!! TO BE IN PERPETUAL MOVEMENT!!!! conservation of energy ?but if movement was generated , what caused its generation ?

  101. Hello Matt,

    Incredible what a interesting subject physics really is, how much there is to say about it and what thorough knowledge you have of every detail of physics! It reminds me of Feynman. For me having studied theoretical physics but not actually working as a physicist, the first two volumes of Weinberg’s “The Quantum Theory of Fields” were a gift from heaven. Thanks to these book I understand physics at a much more fundamental level than when I was a student, when they talked about gauge invariance, fields, particles, representations, CPT and renormalizability and I had no idea how they were all linked together.

    A remark:

    To call matter particles fermions is a good thing because of the stability they give to matter due to the Fermi exclusion principle. Usually we see the bosons as force particles and usually this is not too bad a picture. But what about light-light scattering. Here in the box diagram the fermions are the force particles.

    1. Notice Mark Wallace’s comment here, and my reply. You’ll see that I am a little cautious about calling fermions “matter particles” because it runs you into trouble. In fact, your remark suggests another problem.

      Indeed, pairs of virtual fermions (more precisely, appropriate quantum disturbances in a fermion field) can cause forces. (Though we should recall that virtual particles aren’t really particles: http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/ )

      In fact, the force which holds a nucleus together is, from some points of view, due to pions — which are bosons, but are made from fermions (quarks and anti-quarks.) So now we have a force particle made from matter particles. Which means our naming scheme is a mess.

      There is also a (subtle) way to make fermions from bosons (the word Skyrmion appears here.)

      You see that this distinction just causes problems. At some point I think you have to take the physical phenomena for what they are and not spend too much time worrying about finding the perfect naming scheme for them.

  102. Now if the mass of the proton is all of its quarks E divided by c^2 , how can we express the mass of electron or any primary ” particle ” ? if an electron is at “rest” –whatever that means — what is the meaning of its mass ? even what is its E then? are we running in a circle ?

    1. The mass of the proton is not merely all of its quarks’ energies E divided by c^2 (and to the extent a more precise statement is true, it is true only of a stationary proton.) It’s more complicated; that article is coming.

      An electron can have definite momentum (including zero) as long it is in a state where all position information is lost. So it can be at rest, yes. And I can figure out its mass-energy E_rest in many ways experimentally. One way is to bring an anti-electron close by, watch the two annihilate into two photons, and measure the energies of the photons (which are pure motion-energy, since the photon has no mass). Since energy is conserved, and the initial energy was (to a very good approximation) the mass-energy of the electron plus the mass-energy of the positron, which is 2 E_rest, the energy of each of the two photons is equal to E_rest for the electron. Divide by c^2 and you have the mass of the electron. See for example http://astronomy.nmsu.edu/tharriso/ast536/gcannihilationspectrum.gif

  103. A good direction to take the discussion:

    Why do fermions feel more like “stuff” than bosons? This brings in a little quantum mechanics, which you might not be ready to do yet. But the “rule” that two fermions cannot be in the same quantum state, while bosons can, seems central to a working definition of “matter.” Intuitively, we expect matter to “take up space,” which fermions do, but bosons not so much.

    Of course fermions don’t take up space by themselves, since any collection of fermions is always accompanied by bosons transmitting forces between fermions, and so on.

    Thanks for all the great articles!

    1. Well, if you keep running with this too far you start to stumble…

      For example: in a world with only gluons and no quarks, the gluons would bind together to make hadrons that are called “glueballs”. Those take up some space. Granted you couldn’t make anything macroscopic out of them.

      If the electron were a boson, you’d still have hydrogen. That takes up space. And hydrogen’s a fermion; you could make things out of it.

      In our world, hydrogen is a boson, deuterium (heavy hydrogen, whose nucleus contains a neutron as well as a proton) is a fermion. Is one of them matter and the other not?

      In certain hypothetical universes, you could make a proton-like fermion out of combining a fermion and a boson. And you can make bosons out of combining fermions. Even in our world, protons contain quarks (fermions, which you’d like to call matter) and gluons (which you’d like to say aren’t part of matter so much as representing the force that holds the fermions together.) But you can imagine a world in which some quarks were fermions and others were bosons, and the number of types of gluons was different — and then you could get fermionic proton-like objects which were made from quark fermions and quark bosons as well as gluons. What would you call the quark bosons? Matter or not?

      The theory of supersymmetry causes a problem, because it combines fermions and bosons in pairs. It doesn’t make sense to say these pairs are part matter and part force; when you write the equations down, the boson-fermion pair appear in a single mathematical object.

      And in string theory all of these particles can be made from the same type of string.

      Let’s not forget what we call “dark matter” may be made from bosons.

      So there’s all sorts of ways in which this line of thinking can break down. At different layers of structure, what you’d want to call matter might change in a profound way. I don’t view the current distinction as likely to survive into the future too much further.

      1. Which is valid, matter is standing spherical waves oscillating at the Compton wavelength or is matter a Fermi sphere with such a radius so as to give a Fermi energy equivalent to the mass-energy of that particular particle?

        I can understand Pauli exclusion principle via the Fermi sphere definition but not with the standing wave theory. Are we missing some math?

      2. Well, calling fermions the essential ingredient to “matter that takes up space” still seems consistent to me, as long as we add a caveat about how closely you look. An atom or molecule can have the properties of a boson when viewed from the appropriate distance, but when you get “too close,” the properties of the fermions that it is made of become important. How about, for now, say “matter that takes up space” must contain quarks, leptons, or both. Whether or not it has the properties of a boson when viewed from a sufficient distance does not keep it from being “matter that takes up space.”

        1. In a theory with no quarks, the gluons would bind up into hadrons called “glueballs”. These hadrons would take up some space too, individually. Granted I couldn’t make a lattice out of glueballs. But I suspect there are bosonic systems where I could do make a lattice, if I could arrange for some short-distance repulsion from a short-range force.

          And it is possible to build fermions as solitons in a theory with only fundamental bosons.

          So this still raises questions about your dichotomy… I think you’re still relying on very specific properties of our universe that would not necessarily be true in other ones.

      3. How do theoretical physicists verify the validity of using the gamma function and the rather very simple energy – momentum (dispersion relationship, E = ap^s) for deriving the thermal de Broglie wavelength. Does this derivation fall in the argument of whether the renormalization is appropriate for quantisation of the “quantum nature of gas?

        This approximation seems so critical in defining the true natural of the vacuum, how has it been verified and conversely how do you rule out dimensions above the usual 3 that we perceive to live in?

  104. once upon a time in space,i tried to write a thesis.I went back in time and forward in space…today became yesterday and zero was squared…BANG!!! the singularity of zero was infinite(-0.0000….)and eternal (+0.0000….)…and thus the first law was laid,from which the universe arose…the expanding singularity of infinite totality,,,a total of 1,and a value of 0…as a totality of one singularity,one could not be measured therefore totality was 0-,or 0+ depending on direction as it relates to the opposing direction…giving rise to every thing that followed,,what i speak of is a singularity of time,,,but could have easily mistaken it for the higgs and thee higgs field…or possibly or on a larger scale dark energy,and dark matter…its very hard to make strong case to include all the that this theory covers,without producing a thesis…so just a little snippet for now,as i reduce it to simplicity,,,its a binary universes…where zero has two values,,0,and minus 0,from minus0,0 has the value of enxpanding 1,or 0.9999……and from 0,minus 0 negative 1infinte,or -0.9999

    the simplest way to put it is ‘for every action is an equal and opposite reaction’…sir issac newton’s theory of pure simplicity standing the test of time,,,governing totality,and every singularity…eternity is a very long time in space,any inbalance beteween space time no matter how insignificantly minute has catastrophic cosequences…if for example; the mass value of the universe increased by as little as one quark for every googlemilllion lightyears,eventually the entire universe would become one block of mass…(please note) if you think im being a little flippant to exagerate,im absolutely not!!mass has an eternity to do it in…as does energy.the first most fundamental law governs from totality to infinite singularity…the higgs bozon,and the higgs field,interact with mass in the same manner as time in space,…
    Time is the equal and opposite reaction,preceeding the action of forming space,,,just as all mass is basically congealed energy,all of space,is congealed time,both the positive,and negative…quantum at the particular level,yet in general its relative…

    thank you for reading,and i value any input

  105. I think no time is wasted once they are on the grand march to understand existence , no one will put his hand on the ultimate truth , but science and philosophy are 2 faces of same coin……the sacred search for what IS and our place in it , it is the most precious effort humans can perform, even a simple layperson question can lead to some great answer it is our duty and our destiny as humans to think ,to reflect , and to wonder ……nothing is greater than our feeling of awe in front of beauty , design , perfection in a realm which is not perfect itself ….this is the meaning of being human…to enjoy life , to love , to care , to share , to embrace the whole of creation.

  106. But my dear friend , physics is an ontological science , it is interconnected to philosophy, any thing you say about fundamental level of existence IS philosophy.

    1. (THANKS). This is an interesting point, and I do think I disagree.

      Physics is interconnected to philosophy, yes.

      But physics is a quantitative, predictive enterprise. Theoretical physicists will often accept levels of understanding or ambiguity that are unacceptable to philosophers. (And to mathematicians!) Collectively, we are typically much more practically minded than our colleagues in either of these subjects. This allows us to make rapid, but often very ragged, progress. Often when we learn how to calculate something, it is some years, even decades, before we understand what we’ve actually learned well enough for either mathematicians on the one hand, and philosophers on the other, to engage with it.

      For instance: what people said about particles and fields in the 1950s, before quantum field theory was understood at the much deeper level that is available to us today, was in many cases deeply misleading philosophically. The story I tell you today is based on insights that emerged in the 60s, 70s, 80s and 90s. Indeed, a good chunk of what I learned in grad school was misleading philosophically.

      Meanwhile mathematicians still haven’t figured out what we’re doing in quantum field theory… and I wish they had, because there are many puzzles about it that we can’t solve.

      1. “physics is a quantitative, predictive enterprise” up to the point where we decide what DoFs and what formalism to use when we construct models for experiments. If we choose the wrong number of DoFs or formalism, we find the accuracy is OK, but not great, but the inaccuracy gives us precious little clue as to what different DoFs or formalism to use. We can’t do much better than guess again. Hence the enormous disparity of models that are published in journals. We also can’t measure the Lagrangian in a comparable way to measuring the field strength, say, supposing we have managed to guess the right DoFs and formalism.

        The process of guessing again is done slightly better by some Physicists than by others, but that x-factor is not as quantitative and predictive as we’d like it to be. We can call this guessing Foundations of Physics (or we could call it Philosophy done by experienced Physicists, but that’s just names, silly to argue over), in contrast to Philosophy of Physics (Physics done by Philosophers), but there’s a lot of crossover between these two academic communities, with good ideas on both sides being taken seriously by people on both sides. Of course it’s much easier to generate bad ideas, when the subject matter is beyond computationally complex because we don’t know what questions are possible. In the end, however, we can waste 50 years in quantitative predictions if we are using the wrong DoFs and formalism, so it’s worth some people working concurrently on what we think we’re doing, even if many of them waste their time.

  107. I read in an article about quantum gravity in stanford encyclopedia of philosophy that fields are specific properties of space-time itself , is this correct ?

    1. No. They can be. But often they are not, even in string theory.

      My advice: don’t get your physics from philosophy encyclopedias (and I wouldn’t get your philosophy from physics encyclopedias either.)

  108. In all your posts you mentioned fields so many times , you never explained what is it , the max. you said is ; fields are stuff that can have E , m , charges…. but is this all of what we can define a field ? what are fields , i know that fundamentals cannot be defined as there are nothing more basic to refer to it .
    Are we to stop at a word ; field?
    Are fields an ontological reality of a mathematical representation of our observations?
    Forgive my insistence but i cannot stop at mid road.

    1. In the current way of thinking about the world, fields are about as far as you can go.

      In specific attempts to go beyond this way of thinking, fields can be manifestations of other things. For example, in theories with extra dimensions, some (but not all) fields can be manifestations of the shapes and sizes of dimensions that are too small for us to see.

      In other attempts, some of the known fields can be themselves made out of other fields which are more fundamental.

      But all of these attempts are speculative; we don’t know which ones are correct.

      So I would say that the fields are currently viewed as the fundamental ingredients; that is where things currently stop. Even space and time are to be understood in terms of gravitational fields.

      However, knowledge accumulates over time, and what we think is fundamental may change. There can also be multiple equivalent interpretations of the same information — two ways of looking at a problem that have exactly the same mathematics and the same physical predictions. Philosophers are frustrated by this ambiguity, but theoretical physicists have learned that we have to remain light on our feet.

      1. Is it valid to say fields are any change (quantitatively and/or qualitatively) of one or more quantum numbers over the space and/or time domain? In other words, they are defined by the topography of spacetime.

        I speculate this way because as fundamentals they must all be derived back to the initial field, whether it is gravitation or something more fundamental like vortices created by the rotations of the three dimensional space.

        This is why in my early post I speculated that the sum of all fields must be constant, because spacetime has an orderly progression. So my logic is there must be a constant constraint that drives order otherwise we would have global chaos.

        1. It’s very important to distinguish what is known (by combining experiments with a clear theoretical framework) from what is speculation and may not end up surviving experimental tests.

          You say: “as fundamentals they must all be derived back to the initial field”. We don’t know that.

          You say: “spacetime has an orderly progression. So my logic is there must be a constant constraint that drives order otherwise we would have global chaos.” Again, we don’t know that.

          You can’t really talk about fields as a change in quantum numbers, no. Quantum numbers are very specific things: they are labels of certain quantum states; in particular, they are eigenvalues of overall quantum operators that are meaningful in specific quantum states. Quantum fields are a more general concept. For example, the electric charge of an electron is a quantum number; but there is no field for that. And conversely, most states involving the electromagnetic field do not have a definite value for the field, and so there’s no sense in which there is a suitable quantum number associated to those states.

          The electromagnetic field from freshman year physics is the best place to start really understanding classical fields. Quantum fields are like classical fields in that they can support waves; they are unlike them in that the waves cannot come with arbitrary amplitude, but instead must have an amplitude equal to a minimal value (one quantum) times any integer. I’m afraid they are unlike them in a lot of other subtle ways too.

      2. “.. but instead must have an amplitude equal to a minimal value (one quantum) times any integer …”

        Interesting, is that because we over simplified the math by introducing renormalization because of our inability to visualize the physics, (reached our limit of our conscious awareness to map nature’s secrets).

        I know that Dirac and Feynman were concern with renormalization because it would contaminate the math in to most of fundamental ways and get us trapped in a our own math. Is renormalization prevent us to involve naturally into more advance physics?

        Dirac’s criticism was the most persistent. As late as 1975, he was saying:

        “Most physicists are very satisfied with the situation. They say: ‘Quantum electrodynamics is a good theory and we do not have to worry about it any more.’ I must say that I am very dissatisfied with the situation, because this so-called ‘good theory’ does involve neglecting infinities which appear in its equations, neglecting them in an arbitrary way. This is just not sensible mathematics. Sensible mathematics involves neglecting a quantity when it is small – not neglecting it just because it is infinitely great and you do not want it!”

        Another important critic was Feynman. Despite his crucial role in the development of quantum electrodynamics, he wrote the following in 1985:

        “The shell game that we play … is technically called ‘renormalization’. But no matter how clever the word, it is still what I would call a dippy process! Having to resort to such hocus-pocus has prevented us from proving that the theory of quantum electrodynamics is mathematically self-consistent. It’s surprising that the theory still hasn’t been proved self-consistent one way or the other by now; I suspect that renormalization is not mathematically legitimate.”

        I am inclined to agree with Dirac and Feynman in that we need a better handling of the infinities and constraints to make real progress. I am afraid our ability to experiment is getting very quickly to a stagnation point because of the limits of our machines. I also want to take this opportunity to stress how important it is to convince NASA and their handlers that more resources should be spent in sensors, telescopes, and space experiments than the very expensive human spaceflight projects.

        1. If you think renormalization is about infinities (or that it has to do with an inability to visualize the physics), you have not understood it. Unfortunately most textbooks still talk about it in terms of removing infinities. This is deeply unfortunate and misleading, because in fact, even in theories with no infinities, there is renormalization. Even in quantum mechanics, in the anharmonic oscillator, there is a perfectly finite renormalization. Once you have understood that, then you can understand that renormalization (both perturbative and non-perturbative) has nothing to do with the infinities themselves, but with something more physical and deeper; and you can also see which types of infinities are acceptable in quantum field theory and what types are not. Dirac clearly never grasped this point. As for Feynman, I am sorry I never got to ask him exactly what he meant by his comment. But let’s just say that our comprehension of quantum field theory has come a long way since 1985.

          Unfortunately this is an extremely subtle and technical subject (which is why almost nobody does it in a sensible way) and I doubt I will be able to explain it on this website. At some point I may write a short technical monograph about it. But suffice it to say that I think you’re not even close to being on the right track.

      3. There are interesting discussions going on below this very nice article 🙂
        In particular, I feel really affected by the second paragraph in Prof. Strassler s above comment ending with

        “… fields can be manifestations of the shapes and sizes of dimensions that are too small for us to see.”

        😛 😉 🙂

      4. Hi Matt,

        Since you mentioned that “Even space and time are to be understood in terms of gravitational fields”, I want to remark that I have found this concept very tricky to explain to non-experts. We’re so used to thinking about fields as things that “live in” static space and time that understanding space and time themselves in terms of fields is hard to wrap our minds around.

        If someday you have the time and inclination to tackle an article about this issue, I think many of your readers would appreciate it, and I would be interested to see what approach you take.


  109. Hi Matt !

    An experiment consisting of a holometer is currently in the design stages at the Fermilab centre. Headed by Dr Craig Hogan, the aim is to determine if spacetime has holographic properties by attempting to measure a quantifiable planck unit. I know that a holographic field is a constructive interference pattern with information encoded in the boundary of the pattern.I also know that I am voyaging into the realms of speculation by suggesting this, but could the fermions be nodal points of a standing wave? Certainly, the fact that they are non-locally connected seems consistent with this. If they are, then could this also mean that mass is a measurement of the negative interferometric-visibility density of a Higgs scalar field instead of a particle ? Could it also imply that the laws of physics are an hierarchical layer of anti-nodal displacement cycles, generated by an underlying constructive interference pattern state, with the gauge bosons being the anti-nodes themselves ? I apologise if these questions seem rather wacky, but ever since I heard of the Fermilab experiment I’ve been racking my brains trying to figure out how the holographic principle would work in practice, and how it could relate to the search for a non-standard model Higgs effect !

    1. Much as I like and respect Craig Hogan, I’m pretty skeptical about this experiment, I must say. I suspect that the effects he’s looking for are vastly too small to be detected.

      As far as I can see, there’s absolutely no need for there to be any connection between the Holographic Principle and the Higgs mechanism. One operates on the weak nuclear force at the energy scale of 250 GeV or so; the other relates to space-time viewed at the energy scale of 10,000,000,000,000,000 GeV or so.

      I’m afraid that the answers to all of your questions are “no” — or better, “be a lot more precise”. Remember particles aren’t little marbles; they’re ripples in fields, and you have to explain the fields first. We have very successful quantum field theory for fermion fields and gauge boson fields, working in some cases to one part in a trillion; so you have to tell me how you could reformulate all of what we know about quantum fields to make the fermions come out as nodes in some kind of standing wave and interacting properly with gauge bosons that come out as anti-nodes in some kind of standing wave. Sounds like an extremely tall mathematical order and I have no idea whatsoever how you would start to make that work.

      You can’t do theoretical physics with words, because you end up just speaking ambiguities. You have to do math — that’s both the essential part and the hard part, not just because math is technical but because most math you try to write down will be self-inconsistent or inconsistent with existing experiments.

      Einstein is widely quoted in our culture. But if you read his papers, you’ll find that all those nice-sounding words are backed up with solid calculations — and that’s why it isn’t ambiguous what he means when he starts talking about the subtleties of special and general relativity. And he always checks that what he’s proposed is consistent with existing experiments.

  110. Hi
    I was woundering if energy is conserved in general relativity. what i have read on the internet has left me confused. Also woundering where the energy of the cmb has gone.

    1. Ummm… I don’t think I can give a very good answer here that I’m ready to stand behind. Let me say two things.

      1) LOCALLY (that is, in any small region of space, for a short time) energy and momentum are conserved the way we are used to.

      2) GLOBALLY (this is, across regions or across eons where gravitational fields are very important, such as the universe as a whole) you have to be much more careful about how you define the total energy of a system. It’s quite subtle, and can’t always be done. And I’m not expert enough to answer off the cuff and get all the details right as to when you can and when you can’t, and how you do it in the cases when you can. [Been too long since I reviewed this subject, which is mostly outside my research…]

      If what you mean, in asking about the energy of the cosmic microwave background radiation (cmb), is how did the photons lose energy as they cooled off during the universe’s expansion, one way to answer that is to say that the expansion of space itself took the energy from the photons, and from all the other particles too. But I’m not sure that’s super-intuitive. I know an intuitive answer that isn’t really correct (namely, to consider how photons in a box lose energy if the box expands). Maybe a general relativity expert here knows a better intuitive and also correct response.

      1. “I know an intuitive answer that isn’t really correct (namely, to consider how photons in a box lose energy if the box expands).”

        H = U + pV

        H is the enthalpy of the system
        U is the internal energy of the system
        p is the pressure at the boundary of the system and its environment
        V is the volume of the system.

        As lup mentioned this equation is somewhat confusing. It can be interpreted as the energy is spent to apply pressure to the boundary and expand the volume. But that interpretation implies there is an external environment outside our universe.

        Are we living in a bubble within a bigger bubble, in a asymmetric phase within a symmetric environment. Are there other asymmetric bubbles nearby?

        The thing that amazes me Professor is regardless of which theory you believe non explain the real nature of energy. Why was the temperature so high at the Big Bang? Is the symmetric phase an “infinitely” stretched spring that when broken releases all its energy at a very short time (space) and hence the large energy density, temperature?

      2. So energy is conserved when cmb photons have thier wavelength stretched by the expanding universe? is this energy helping to expand the universe further or is it more like a stored potential energy?

      3. The thing about energy in general relativity is that for it to be defined globally the spacetime must be stationary, which is a form of saying that “the space is the same at every time”. The problem is that exapanding universes are not the same at every time, so that energy is not conserved.

        With that in mind the cmb energy has not gone anywhere but just disappeared. We can’t really ask where has it gone because that implies it is conserved. Since it’s not, the energy has just gone away. I don’t think this has any intuitive answer. The closest to intuitive I have heard is the “photon in a box” thing, which I kind of like even if is not precise. The only thing one must remember is that in general relativity there is no “potential energy” related to gravitational fields, so the energy of photons is not stored in gravity, it has really gone away.

        To sum everything: the energy of cmb is not conserved when the wavelenght of photons is increased by universe expansion, and the energy is not “stored” in any potential form; it has really gone away.

      4. I’m sure you have heard of the seemingly obsolete theory of “tired “light – could the “hot”photon’s energy not drive the expansion of the universe : in other words red-shifting because the wave packets are themselves expanding (such as water waves dissapate their energy over distance) – rather than being stretched to red because an unknown dark energy is pulling them apart?

        1. Einstein’s equations for the expansion rate of the universe work very well; they are used in deriving the prediction for how much helium there is relative to hydrogen, and in predicting the cosmic microwave background spectrum, both of which agree very well with data. [A nice (if a little out of date) discussion of the latter appears here: http://backreaction.blogspot.com/2007/12/cmb-power-spectrum.html ]

          This is all done without appealing to anything like “tired light”.

          Moreover, the dominant energy density in the universe hasn’t been from light (and other very light-weight particles such as neutrinos) since the universe was 100,000 years old or so. So it’s hard to suggest that light could be essential to the expansion during most of the last 13.7 billion years.

          I’m not the world’s expert, but I suspect that with the current precision available in cosmology, there isn’t a lot of room left for exotic theories of why and how the universe is expanding. Of course we don’t know for sure what got the Big Bang started, though there are plenty of theories of that (under the name of “reheating following inflation”).

      5. yes-but as far as I understand Einstein introduced the cosmological constant to make his equations fit the observable reality (non-collapsing universe) rather than this being a mathematical necessity per se and as you point out he seemed have done so particularly well. I also did not want to imply that dark energy be the dominant energy of the universe – it only has to be stronger than the universal gravitational force and supposedly wins the upper hand the further the mass particles are apart. But on the same note, if the universe continues to expand eventually the photons of the background radiation will be stretched beyond the temperature of absolute zero – do they then cease to exist?, do they blend into and become (non-particular) elements of the electromagnetic field? – or could that result in the end of the expansion phase and gravity, however weak, but now unopposed lead to the beginning of the hypothesised big crunch?

    2. Thanks heaps…thats certainly answered my question. The only remaining puzzle for me is that i thought that energy conservation was a consequence of a symmetry..ie the laws of physics dont change with time?

      1. So the subtlety here is: if time is just something that sits there and the laws of physics operate within it, then yes, conservation of total energy follows from Noether’s theorem.

        But once time starts participating in the physics — as it does in Einstein’s theory, where space and time are actually part of the physical phenomena — then to ask whether the laws of nature change with time becomes subtle. For example, you can’t even necessary define a global notion of time in a sufficiently curved space.

        What survives of our usual notion is that within sufficiently small and weakly-curved regions of space and time, the laws of nature do behave in a time- and space-independent way, to a sufficiently good approximation that energy and momentum are conserved there. This is the notion of LOCAL conservation of energy and momentum. There is still a Noether theorem and still a conservation law, but it applies locally, not globally across all of space and all of time (except in special circumstances, such as a time-independent space-time.) (Technically: there are energy- and momentum-currents that are locally conserved.)

      2. Thanks Matt, thats cleared up a lot of things. Cesar mentioned that the cmb photon energy is really just going away (ceasing to exist) as the universe expands. Can we have the opposite – can we have energy appear that wasnt there before?

      3. Well lup, yes we can have the opposite and it’s pretty much standard. The idea behind energy “going away” is that since the universe is expanding it “stretches” the photon wavelenght and consequentially it’s energy decreases. In order to have the opposite effect all we need is a contracting universe, like those cyclic universe models.

        To be very clear, in those cases there is so much mass in the whole universe that at some point is stops expanding and starts collapsing. During the contracting phase the photon wavelenght is “compressed” by the contraction of space and the energy increases. It’s really like watching the expanding universe going backwards in time.

        But remmember that this is just a model, the current astrophysical data supports the accelerated expanding universe which kind of eliminates the recollapsing universes in such a naive way. But from the theoretical point of view there are no problems with photons “heating up”.

  111. Is mass constant? Or should I be asking is the Higgs field constant?

    In the beginning of time (and space) there was finite temperature within the absolute maximum of Fermi spheres, the singularity that created the Big Bang. The expansion of this sphere created time and space and hence a field (presumably the gravitational field). With further expansion and lowering of temperature (energy densities) resonances where created and hence more fields, like EMF and Higgs. Now, if energy is a conserved quantity then the sum of all fields must also be constant. So with the continued expansion of time and space (spacetime) the magnitudes of the various ripples as created by the various fields should be reducing. (I say should because the densities continue to lower both absolutely (larger expanse of the entire universe) and locally around the smaller gravity wells.

    1. 1) We do not understand the Big Bang at the very earliest times with the precision that you suggest.

      2) Energy is not in any simple sense a conserved quantity in a rapidly expanding universe. Even if it were, fields are not energies and the sum of all fields isn’t even well defined, so it certainly need not be constant.

      3) The mass of particles like electrons is not believed to have been constant over time, because the Higgs field was not constant over time. At very high temperatures the Higgs field would have been zero on average. As the universe cooled, an “electro-weak phase transition”, which must have happened a microscopic time after the Big Bang began, must have taken place — its details are not yet known, because we don’t know enough about the Higgs field yet. But the Higgs field is believed to have changed very rapidly and then settled down to its present non-zero value during that transition.

      4) As far as we know, the Higgs field’s value, and the electron mass, have not changed a bit since then. In principle they might have varied over space and time, but there is neither experimental evidence nor good theoretical reason to think they actually did, at least within the part of the universe that we can see and over the time since the electroweak phase transition. (For instance, the success of Big Bang Nucleosynthesis in predicting the original helium to hydrogen ratio of the universe could easily have been messed up had the electron or proton or neutron masses been significantly different from what they are today.) Scientists continue to try experimentally and observationally to test whether there is any sign of variation.

  112. Great stuff, Matt. Thanks. A parenthetical question: This is a whole new way of thinking for me, having spent my career in applied physics before 1980. In my struggle to adapt to your post-classical, if not post-modern, way of thinking, I am trying to understand where and how the Higgs mechanism appears in the mathematical constructs that underlie the standard model (what are those mathematical constructs?) and how we know what decay products to expect from Higgs particle decay. If I wanted to find an answer to those two question on Google, what should I google?

    1. Do you understand superconductivity? The photon obtains a mass inside a superconductor when Cooper pairs (represented by a charge-2e scalar field) condense. The W and Z particles obtain a mass within the universe when the Higgs field condenses. The mathematics is almost the same — relativistic instead of non-relativistic, non-Abelian instead of Abelian, but it is the same idea.

      The most important difference is that we know that for the superconductor, the charge-2e scalar is a kind of bound state of two electrons, but for the universe, we don’t know what the Higgs field is yet — whether it is a composite of something else or not, whether it is just one field or several — and that’s what the LHC is aiming to find out.

      As for how the Higgs decays; that’s a little more complicated. Did you read what I wrote on Standard Model Higgs decays? http://profmattstrassler.com/articles-and-posts/the-higgs-particle/the-standard-model-higgs/decays-of-the-standard-model-higgs/

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  113. According to all of your articles the end most fundamental stuff is the ripples in fields , i mean if fields are extended stuff , ripples are ” real concrete stuff relative to our senses ” which can have mass , energy , etc. , but if fields are stuff then we reach an absurdity : what is stuff ? stuff is stuff !!??

    1. Fields are not traditional ‘stuff’ as we know it. They’re almost like things that can have stuff in them. (The ripples.) I think that a nice definition of ‘stuff’ would be ‘particles’ (Ripples.) since they’re the things that ‘have’ all the other things, such as speed, mass, energy and so on which we usually associate with ‘stuff’.

      But in the end ‘stuff’ is just a label we attach to things. Matter, particles, objects, squiggles, these are all just names that we use. Nature does not care about our neat little ordering systems and so sometimes things can get a bit confusing.

  114. I think is quite misleading to say such a thing as “you can’t have an elementary particle without a field, but you can have a field without any particles” because the concept of particle depends on the observer, what is vacuum in one frame of reference has lots of particles in another (accelerated) frame. If the Higgs is the caveat of the phrase then, in my mind, not founding the corresponding particle indicates that such a field does not exist. But I’m by no means an expert in elementary particles and could be (very) wrong about this statement.

    As a complementary note on the anti-matter in the large scale, there are experiments on producing some dozen anti-hydrogen atoms also. Of course nothing macroscopical.

    Sorry for being somewhat pedantic.

    1. I did not explain what I meant here, because it is technical, but since you ask…

      A field that strongly interacts with itself, or with other fields, may have no particle states at all. This is a well known fact about conformal field theory. There are many concrete examples in the context of solid state physics, and many hypothetical examples that arise in high-energy physics.

      Said another way: a non-interacting field always has well-behaved ripples (which in quantum mechanics are made from quanta), a weakly-interacting field has largely well-behaved ripples (though these may have a finite lifetime), but a strong-interacting field may have nothing resembling a ripple at all.

      So no, what I said is not misleading — it is the particle picture of fields, which assumes that fields are weakly interacting, that is misleading. And you used that weakly-interacting-field intuition in your comment.

      1. Hum, that’s quite interesting and a sign that I should be studying a lot more. My comment was really made with non-interacting fields in mind, so I see what I got wrong. Just to make clear what I meant was that for non-interacting fields the concept of particle is observer-dependent because of things like Unruh Effect.

        But I couldn’t agree more with you that fields are the essential concept and not particles (the point I was trying to make). Thank you for the explanation.

  115. Now you reduced everything to a word ; stuff , which can have mass , energy , can do work ……but what is stuff , you said what it can do but if we want to go deeper is it the end of our search ? it is all some kind of circular definition ….some kind of dna-protein closed cycle !! where we are lost.

  116. I am an IT pro and we have trouble with overloaded terminology just within our field. As with particle physics, our objects keep splitting into pieces, too. The only thing to do is have fun with it!
    What are your thoughts about the popular vision of an object made of matter meeting an object made of antimatter?
    Now that I’ve read your article, I realize that “an object made of antimatter” is not a well-defined concept, and it might fall apart if we look at what the statement really means, compared with how matter is really composed.
    Being that “antimatter” is at the center of the popular imagination, what are your comments on hypothetical, macroscopic anti-objects?

    1. If you could collect enough anti-matter [definition #1] and shield it from all the matter [definition #1] that’s flying around (stray electrons and the like), then there would be no problem in principle to construct anti-salt and anti-steel and anti-cells and anti-cars. The laws of nature are sufficiently symmetric (not exactly, but very close) that anything you can do with matter you could do with anti-matter.

      And indeed if you brought any significant amount of matter in contact with any significant amount of anti-matter you’d make an explosion.

      But no one has any practical reason to try to construct large amounts of anti-matter. The closest we’ve gotten is making powerful beams of anti-protons and anti-electrons (positrons) for use in particle physics experiments. But the amounts of energy that you could obtain by slamming those beams into a wall is small. In fact that’s exactly what happens to those beams when we’re done with them; we slam them into a wall, underground somewhere. The wall does heat up, but mostly because the anti-electrons or anti-protons are traveling really fast and have lots of motion-energy — not because of the energy released when they find an electron or proton and annihilate to something else (photons or pions, for instance.)

      And as far as we can tell, the part of the universe that we can see does not naturally have large amounts of anti-matter anywhere. [If there were regions of the universe with large amounts of anti-matter, at the border between regions of matter and regions of anti-matter you’d expect to see large quantities of photons with very particular energies emitted. We don’t see signs of such borders.]

      1. Thanks, Professor. Two things about our hypothetical antimatter #1, that I hope might surprise me.

        One, is that I don’t understand what happens when two macro objects “touch,” but I’ve been told it has mostly to do with the electromagnetic force. Are there subtle effects, like the exclusion principle, that changes the way antielectron shells would behave near electron shells?

        Two, is that I’ve read some interesting history about the early atomic energy laboratories, and the way that fission materials went “prompt critical” almost always interrupted the nuclear reaction, milliseconds after it began. It was as if the nature of the reaction was to defuse itself, contrary to popular imagination.

        So when the first few leptons meet their anti-partners, and throw off some lightweight particles, what happens next? Their atoms become ions and their molecules would break apart, for one, if they have time. But how do we expect the nucleii to come in contact? Would we get more of a chemical than a nuclear reaction?

        And if there was an explosive force, wouldn’t it force the macroscopic objects apart? That’s assuming they were solid objects, as in the popular imagination; if gas met anti-gas, or liquid met anti-liquid, the macroscopic dynamics would be quite different.

        That’s why I wonder if, perhaps, objects and anti-objects might behave differently together than the popular imagination dictates.

        1. Ah, I see what you’re asking.

          There is no question if you took two cubes, one of matter and one of antimatter, and brought them safely together, the actual contact would be instantly different from the contact between matter and matter. At the surfaces of contact, the electrons on the outskirts of the atoms and the positrons (anti-electrons) on the outskirts of the anti-atoms would start finding each other on very short microscopic time scales, and immediately begin turning into pairs of photons of 511,000 electron-volts of energy each. These “gamma rays” would then create an electromagnetic shower of particles: lower-energy electrons, positrons and photons. Since it only takes a few electron-volts of energy to rip the electrons off an atom (or positrons off an anti-atom), all the atoms and the anti-atoms near the surface would be quickly disrupted, vaporizing the material in that region. The force from the released energetic particles smashing into the remaining atoms of the cubes would most definitely push the cubes apart, just as in the fission experiments you mentioned. So there’d be an explosion, but only of the material nearest the surface of contact, and unless the two cubes were slammed together with enormous energy, as in a fission bomb, you’d only get annihilation near the contact surface.

      1. I am sure that someday soon people will make many millions of anti-atoms. One just has to remember that a glass of water has something like a million million million million atoms of hydrogen. I might be off by a factor of a thousand or so (I didn’t check the number carefully), but you get the point.

  117. Haha, that is true! I’m not sure Lemaitre’s “primeval atom” was much better than “Big Bang.” All the really dramatic names I can think of smack of religion.

    Besides, who wouldn’t want to write a poem about the charmed quark? It’s so… charming. (Yes, I’ll be here all night, folks.)

    I’ve also heard Dark Energy described as a sort of cosmic “pressure”. I’m not sure how valid that comparison turns out to be.

    1. Yet, his ‘atom primitif’ suggestion sounded better than his other suggestion to name it the ‘cosmic egg’ which was probably inspired by one of many eastern mythologies. That would really have been the worst possible name.

  118. You say that “matter is always some kind of *stuff* …” and “photons are *stuff*”; this would appear to mean that photons are matter (unless photons are *stuff* that is not matter, of course). Yet photons fit none of your green-paragraph definitions of “matter”. I’m mindful that the whole thrust of the article is that matter is an ill-defined concept (and, as usual, I learned some things from it — thanks!); I am perhaps reinforcing that point by noting that your green-paragraph definitions are yet not enough.

    1. Photons are “stuff”, but they are not matter — for almost every definition of “matter”. Matter is a subset of stuff, though which subset depends on context. I do know of one or two contexts where photons would be called “matter” too — but these settings are ones that you won’t come across often, and usually different terminology is used anyway.

      What I mean by “stuff”, in general, needs a little more working out. A silly but useful working definition is that something is stuff if it can be used to damage other stuff. I can’t damage your cells with mass or energy — I can’t make an “energy beam” or something like that. I have to make a beam of photons or a beam of electrons or muons or protons or neutrinos. That “stuff” carries energy, sure, but the energy has to be carried by a physical object — a particle — stuff — for it to be able to do anything.

      (The particles of dark matter — whatever they turn out to be — are stuff too, though I’d need one heck of a beam of dark matter particles to damage anything!)

      Fields are stuff too: they can be used to pull other stuff apart.

      Maybe you can point out a flaw in that definition? A challenge to the reader…

      1. Space-time can be curved in ways to ripple ‘big’ stuff apart. That means spacetime itself is a “stuff”?
        If thats the case, can stuff ‘damage’ spacetime?

        1. Sure. That’s Einstein’s point.

          You can make two black holes, made entirely from space-time curvature, and arrange for them to orbit each other. The two orbiting black holes form a system — a sort of “atom” — which can be stable for a fairly long time. A sufficiently powerful beam of photons, or electrons, could break that system of two black holes apart.

          It’s not very different from disrupting an ordinary atom using a extremely powerful gravitational wave, which is also possible in principle.

          In the first example you would be using something which is obviously stuff to damage an object made entirely from curvature of space and time. In the second you would be using space-time to damage an object made from other stuff.

          Not that doing either of these is practical — but in principle you could do either one.

  119. There are a contradiction here :
    1- E is something mass have
    2- Mass is E/c^2
    3- E is something E/c^2 have !!??

    1. You’re making some classic mistakes:

      First, #2 is false. Mass is only E/c^2 for a particle at rest and sitting on its own. [If you define m to be E/c^2, then you’re using the archiac notion of “relativistic mass”, which particle physicists avoid for several reason (to be explained soon.) And I’m not using “m” in this way anywhere on this website.]

      For a particle on its own, but moving, E = mc^2 + motion energy .

      For a more general system of particles and fields, you also have to account for other contributions to the total energy that cannot be assigned to any one particle.

      Second, #1 is false. Energy is something that stuff can have. Mass is also something that stuff can have. Stuff is not mass; it’s something that can have mass. But not necessarily. Some stuff has no mass — photons, for instance. And it is an accident that electrons are massive; remember that the Higgs field being non-zero on average is responsible for this. Electrons would still be stuff even if the Higgs field were zero on average and electrons were massless.

      [Experts: I know there’s a tiny subtlety with this statement; let it pass. To make the above statement precise I should also turn off some other interactions when I turn off the Higgs field’s value. But the substance of the remark is true.]

      Part of the point of this article (and my earlier particle-antiparticle annihilation and mass-and-energy articles) is that photons and electrons are both particles. They are both stuff. It happens that photons are massless and electrons are massive, so they behave quite differently. But the equations that govern them are very similar, and one should not think of electrons as stuff and photons as something else. Mass is something they may or may not have; energy is something they have too.

      1. E=mc^2…
        1 the energy content isnt determined by either. As you point out energy is intrinsic to the stuff aka it allready poses it.in order to reject the fact photons have 0 rest mass you assign it velocity to give it relative mass . The problem is if the universe is a closed system there is an objective standard & all frames of reference consolidate into 1 objective frame of reference. Relative speed then becomes an objective speed & the phase space oscilates in a uniform fashion (higgs field). If it were not as such higgs field tensor values would varry & we can only imagine the chaos that would ensue as the phenomena of matter would dissolve along with our physical existence.

  120. Can we say that the building stuff of the cosmos are mere 2 types of vibrations — organized ripples and psuedo ripples — which we call real or virtual particles ?in something we call fields ?

    1. No — you really don’t want to approach it this way. The basic stuff is fields. Now you want to ask what fields can do and how that contributes to the stuff we see around us. You can’t reduce that the two types.

      1. Is field stuff though? Field is more of an information matrix. Strictly speaking, you have a field of mass or a field of properties, but that doesn’t mean the field itself is either mass or energy.

        I don’t think we should give definition to ‘the basic stuff’ just as yet. I think we need to learn how to distinguish fields from mass-energy, and mass-energy from its carrier particles for this discussion to have any merit. And why are we so intent on reducing everything to one thing anyway? What good does it even do? Even the scientific world sometimes…

        1. In my experience, a field is a mathematical construct, nothing more. Problems arise when one attempts to interpret a field as some sort of physical entity. This is not to say physical phenomena do not exist. Rather, fields are a mathematical device (the best we presently have) to describe physical reality at the micro level. It’s simply a theoretical framework based on mathematics.

  121. “Energy is something which objects can have”. I can’t say I’m happy with this. The energy of an object, in classical or SR models, at least depends on the frame of reference. I don’t see the Hamiltonian as the generator of time-like translations anywhere here, which at least deserves a mention if we move to QM models. Energy in GR is different again. If we move to signal processing, time-series analysis, we can define an energy of a signal mathematically, but that may not be reducible to phase space concepts (this is arguably engineering, but Physicists do use such concepts in some measurement contexts). I don’t see energy to be as settled in Physics as you suggest.

    1. I think I understand your first point. Energy is a property of an object (or system) but the amount depends on the observer. I emphasized this in my mass and energy article, but not here; based on your comment I’ve added a remark to that effect in the text.

      Your second point about the Hamiltonian: this technical point is not appropriate for the main readers of this article. The fact that energy conservation is related to the time-independence of physical law has been covered on this site elsewhere; this particular article wasn’t the place for it. The notions of Lagrangian and Hamiltonian are above the assumed knowledge of my readership.

      Energy in general relativity is an advanced subject, again beyond the scope of this article.

      Finally: engineering notions of energy in the context of signal processing are beyond the scope of this website. It never arises in any of my research or that of any of my immediate colleagues. I am always referring to that conserved quantity (even in general relativity) that follow from the (local, in GR) time-independence of physical laws.

      1. Just read your article. I think you are right about one thing: We still use language left over from another time. I think you are guilty of this yourself when you use the word “particle.”

        Sorry, there is no such thing as a particle. Everything is energy. Energy exists as a wave. A wave has momentum. Either that momentum is dedicated to travelling through space at some fraction of the speed of light, or it is turned in on itself as a standing wave to stay in one place as “mass.” Even as mass, it is still a wave. That wave is still energy, it’s just energy that stays in one place rather than travelling through space.

        When I put my hand on the tabletop, I’m not actually touching it. The electron waves of all the atoms on the tables surface repel the electron waves on the surface of my hand. There is no physical mass or particles touching, merely waves of negatively charged energy repulsing other negatively charged waves of energy.

        There is no such thing as a “particle.” That description is outdated.

        1. interesting way of explaining the outdated term “particle “…. but isn’t “mass” made of “particles” ? how different is a particle from mass ? Isn’t a standing wave everywhere ?

        2. No. The wave function is just a mathematical concept used to describe the momentum of a particle. It predicts the possibility of where one particle may exist in a single frame of time. It is not the same thing to say that the particle IS the momentum OR the mass. It doesn’t make any sense.

          This is exactly what the writer is referring to. The use of the words such as mass and energy which are fairly consistent in the macrocosmic world of ours fail to describe anything in the subatomic regions. None of which the writer says is outdated, but a lot of people who don’t really understand the underlying mechanism try to hijack the bandwagon with vague mystical sayings such as ‘Everything is Energy’ and the forth. Energy describes how the particle functions, it is the property of a particle. It is not the same thing as the particle itself.

        3. Strassler made it pretty clear that fields, and not particles, are the fundamental ingredients of the world. He called particles “ripples” in these fields. You saying “everything is energy” leads me to believe you actually wanted to say “all things are fields”.

        4. Thank you, Craig. Your entry equals what I have learned to be the current understanding of reality by physicists. Unfortunately, It is questionable whether Professor Strassler understands this.

      2. Hello. I am not a physicist at all. I came upon this article in a search because I could not accept the concept that energy and matter are separate entities and it’s what I keep reading over and over again. That matter has mass but energy doesn’t. Then, how can E=mc^2??? I realize it has been several years since this article has been published online, but I’m still not satisfied with the explanation. How can matter and energy not “be” the same thing? One can’t exist without the other. Where is the example of matter that has no “energy” associated with it? To me its like saying that lung tissue is not “human” even though it contains all of the same DNA as every other cell in the body. The lung tissue is just expressing or taking on the function that it needs to do. Otherwise, how could stem cells be used for various items. I feel the same way about matter and energy. How can you accept E=mc^2 but not accept that matter and energy are just expressions of the same thing? Or like when you say that you “have” height and weight, but you are “not” height and weight. Then what exactly are you? You don’t carry height and weight around as a separate entity in your hand that you can walk away from. It is you, just as the energy that animates our human body “is” each one of us. I am by NO way a scientist, but these concepts have been driving me insane for years. I guess what I’m getting at, if you still access this site: Where is a book, an essay, a study I can turn to that provides some kind of proof? I would be interested to study these concepts further. Thank you.

        1. Even through Quantum Physics and the ToE we find that an ‘unexplained’ conscious ‘force’ is necessary for existence to occur; or something to that effect. The answers will only be found in the quantum realm and common sense. Every atom is built with frequency, energy and vibration which is ‘energy’ regardless of how the textbooks warp the mind.

        2. Sarah, it has been a long time since you asked the questions here. I can answer one of them. You ask “How can matter and energy not “be” the same thing? One can’t exist without the other. Where is the example of matter that has no “energy” associated with it?” This last question should be reversed. There is no matter that has no energy, but there is energy that is not associated with matter. Photons, for instance, have energy, but they are not matter by anyone’s definition. The same is true for gravitational waves; they have energy, but I’ve never heard anyone suggest they should be called matter. Do not be confused by E=mc^2. First, “m” is mass, not mattter, and not all matter has mass, either. Second, “E” does not refer to all possible forms of energy. E=mc^2 means only that: the rest mass m of a particle that has some arises from E, energy, stored inside it.

          1. Hi Matt,
            I am also bothered by the same question as Sarah.
            I understand your distinction of matter from energy and, as I’m sure you’re familiar with, the commonly surrendered definition of energy is “the ability to do work”, so its treatment as a property is entirely sensible.

            The part that spins me for a loop – and I suspect this is why people commonly insist that everything IS energy – is that I don’t know of anything that can exist without energy as a basic property. Even quantum fields have zero-point energy at their lowest-energy state. Then there’s the idea that energy is that thing which is the particle-producing ripple in the field.

            So if:
            a) everything Has energy as an irremovable and universal property, and
            b) things are defined (categorized and distinguished) by their properties,
            does it not follow that the essence of all things is energy?

            Even those conceptions which are themselves the absence of things (ie. shadows, absolute zero) are defined by their quality of energy.
            Maybe I am failing to consider something.

            Is there anything that can exist without energy? Or is the problem really about the practical issues with using the concept of energy so broadly? Or am I misunderstanding a subtle idea very seriously?

            Really appreciate your feedback, and the article!

            1. Every human has age. We cannot imagine a human without it. Does that mean every human IS age?

              Every human has volume. All ordinary objects have volume, in fact. Does that mean the essence of objects is volume?

              We must not confuse properties that objects have — sometimes even necessary properties — with what those objects *are*.

              The fact that energy is a property of all objects and even non-objects reflects the fact that time is a fundamental property of the universe. It tells us nothing about the nature of those objects.

              Does this help? Nothing is made from energy, but everything has energy.

        3. Energy reacts with matter to get mass that has a function, a lot of things won’t react, that’s protection to humans

  122. Thanks again for an excellent review. Even though most of it is known as bits and pieces by us the lay readers, this clearly, and coherently explains the intricacies of the commonly misused terms.
    You write that all fields have corresponding particles and only Higgs field and it’s particle is in doubt but LHC has tantalizing clues of its presence. Wouldn’t gravitational field is something for which no known particle exists even though it is hypothesized?

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