Of Particular Significance

Getting (Un)Confused About Matter and Energy

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 04/12/2012

In the last couple of weeks I produced an article on Mass and Energy (along with a bit on Momentum).  But I warned you in that article not to confuse “Mass” (which is somewhat related to Energy, after Einstein’s work) and “Matter” (which is not related to energy, despite the fact that the phrase “matter and energy” can be found all over the place.)

I’ve just finished a new article “Matter and Energy: A False Dichotomy”.  This article points out that “matter” is defined differently in different contexts.  And in each of those contexts, matter and energy aren’t opposites, partners, or in any other way crisply related.  The situation is inherently confusing — but I hope the article itself cuts through some of that confusion and helps clear up the matter.

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4 Responses

  1. Dear Prof. Strassler,

    Thank you for the time you spent on this and apologies for my poor phraseology: it’s the mechanism of converting from one form of energy to another what I was after. Option (1) is probably best – some references would suffice.

  2. Thank you for an excellent site. I have read your particle/antiparticle article and would like to know the mechanism that actually converts mass in to energy – I am happy that +/- chatrges annihilate etc but what causes two equal masses to annihilate?

    1. First, I’d like to rephrase your question because your phraseology, though very common in public discourse, is actually not correct and quite misleading, and will actually end up confusing you very deeply.

      I encourage you to read my mass and energy again (and if you already have, read it again, after reading this reply.) http://profmattstrassler.com/articles-and-posts/particle-physics-basics/mass-energy-matter-etc/mass-and-energy/ What is happening in electron + positron –> two photons should not be phrased as “mass being converted to energy”. What is happening is that “energy stored in mass is being converted to energy of motion“. Mass-energy –> Motion-energy.

      Mass simply isn’t conserved. It can disappear. Or appear. And it does, all the time, in particle physics. The mass isn’t annihilating in these processes; it’s just not something that has to stick around in the first place. Massive particles turn into massive ones; massive particles turn into massless ones. Or ones of large mass turn into ones of small mass.

      But always, always, always in particle physics, the energy (and the electric charge) is the same before and after any of these processes; it is the energy that is being converted from mass-energy to motion-energy or from motion-energy to mass-energy, or even to other types of energy. And notice that unlike the electric charge, which is positive for the particle and negative for the anti-particle, or vice versa, and so in total is zero, the energy for the particle and the anti-particle is positive for both — so it doesn’t annihilate at all. The total energy is positive, and it remains so.

      Ok — now, how can mass-energy be turned into motion-energy. Well, here we’re in danger of hitting a wall, I’m afraid. You know from your experience with little kids that every answer to a why question itself allows another why question, and at some point you hit the end of the road where the only answer is “because.” We’re close to that here. The only answer I can easily give you is that “this is something that particles (which are little ripples in fields) can do.” That’s not very satisfying.

      What I would need to give you a more satisfying answer would be either

      1) a description of the phenomenon in equations, which you wouldn’t probably want, but is the easiest way to explain it, unfortunately.

      2) an example from nature, with which you are already familiar, that exhibits an analogous phenomenon. Unfortunately, I don’t have a good one (yet). The closest example I have — but it involves an analogy which is partly apt and also partly misleading — is to focus not on particle-antiparticle annihilation but on particle decay. When a particle decays (say, a Higgs particle turns into two photons) there is a similar disappearance (partial or complete) of mass, but with mass-energy converted to motion-energy. The analogy here is to dissipation, where a vibration of a violin string (which, notice, doesn’t move anywhere — the vibration is pinned to the violin) is converted to sound waves (which can travel outward from the violin to your ear.) http://profmattstrassler.com/articles-and-posts/particle-physics-basics/why-do-particles-decay/most-particles-decay-why/ But the mathematics for this, while vaguely evocative of the math for particle decay, is really not the same in detail, so it doesn’t really answer your question properly.

      3) a video or mathematical simulation which would allow you to watch how this kind of thing can happen, either for particle-antiparticle annihilation or (more likely) for particle decay. I’m not sure if I know how to do this yet, and it would be a lot of work, but it is a direction that I might take this website in future.

      Sorry I can’t do much better at this time. Following how energy moves around from place to place is one of the most important things to understand about nature, and I have to figure out some better ways of explaining it…

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

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