Of Particular Significance

Which Parts of the Big Bang Theory are Reliable, and Why?

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 03/26/2014

Familiar throughout our international culture, the “Big Bang” is well-known as the theory that scientists use to describe and explain the history of the universe. But the theory is not a single conceptual unit, and there are parts that are more reliable than others.

It’s important to understand that the theory — a set of equations describing how the universe (more precisely, the observable patch of our universe, which may be a tiny fraction of the universe) changes over time, and leading to sometimes precise predictions for what should, if the theory is right, be observed by humans in the sky — actually consists of different periods, some of which are far more speculative than others.  In the more speculative early periods, we must use equations in which we have limited confidence at best; moreover, data relevant to these periods, from observations of the cosmos and from particle physics experiments, is slim to none. In more recent periods, our confidence is very, very strong.

In my “History of the Universe” article [see also my related articles on cosmic inflation, on the Hot Big Bang, and on the pre-inflation period; also a comment that the Big Bang is an expansion, not an explosion!], the following figure appears, though without the colored zones, which I’ve added for this post. The colored zones emphasize what we know, what we suspect, and what we don’t know at all.

History of the Universe, taken from my article with the same title, with added color-coded measures of how confident we can be in its accuracy.  In each colored zone, the degree of confidence and the observational/experimental source of that confidence is indicated. Three different possible starting points for the "Big Bang" are noted at the bottom; different scientists may mean different things by the term.
History of the Universe, taken from my article with the same title, with added color-coded measures of how confident we can be in our understanding. In each colored zone, the degree of confidence and the observational/experimental source of that confidence is indicated. Three different possible starting points for the “Big Bang” are noted at the bottom; note that individual scientists may mean different things by the term.  (Caution: there is a subtlety in the use of the words “Extremely Cold”; there are subtle quantum effects that I haven’t yet written about that complicate this notion.)

Notice that in the figure, I don’t measure time from the start of the universe.  That’s because I don’t know how or when the universe started (and in particular, the notion that it started from a singularity, or worse, an exploding “cosmic egg”, is simply an over-extrapolation to the past and a misunderstanding of what the theory actually says.) Instead I measure time from the start of the Hot Big Bang in the observable patch of the universe.  I also don’t even know precisely when the Hot Big Bang started, but the uncertainty on that initial time (relative to other events) is less than one second — so all the times I’ll mention, which are much longer than that, aren’t affected by this uncertainty.

I’ll now take you through the different confidence zones of the Big Bang, from the latest to the earliest, as indicated in the figure above.

The Green Zone: Confidence

A key clue that the observable patch of the universe was once hot and dense, and cooling as it expanded — i.e. that there was a Hot Big Bang period (preceded perhaps by cosmic inflation, but we don’t need to focus on that yet) — is the presence in the universe of the cosmic microwave background [CMB]. From all parts of the sky, an easily detectable sea of electromagnetic radiation in the form of microwaves (photons with energy about 1000 times less than photons of visible light) is streaming across the universe, and onto the Earth. Not only is the CMB a broad clue as to the universe’s past, it is also a key tool for scientists to use in finding even more precise and focused clues. Much of the history of the observable patch is imprinted in the details of the CMB.

A prediction of the Hot Big Bang is that the microwaves are just a sign of past heat, and of nothing else. Specifically, if you measure the microwave photons’ energy, and plot the amount of energy coming from a patch of sky due to photons of a particular frequency, you should see the same plot (a “black-body spectrum”, as it is called) as you would see for photons emitted by a cold piece of ice or rock or metal.  [Yes, ice at 2.7 degrees C above absolute zero does glow in microwaves.]  The fact that the COBE satellite’s data agrees closely with the prediction of a black-body spectrum (shown in the figure) is overwhelming evidence that there was a Hot Big Bang going on at the time that atoms first formed, when the observable patch of the universe became transparent to light — a time now believed to be about 380,000 years after the Hot Big Bang began.

Amount of energy in CMB photons as a function of the photons' frequency.  Data from the COBE satellite is the red crosses; the green curve is the prediction of a black-body spectrum.
Amount of energy in CMB photons as a function of the photons’ frequency. Data from the COBE satellite is the red crosses; the green curve is the prediction of a black-body spectrum.

The most powerful evidence that a simple view of the Hot Big Bang is correct even earlier is the success of the theory (i.e. equations) for nucleosynthesis: the formation of atomic nuclei for the lightest atoms during the Hot Big Bang.  (Note the atoms themselves formed hundreds of thousands of years later, when the temperature was cool enough for the nuclei to capture electrons.)  The equations of the Hot Big Bang include

These equations can be used to calculate how abundant certain light atoms should be, if there was a Hot Big Bang.  Specifically, one can compute the ratios of how much hydrogen (normal and heavy [“deuterium”]), helium (normal [“helium-4”] and light [“helium-3”]), and lithium should be present in pristine parts of the observable patch, if the atomic nuclei of those elements were mainly forged during the cooling stages of the Hot Big Bang. If the elements other than hydrogen were only formed in stars, then there should be very little helium and virtually no deuterium in the observable patch of the universe. (Deuterium is actually destroyed in stars.) But in a cooling Hot Big Bang, a lot of helium — about 1/4 of the amount of hydrogen — and a small but measurable amount of deuterium should be produced.

These predictions of the Hot Big Bang depend in great detail on our understanding of particle physics and gravity — of the weak nuclear force, the strong nuclear force, the electromagnetic force, the gravitational force (in Einstein’s version of it) and on the properties of neutrinos, electrons, photons, protons and neutrons. And the numbers work! The amount of helium, relative to ordinary hydrogen, is predicted to be in the 20 – 25% range; deuterium is predicted to be in the range of one part in 10,000 to 100,000, helium-3 a factor of 10 smaller than that, and lithium in the part per 10 billion range. The data agree!

Data showing the prediction for various element abundances (yellow band), data (colored horizontal bands), and predictions (solid colored curves).  The fact that the colored curves, colored horizontal bands and the vertical yellow band all meet -- except lithium, which is slightly off but not too far --- indicates that the Hot Big Bang occurred.   That Lithium is a bit low has been studied extensively and might mean that a bit of particle physics is missing from the theory.    From http://www.einstein-online.info/spotlights/BBN/ ; Adapted from an image by E. Vangioni, Institut d'Astrophysique de Paris]
Data showing  data (colored horizontal bands) and predictions from the Hot Big Bang (solid colored curves) for the  abundances of helium-4, deuterium, helium-3 and lithium relative to hydrogen.  The quantity on the horizontal axis is essentially the amount of ordinary matter in the observable patch of our universe.  The fact that the vertical yellow band meets the colored curves and the corresponding colored horizontal bands — except lithium, where the data is slightly too low — strongly indicates that the Hot Big Bang really occurred. (That Lithium is a bit low has been studied extensively and might mean that a bit of particle physics is missing from the theory; or it might be a problem with the actual measurement of Lithium abundance.) From http://www.einstein-online.info/spotlights/BBN/ ; Adapted from an 2007 image by E. Vangioni, Institut d’Astrophysique de Paris.

That these predictions agree with observations of the distant cosmos (see the figure below) provides a strong argument that the Hot Big Bang really occurred, and was originally hot enough to break apart nuclei.  That means that temperatures were initially at least hot enough that the typical particle had an energy of about 0.001 GeV, which would have happened a few minutes after the Hot Big Bang began.  More precise measurements even help us understand how much ordinary matter there is in the observable patch of the universe, with results that agree with other measurements of the same quantity.

For this reason, I’ve marked the nucleosynthesis period and what follows it in green, to emphasize that we have strong observational evidence that the Hot Big Bang did occur, and was so hot — hot enough to destroy atomic nuclei — that the atomic nuclei around us today had to form from scratch as the temperature cooled.

The Yellow Zone: Extrapolating a Bit Using Particle Physics

However, for times before nucleosynthesis, the arguments are weaker. We don’t have much direct evidence for what was taking place. But we have a lot of knowledge about particle physics, up to energies of a few hundred GeV, thanks to the Large Hadron Collider [LHC] and its predecessors over the last few decades.  So if we assume that the Hot Big Bang started at temperatures so high that a typical particle would have had an energy of a few hundred GeV, we can calculate the observable patch’s properties from that temperature downward. At such a high temperature,

As the temperature cooled, we can calculate (now that we know the Higgs particle’s mass, and if we assume there aren’t any lightweight particles that we don’t know about) that first the Higgs field would have turned “on”, making the weak nuclear force henceforth weak; and then, a bit later, the strong nuclear force would have become very strong, so that quarks and gluons and anti-quarks would have been trapped henceforth and forever into protons, neutrons, anti-protons and anti-neutrons, as well as other very short-lived hadrons.

However, we can’t yet directly confirm by cosmological observation that this is true.  It’s not entirely impossible that there was something odd and unknown about the universe that makes some of these conclusions premature. Someday we may be able to be more certain, but not yet. So in this time period, starting just before the Higgs field turns on and going until nucleosynthesis, we have a highly educated guess as to what was happening, though no direct experimental checks.  That’s why I’ve marked this time period in yellow.

The Orange Zone: What Started the Hot Big Bang?

Even earlier? Well, at even higher temperatures we don’t know the particle physics with confidence; we’d need particle accelerators more powerful than the LHC.  To figure out what happened in the Big Bang in detail, we have to make assumptions about the particles available, without any way to check them. But still, we are not without information, because we do have an experimental probe: the CMB itself.

It is a remarkable fact that the CMB is incredibly uniform, to one part in 100,000. That’s already information, and explaining why it’s true is one of the arguments in favor of cosmic inflation.

But there’s much, much more information in the imperfections in that uniformity. The non-uniformities, which were discovered by the COBE satellite, have been studied in detail by the WMAP and Planck satellites, along with many other experiments from the ground. And it was in studying the non-uniformities in the CMB and their tiny bit of polarization that BICEP2 made the big (but unconfirmed now discredited) discovery that was announced last week (here’s some background information on that discovery, in the form of FAQs, that you may find useful).

The photons in the CMB are astonishingly sensitive. There are very few things that affect them, and fortunately, most of the things that do are relics from the extremely early periods of the observable patch of the universe. It’s an unexpected gift for scientists that this is true! The CMB photons were created about 380,000 years after the Hot Big Bang, and yet they give us insight into the entire period before that, all the way back to a period just before the Hot Big Bang!!!  (They also can give us important insights into what happened after 380,000 years, too.)  To me, this incredibly sensitivity of the CMB is one of the most amazing natural phenomena in all of science… and it has been the key to progress in cosmology in recent years.

Detailed measurements of the CMB have increasingly given us insight into the zone marked in orange, where we don’t have any particle physics data — just guesses, and calculations based on those guesses.  The reason insights have been possible is that our calculations rely on very general properties of the Hot Big Bang and the pre-Hot Big Bang period to make predictions.  What I mean by this is that these calculations begin with very simple assumptions about the patterns of non-uniformities that were present at the start of the Hot Big Bang, and then we check if these assumptions give predictions for non-uniformities in the CMB that agree with data.  They do!  This is shown in the figure below, where predictions of the Hot Big Bang theory, with these simple assumptions about the starting point, are compared with data from the Planck satellite. (Similar but less precise measurements were made before Planck, by WMAP and a number of ground-based experiments.)

Data (red dots) from the Planck satellite, showing the average size of non-uniformities on different angular scales on the sky.  The solid curve is the prediction of the current standard cosmological model, which assumes a very simple type of non-uniformity, of the sort that cosmic inflation would produce.
Data (red dots) from the Planck satellite, showing the average size of non-uniformities on different angular scales on the sky. The solid curve is the prediction of the current standard cosmological model, which assumes a very simple type of non-uniformity, of the sort that cosmic inflation would produce.  The agreement is remarkable, and strongly supports the notion of a Hot Big Bang, but by itself does not confirm there was a period of inflation before the Hot Big Bang.

Thus, simple assumptions about the non-uniformities at the start of the Hot Big Bang seem to be right, more or less.  This lends support to the hypothesis of cosmic inflation, which can produce simple non-uniformities. But it’s not convincing, because one can imagine simple non-uniformities arising in some other way.  There is at least one alternative — the ekpyrotic universe — that is also largely consistent with this data, and there might have been others that no one has thought of.  Meanwhile, there were many qualitatively different forms that cosmic inflation might take, some of which could have been consistent with universes quite different from those with a simple Big Bang.  For example, the data has been consistent with universes that, at temperatures a bit higher than reached in the yellow zone in the figure, have more spatial dimensions than the three we’re used to. So the number of possible options in the orange zone has been very large, and the degree of speculation involved has been very high.

Data from BICEP2, black dots, is compared with the prediction from a model of cosmic inflation (upper dashed line).  The prediction is the sum of the solid line (an effect from gravitational lensing in the last few billion years) and the lower dashed line (the effect of gravitational waves from inflation with a very large amount of dark energy.)  Had inflation not occurred, or had the amount of dark energy during inflation been small, the dots would have followed the solid "lensing" curve instead of the upper dashed line.  See this post for more comments.
Data from BICEP2, black dots, is compared with the prediction from a model of cosmic inflation (upper dashed line). The prediction is the sum of the solid line (an effect from gravitational lensing in the last few billion years) and the lower dashed line (the effect of gravitational waves from inflation, if inflation involved a very large amount of dark energy.) Had inflation not occurred, or had the amount of dark energy during inflation been small, the dots would have followed the solid “lensing” curve instead of the upper dashed line. An alternative interpretation, that this is an effect of galactic dust, is supported by 2015 data.

This may have changed with BICEP2s new measurement, which gives unfortunately did not give powerful new evidence for cosmic inflation through inflation’s generation of gravitational waves… assuming the measurement itself, and the interpretation of the measurement, both hold up over time.  [The interpretation did not.] Since a measurable amount of gravitational waves can only be produced, as far as we know, if a period of inflation occurred and was driven by a very large amount of “dark `energy’ “, BICEP2’s result may rule out all known alternatives to inflation, and significantly narrow down the options for how inflation may have occurred, excluding many of the more radical options as well as many simple ones. As such, it may increase confidence in the inflation hypothesis to change the color of the orange zone to yellow, or even, as more measurements come in and become more precise, to green.  [But it did not.]

However, let’s not jump to conclusions until the measurement is confirmed with more data and by other observing teams.  [You see how important it is that I write these cautionary caveats in my articles.  I have seen many measurements come and go; the fraction that stick is much less than half.]

The Red Zone: Scientific Guesswork

But BICEP2 can really only tell us about the late stage and exit from inflation. If we go deep into the inflationary period and try to go earlier, into the red zone in the figure, we face two problems:

  • we don’t have any experimental probes of this early time, and
  • we don’t know which particle physics and/or gravity equations we should be using.

We do not yet have any cosmological observations that access this time period; the CMB photons bring us back to the late stage of inflation, but not further. We cannot infer much yet from CMB measurements about the “inflaton” field (and its particle) that is supposed to play the dominant particle-physics role during inflation, and we have no idea what other types of fields it may interact with, so it is hard to be sure what type of process got inflation started. Meanwhile, theoretical physics doesn’t help much either. We can try assuming that string theory is the true theory of quantum gravity in our world, but if we do that, we still find the equations are hard to solve and give, at best, a variety of possibilities. And trying to work in greater generality, without assuming string theory, doesn’t help; the calculations are still ambiguous and difficult. This doesn’t stop theoretical physicists from making educated, scientific guesses — i.e., speculations backed with concrete equations and calculations. But until we get some data that allows us to distinguish the many possibilities, we can’t say for sure what was actually happening back then.

So if people tells you that the universe started in such and such a way, perhaps “with a singularity” or “with a quantum fluctuation out of nothing” or “in the Big Crunch (i.e. the collapse) of a previous phase of the universe”, remember that they’re telling you about the red zone. They’re neglecting to tell you that what they’re saying is pure theory, with neither an experiment to back it up nor a clear theoretical reason to believe their suggestion is unique and preferable over someone else’s alternative. Only a bit later in cosmic history, once we focus on the late stages of inflation, and forward in time from there to nucleosynthesis, do we have both data (cosmological observation and particle physics collisions) and reasonably reliable theory (Einstein’s theory of gravity plus the Standard Model of particle physics). Our confidence grows as time moves forward, the observable patch of the universe cools, and physics becomes of a sort that we’ve tested in numerous experiments already.

From this, I hope that you can see that the Big Bang Theory really isn’t a single, undifferentiated structure.  The most reliable part of the theory is that there was, at one point, a Hot stage of the Big Bang. (Some people call that the Big Bang, in fact.) If BICEP2’s measurement is accurate, and correctly interpreted, then the reliable portion of the theory may then include a period of inflation that preceded the Hot Big Bang. (Some people would call “inflation plus the Hot Big Bang” the “Big Bang”.) But anything before inflation is not in the least reliable… in particular, the notion that the universe’s heat and density increased to the extent that Einstein’s equations have a singularity, presumably indicating that they’re not sufficient to describe what was going on, is an assumption. So that part of the Big Bang Theory may not survive the test of time. You should be prepared, as scientists are, to let it go.  After all, from 1960-1980 people had a vision of the early Big Bang that didn’t include something like inflation; their version was significantly adjusted as knowledge was gained, so why shouldn’t ours be?

Moreover, it is quite possible that the start of the universe, which people often refer to as the ultimate Big Bang, may not have had anything “Bang-ish” or even Big about it.  Yes, we might even need to let go someday of the idea that the universe truly began with a Big Bang. The scientific community won’t have any problem with this, because many of us have never taken that idea very seriously in the first place.  But what about the rest of our society, which seems to hold to this name and notion far harder than do scientists themselves, to the point of (egad!) naming a television show after it?!  The loss may be more shocking than necessary…

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255 Responses

  1. “the observable patch of our universe, which may be a tiny fraction of the universe” this “may be” always irritates me and for this reason: as the astronomic community became aware recently, there are minor planets beyond Pluto which have orbits that seem to be disturbed in a way that suggests “out there” is another giant (maybe Jupiter size) planet, as yet unobservable. Unobservable as it may be, it leaves traces that show in the behavior of nearer objects. Now if the universe were indeed larger than our “observable ‘patch'” – and IF there were big objects / dark matter / dark energy, galaxies, black holes etc. etc. just beyond “observable” surely they must interact with what is still observable in such a way as to leave traces just as the potential second Jupiter leaves on observable objects in our solar system? And is this or is it not, reflected in some of the branches of inflation theory?

  2. Professor Strassler’s articles are always fantastically good, but they always leave unanswered questions AND generate new questions that he does not have time to answer (we all need to work sometimes for a living from our day job). Some of the unanswered questions I have (as, in an inflating universe with only a tiny speck of mass, where did a universe’s amount of mass come from?) are neatly answered by Max Tegmark in a free excerpt from his book, “Our Mathematical Universe: My Quest for the Ultimate Nature of Reality”, in which he gives an explanation of inflation. You may read the free excerpt at http://space.mit.edu/home/tegmark/pdf/inflation_excerpt.pdf . It has also motivated me to buy his book! Now, when will Matt’s book come out?

  3. In AWT the red shift is the result of light scattering at the density fluctuations of vacuum and the Big Bang did never happen. After all, the FLRW metric is inverse metric to black hole and we aren’t saying, the inflation happens at the event horizon. It’s all stationary. The omnipresent inflation brings Einstein expansion paradox and it can be explained with light wave scattering together with dark energy. This model brings testable predictions, by which it can be tested (like the dependence of red-shift to wavelength of light). And it remains fully physical and it doesn’t bring any ad-hoced assumptions about past of Universe.

  4. Quote: ”By virtue of being awareness, transparent to itself, consciousness emerges from within its pure potentiality and, curving back on to itself, establishes an ‘observer-observed’ relationship within its own structure. This process of consciousness becoming aware of itself creates an unmanifest space-time geometry within the field of consciousness. The unmanifest space-time curve within the field of consciousness is at the source of space-time curvature, which Einstein’s general theory of relativity shows to be the basis of all objective creation.”

  5. Someone commented recently that we are in the era of data-driven cosmology and that the standard model agrees with “ALL” of the data.

    A few facts might be helpful here.

    In model-building, as opposed to theories of principle, the model fits the data virtually by the definition and modus operandi of model-building. The model is constructed to FIT the data, and ad hoc modifications (like epicycles) are added whenever new data “require” modifying the model.

    That does not by any stretch of the imagination mean that the model accurately represents how nature actually works. Think of the Ptolemaic “universe”; it fit the data quite well, but it was complete rubbish CONCEPTUALLY.

    The only scientific way to demonstrate that one’s model accurately represents nature is through the predictions/testing steps of the scientific method.

    In light of this science 101, the Big Bang is not on very solid grounds. Global expansion is on strong grounds, but there is no justification for an acausal “beginning to the entire Universe”; there is no explanation of what the inflaton field is; there is no coherent and tested explanation for how the temperature could be very cold at the “beginning” and then suddenly become very hot for the hot Big Bang; extrapolating from the polarization of the CMB observed NOW to the just-so story about what was happening at 10^-35 sec is laughably speculative; there is no well-accepted explanation of the “recent” accelerated expansion, or Planck’s new unexpectedly slower quantification of it; dark matter (i.e., nearly all of the matter of the Universe) continues to be a complete mystery; the Planck mission recently confirmed an unexpected directional anisotropy for the observable universe; … . Should I go on for a few more pages?

    Let’s try to show less hubris and more scientific humility about what we know and what we do not know. Let’s not be: “Often wrong, but never in doubt”. Let’s be scientific.

    Robert L. Oldershaw

    1. Robert, thank you for the post about model building. I am in agreement with you on that. Where I don’t necessarily agree (from one BB critic to another) is the statement that global expansion is on strong grounds. Do you happen to have a list handy of reasons why global expansion should be considered to be on strong grounds? If you do, I would like to provide a rebuttal.

      1. Fixed ideas are the enemy of scientific progress.
        A balance of open-mindedness and skepticism is the ally of scientific progress.

    2. I agree with you— The big bang, as presented in the SM, is a house of cards balanced on the point of a pin. The big bang notion has inspired a lot of clever ideas and encouraged the development of useful math techniques; while at the same time granting validation to a number of rather silly schemes to accommodate a big bang with scientific observation.

      1. If both of its polarization had high energy like gamma rays, they travel in opposite direction and one of them enter dark matter, then they were entangled. The chaos inside dark matter also affect another one. This will disturb the harmony of vacuum energy, creating the VEV to “pull” other energy densities to lowest energy level – making spontaneous symmetry breaking. So the rest mass constancy inside our 3D spacetime could be changed by very high energy gamma rays.

        1. Space expansion is evaporation of dark matter into dark energy (like black hole evaporarion – takes billions of years).
          Changing of mass energy into vacuum energy like dark enetgy star – creating “new space”, leaving the movementum (responsible for mass) to create volume for accommodating the new space.

  6. Matt or Kunzu,
    In my schedule speculation I made some questions (look above). Is this my schedule, of what “has” happened, the right one as understood today?

    1. At the present time we do not know if there was a ‘mother of all beginnings’ even one ‘infinitely long ago’. But this can be ignored.

      We are also not *completely* sure that during inflation fields worked as they do now; the inflaton field would have (as yet) unknown effects. In the same way the fact the Higgs field is now ‘on’ affects the very basics of our universe the inflaton field being ‘on’ during this period also affects things.

      We are not sure whether there were any particles at this time; that would depend on the state of the universe before inflation. If there were they wouldn’t matter as they are so quickly diluted.

      The situation of these particles is interesting. Inflation is an incredibly short process; many particle interactions or decays would simply not have time to occur. Also since space itself is expanding faster than light all particles are totally isolated, they will not be able to interact with any other particle. This includes interacting with the Higgs field and in any case mass is a rather tricky concept when dealing with a particle in this situation.

      At the core of your question is a misconception; electroweak symmetry breaking is not a one way street, an irreversible transition. It is more like water freezing; it reverses at high enough energy. As such it is quite possible for the symmetry to be broken during inflation then to reform at the end of inflation before breaking again. It may even be possible one day for humans to collide exceedingly high energy particles and watch electroweak symmetry reform in the lab.

      Interestingly you state as much when you say ‘Now around half past one the Higgs field got enough of energy in order to turn “off”’ so I am not entirely sure on your understanding of this subject. You are correct in saying that the energy of the inflaton field turns into both kinetic energy and the birth of particles. The precise temperature cannot be larger than 10^16 GeV, but it is possible for it to be *lower* for various reasons. Inflation ‘stops’ at this time, not after.

      The exact relationship between the current dark energy and that if inflation is not entirely clear and we will need more information on both before the link becomes apparent.

      1. /It may even be possible one day for humans to collide exceedingly high energy particles and watch electroweak symmetry reform in the lab./–

        At the technical level the spontaneous symmetry breaking means just that the lowest energy configuration, the vacuum, does not have the symmetry of the Lagrangian. A particular vacuum to be realised in nature is chosen spontaneously. In the sense, that there can be another vacuum configuration chosen.

        Here comes the masslessness of photons. Masslessness was realized at lowest possible potential energy and highest possible kinetic energy. the possible more potential energy is “heated (decrease in entropy) up” (don’t know why?) – thus forms the reference frame to define mass-energy (or mass).
        The angular momentum (mass x velocity) “c^2” in E = mc^2 represent this potential energy (or rest mass).
        The term “Spontaneos symmetry breaking’ is used in statistical physics for the change of symmetry of the ground state of a system due to the change of its TEMPERATURE, i.e., not due a change of a parameter in the Hamiltonian.

        As far as cosmological SSB goes, many effects are clearly due to virtual energy borrowed from the quantum foam, tipping a precipitation down one particular way and at a particular time rather than down another route.
        Gauge fields spontaneously interact with scalars because they are not singlets.
        A good example from our daily experience is a round dinner table. At some point you have to make the choice whether you take the glass to your left or to your right. Once someone selects one, all others at the table have to follow. The left-right symmetry is broken. 🙂

        So the mass in momentum (mass x velocity) is removed by high energy collision – means, the symmetry of lowest energy level of gauge fields will be retained, like masslessness of photon field – creating “new space” by leftover velocity – like in dark energy star ?

      2. OK Kudzu, thanks a lot for your kind answer. Seems there are a lot of uncertain things prevailing

        “At the core of your question is a misconception; electroweak symmetry breaking is not a one way street, an irreversible transition.”

        OK thanks. So the electroweak symmetry breaking might have happened twice.

        “Interestingly you state as much when you say ‘Now around half past one the Higgs field got enough of energy in order to turn “off”’ so I am not entirely sure on your understanding of this subject.”

        While the lowest value of the Higgs field is nonzero, it needs energy in order to be zero. At most of the inflation time the Higgs field was “on” (cold) and the particles had mass, but at the end of inflation the field turned “off “ (hot) and the particles turned to be massless, and then again at electroweak symmetry breaking “on” (cold) and the particles gained again mass and that situation has stayed “on” since then.

        But as you say, in spite of the Higgs field being “on” or “off” the particles had no chance to interact with the field during inflation. The question of mass at this stage is tricky. Might there have been other alternative ways for particles to get mass (inflaton field itself)? Or is the question of particle masses totally irrelevant here?

        1. There are many, many theoretical possibilities covering the period of inflation and what they do to particles. The problem with questions about this time period is twofold, firstly we don’t know everything (or even very much at all) about this time so any answers we give are only best guesses, if that.

          And secondly a lot of things we take for granted in everyday life become rather more difficult to define and describe under such conditions. For example, to define a distance we need to be able to measure it, but these particles cannot be measured during this time so do questions of distance and speed mean anything? Or are they the same as asking what the color green sounds like?

  7. @Stuart – I liked the definition for dark energy of being a ”dynamical quantum vacuum energy”.

    1. In my work on quantization of spacetime, gravity and the quantum vacuum I find that the graviton is inextricably linked with an element of the quantum vacuum. This graviton is different from the one discribed by the standard model.The wave function of this graviton is a wave packet that spreads in quantized time evolution steps by emitting a low energy graviton of energy E=hH.This is the dynamical aspect of the quantum vacuum in my theory.

        1. Sounds wonderful! Unfortunately I am not in the situation to comprehend in detail what you have written. Did you read the paper by Basilakos and Sola? Did they define dynamic vacuum in a similar way?

  8. I have tried to figure out the time schedule:

    Let´s say the Very First Beginning (the Mother of all Beginnings=MAB) occurred at 12.00 noon (whether it is true or not, we simply do not know). Time between noon and one o´clock unknown.

    At one o´clock pm a tiny part of the universe started to inflate and expanded with exponential speed (for the reasons we do not know for sure). The expansion was so rapid that it soon cooled out the universe to an extreme coldness.

    All the fields of the universe have been present since the MAB. So at this low temperature the Higgs field must have been “on”. Question: were there in the first place any particles present at this time? If yes, all the particles (the ones that feel the Higgs field) should have mass? But how is this possible, as there was no symmetry braking of electroweak interaction at this stage?

    At half past one the inflaton field started to slow down and thus the temperature got higher. The energy which the inflaton field lost at this stage, was turned to the birth (?) and kinetic energy of different particles. As the clock approached two, the universe (our part of it) was heated up to a temperature corresponding energy level of 10^16 GeV. Now around half past one the Higgs field got enough of energy in order to turn “off” (it needs energy in order to be “off”, zero value).

    At two o´clock the inflation (or at least the most of it) stopped (all the energy, or almost all of it, had gone to the birth of particles). The universe again cooled very rapidly. Because the Higgs field was now again “on”, it resulted in the symmetry braking of the electroweak interaction (and hence some particles remained massless and some got restmass).

    Not all of the inflaton field (dark energy) was gone but is working even today and expanding the universe. Although the energy of this field is very tiny it has won (because of expansion) over gravitation some 5-7 billion years ago, and hence the accelerating speed of expansion.

    1. Is this really any better than the cosmological creation stories we told each other hundreds and thousands of years ago? In my humble opinion today’s stories are not a real advancement over any of the thousands of other stories we have created over the generations. Yet, every generation thinks their story is the right one.

      I recall years ago informing a women up the hill at the Chabot Space and Science Center here in Oakland California (where I would commonly bring my telescope to share the views) of my alternative views on cosmology. She then expressed her sadness that my view of an infinite non expanding universe, if correct, would be a let down from the point of view of a great story. She really was preferring a great creation story over my possibility.

      1. @Vincent Sauvé: Well! As for which story is better(!) we can point to the success of physics’ method of making mathematical models and comparison with experiments. This has been working since the time of Galileo and Newton. Matt has emphasized this point repeatedly. Any one can sit in his/her room and scribble some wild ideas. What makes them acceptable is the peer review system and eventual confirmation by experiments. There may be lot of confusion from time to time. Beginning of 20th century was such a time. Current confusion is somewhat similar to that period. Eventually the best theory will win. I do not have any doubt about it. The cell phone in your pocket (if nothing else) is an indication of success of scientific method. It may be harsh to say but one has to say that if some theoretical idea cannot be put in a mathematical form it can be safely ignored!

        1. Kashyap, I love the scientific method. At issue is what is being speculated by many in this thread doesn’t really fall into the category of science. And some people here can’t even form a real sentence or a thought. Throwing around physics jargon is not science. Theoretical ideas must be grounded to real physics, not to mathematical make-believe.

          While my opportunities to observe the behavior of scientists mainly comes from what I’ve learned by way of books, I have observed engineers in action and have witnessed colossal mistakes, including biases that turned out to be wrong that led to wastes of time and products that weren’t their best. In the field of smartphone technology we are all amazed at how great they have become, but let’s not ignore the fact that the ones that make it to market are the result of many trials, and the filtering out of failures, and the filtering in of what the public likes. Cosmology is also like that, and the public likes a good story, and if it is dressed in the clothing of science all the better in this new world of high technology.

  9. •”However, quintessence and phantom fields are still more problematic; therefore the explanation based on the dynamic quantum vacuum could be the more simple and natural one,” Sola said.
    Cosmologists believe that some three quarters of the universe are made up of a mysterious dark energy.
    • “What we think is happening is a dynamic effect of the quantum vacuum, a parameter that we can calculate,” explained the researcher. The concept of the quantum vacuum has nothing to do with the classic notion of absolute nothingness. “Nothing is more ‘full’ than the quantum vacuum since it is full of fluctuations that contribute fundamentally to the values that we observe and measure,” Solà pointed out.
    These scientists propose that dark energy is a type of dynamical quantum vacuum energy that acts in the accelerated expansion of our universe. This is in contrast to the traditional static vacuum energy or cosmological constant.
    The drawback with this strange vacuum is that it is the source of problems such as the cosmological constant, a discrepancy between the theoretical data and the predictions of the quantum theory that drives physicists mad.
    “However, quintessence and phantom fields are still more problematic, therefore the explanation based on the dynamic quantum vacuum could be the more simple and natural one,” concluded Solà.

    • Spyros Basilakos, Joan Sola. “Effective equation of state for running vacuum: “mirage” quintessence and phantom dark energy”. Monthly Notices of the Royal Astronomical Society 437(4), February 2014. DOI:10.1093/mnras/stt2135.

    1. @Margot the value of the cosmological constant has been calculated from Quantum gravity to be lambda=3(E/hc)^2 where E =hH
      here H is the Hubble constant 2.3 x10^-18 s^-1
      and h Planck constant
      The cosmic expansion is a result of the emission of a graviton of least energy E=hH by spacetime

      1. I am merely saying the Cosmological constant problem which you mention above is as good as solved.So far experts in this field have not found a problem with the solution.

    2. Margot, “the Self” or consciousness were the sedimentary sediments of adopted informations”. Like RNA, the oldest data storage medium. These are the past leftovers of Evolution. If you remove aside those informations, there is selfless consciousness. The dynamics of those informations increases the entropy, contradictions and conflicts.
      “Storage of informations is always accompanied by an increase of entropy. Stroring and retrieving information is part of what makes up our consciousness”.

      The fundamental law of quantum mechanics is that the “Evolution” is linear, meaning that if state A turns into A’ and B into B’ after 10 secondy, then after 10 seconds the superposition Ψ turns into a mixture of A’ and B’ with the same coefficients as A and B. Quantum superposition, a property of Schrödinger equation.
      But “The vacuum expectation value” is bedlam here, not having universal arrow of time – the arrow of time is inertial. But there may be also entangled part of vacuum expectation value, whose “amplitude interferes” and allows energy to briefly decay into particles and antiparticles and then annihilate without violating physical conservation laws.

      Einstein envisaged the rest mass and cosmological constant for a static universe. I could not understand its reverse evolutionary cauchy? http://arxiv.org/abs/1311.0700
      “Their developments backwards in time induce a set of standard Cauchy data on space-like slices for the Einstein-massive-scalar field equations which is open in the set of all Cauchy data for this system”.

      So information and entropy is evolutionary only in some conditions (relative) like “un-naturalness” ?

      1. @veeramohan Consciousness is the Self (Atma). Self is no information. But otherwise I agree. Consciousness is only the screen on which information (events) appears. But in itself the screen is untouched by it. The events are different in different states of consciousness. In the end those events come about by forgetting the totality of the infinite dynamism of the Unified Field in favor of isolated aspects of this dynamism –as formalized in Physics by so-called conditional observations. Events thus are conditional operations in reality, a certain perspective which blends out or ignores relations. A mistake of the intellect – which is exposed when consciousness is fully developed.

  10. Interesting debate about direction of arrow of time, 2nd law of thermodynamics and entropy increase. As far as I can tell, no one (including Sean Carroll) has solved the problem. Why a small (or large) fireball of immensely high temperature and high density can have entropy smaller than today defies explanation.And in case of big crunch whether entropy will decrease again also is not clear. BTW, time reversal invariance of microscopic laws of physics has nothing to do with your philosophical belief whether time flows or not. It is merely a mathematical operation t -> -t in the equations and subsequent invariance. Yes. It would be nice if Matt writes a blog on this.

    1. The expansion of the universe generates the arrow of time i.e. increases the degrees of freedom (entropy)

      1. Even hot atoms traped in a container of dimensions comparable to the number of atoms is ordered i.e less entropy

        1. @Stuart: Your first answer will have problem with time reversal invariance of microscopic laws. After all in the spirit of physics, macroscopic laws should follow from microscopic laws. About the second (less entropy), are you sure this works out mathematically? You need believable size of the container and the correct number of atoms. Do you have a reference?

          1. The early universe although in a high energy state is dense and compact leaving little or no room for particles to randomly move. As expansion comences more room is created and entropy increases. I do not see a violation of time reversal invariance.

          2. PS for reference read about negative temperature or population inversion. I also have a paper accepted for publication in the peer reviewed journal IJGMMP on Quantum gravity, DE and DM which may help clarify issues regarding the arrow of time and inflation.

          1. @kayshap The paper is yet to appear online will do so as soon as it does but you find it behind a paywall £20 high.

            1. Quote
              ”Quantum Cosmology offers a unique explanation of how all the change displayed by Nature has its basis in the unchanging, self-referral state of the Unified Field, by showing how the quantum-mechanical correlations between observer and observed give rise to the emergence of a sequentially evolving universe.

              Quantum Cosmology starts its investigations with a formula called the wave function of the universe, which actually describes both the quantum regime of Cosmology where the classical universe has not yet emerged out of the Unified Field, and simultaneously the emergence of a classical universe. The actual formula of the wave function of the universe does not contain the notion of time and thus can be understood to be beyond any change in time – and this just signifies the completely unchanging nature of the Unified Field.

              The wave function of the universe can be seen as the formula which describes how all possible states of an infinite number of vibrational modes of the unified Field –also called degrees of freedom of the Unified Field – are coexisting to form a kind of a quantum-mechanical state of superposition. Simultaneously, from a different viewpoint, the wave function of the universe expresses the quantum-mechanical correlation between selected sets of these vibrational modes of the Unified Field – and in Quantum Cosmology this is the origin of the interplay between observer, observed and observer-observed-relationship. One aspect of the infinite number of vibrational modes of the unified field assumes the role of the object of observation, and another part the role of the observers (Information Gathering and Utilizing Systems, IGUS. The observer-observed relationship is the n quantified through the quantum-mechanical correlations contained within the wave function of the universe. There is however no fixed assignment that invariably determines, which is the observer and which is the observed, rather there is an infinite number of different ways to make suitable selections.
              The conceptual emergence of a classical universe evolving in time out of this unmanifest state of the Unified Field is now achieved by a further step.

              Sequence of states of the object of observation which are directly step-by-step correlated to a corresponding sequence of state of characteristic aspects of the observer. The conceptual location of such a sequence of states gives rise to the notion of time and thereby creates the impression of a universe which evolves and changes in time.

              The emergence of the evolving universe is only a conceptual notion that results from a kind of ignorance through which the totality of the infinite dynamism of the Unified Field is forgotten in favor of isolated aspects of this dynamism –as formalized in Physics by so-called conditional observations. In particular, the real infinite quantum-mechanical correlations between observer and observed is neglected or reduced to such a degree that the impression of an independent, objective universe can arise (appearance of a snake in a string).

              Quantum Cosmology furthermore confirms that the whole universe emerges out of the Unified Field through its own eternal process of self-observation.

              (…)creation arises from and always remains submerged within the eternal silence of the unified Field. The display of this phenomenon is in the eternal galactic dynamism within the eternal empty space of the universe.”

  11. The Eternal Inflation multiverse introduces two important concepts into cosmology. Firstly, it finally recognizes that our observable universe is probably only a drop in the infinite ocean of the Universe. Secondly, it proposes that the structure of the infinite Universe is fundamentally fractal.

    At least, that’s what Linde has said for a decade. Of course, fractal structures can come in a large variety of different forms, but a crude start is still a start. Better than pacing forever in a cage whose bars are merely an illusion caused by a lack of imagination.

  12. I agree with Matt about being prudent with the BICEP2 results. For example, why did PLANCK2013 NOT SEE THESE RESULTS?

    1. It may have. The full polarization data isn’t released yet, now delayed into October/November due to difficulties.

      There are papers on arxiv that pick up the signal from WMAP and Planck by some non-standard procedures FWIW.

  13. @Edwin Steiner, thanks for your response. By “driving force of the universe” I mean that entropy was at one time said to be the reason why things happen. Is was said to be responsible for “the arrow of time” and thus the ultimate explanation of cause and effect. Cause precedes effect and the effect is that entropy and disorder must always increase over time. The concept of entropy, and its inevitable increase, are as engrained in our popular culture as the concept of the Big Bang itself. It was, and I think still is, a big deal for (some?) cosmologists. I get the impression that for particle physicists, entropy is not such a big deal. I was hoping to find out what the physicists of today think of entropy. What is its proper role in cosmology and the Big Bang Theory? Specifically, should we say the universe is expanding because the second law of thermodynamics is true, or should we say the second law of thermodynamics is true because the universe is expanding?

    1. This is actually an interesting area of research. By and large the interactions that are studied by particle physicists are time symmetric; they look the same if time is run backwards. (Velocities are reversed of course, but otherwise…) But on large scales the universe is *not* time symmetric. (A smashing cup looks very different to one suddenly forming out of shattered fragments.)

      The problem quickly gets bogged down in defining time itself and why it proceeds only in one direction. (The universe is expanding? You mean it gets bigger over time? Why can’t we reverse time and say it gets smaller instead?) An interesting discussion of this for laymen is Sixty Symbol’s ‘Arrow of time’ video: https://www.youtube.com/watch?v=9VFGuupXwng

      1. @Kudzu, Thanks for the video link of Sean Carroll talking about the arrow of time. I see the meme of entropy defining the arrow of time is still alive and well. However, I am not sure this kind of talk is serving the interest of science. In my opinion, this is an example of how a simple concept can be made more complicated than it is and in the process make science seem more mysterious (or even mystical) than is warranted. Sure, it is great entertainment, but I think the mission of science ought to be to clarify, not mystify. That is what I find so valuable about Matt’s articles such as this one on the BBT – he separates the entertaining hype from the hard science.

        We all know what time is. It is what distinguishes yesterday from tomorrow. As the questioner in the video put it, time flows from the past to the future. Sean was making the argument that on the microscopic level, there is no direction of time, while on the macroscopic level there is a direction of time. This is a misunderstanding of what time is. By definition, time has direction on all levels – microscopic and macroscopic. The fact that the equations for microscopic processes are symmetrical with respect to the time variable and the equations for macroscopic processes are asymmetrical does not mean time can reverse itself for the former and not reverse itself latter. Time never reverses itself, by definition. Processes can reverse themselves, but time cannot. Witnessing an omelette unscramble itself and assemble itself back into an egg, would not be witnessing time running backwards. It would be witnessing time running forward and a process running backwards. Time is a prerequisite for process.

        I think it is time for talk of entropy to be removed from cosmology.

        1. Regarding “the mission of science ought to be to clarify, not mystify”: Yes, but there is profound clarity and false clarity. If you claim that time or entropy are simple concepts, I think you are going for false clarity.

          We all have the perception of time passing, but that does not mean we know what time is (by which I mean how to precisely describe it and which role it plays in a fundamental description of nature). In your comment you seem to define time by this mental time arrow of ours. But where does this sense of direction of time originate if our consciousness is an emergent phenomenon based on fundamentally time-reversible processes?

          The connection between the increase of entropy and the mental arrow of time is more than a meme. As far as I know it can be shown under some rather generic assumptions that storage of information is always accompanied by an increase of entropy. If you accept that storing and retrieving information is part of what makes up our consciousness, the mental arrow of time must be identical with the thermodynamic one. (If you do not think of consciousness as an emergent phenomenon on the other hand, then you face the question why these two arrows are aligned and how our mental time is related to the physical time.)

          As cosmology deals with a huge physical system with an enormous number of constituents, statistical mechanics and thus entropy naturally come into play. Even if it may not always be clear how to define or apply it, the concept of entropy will not be removed from cosmology any time soon, I think.

          1. Edwin, I agree that one can err on both sides of the clarity target. As Einstein is said to have said, “Everything should be made as simple as possible, but not simpler.” However, I still hold that talk of entropy in cosmology is erring on the side of introducing more confusion than clarity, at least in popular media. I believe the term invites undue philosophical interpretation and unfounded conclusions in much the same way that talk of “the singularity at the beginning of the Big Bang” does. For instance, one might cite the second law of thermodynamics as a reason why the universe is expanding and why it must expand forever and why it can never reverse itself back into a “Big Crunch”. I think this kind of reasoning is a misuse and a misunderstanding of thermodynamics. An authoritative article separating what is true and useful about the concept of entropy and what is misleading and misapplication, would be very helpful. The interest of science would be well served if we could clean up the messy thinking the concept of entropy has spawned.

            1. Have you read Sean Carroll’s “From Eternity to Now”? It’s the most thorough examination of the question of entropy as it relates to cosmology that I’ve come across (though you may or may not agree with his tentative conclusions).

          2. @papanca2, I have looked at but not read Sean Carroll’s “From Eternity to Now”. Best I can tell at a glance, he has reiterated all the popular memes concerning time, entropy, relativity, and cosmology. What put me off from reading the book is that I could not agree with his very first premise as stated on page two of the prologue, “The most mysterious thing about time is that it has direction; the past is different from the future.” My immediate response was, no, that is not a mystery of time. That is the definition of time. If the past were not different from the future, what would it mean to speak of time. The fact that time has direction is natural and expected. For time not to have direction would be more than mysterious – it would be meaningless. Asking why time has direction is like asking why counting numbers increase in the positive direction.

            The error, as I see it, is that Carroll is conflating time with events and processes that happen in time (a process being a sequence of events ordered in time). The proper question to ask is 1) why do events that happen, happen, and 2) why do they happen in the order that they happen. This is precisely what all of science, in one form or another, is tasked to find out. The answers are coming. The answers are coming and they are coming with a deeper and deeper understanding of how nature works on a more and more fundamental level.

            As for the apparent conflict between the laws governing the ultra-small and the laws of thermodynamics which govern the larger, I think it is fair to say that thermodynamics is an incomplete theory. It does not provide a complete picture. It is this incompleteness, not some mystery of time, that is the true source of the apparent contradiction.

        2. @Steve Donaldson: Thanks for your thoughtful reaction to Carroll’s book (even though you admit to not having read it!) I don’t know enough to be familiar with “all the popular memes concerning time, entropy, relativity, and cosmology.” Do I understand that you view time as something “real”, in a sense “absolute” (a la Smolin)? I used to feel as I think you do, that past is past and future is future. But what does one make of the problem of simultaneity for different observers?

          I like the distinction you make between the omelette “unscrambling” itself as an example of a “process running backwards” and not of time running backwards. That has been my intuitive reaction to such examples of processes (not time) reversing themselves.

          1. @papanca2: Yes, I think it is safe to say time is as real as the Universe itself. And yes I am a big fan of Lee Smolin. I have read his first three books and I am working on his most recent, “Time Reborn”. I don’t agree with everything he says, but by and large I think he is on the right track. As for relativity, that is another whole can of worms, that I am not sure I want to open right here. Let me just note that Einstein was not suggesting time was an illusion or that it could run backwards. He took a very practical approach, limiting talk of time to time that can actually be measured. It is the measurement of time (which is a process) that can be affected by your frame of reference. So yes, clocks can and do run faster or slower in different frames of reference in different circumstances and the equations that predict those time differences have been extensively tested and found to be true. No argument here.

  14. (1) Done, many times over.

    (2) Newest Planck results are not well understood. Go to arxiv.org or more information on these observational results and their implications. The dipole anisotropy I am referring to is in addition to the old motion of the Solar System Doppler anisotropy.

  15. The latest Planck results indicate a slower accelerated expansion than was previously determined from supernova data.

    The Planck mission also confirmed a surprising dipole anisotropy in the CMB temperature fluctuations.

    The cosmological constant is only one of several theoretical explanations for the late period of accelerated expansion.

    Reality is so much more complicated and uncertain that the just-so stories of the currently fashionable liturgy.

    1. @Robert L. Oldershaw. I am just repeating what seem to be some kind of peer reviewed theoretical models. If you have rival models, then let them go through peer reviewed process. BTW, dipole anisotropy is no mystery. It is due to the motion of solar system with respect to CMB.

  16. Dark Energy is purely vacuum energy, but not purely – what else is it dependent on? It drives inflation and the accelerated expansion of the universe. It does not interact with matter at all. Right? What else?

    1. @Margot: Since Matt may be busy these days, let me try to answer some of your questions, the way I understand them. Of course, experts are welcome to correct my answers. According to the current model, there was a field called inflaton which gave rise to exponential expansion in first 10^(-35 to -37) sec or so. This increased the size of our observable universe by a factor of 10 ^(90) or so, starting from an extremely small size like 10^(-30) cm or so. All these numbers are tentative. During the expansion or after the expansion (it is not clear to me) whole bunch of particles , quarks, leptons etc were produced by quantum fluctuation. The expansion cooled off the universe to perhaps near absolute zero (?) . Then or perhaps while inflation was going on the potential energy of inflaton was converted into kinetic energy of particles . That process is called reheating.Since that time the universe is expanding at a much slower rate (non exponential, at rate of some power of time). Some time during the first second Higgs field was turned on which gave rise to masses for quarks and leptons.During the last 5-7 Billion years , there has been a new effect called cosmological constant which gives rise to accelerated expansion. This constant is present in Einstein’s equation. I have been trying to find out if people think that this constant is somehow related to the original inflaton from this and other physics blogs. But it seems that in case there is a connection, no one knows at this point. BICEP2 may have verified existence of inflation and the prime cause inflaton. But it remains to be confirmed. Cosmological constant has been verified and three scientists won Nobel prize for that discovery.

      1. Thanks, Kashyap. I knew some parts of your answer already, but good to hear them again. So coming back to dark energy – it is in part vacuum energy, in part inflaton field energy? Yes, I know that dark energy is the cosmological constant which Einstein to his own dismay needed to add to his equations. I know it’s also called quintessence. I guess since Matt and others here are reluctant to go beyond the inflaton field or quantum jitter maybe as still acceptable and talk about the quantum vacuum state, my question might not be answerable. Most of what you wrote I knew, Kashyap. Matt explained it quite well:-) in his history of the universe.

        Dark energy fills the universe to two thirds, I read. Such a mysterious, in my eyes, power!! I wanted to learn more about it.

        By the way, you have probably all heard about the new arxiv paper by James B. Dent, Lawrence M. Krauss and Harsh Mathur arxiv.org/abs/1403.5166 : Killing the Straw Man: Does BICEP Prove Inflation?
        Theoretical physicists and cosmologists James Dent, Lawrence Krauss, and Harsh Mathur have submitted a brief paper (arXiv:1403.5166 [astro-ph.CO]) stating that, while groundbreaking, the BICEP2 Collaboration findings have yet to rule out all possible non-inflation sources of the observed B-mode polarization patterns and the “surprisingly large value of r, the ratio of power in tensor modes to scalar density perturbations.”

        “However, while there is little doubt that inflation at the Grand Unified Scale is the best motivated source of such primordial waves, it is important to demonstrate that other possible sources cannot account for the current BICEP2 data before definitely claiming Inflation has been proved. ” – Dent, Krauss, and Mathur (arXiv:1403.5166 [astro-ph.CO])

        1. @Margot: Yes. There are lots of controversies about interpretation of BICEP2 and even that experiment has to be confirmed by BICEP3 or Planck etc. But this is all part of how science progresses and the controversies are very healthy. There is more agreement about cosmological constant (CC) than about inflatons. We know about CC (it could be a quintessence field also, dark energy) from well established analysis of well established experimental data using CMB and lots of other research. The main reason is that we are talking about what is happening *now* rather than in the first second. I suppose in the beginning there was vacuum and inflaton field turned on. So that makes it vacuum energy or dark energy. Most scientists may not want to speculate about whether there was any other energy. There was this inflaton field obeying certain equation and there was potential energy associated with it. But that is it as far as anyone wants to say anything about it!!! Let us see if Matt says something about these things in next few days.

          1. As far as I understand, quantum (vacuum/) fluctuations, i.e. dark energy, produced fluctuations or density perturbations in the inflaton and these small density perturbations grew via gravitational instability to form the large-scale structures observed in the late universe. Is that correct? Quantum fluctuations during inflation induce a non-zero variance for fluctuations in all light fi elds (like the inflaton or the metric perturbations). ”Light” here means…..? Read this in TASI Lectures on Inflation by Daniel Baumann, 2009 (rev. 2012)

        2. @Margot: This is reply to your latest comment, but there,there was no reply button. Well, I am not qualified to criticize Daniel Baumann!!! So we have to wait for someone more qualified to say if what Baumann says is right!

          1. I might even not have expressed what he says correctly….. that could have happened as well. But I would understand that.

            Description of ancient subjective science of consciousness:

            From the unmanifest, totally abstract transcendental field of Being, the first manifestation of creation is the self-illuminant effulgence of life. The second step in the process of manifestation is the rise of vibration. Just before the beginning of action, just before the beginning of the subtlest vibration, in that self-illuminant state of existence, the self-illuminant effulgence of life, lies the source of creation, the storehouse of limitless energy.


          2. May Indra knock some sense into Margot with his thunderbolt.
            May Agni burn the “subjective science of consciousness” nonsense to ashes and may Vayu blow the ashes away.

  17. Hello Matt,

    The way you distinguish between popular misconceptions about the BBT that have have become entrenched in our culture and what is actually known based on evidence, is very helpful. Thank you.

    Could you similarly say something about the concept of entropy? One popular conception is that entropy is the driving force of the universe and indeed is responsible for the BB and the expansion ever since. But entropy is not really a force is it? So how can it be the driving force of the universe? Also, at one time it was popular to say that the universe would end in “heat death” due to the ever increasing entropy. Could you explain what is right and what is wrong about this popular conceptions?


    1. I also hope Matt will address these good (and big!) questions. Maybe I can answer a small part: Yes, entropy is not a force itself. However, the second law of thermodynamics, which says that in a closed (isolated) system entropy will always increase until equilibrium is reached, can cause effects that appear as if a force was acting. One example is osmotic pressure.

      The conventional explanation for the second law is that entropy is a measure for the probability of a state – or for the number of possible states that look the same when seen through smudgy glasses – and that a system with a large number of particles is just enormously more likely to change from one state to a more generic state (higher entropy) than to a more special state (lower entropy). Thus entropy (almost) always increases.

      What does this mean for the universe? If the universe can be regarded as a closed thermodynamical system and if it makes sense to define an entropy of the whole universe and if gravity or unknown physics do not change the story, then we can expect the universe to reach thermal equilibrium in a very very far future and thus become tremendously boring.

      I have no idea about those “if”s. Entropy is one of the most subtle concepts in physics and it has bothered some of the greatest giants of theoretical physics for ages. I have the feeling that not all has been said and done about it. BTW, I was not aware that there is a popular conception that “entropy is the driving force of the universe”.

      1. It is very easy to think of many situations where gravity leads to more ordered states. The second law of thermodynamics never included scales where gravity is important.

        1. The law of the conservation of energy, which assumes the form of the law of the equivalence of heat and work.
          The concept of time came from thermodynamics, without that, no relativity.
          “Time is just an illusion. Einstein told us that.” “What quantum physicists and Einstein tell us is that everything is happening simultaneously.” ding kinematics and “inertia” of momentum, the arrow of time: (1) It is vividly recognized by consciousness.
          (2) It is equally insisted on by our reasoning faculty, which tells us that a reversal of the arrow would render the external world nonsensical.
          (3) It makes no appearance in physical science except in the study of organisation of a number of individuals. Here the arrow indicates the direction of progressive increase of the random element. – Sir Arthur Eddington.

          1. Veeramohan, I disagree with what you wrote and/or Sir Arthur Eddington. The concept of time comes from the motion of matter, not thermodynamics. Relativity can exist independently from thermodynamics. And Einstein had a good definition for time. Please read original sources for more reliable facts. Here is what Einstein wrote on the subject:

            The measurement of time is effected by means of clocks. A clock is a thing which automatically passes in succession through a (practically) equal series of events (period). The number of periods (clock-time) elapsed serves as a measure of time. The meaning of this definition is at once clear if the event occurs in the immediate vicinity of the clock in space; for all observers then observe the same clock-time simultaneously with the event (by means of the eye) independently of their position. Until the theory of relativity was propounded it was assumed that the conception of simultaneity had an absolute objective meaning also for events separated in space.

            This assumption was demolished by the discovery of the law of propagation of light. For if the velocity of light in empty space is to be a quantity that is independent of the choice (or, respectively, of the state of motion) of the inertial system to which it is referred, no absolute meaning can be assigned to the conception of the simultaneity of events that occur at points separated by a distance in space. Rather, a special time must be allocated to every inertial system. If no co-ordinate system (inertial system) is used as a basis of reference there is no sense in asserting that events at different points in space occur simultaneously. It is in consequence of this that space and time are welded together into a uniform four-dimensional continuum. –Einstein, A., 1992, Fadiman, C., general editor, “Albert Einstein On Space-Time,” The Treasury of the Encyclopedia Britannica, (Viking Penguin, a division of Penguin Books USA Inc., New York, NY), pp. 371-383.

          2. Thank you Vincent Sauvé, propagation involves invariant sequences between events, which become central for the understanding of time.
            At free fall, kinetic energy is increased – means increase in temperature. More heavy, more lowest energy level. Massless (like in inflation) at most lowest energy level (more cold) – then got “reheated”. Which maintain its kinetic energy at the maximum level – what we call as spacetime. The energy densities whose potential energy not fully converted to kinetic energy forms particles, which makes “invariant” sequences between events – making speed of light as reference point ?

            The axioms of thermodynamics (like kinematic geometry) were extrapolated to relativistic equations to define the dynamics of time ?

            The non-zero value of the cosmological constant (uncertanity principle) represents the point of “reheating”?

            The energy density of the vacuum of space is maintained by moment of “inertia”- otherwise the energy allowed by Heisenberg uncertainty principle to briefly decay into particles and antiparticles and then annihilate without violating physical conservation laws – will become Dark-energy star ?

  18. I completely agree with Robert here. I’ve seen the same thing going on over many years of observing the field. I’ve also read from commentators who have pointed this out, but as I recall those were the critics of the BB, not the supporters.

    Another aspect is how ugly the model building became to fit their wrong ideas to the observations. Very few seem attuned to the problem. I can image that real professionals have encountered those thoughts from time to time but probably lacked the wherewithal to change the momentum of the field, or to challenge their professors, or the field leaders.

  19. Here is how the illusion of highly accurate definitive predictions is created by model-building in theoretical physics.

    In the early phase the theory/model makes a genuine prediction before the initial observations are made. Unfortunately, the genuine prediction usually compares rather poorly with the subsequent observations. For example, someone pointed out that the original prediction for the temperature of the cosmic background radiation (CMB) was off by 400%.

    Early failure is no problem in model-building. In the middle phase of model-building one just “adjusts” and tinkers with the model until it “predicts” the previous observational results. When the next round of observations become available, the adjusted “predictions” do much better than the initial predictions, but further adjustments to the model and its “predictions” are required. The iterative process of observation, adjusted “predictions”, new observations, further adjustments to the “predictions, goes on until the observations become ever more consistent and change by increasingly tiny amounts.

    Now comes the final phase wherein the predictions have been repeatedly adjusted to fit the increasingly refined observations. The model–builders say: “ See! We made highly detailed predictions and the observational data confirm our predictions perfectly – it’s uncanny how good the fit is!”
    The problem is that only the initial mediocre/ poor prediction is genuine. The subsequent “adjusted predictions” are not definitive predictions by any scientific definition. At best, these pseudo-predictions and are highly massaged retrodictions, which have far less scientific credibility.

    And that’s the truth of pseudo-predictions in the pseudo-science era.

    1. “And that’s the truth of pseudo-predictions in the pseudo-science era”. I am an outsider but even I get upset by this kind of assertions. In science, people also learn from trials and errors. Why do you find that so problematic? If you think that finding a good model with a relatively small number of initial assumptions is trivial, do it better if you can! Nobody stops you. It would be much healthier than spitting on other people’s work.

      1. I am not rejecting model-building as a tool of science.
        Sometimes we need this tool to make progress.
        I am condemning the treatment of model-building retrodictions as if they were definitive predictions. There is a very important distinction here.
        Definitive predictions and testing define the scientific method.
        Model-building runs the risk of descent into the Ptolemaic method, i.e., keep adding epicycles until the model fits the data, and never consider alternative approaches.

        1. I feel that some of what you say is right. Namely we may be in a time when science is adding epicycles. However I think it is unrealistic of you to expect otherwise. If you read: ‘The Structure of Scientific Revolutions’, you will find that ‘adding epicycles’ is part of Normal Science. What would you suggest as an alternative? A hodgepodge of theories where no one gains ascendance over the others? Or perhaps (and as hard as this is, please don’t take this personally) only yours does?

          There are many theories out there, only a few are recognized as keepers by mainstream science. Those theories like Special & General Relativity, Quantum theory form the pillars of modern physics.

          Now it is possible that dark matter, dark energy, and now inflation are telling us that something is very wrong with General Relativity (GR). However, 1) until an EXPERIMENT blows a decisive hole in GR, or 2) until the 21st Century’s Einstein comes along with a wonderful theory that neatly explains all these things or more likely (1) and then (2) you should not expect anything but epicycles.

          1. As I see things the issues of the hypotheses of dark energy, dark matter and inflation stand separately from general relativity. GR is rather simple and strong at its core like a sturdy dinning table. The plates being placed on that table may or may not be edible.

  20. The polarization of the CMB is further evidence our Universe spins about a preferred axis.

    Our Universe is a larger version of a black hole polar jet.

    It’s not the Big Bang; it’s the Big Ongoing.

    1. There are a few problems with that reasoning. Firstly there is no ‘big spiral’ in the CMB. We (apparently) see a lot of small ‘spirals’ at various points in the sky but not ‘universal spiral’. (If it were present we should have easily detected it by now.) Secondly if the universe were spinning (That is the space within it were moving in such a way.) then it would have a far greater effect on the CMB’s temperature then we see.

      There are of course many theories that postulate a universe of infinite age, you may wish to look into ‘eternal inflation’.

  21. To Matt. /Kudzu ?? :
    Are you saying now that what you said before about a small patch of extended expance of space started to inflate is no longer represent but a pre-speculation status ? Or Not even wrong status ?

    1. I am not Matt, he answers far better than I could ever hope to.

      At the present time we do not know anything about the pre-inflation universe. We do not know if the entire universe inflated or a small patch of it or whether those questions even make sense. Theories about that time are speculative and may not be confirmed for a long time, but should still be considered scientific.

      1. A little better, but I would say our ignorance extends up until the generation of the CMB. After that we have enough empirical evidence to produce something more than just-so stories.

  22. I would like to understand more about how information about the structure of the early universe can be gleaned from the CMB
    How can physicists tell from a bunch of microwave noise that its constituent photons originate from some particular place and time?
    I am guessing that you could detect something like red-shifted atomic spectra and deduce an age.:
    -> a redshift implies a speed (Doppler effect), a speed implies a distance (Hubbles’ law), and a distance implies an age (speed of light)
    So I imagine you would need to start by finding a signal in the noise which matches e.g. “red-shifted hydrogen atom spectrum”. but given the amount of rubbish that must e floating around out there I’m surprised that any such signal is still detectable

    1. I probably have a so many questions I should spend a week writing them down and structuring them somehow…

      Is the dark energy during inflation the same kind of balancing act as now; with bosons adding their mass^4 and fermions removing theirs? Why didn’t we have a huge jump in some direction when the Higgs field switched on and gave masses to particles that were massless before?

      If the energy density at the end of inflation was roughly that of GUT symmetry breaking, shouldn’t stuff that generically happens in GUTs like magnetic monopoles have been created then, rather than at the start of inflation so they had time to get diluted? Or did inflation start at GUT symmetry breaking and remain constant until… what exactly happened? A bunch of particles were created to even out the cosmological constant but they aren’t related to either GUT or electroweak symmetry breaking?

      Also; unitless constants at low energies like the fine structure constant aren’t expected to have a simple explanation, but how about the ratio of Planck scale to inflaton scale? Are there inflation scenarios that give an exact number?

      1. There is no ‘balancing act’ in the universe now; dark energy is in fact not at all balanced by the matter and radiation in our universe, which is why its expansion is accelerating. Likewise during inflation is massively overwhelmed anything in the early universe, the entirely of all the matter and radiation in our universe now is believed to have been created from dark energy at the end of inflation. Interestingly the Higgs field *did* change the pressure dynamics of the universe since it converted ‘radiation-like’ massless particles into ‘matter like’ massive ones, though the details are rather complex.

        We are still not entirely sure as to how much energy was available at the end of inflation (though we now have a surprisingly high upper bound.) And our understanding of GUT-like phenomena is still very incomplete. It is quite possible that all sorts of high energy phenomena, from magnetic monopoles to cosmic strings were created in the early universe and we are working on their detection and theories.

          1. Okay, forget that I tried to respond to you up thread. You are clearly trolling, and doesn’t belong here.

    2. @Pat Ryan: All of this is based on multipole, spherical harmonics analysis, together with some Fourier analysis of the microwave spectra.Technical articles are available on web if you search in google.

    3. @Pat Ryan: All of this is based on multipole, spherical harmonics analysis, together with some Fourier analysis of the microwave spectra.Technical articles are available on web if you search in google. Sorry. This reply appeared at a different place at first.

  23. Matt makes a statement that at high temperatures quarks and gluons were free. I thought that the requirement was that both temperate and density were high. The density required being high enough that any given quark interacts through gluons to multiple other quarks, each of which interacts to yet more of them, like the interactions of atoms in a liquid. Comment?

    1. @Doug McDonald: The fact that quarks and gluons are free at high temp (high energy) has nothing to do with density. This is called asymptotic freedom i.e coupling constant which determines interaction goes to zero at high enough energy. You may want to google for “asymptotic freedom”

      1. I thought I understood asymptotic freedom. But I didn’t realize that
        it permitted free electric charges of 1/3 or 2/3, also free color charges.

        I took the word “free” to mean “unconfined”. Is he (Strassler)
        using the work “free” to mean “asymptotically free”? I took it
        to mean unconfined (i.e. not in color singlets).

        1. @ Doug McDonald: I believe, at these energies, the two words, free and unconfined may mean same, with no coupling between them. The moment there is coupling, they appear in the form of hadrons (protons ,neutrons etc). So no one has seen free quarks or gluons. Even in high energy experiments, the evidence for quarks and gluons is in the form of jets of large number of hadrons moving in close directions or heavy quarks decaying into known particles. No one has seen any fractional charge.

  24. What about the temperature of the Higgs field? After correcting the CMB for the Higgs structure’s temperature there is little CMB left for the “big bang.” And the polarization patterns also disappear.

    1. How so? I can’t say I have heard of this. Are you talking about the current ‘temperature’ of the Higgs field or something tod o with the early universe? Do you have links to anything that discusses this?

  25. Inflation is a problem not needed in a non-expanding infinite universe. But due to historical cultural preferences for a beginning, cosmology has taken the road down a path that is consonant with creationism, and now it is very difficult to climb out and away from where that road led acedemia. I’m sorry if those of you in academia strongly disagree, but that’s how my decades of study has led me to see things in current western cosmology. Our flat, homogenous (at aprox. 300 million light year scale) isotropic universe as observed, best fits a non-expanding infinite cosmology just as Hubble went to his grave prefering.

    1. That is an interesting viewpoint, do you have any explanation for the fact that galaxies largely appear to be moving away from us or the origin of matter? Something must be inserting new useable energy into the universe or everything would have run down by now. I would be interested indeed in a proper steady state theory.

      1. Galaxies do not appear to be moving away from us. They are inferred to be moving away (all but some in our local group) due to the interpretation that the cosmological redshift is essentially Doppler-like. Neither Edwin Hubble nor I favor that interpretation. There is a redshift that is accounted for by Doppler effects. Yet, their is another component in cosmology that causes a redshift. There are many tired-light theories, but they haven’t been given much attention by academia due, I think, to the entrenchment with the standard creation paradigm.

        1. could you comment on this please ?


          By the 1990s and on into the twenty-first century, a number of falsifying observations have shown that “tired light” hypotheses are not viable explanations for cosmological redshifts.[2] For example, in a static universe with tired light mechanisms, the surface brightness of stars and galaxies should be constant, that is, the farther an object is, the less light we receive, but its apparent area diminishes as well, so the light received divided by the apparent area should be constant.

      2. An infinite non-expanding universe wouldn’t “run down.” Gravity is the negation of increasing entropy. The only problem I haven’t yet figured out is how matter-energy is recycled from black holes.

        Matter-energy doesn’t need a causal explanation.

      1. Please be specific and pick one point. But generally I don’t have any theories. I mostly just point out the flaws in what many have mis-learned. Science is like that. It is not about beliefs, unless they are really well grounded in physical tests and very solid interpretations.

  26. Matt: a nice read. But I wasn’t sure where inflation fits. I was looking out for that because I’m thinking there are some big issues with inflation. Like it’s a solution to a problem that never really existed.

  27. “As the temperature cooled, we can calculate (now that we know the Higgs particle’s mass, and if we assume there aren’t any lightweight particles that we don’t know about) that first the Higgs field would have turned “on”..” Could you explain how and why “Higgs field” can turn on as the temperature cools? Why is the kinetic energy of a particle(s) (or the temperature) is related to if they acquire mass via Higgs field or not?

    1. The Higgs field ‘turns on’ because being ‘on’ takes less energy than being ‘off’. This is the opposite of most fields which take less energy to be ‘off’ As such in the early universe there was enough energy to keep the Higgs field’s value at any desired level. But at a certain point there was no longer enough energy to do so and it settled into its current universally high value.

      The same thing happened to other fields except their preferred value is nothing. It is possible to reverse these transitions, at least for a short time, by pumping a lot of energy into a small volume of space. This is how we hope to learn a lot about the early universe.

      1. Do you have a Higgs field meter with which you measure whether its on or off?

        Is any of your story scientifically testable, or is this just theoretical hand-waving?

        1. Indeed we do, do not forget that the Higgs field gives many particles their mass as well as being responsible for electroweak symmetry breaking. The standard model of which the Higgs mechanism is a part has been fantastically (some would say infuriatingly) successful. We even have a precise value for the Higgs vev of 246Gev. Discerning this value is not quite as simple as pushing a button on some detector and Matt is better qualified to give you the details but suffice to say we’re very confident that it’s ‘on’.

          1. I do not feel the slightest scientific compulsion to regard the Higgs mechanism as anything but a Ptolemaic just-so story.

          2. @RLO: Except of course that LHC _did_ find a Higgs with the expected prioperties (so far). So the mechanism is considered more or less acceptable right now.

      2. “The Higgs field ‘turns on’ because being ‘on’ takes less energy than being ‘off’. This is the opposite of most fields which take less energy to be ‘off’” -> If this is the case, could you explain why Higgs field has this property or behaves this way while the other fields do not? Why/how Higgs field gives mass to (interact with) only certain elementary particles (electron, quark, neutrino etc.) but not to the others(photon, gluon etc.) at current relatively low temperature? What is the mechanism?

  28. Lest there be any confusion about what I am proposing, the object that is hypothesized to undergo the putativeType-II supernova Bang would be a Metagalactic Scale B star with an initial radius on the order of 10^47 cm.
    The observable universe would be an infinitessimal region deep within the interior of this event.

  29. Could anyone offer empirical evidence that would falsify the idea that virtually infinitesimal regions in the deep interior of a Type-II supernova event undergo space-time EXPANSION.

    Given our lack of understanding of supernova events, I do not think the idea cited above can be falsified at present.

    Dr. David Arnett, who has developed one of the newest and most sophisticated SN models says of its inability to reproduce all observed phenomena: “Perhaps what we need is a more sophisticated notion of what an explosion is to explain what we are seeing.”

    Are we missing an important alternative to the standard cosmological paradigm simply because it conflicts with the standard cosmological liturgy?

    1. Develop an SN model that includes space-time expansion, and see if it matches the data better. “Our current models aren’t perfect… space-time expansion?” is just a stab in the dark until it’s shown that it actually helps explain supernovas.

      Calling the ideas that currently have the most evidence behind them a “liturgy” does nothing to help your case. It shows more of a desire to win a debate through narrative framing than to discover reality through science.

      1. I think the word liturgy quite accurately describes the situation in some areas of cosmology and particle physics where just-so stories are substituted for evidence-based understanding because there is just not a lot of empirical evidence to guide us.

        The problem then, as de Vaucouleurs so aptly put it, is that the dogged repetition of the just-so story transforms it into “common sense” or “how we should think” or “the best science”, or worst: “the only scientific way to see things”.

        The initiates gradually become evermore closed-minded to alternative paradigms. It is they who insist on winning the debate because their liturgy is the only possible liturgy that makes sense to them. Alternative ideas are anathema.

        And feel free to come out from behind the “anon” and into the open.

        1. I don’t personally see this as much of a problem with things like the standard model. Most physicists are deeply troubled by the fact that there are various parameters that ‘just are’ in various models. Notably the Higgs mechanism doesn’t ‘solve’ the problem of the various masses of particles but merely replaces the question of why asses differ with why the interactions of various particles with the Higgs field differ.

          This is why so many look for ‘new physics’ beyond the various models we have so far. It is why we look for supersymmetry and evidence that the Higgs is not the simplest standard model variant. It is why we have pursued string theory for so long; our current models work well, annoyingly well in fact and many feel progress will only be made if we can find something that makes them break down. But alternatives are hard to come by.

        2. Liturgy… Liturgy… Liturgy… Mainstream cosmology is liturgy… Particle physics is liturgy…

          You do seem to repeat that a lot. It must bring you great comfort. Almost like a…

  30. The key word here is TEMPERATURE. What are the microscopic elements of the vacuum that give rise to the macroscopic phenomenon of temperature?If we identify these elements then the problem of quantum gravity is as good as solved.I think Verlinde is onto something with his work on the origins of gravity.

  31. Robo
    Whatever temperature it happened to be beforehand, during the expansion the energy is dispersed across the greater volume thus dropping the temperature. Much like when you spray a can of deodorant , it feels cold to you because of the gas expansion.

  32. When you build a house, you always begin with foundations… This is the major problem of physics… That’s why imagination is necessary.
    Nice work!

  33. Maybe a stupid question, but in reference to the “red zone” in the chart at the top, how could we infer that it was extremely cold? Since everything is speculative about that era, wouldn’t the temperature be also?

    1. The temperature IS speculative but it is firmly tied to the speculation of inflation; since space is expanding incredibly rapidly anything in it (Any energy and ‘heat’) is diluted to nothing so the space is at a temperature near absolute zero. Thus this is only true if inflation is true and happens the way we think it did. If we live in an ekpyrotic universe for example there is no inflation and thus no time of extreme cold.

  34. “As the temperature cooled, we can calculate (now that we know the Higgs particle’s mass, and if we assume there aren’t any lightweight particles that we don’t know about) that first the Higgs field would have turned “on”, …”

    ” …turned on …” What does “on” mean and was it created by quantum fluctuations? By that I mean was there (Higgs and/or gravitational field) fundamental resonance when the “universe” was a certain size and density?

    Is the universe a spherical spring, an expanding and contracting shell?

    1. ‘On’ in this case is its vev going from 0 everywhere to its current value. This wasn’t a random process initiated by some quantum spark but rather a simple result of the fact that having the Higgs vev at 0 takes more energy. When the universe was no longer hot enough to keep the Higgs vev at 0 it settled into its current value. If you were to energize a volume of space enough the Higgs vev there could be made to go back to, at least for a short time.

  35. I like this article a lot. It shows clearly a decreasing confidence in our knowledge as we move back in time. Let me quote an inflation theory from John Preskill’s “Inflation on the back of an envelope”

    “… a nearly homogeneous scalar field called the inflaton (denoted by ϕ) filled the very early universe. The value of ϕ varied with time, as determined by a potential function V(ϕ). The inflaton rolled slowly for a while, while the dark energy stored in V(ϕ) caused the universe to expand exponentially.”

    Of course, mathematically there is much more to it, but favorite fairy tales of my young years started in the same spirit.

    1. Very cute, I like it:

      “Of course, mathematically there is much more to it, but favorite fairy tales of my young years started in the same spirit.”

      But let us not forget, in 1919 Eddington had fewer than BICEP2’s 4 data points when he confirmed GR – and THAT also made the front pages.

      1. James – the “proofs” that we see are increasingly indirect. Nothing wrong about it; direct measurements have mostly been done decades ago. But an inflaton, dark energy, and dark matter are not GR constructs – we postulate them in addition to GR to make sense of observations after postulating the Big Bang. I am not very happy having to postulate four different things. Nice that two postulates support each other, though.

  36. IMO it’s time to return to tired light model represented with analogy with scattering of ripples at the water surface. The older tired light models considered, that the light was scattered with tiny but stable particles, whereas we know today, that the light would be scattered with quantum density fluctuations of vacuum, which manifest itself with CMBR photons with 2-spin component, which are temporal but larger than the wavelenght of visible light in general Such an emergent scattering would lead in formal agreement with inflation and Big Bang scenario and it doesn’t suffer with various paradoxes, which are common for Big Bang cosmology.

    1. Tired light is an interesting possibility which could oppose the accelerating expanding universe even into an contracting universe into a big crunch! so;We should postulate, that the Big bang was the splitting and evaporation of the big crunch black hole into what I call a black hole splitting fractal inflation creating the Lyman Alpha tree structure. What we observe in the B-Modes of the BICEPS 2 image should be the END of the Fractal splitting black hole inflation process at the rim of our own Universe.

  37. Matt is right to spell out the zones of confidence and speculation. Regarding the green zone of high confidence, I would suggest some caution for more reasons than the statement below.

    The following is one of three paragraphs of the physicist Anthony Peratt, in reply to some critics of his article “Not With a Bang.” This excerpt below appeared in The Sciences July/August 1990, page 12:

    Ralph Alpher and Robert Herman attempt to perpetuate the twofold myth that only Big Bang advocates (themselves) predicted the cosmic microwave background and that only the Big Bang produces a blackbody microwave background. In fact, the discovery of the microwave background might have come as early as 1940, when the astronomer Andrew McKellar interpreted a 2.3-degree-Kelvin temperature for interstellar molecules; according to the pioneering radio astronomer Grote Reber, however, the cosmologists of that period were not interested in microwaves. In 1953 Erwin Finlay-Freundlich, a critic of the big bang, calculated a blackbody temperature for the universe of 2.3 degrees Kelvin, within 16 percent of COBE’s 1990 measurement. In the same year the Noble laureate Max Born, another big bang critic, verified Finlay-Freundlich’s prediction and suggested radio astronomy measurements at fifteen centimeters–precisely the wavelength at which data were obtained little more than a decade later.

  38. The only reliable portion of theory is this one, which we already understand both from formal perspective (i.e. we already have a reliable mathematical regression verified with experiments), both from intuitive perspective of physical analogies. The epicycle model failure teaches us, just the formal agreement with data is not enough, no matter how good such an agreement can be.

    From this perspective the whole Big Bang theory still holds water, because the mainstream physics has absolutely no idea, why the Universe should explode, why this explosion should suddenly stop for to continue with another explosion (inflation) in another moment, which subsequently stopped again and it has been replaced with accelerated expansion of Universe. The proposal and explanation of such a scenario actually really requires a pretty huge physical fantasy.

  39. Reblogged this on Patrice Ayme's Thoughts and commented:
    I long held that there was no proof whatsoever that the universe was 13.7 billion year old, as all too many Big Bang theorists have long claimed, right and left, and all over the Main Stream Media They have exclusive access to.
    Now I am happy to report that a main stream physicist, the very honorable professor Matt Strassler supports this point of view in an excellent article:
    Professor Strassler’s broad reasoning is exactly the one I long put forward: the equations and the experimental date we have break down at very high energies, so we cannot use them to extrapolate at such energies (something similar happens with gravitation: we have no proof it holds beyond the Solar System… and some hints that it does not).
    To be doubtful about the simplistic Big Bang model holds, even in light of the interpretation of the latest data, which supposedly shows gravitational wave ripples consecutive to cosmic inflation. Yet, as professor Strassler says: “BICEP2 can really only tell us about the late stage and exit from inflation”.
    I guess I will have to get more subtle with my own, much older “Universe: 100-billion years old?” . I proceeded to thank professor Strassler:
    “In any case, thank you for this detailed analysis on how certain we are of the various elements of the concept of Big Bang. This is the sort of subtlety that needs to be taught to the public: that there are degrees of certainty in science. And even on physics.
    By preaching the Big Bang as if it were a religion, as many scientists have done in popular shows (latest on “Cosmos”, complete with multiverse, presented as part of our “address”!) one did a disservice to science, or even to reason itself… And there could be a backlash, if the public discovers that they were lied to. So the earlier the subtleties are taught, the better.”
    Unfortunately, the great professor Strassler then removed by comment from his own blog (scientists’ ways are exclusive, and do not have to do with the scientific process). In any case, here is professor Strassler’s excellent post, which demonstrates, in fascinating detail, the broad point I made previously:

    1. Patrice Ame:
      It seemed clear to me the start of the Hot Big Bang epoch could be estimated to within ~1 second — see the timeline in the Green part of the diagram.

      It’s the “before Inflation” epoch that doesn’t have any theory or data to back it up.

      So when you opine the universe may be “100 billion yrs old”, how are _you_ defining “age of universe”?

      And if you have some equations or theory to support this, maybe you should publish it at Arxiv or something ….

      1. TomH: I have a problem with time. At this point I distinguish two notions of time, one of which I called holonomic time, because it’s locally, but not punctually, defined. I can’t see how holonomic time could be defined during inflation, let alone being equal to punctual time (normal space-time physics makes no distinction between two different of time). Thus that “second” could well last an eternity.
        I will put more details on my site.

    2. No evidence our equations of gravity work outside the solar system? Are you mad? Don’t answer that. Instead, please follow the proper path for overturning the mainstream cosmology:
      1) Understand the existing theories and evidence behind them
      2) Revolutionize physics.
      No skipping steps!

      1. Anon: OK, let’s apply your own recommendations, to… you. You have been skipping steps from the raw evidence.So learn this:

        1) the rotation curves of galaxies do not work. Galaxies do not rotate according to the 17 C gravitation theory (attributed by Isaac Newton to a Frenchman, let it be said in passing). This is “explained” by, and “evidence” for, Dark Matter.

        2) Strictly speaking the same situation is true for galactic clusters. That, again, is “explained” by Dark Matter.

        3) I will not insult you by mentioning Dark Energy, a significant complication you probably heard of.

        Let’s forget for an instant the added hypothesis of “Dark Matter”. Strictly speaking, in first approximation, the fact is, that, the direct experimental evidence is: gravity according to 1/dd, does not work outside the SS.

        Dark Matter is just an interpretation of the raw data, to save 1/dd. (BTW, I am ready to believe in DM, because, you guessed it, I have an implausible explanation… completely outside of the SM, or any SUSY…).

        I understand that, the way I put it, I am violating cosmological Newton, thus cosmological “General Relativity”, and that there is solid evidence for both in the Solar System, and that the instinct of physicists is to extrapolate known laws. But the whole spirit of denouncing, as professor Strassler just did, the red zone non sense, is to point out that the general method of extrapolating known laws works only so far.

        1. I’m familiar with the issue of galaxy rotation, thanks, but that’s not what you said. You said there was no evidence our theory of gravity worked “outside the solar system”, which is utter nonsense. The number of observations of phenomenon outside the solar system that are in precise accordance with General Relativity are multitudinous, including predictions of energy lost through gravitational radiation. Your statement was ridiculously out of touch with the observational status of GR.

          I could go on and on about how the evidence supports the idea that General Relativity is correct and that there is unseen mass, far better than it supports the idea that GR is incorrect. While hardly settled, it’s hardly up in the air as anyone’s game either. Certainly the statement that there is no evidence that gravity works at those scales is false. But far more important is to clear up this nonsense about their not being evidence that it works anywhere outside the solar system.

          1. Anon: We can use only so many words: check the Incompleteness Theorems in mathematical logic. If you decide to make a ridiculous over-interpretation of what I said, I feel sorry for you, and beg forgiveness. I know about rotating neutron stars and the support they provide for gravitational waves (a necessary sub-logic of GR that I am very comfortable with).

          2. Yes, how ridiculous of me to interpret “outside the solar system” to mean “outside the solar system”. And using Godel to justify your inability to express yourself clearly, that’s definitely not ridiculous.

            I guess it would also be a ridiculous over-interpretation to take “no proof” to mean “no proof”. I’ll assume you also know that in addition to galaxy rotation curves, galaxy cluster behavior including collisions, there’s also the power scale of the large-scale structure of the universe and the CMBR all of which GR+DM explains very well with the same DM fraction, and which alternative gravity theories do terribly at. I’ll assume what you meant to say was “There’s actually lots of evidence (not proof because this isn’t math) that GR works at the relevant scales, but I feel there’s enough wiggle room for some future alternate gravity theory to possibly explain these things better even though none have come close yet.”

            Fair enough!

  40. What does “the Higgs Field turns on” signify? Is it the point at which it assumes a non-zero average value, or does it mean ‘comes into existence?’

    In general, how do quantum fields arise initially? Can they exist without “real” particles’, and without quantum fluctuations? The description of the inflaton field made it sound like it may exist with few (no?) particles. (From your post on inflation: “dark energy (really a combination of energy and negative pressure) is never associated with particles. . . . Basically, the dark energy is stored in a field (the inflaton) and at the end of inflation the inflaton field starts oscillating, becoming rapidly larger and smaller by turns. . . . This is like having something like a laser made from inflaton particles. The inflaton particles, however, have a large mass and are unstable. They will decay into other particles, which may in turn decay into yet others.”)

    Could you please clarify this for me?


    1. The Higgs field exists from ‘the start’, like all fields in nature. They are in a way intrinsic to space in our universe. When the Higgs field ‘turns on’ its vev changes from zero (like most fields) to its current value. (An odd situation indeed.)

      Fields can indeed exist without particles in the same way air (a sound field) can exist without any noise in it. As to how they arise, that is similar to asking how space starts.

      The inflaton field doesn’t have any particles worth mentioning (If it had any in it they would quickly be diluted to nothing.) When it ‘flips’ there is something particlish (How much so is up for debate.) before its energy is converted to more usual particles.

      1. @Kudzu

        Thanks for that. You’ve answered the question that was really behind my original question: Are all the fields described in quantum theory present before the hot big bang (i.e., during the inflationary period), or do they come into existence later.

      2. Kudzu, air is a field of particles that can transmit sound, which are compressions and ratifications of the field particles.

        In my mind, fields are always full of particulate entities that have mass.

          1. While there are numerous problems with the idea the biggest problem is the most obvious; had I been Matt I would have seen it instantly, but I am not that smart. On further thinking problem 3 becomes more meta. If fields are composed of massive particles then what we call particles currently…aren’t particles. There would be no photons only ‘light field particles’; no protons, only ‘proton field particles’ If this is so… what IS a particle? It can’t be a wave in a field because that would lead to an infinite stack of more fundamental ‘field particles’

            So the question I must ask is ‘What ARE the massive particles that make up your fields’? They must ‘really’ be something different from what we call particles ordinarily, they must behave in a different way or arise from a different mechanism.

        1. There are some problems with that idea and indeed realizing that there were fields that were not made of particles was a big discovery in science. (You may recall that light was believed to move through a field of ‘ether’ at the dawn of the century.)

          The first problem is the mass of these particles; when you have any other mass in the field (say a lump of rock or earth) it starts attracting and compressing the field. Air for example is denser at sea level than near space. Massive particle fields that permeate the universe would thus feed things like black holes or even ordinary stars with incredible amounts of mass.

          Secondly a particulate field by its very construction has places where it ‘runs out’; there is no air in space, no ocean above sea level. Yet we have not seen any evidence of places where say light or gravity can’t go because there are no ‘field particles’ there.

          Thirdly if a field is made of particles then we should be able to detect them in the way we can detect air molecules. Fourthly a field of massive particles alters how waves move through it, we would see light speed change depending on how we move through that field. There are about a dozen other problems.

          The concept of a field almost as a part of space, not being composed of a particulate substance being ‘smooth’ and continuous and throughout all space is a tricky one sometimes to grasp but was a great advance to science,

          1. Kudzu, I’m not sure that the problems you list are significant.

            Problem 1, Attraction and Compression: Why is this a problem? The field in space is dilute. Maybe the compression can be the explanation for the “gravitational” bending of light, with more bending the closer to the large mass? Feeding stars and black holes with dilute field particles? I’m not seeing that as a problem. Stars may be generators of field particles.

            P2, Field running out: I don’t know under what circumstance such particulate mass fields should run out. Neutrinos don’t run out as far as I know. I’m not saying that neutrinos might be a field source for electromagnetic field effects, but if they have mass and can be everywhere then I don’t see a problem here.

            P3, Detecting field particles: Inferred by the way light behaves just as we infer many things in particle physics.

            P4, Light speed change depending on how we move through field: Are we referring to the Michelson–Morley experiment or the Doppler effect? The null result of the M-M experiment can be explained by the earth dragging the local field along. The Doppler effect can be explained the same way and thus light from the edge of a galaxy that is rotating toward us is blue shifted relative to the opposite edge that is moving away from us. Yes, that implies that light moves toward us somewhat faster from the blue shifted side and somewhat slower from the redshifted side. If we are able to measure that light in our earth-bound equipment we would measure it as moving at the normal speed of light because the local nearby field that it interacts with first would interfere with the raw original speed, i.e., we detect the wavelength energy shift but not any difference in speed because after the local field interactions which include our atmosphere, windows, lenses, other equipment, etc. the light leaves these things at the normal velocity relative to us.

            What are the other objections to a particulate field in space that has mass?

          2. What I should rather have said in my reply to Problem 1 is that maybe the attraction and compression of field mass particles can be an explanation for the excess bending of light as in a possible role in explaining why astronomers think there is unseen dark matter.

          3. Kudzu, this reply is to your statement of March 31, 2014 at 7:14 AM,

            I don’t follow your reply. Logically it is like saying the particles of air or water aren’t particles. Air and water transmit sound but sound isn’t transmitted without particles. It seems many in physics want to say that light is not a massive particle, or a collection of particles, (or the result of a collection of relatively moving particles?) and doesn’t need a field of particles to be transmitted. I could grant that photons may only be a disturbance of a field that has massive particles such as a vacuum field of electron-positrons, but at least there is something with mass involved.

            The following paragraph is from http://en.wikipedia.org/wiki/Vacuum_state:

            “Photon-photon interaction can occur only through interaction with the vacuum state of some other field, for example through the Dirac electron-positron vacuum field; this is associated with the concept of vacuum polarization. — Jauch, J.M., Rohrlich, F. (1955/1980). The Theory of Photons and Electrons. The Relativistic Quantum Field Theory of Charged Particles with Spin One-half, second expanded edition, Springer-Verlag, New York, ISBN 0–387–07295–0, pages 287–288.”

            Kudzu, for me this is analogous to a room of air molecules where we are not attuned well to hearing the background fluctuations because we are normally hearing things that are much louder. In this analog a photon is like a sound pulse in a material field (for light–of electron and positrons?). Light then has wave and interference patterns in the same way as sound in air and water.

            In my epistemology, my theory of knowledge, a source of energy must have to do with particles that possess inertia natively, without any cause, and occupies space to the exclusion of other particles. Otherwise, nothing can make sense. To me it is best to try to understand nature from that starting point. No one, regardless of your personal epistemology, can know everything about how the universe works. We just are not the kind of animals that have the intellectual facilities and life-span for that, but we have come very far.

  41. Hi prof Matt
    You says about 380,000 years, but if we know that our time reference were created in earth’s translation bases, how to say something about a very far past before this existence? Is it correct that observation calculus? Is there any other reference? How can we talk about billion years before earth’s existence?

    1. The physical laws that we use to make sense of our measurements originated at least early on in our universe. As such we can use these to determine earlier times. As an example, we know light travels at a constant speed and gets dimmer the further from a source an observer is. S things far away are dimmer and take longer to see. We can see light from some objects that we can calculate was emitted before the earth was formed and that therefore the universe has to be at least old enough for those objects to exist.

      If the laws of the universe were so impermanent as to change during the time we were here the universe would be a very strange place indeed, and likely too inhospitable for life or even planets to form.

      1. Thanks, but I think that you dont had assimilated my question: You talk about constant speed and this is my exactly question about. How can you says about a “constant” term? It is clear that in those moment, light speed was impossible to had the same proprieties like now. If you says yes, how you can fundament it? If not, our calculus about everything at that moment (1/10³³ sec or less) are no fundamented

        1. Right. So your question then boils down to ‘how do we know the universe now works like it did before we were here?’

          Basically it’s very hard for it NOT to. Things of course change; the universe is hotter and smaller going back for example, but even then usually in a smooth and predictable manner. And many fundamental things upon which we base our calculations are very hard to tweak.

          Take the speed of light. You might well say ‘What if it moved faster a billion years ago?’ But the speed of light isn’t just a lone fact; it affects many things, the size and energy levels of atoms, doppler shifts, the very stability of matter. Any change would be ridiculously easy to detect, the universe’s basic structure would have been messed with, planets might not form, or stars, or life.

          In fact scientists have been looking, all the time, for things like you suggest. Recently the ‘fine structure constant’ has been checked and found to be quite well… constant. As for ‘1/10³³ ‘, we *don’t* know what happened then, we have some nice guesses but anything before a few seconds past the HBB scientists are busy asking your question.

          So far yes, it’s always possible that we are deceived and that somehow the universe didn’t work the way we think ‘back then’; but we have no evidence it until a few seconds after the HBB and no reason to expect it to.

    2. What, pray tell, are you talking about?

      For instance, what does ”earth’s translation bases” refer to?

      Are you aware that the statement/potential question ”Is it correct that observation calculus?” makes no sense? It is not a complete sentence. Neither is it a complete thought.

      Finally the question, ”How can we talk about billion years before earth’s existence?” We can easily look into the sky and see things that are billions of years older than the duration of the Earth’s existence, and it’s not a problem to talk about them, so . . . What are you asking?

      1. @Michael, I don’t know if Edward is a “crackpot” or just someone with less than perfect English, sincerely trying to understand what we know about the history of the Universe. Giving him the benefit of the doubt, my guess is that he was asking the following. If we define a year as the time it takes for the Earth to make one trip around the Sun (”earth’s translation bases”?), then what does it mean to talk about so and so many years, before there was an Earth or even Sun? It is actually a pretty insightful question. Fortunately there is a pretty straightforward answer. Yes, if we are to speak of time measurements spanning the vast history of the universe, we need to use a time standard that also spans that whole period. Well, we know light existed very near the beginning of the Universe and we know a lot about how light vibrates. For instance, the specific light from a specific excited state of Hydrogen will vibrate at a very specific number of times per second. Thus we can define a second based on light from Hydrogen and we can define a year as being a specific number of seconds. Now our definition of a year no longer depends on the Earth revolving around the Sun. I am not an astrophysicist or cosmologist, so I don’t know exactly how they define their time units, but you get the idea of how the measurement of time does not need to be in reference to Earth any more. I hope that helps. (P.S. Kudos to Kudzu for also trying to help.)

        1. @ Steve Donaldson:
          I don’t know if Edward is a *crackpot* either, however, I didn’t call him one. Careful reading above will show that a contributor with the stated name of “Notacrackpot” was the entity who so cavalierly spewed out this term. Not me.

    1. As you are aware all fields have a lowest energy vev. But they can have other values, it just takes more energy. We can visualize this by plotting the ‘field’ on a 2D graph (one axis real, one axis imaginary, the details are beside the point here.) and get various results. For most fields we end up with a ‘well’ centered at 0. If we add energy the value of a field can ‘climb’ the well but never leave it.

      The Higgs field however has its lowest energy point at 246Gev. This results in a ‘sombrero’ plot, like the well plot where someone has pushed up the middle. At its lowest energy the Higgs field lies in the ‘brim’ of the sombrero and again raising the energy lets it climb the walls of the sombrero.

      But for various reasons the energy at 0,0 cannot be infinite; it is a hill with a top. And as such as energy is added the Higgs field can ‘climb to the top’ of this hill and get stuck at a value of 0. Since the conditions of the early universe had sufficient energy for this, this is what we believe happened.

      1. We already are condensed matter; solids and liquids (the stuff of which we are made.) is condensed matter. Our existence now is indeed only possible because the universe now is quite cool on average.

        1. Thank you……, I mean, the Meissner effect. Below the transition temperature, a massless gauge field can aquire a mass in the presence of a coupling to a spontaneously broken field. A concrete realisation of this occurs in superconductors. This is like the photon acquires a mass.
          The universe we live is a kind of cosmological Meissner phase, formed in the early universe (vortices).
          This low-temperature expression is completely analogous to the one in the high-temperature phase for the correlation function.
          So below “0”K, there will be decrease in entropy – making a “Dark-energy star” ? – based on the physics of superfluids, avoiding a singularity. which is analogous to “blobs of liquid condensing spontaneously out of a cooling gas” ?

          1. Aaah. I see. I don’t think we will ever get below 0K (even inflation didn’t manage that.) but the phenomena you mention are interesting. I am unqualified to answer but I am sure others will speculate.

  42. There is a saying. “Imagination is the mother of invention”. I say speculation is a necessary ingredient to research, it fires the urge explore new frontiers, even in the red zone. Even if eventually proven wrong.

  43. Another very nice post Matt. Don’t know where you find the time or energy. But no mention of antimatter?! Where is all the antimatter? Isn’t that still a mystery?

    1. Well he does mention anti-quarks, anti-protons and anti-neutrons, so it’s there. But I don’t think it’s a relevant detail in this very broad brush treatment of the topic. (I do believe antimatter-matter imbalance would be sorted out far before nucleosynthesis and maybe before the Higgs field turns on, in the speculative zone.)

      1. Yes, you are right it is mentioned, but then just left hanging: “…so that quarks and gluons and antiquarks would have been trapped henceforth and forever into protons, neutrons, antiprotons and antineutrons…”

        To his credit Matt does say: “It’s not entirely impossible that there was something odd and unknown about the universe that makes some of these conclusions premature.”

        However I disagree with your notion that this is an irrelevant detail here. I think, and I know I’m not alone in this, that it is one of the universes greatest unsolved mysteries, so shouldn’t it at least be noted as such?

        So I say again: Where is all the antimatter?

        (And anyone replying to this post – Please don’t offer the standard ‘explanation’ concerning differing decay rates. I know all about it – those rates are woefully inadequate, by many orders of magnitude, to produce the matter dominated universe. So save it – I’m looking for a more creative solution).

        1. I agree with you that this is indeed a big mystery and worth an entire post of its own (maybe several.) but I can see why it was not much commented upon; even in the ‘green zone’ there are many things we don’t know well if at all. Dark matter too is given a wide berth and I’m sure some astronomers here would have liked a mention of star and galaxy formation. There’s a lot to cover and it may have been simple oversight or deliberate choice just to save space.

        2. @ S. Dino: The last I heard was that people have found larger CP violation in heavy quarks (b, bbar) than K meson decays. So it is not unlikely that at extremely high energies, there was a very high CP violation which would explain matter-antimatter asymmetry. But at this point nobody has pinned it down.

        3. My solution:

          There are three dimensions for the space, one for the causality and one for the duality, in total 5 dims. The duality dimension is curled and interaction spacetime cycles between matter and antimatter. We see it always as matter although there is a ticking rhythm of magnetic monopoles in elementart particles (just like Higgs mechanism) creating inertia and balancing the dynamic vacuum energy and the mass energy. The phase of the matter duality state is in coherence with a causal distance in accordance with the speed limit of c (in the same coordinate system with neutrinos – see the oscillation phase difference between neutrinos and electromagnetic fields).

          So at a proper distance matter change to antimatter in respect to the common background coordinate system – the distance could be the longest distance in the unverse or something like that.

          The idea demands a radical definition of dynamic vacuum energy and it’s possible we have two nested net structures: one for matter and other for antimatter both interacting with light in a same way so that we cannot see any diffences getting radiation from galaxy or from antigalaxy. The potential relation to the local vacuum energy field has the same value and the same math in respect to the excited states of particles. Light propagates via both of duality dimensions phase, particles are divided to prpagate either via matter-phase or via antimatter-phase.

          If you got some reasonable thoughts, good – if not, it’s not very odd, I’m in trouble to be understood even in my own native language…

  44. In my lifetime I have seen the age of the universe revised several times. Even Hubble finally realised that the age he had arrived at through observation had to be wrong as evidence appeared that the earth was older than it. Now I accept that’s the way science works, more measurements are made and results improved. Are we so sure on the current age as most people seem to be or is there something yet to be discovered that will jump up and bite us in the ass.

    1. For what it’s worth, the estimates of the age of the universe have been converging (error bars narrowing) over the last twenty years. People now quote a third significant digit (13.8 Gy), while in the mid-90s it was more like “12-15 Gy”. (Actually, the estimate derived from the observed expansion of the universe was more like 8-15 Gy, but we knew the low end was wrong because there are old stars aged 12 Gy or more.)

      1. Yes but scientists have merely measured those parameters that they believe indicate the age of the universe more accurately. My question really is are those parameters the only ones or are we missing something.

        1. We can be quite confident that the parameters we’re measuring are them ‘right’ ones *from the start of the hot big bang* since we’re pretty much looking at *all* of the parameters we can think of. They fit nicely into our current theories and it’s very hard indeed to imagine how something may be otherwise yet still rpeserve what we know to be true.

          For example, to change the age from 13.8 to 13.9Gy we need to insert 100 million years into the universe somewhere. There is little room for a ‘smooth’ insertion (Where nothing abrupt happens. Say the universe expands slightly slower than we think it does now.) because this would produce significant deviations from what we have already measured (Such as the ages of the oldest stars, galaxy structures and so on.)

          Instead it would need to be something ‘abrupt’ (Say a sudden stop in expansion followed by a bit of ‘catch up’ later.) which is rather unnatural and begs the question of what mechanism could be responsible. Nothing is ever ruled out in science but it seems quite unlikely that our current estimate is significantly wrong.

  45. A question about “times” and “durations” in the very early universe.

    Presumably a very dense universe would have extraordinarily high gravitational fields, which would lead to extreme time dilation effects.

    So when we say some epoch lasted 1 second or 1E-30 seconds, in which frame of reference? Us in the present epoch, or some imaginary observer in the early universe?

    1. We actually don’t have to worry too much about this; the HBB wasn’t particularly incredibly dense, had it been then the universes expansion would have been severely curtailed or even reversed. What is more of a problem is our simple lack of knowledge. Inflation would have involved a nearly completely empty volume of space, but we are unsure as to how long it lasted and anything before that is theoretical guesswork.

  46. Matt: When inflation was first hypothesized, and at least into the last decade, Stephen Hawking objected that it violates the general co-variance requirement of General Relativity because a specific reference frame is chosen in which one dimension of space-time becomes that along which the inflation of the other three expand. Is this now considered a serious issue?

    1. The universe expands, so inflation can happen.

      Hawking’s objection seems directed toward the speculative part of if and how inflation started.

  47. Matt: Excellent review. I have two questions: (1) during reheating after inflation did the temp go up to 10^29 K (10^16 GeV) or more?. So the quarks and leptons were produced during reheating or they were already there from inflaton field? (2) I guess most people have problem with the concept that space expansion does not require any energy. Alan Guth says it is ultimate free lunch. Also many people say in GR energy is not concerned. The problem is that nowhere else we have seen non conservation of energy, not even in quantum mechanics, except for uncertainty fluctuations. That must be the hang up. What do you think? BTW can this energy come from another universe which is collapsing?

    1. One way to think about (2): conservation laws exist because of symmetries, as first figured out by Emmy Noether (http://4gravitonsandagradstudent.wordpress.com/2013/04/19/theres-something-about-symmetry/). So the reason momentum in a line is conserved is because space is the same if you move in a straight line, but when space isn’t the same (say, because there’s a planet there) then momentum isn’t conserved, so a spaceship moving in a straight line falls towards the planet. Similarly, the conservation of energy is due to symmetry in _time_. If the universe changes over time (say, with inflation) then energy will not be conserved. That’s what people mean when they say in GR energy is not concerned: if you change the shape of space and time, you change the rules for conservation of energy.

      1. Now this is something you seem to have a greater grasp of than I do.

        So energy conservation ‘works’ only if my system is the same at one time vs another time? I assume there is something more subtle to it since *everything* is changing all the time.

        My main question to you is the CMB; these photons were originally much higher in energy but the expansion of space has ‘stretched’ them. Did the energy ‘go’ somewhere or is it simply that under these conditions the total energy in these photons will decrease?

        1. It’s not that the system needs to be the same as a whole, rather it’s the “background” that needs to be the same. If you’re looking at the Earth by itself, then it appears that energy isn’t conserved, because the Sun is changing and you’ve put the Sun outside your system. But if you include both, then energy is conserved.

          You definitely can try to include changes in space-time in your system instead of your background, and conserve energy that way. The problem is that there’s no clean way to separate which part of spacetime is background and which is the change, which is why this isn’t generally the way we think about it.

          This is why there isn’t a clean way to answer your question about the CMB. You can think of the energy as having “gone into” spacetime, or as the photons just losing energy, depending on how you frame the question.

    2. All the particles (Quarks, gluons, leptons and what have you.) are all produced *from* the inflaton field when it ‘flips off’; they appear already high energy (‘hot’), I believe as high energy as the dark energy that drives inflation or less. So ‘reheating’ is actually just particle production.

      1. @ Kudzu:Let us see what Matt says. But according to elementary physics, heat is essentially kinetic energy of the particles. So my inclination is that the particles were produced sometime during inflation and then potential energy of inflaton was converted into kinetic energy of particles. But I am not sure!

        1. The important thing to remember about particles is that they don’t have to be created with a single ;rest mass’ energy. (Otherwise massless photons would never be created!) Nearly all particles will be created moving at some speed, with some ‘heat’. Take for example beta decay radiation, electrons are emitted with any kinetic (‘heat’) energy from ‘none’ to some maximum value. (See the 5th paragraph of this article http://en.wikipedia.org/wiki/Beta_decay )

          So at the end of inflation many particles would be produced already ‘hot’ with a great deal of energy.

          1. @Kudzu: Well, yes it is possible. But I remember to have asked Matt previously a question. He did insist that inflationary expansion has to lead to cooling. No choice. That is why they call subsequent heating as REHEATING! So if particles produced were already hot they would have to cool off. Also remember, before Higgs, these were massless particles! They were moving at c all the time.

        2. No, photons most definitely do not have a rest mass. This is something that all of physics agrees on. The photoelectric effect is a result of the *energy* of a photon being given to an electron and is a good proof that light is particle-like (or quantized.)

          If photons did have a rest mass they couldn’t move at light speed and we could stop them, put them in a box and look at them.

          1. Kudzu, photons have been stopped, see:

            And a photon at rest relative to you wouldn’t be something you could detect directly; it would have to be infered.

            I’m of the school of thought that if it moves, and isn’t a shadow, it must have mass. My understanding of relativity theory does not prohibit something with mass moving at, or above, the speed of light in your reference frame. If something were accelerated beyond the speed of light away from you it would disappear from your universe. Black holes do this.

          2. Thank you Mr.Kudzu, gauge invariance is a fuzzy. Cannot grab, but make us to “feel”, dislocating ?

        3. During inflation the expansion of space both dilutes and removes the energy in the universe. This includes massless particles such as photons. Microwaves are ‘cooler’ than visible light for example.) So yes by necessity it cools the universe. The term ‘reheating’ though is perhaps not the best one to use here as it is not matter that is being reheated but the universe itself.

          You can think of the process rather like a red hot piece of metal. This is converting the kinetic energy of its atoms into photons with a range of energies. (Google ‘black body’ for details) The photons are already as ‘hot’ as the metal; as the metal cools the photons it emits have less energy (They go deeper red and eventually IR and microwave.) Notably it does not emit a single color (energy) of photon like a laser nor does it produce the ‘coldest’ photons possible (which would be infinitely cold!)

          The case of dark energy is the same; at that time most particles as you note were massless so as the energy decayed it would emit all sorts of particles each with a spectrum of energies just like a hot piece of metal. But in this case the amount of energy being converted is much greater, dark energy was very ‘hot’. (Exactly how ‘hot’ is still up for debate.)

          If this was a two step process we have not one but two problems to solve. Firstly, ‘why would the dark energy field behave differently from all other fields where similar things happen?’ and secondly ‘where does the energy come from to heat all the cold particles?’

          1. @Kudzu: Obviously there may be a number of models and lot of ambiguities. But my understanding is that reheating actually comes from the potential energy of inflaton becoming minimum and converting into kinetic energy. That part I am reasonably sure, although I could be wrong!! As an elementary example a falling ball loses P.E. and gains K.E. My main question was that at what stage inflaton materializes particles.

        4. The conversion of dark energy to other forms of energy occurred at the end of inflation. According to Professor Strassler’s article (published earlier on this site.) the inflaton field started to oscillate, in his words ‘become larger and smaller in turns’ which is equivalent to having a lot of inflaton particles. (We see similar effects if you say, take a magnet and wiggle it about near a wire. The oscillating electromagnetic field produced dumps its energy into the electrons present, making a current flow.) So it is not so much the energy becoming a minimum as the field becoming unstable.

  48. Thanks for the great post. I have a doubt: when people say that inflation happened 10^-35 seconds after the big bang, what do they mean?

  49. Matt, your articles have been so helpful in getting the beginning of a grip on what people are talking about with eternal inflation. I have a mental model now of it, derived from the very nice article by Guth you posted last time, which leads me to a question. If you don’t mind, could you tell me whether the following analogy, with two dimensions fewer than what we observe, has any validity, and whether the question at the end is well-motivated: before the birth of our observable universe we have something analogous to a rubber strip, being stretched, endlessly and very fast. At some point one tiny area of the expanding rubber strip “converts”, or phase-flips, or something like that, and is no longer the same “stuff” as the space-time foam. This tiny converted area continues to expand–into our pocket universe or one like it–but much less quickly. Outside our phase-flipped area, the rubber band continues to be stretched, unimaginably quicker than our now converted area, and from time to time other bubbles like ours will nucleate, meaning they’ll exit the hyperfast expansion and continue their own expansion at a slower rate (not necessarily identical to ours). If that is not too misleading an account of the scenario of eternal inflation, my question is: since any pocket universes are being driven apart from one another by the incessant stretching of the rubber strip faster than they are expanding themselves internally, does it follow that there can be no danger of expanding bubbles within the space-time foam eventually intersecting?

  50. You have made mention of the ‘inflation particle’. I realize in general this is just shorthand for ‘the mechanism that causes inflation’ but are there any proposed models that include such a particle and remains consistent with the Standard Model?

  51. Matt,

    I do not understand why the universe cooled after the Hot Big Bang. Energy is conserved, so where did all the heat go? Is the cooling due to the still – if only much slower – ongoing inflation of the universe? And if the inflation had stopped completely after the Hot Big Bang, would the universe still be hot today?

    1. The heat did not ‘go’ anywhere; the total amount of energy in the universe is the same now as at the HBB (Or at least we assume it is.) Three things have however happened to this energy. The first is that it has been diluted; as space expands there is more ‘room’ for a given amount of energy to occupy. The sun is very hot at its surface but if you are a billion miles away it seems colder 9though the energy of the few photons you receive is still the same.)

      The second thing is that entropy has increased. A high energy photon from the sun will hit the earth then be remitted as several lower energy photons (in the infrared\microwave spectrum.) The same total energy is there but less ‘hot’.

      Finally he expansion of space itself ‘stretches’ things moving through it like photons, taking them from a higher to lower energy. (I don’t know where that energy goes myself, but I’m told it all works out.)

      1. As some would say, “morally” the universe is zero energy. (E.g. that is what guys like Linde and Siegel@Starts With A Bang use. There are several ways to derive that, say Siegel uses potential energy of gravity = energy of everything else, so it is still a hypothesis.) The energy doesn’t go anywhere (where should it go?), it is just converted.

        As in any thermodynamic system it amounts to phase changes of internal free energy. (Like how an engine works on combustion of fuel.) E.g. the universe started out in equilibrium (very cold) as I understand it, then got matter out of the matter/antimatter symmetry breaking so the disequilibrium that enables us.

  52. I have a question about the end of inflation. I get that there’s a phase transition of some sort where the energy of the inflaton field is converted into particles. Was this process instant? that is to say, did it happen “everywhere” at the same time?

    Naively, I imagine it starting at a nucleation point and spreading out to encompass the observable patch we live in. Is that possible? Could that process leave an observable imprint?

    Alternatively, are we talking about something more like the pressure in a gas? there’s some property of the inflaton field that’s broadly the same everywhere, less quantum fluctuations, and when it reaches a critical value – bang. If that’s true, is there any reason to believe there would be regions of space outside our horizon where inflation is ongoing? That’s what I’ve understood from some of the “multiverse” models being bandied about.

    1. For clarity (I wish you could edit posts) with the gas analogy, I was visualising whatever this quantity is to be changing over time, as the universe inflates.

      1. This is actually an interesting problem. In the theory of ‘eternal inflation’ inflation stops randomly at various points in space, spreading out as a sphere at the speed of light. Since inflating space expands much faster this means that the universe ends up consisting nearly entirely of inflating space with infinitely isolated bubbles of ‘our kind’ of space appearing in it. This of course is a multiversal theory.

        Or the process could have been instantaneous across ‘all’ space or some weird hybrid. We have theories but no way to know just yet.

    2. Conversion from energy to particles was instant (revolution) everywhere or only in our patch evolved by natural selection ?
      If we look at first fig’s timeline, todays time and inflation time have same darkness of temperature. If it reaches a critical value – again bang – from mass energy to vacuum energy ?

      1. Actually the inflation era was vastly colder than our current one. It is highly unlikely that simple dropping temperature will ‘kick off’ a bout of inflation. (Especially since we don’t know what started the first bout.) It is possible that in a ‘big rip’ scenario we will see a second round of inflation as the universe’s expansion spirals out of control, but details are too hazy at present.

  53. Are we in this stage have the data necessary and suffiecent to say that Inflation IS the only option or another routs are possible without Inflation ?

    1. At the present time there is one ‘big’ alternative to the BB, the ekpyrotic universe (In which case the universe could be infinite in age.) If the current data holds up however it will become heavily disfavored (but possibly not ruled out.) Then of course there may be alternatives we have not thought of.

      At present inflation is the ‘best educated guess’ for what preceded the HBB. We have no theories at all that postulate the universe starting with a ‘plain’ HBB; this was the consensus until a few decades back, but as noted in the article various properties of the universe have forced us to abandon that simple approach.

      1. Then , Am I right if i say that as per now there is no unique inference that we can deduce from all the data we have concerning the begining of the universe ?
        Thanks Kudzu

        1. *If* BICEP2’s results are correct the ekpyrotic universe will be *almost* ruled out, but I don’t believe it will entirely be dismissed. I think this is similar to how supersymmetry is always said to be ‘ruled out’ by the LHC.) and even an inflating universe may be an infinitely old one.

          At the present moment, even with BICEP2 we have only guesses as to the ‘start’ of the universe and we can’t even be sure there was a start at all.

        2. All of a sudden you can compose complete sentences in English?
          You must now be more than one person.

        1. The faults are still with us. So it is important to check the reported results and then, if correct, solve the problems (or find a better theory that matches what we observe).

          Paul Steinhardt

          1. This is what Dr. Steinhardt say about inflation in a correspondance with him yesterday ……inflation is a failure ,,,this is what I understood.

          2. He does make the case that inflation is a failure. For a good reference I recommend his “The Inflation Debate: Is the theory at the heart of modern cosmology deeply flawed?” Scientific American, April 2011, p 36-43.

  54. Thank you for this excellent clear presentation on the cosmic origin in this chaotic sea of speculative bubbles spun out by charlatans and confused physicists.
    Would you point out or tell us the region we might be able to probe with the proposed 100 TeV collider if it were to be built, in your chart? Thanks.

  55. Matt said
    So if people tells you that the universe started in such and such a way, perhaps ”with a singularity” or “with a quantum fluctuation out of nothing” or “in the Big Crunch (i.e. the collapse) of a previous phase of the universe”, remember that they’re telling you about the red zone. They’re neglecting to tell you that what they’re saying is pure theory, with neither an experiment to back it up nor a clear theoretical reason to believe their suggestion is unique and preferable over someone else’s alternative.

    I am writing to suggest that perhaps “pure theory” should be referrred to as conjecture or hypothesis since “theory” has a specific meaning in theoretical physics and science in general. Just a thought.

  56. IMO when one takes into account; that law of thermodynamics that energy only changes form and is neither destroyed nor created and that absolute zero is a tempature never obtained, with statistics and probabilities, combined with extrapolation of a space/time graph clearly shows beyond a doubt, there has been an infinite number of Big Bang Cycles, and will be an infinite number of Big Bang Cycles.

      1. What would need to happen is the ‘dark energy’ would need to ‘reverse’ that is the current negative pressure that is driving expansion would have to become zero or positive. At present we cannot tell whether this will happen naturally, will never happen or will get worse (the ‘big rip’ scenario.)

        1. With your terms, that negative pressure is somehow getting bigger (accelerating expansion), how’s that possible? And in the context of your future answer how things will change in future so that the phenomenon gets reversed?

          1. The questions you ask are deep indeed and we still do not have good answers to them. In regards to your second question the only answer we have is ‘somehow it has to change’ Since we don’t know what dark energy is we don’t know what it can do or how.

            The second question is likewise unanswered; we know that after inflation the universe’s expansion slowed due to gravity, but at some time around 7 billion years ago it started to accelerate again. it’s important to remember too that things get ‘worse’ even if the negative pressure remains the same.

            The reason is that dark energy is a property of space and makes more space. That is, it makes more of itself. Take a small universe with matter and radiation in equal quantities and 1/10th as much dark energy. Each then has some ‘energy density’ the amount of stuff diided by the volume it occupies. This controls how much affect it has on space. After some time the universe’s volume will double. The matter’s energy density will halve (divide by 2x volume), the radiation’s will be 1/16th (Divide by 2x volume, *plus* its frequency is stretched double which gives it 1/8th the energy.) but the dark energy’s density will be the same. (So there’s now twice as much of it.) It now has more effect than the radiation and after a few more doublings, it will out-effect the matter.

          1. During inflation space ‘makes more of itself’ So any two objects in that space continually find more space between them. And the more space there is between them the more ‘new’ space appears. The end result of this is that the two objects see themselves as moving apart faster and faster. At the time of inflation the universe did indeed double in size repeatedly.

    1. What sort of cosmological experiment would allow you to confirm some of the yellow region? Is there anything?

      1. Dang it, that was supposed to be a top-level question. Not sure how it wound up as a reply to you. Sorry.

      2. We have most of what we (currently) think we can get relating to the yellow region via astrological observations, most frontiers lie with the LHC and similar setups. But as BICEP2 has shown astronomy still has a big role to play regarding earlier eras (And in fact alter eras such as determining exactly when the expansion of the universe began to accelerate.)

    1. How precise do you want either of those? It is a simple matter to tell you that next winter will be colder than summer on average. And I can say ‘The universe has stars in it’ pretty easily too. But it’s impossible to describe the position of all the atoms in a single cloud or nebula.

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