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Is matter simply a form of energy?

  1. Sep 9, 2008 #1
    All this talk of the LHC has me thinking.

    I know matter is made of various subatomic particles, but then what are those particles (leptons, quarks) made of? Is matter simply a form of energy? I know this is very reductionist thought, but it seems odd to me that fundamental units of matter would stop at leptons, quarks, and the other particles.

    Also, I know that matter can be converted to energy (nuclear fission for example.) But is the reverse true? Can energy be converted into matter? Are there any examples of this happening?

    Combining the two questions, if matter and energy can be converted from one to the other, wouldn't this at least imply that perhaps one is made of the other?

    I've done a little light research into this on the web but it popped into my head on my way back from class and it'll bug me for the rest of the day :P If there's a previous post on this, I'm sorry for the double post, I didn't see anything in the search. And feel free to link me to other answers/sites, or explain it here. Thanks in advance.
  2. jcsd
  3. Sep 9, 2008 #2


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    You start getting into semantics but basically yes.

    Yes. You need quite a lot of energy in the same place to make matter (e=mc^2 is big). Pairs of X-ray photons can generate an electron-positron pair, it's common in astrophysics.

    Not really - again semantics. But for example a neutron decays into a proton,electron and neutrino but isn't made from them.
  4. Sep 9, 2008 #3


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    the string theorists say that the quarks and leptons are made of strings which are very very small and fundamental.
  5. Sep 11, 2008 #4
    no offense mgb. On another symantic note, matter is basically massive. The distinction separates it from the unmassive stuff that propagates at light speed.
  6. Sep 13, 2008 #5
    If I follow the question I think you are referring to strings as energy itself contained in the string somehow.

    I think you are right about what string theory says in that regard but I am not qualified to answer definitively.

    Is it true that a portion of the advocates of BBT and/or Particle Theory and/or General Relativity that post in public forums are genuinely dishonest?

    Often I see students and amateur science enthusiasts ask questions in science forums that pertain to these theory sets. Most of the time serious questions get serious responses. Sometimes though the answers seem to be definitive rejections of ideas that conflict with the theories. The sincere answer often should be, “We don’t know the answer to that question yet, but we are working on it”, or, "we think …”, or some such genuine response.

    Has anyone noticed this and what suggestions do you have for responding to insincere responses like those.
  7. Sep 13, 2008 #6
    Yes string theorists say that quarks and leptons are made of strings, but if that was implied (I'm not sure) not everybody goes all the way to the "string are pure energy" which is kind of void statement to me. Strings are strings just as particles are particles. One could have decided that particles are pure energy as well, it does not hurt nor does it help. It's just talking. In the standard model indeed, one can argue that truly fundamental particles (left and right separately, zitterbewegung-like interpretations) are massless and hence, pure energy.
  8. Sep 14, 2008 #7
    I always think it's a funny one this one. Energy is in a sense 'just' a conserved quantity in any closed system, and is hence something we can think of as stuff, because it persists just as our notion of substance is basically just the notion of persistence. But of course what stuff 'really is' is quantum field. But if you want to make sense of anything then that thing is just whatever properties it has, one of the most salient being possession of energy.

    So yes, semantics, excpet I'd argue that to say that stuff is energy is the most sensible answer when you define what exists as 'what persists in time'. And you never know when that may not be the most physically fundamental notion of what exists, for example if time is only an emergent aspect.
  9. Sep 14, 2008 #8
    hmm.. indeed energy can be converted in mass and vice versa ! x-ray can be broken into electron-positron pair! this is largely seen in the bubble chamber.
    positron is the positive counterpart of electron. also annihilation of this pair gives out energy in the form of radiation! annihilation and nuclear fusion are the other examples of conversion of mass into energy.
  10. Sep 14, 2008 #9


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    Er... I think you mean "gamma rays". X-rays are typically too low in energy to produce pair production.

    Coming back to the topic, this question has been asked a few times already. Check old threads in, I think, the quantum physics forum. The problem here is that while something can be "converted" into something else, it doesn't mean that one is made up of the other. When one says that "matter is made up of energy", one is only doing one form of accounting - energy accounting - via the infamous Einstein equation. While this is true, this is NOT the only accounting one has to take into consideration. Momentum (linear and angular) must also be part of the accounting. Charge must also be part of the accounting.

    If I grab an electron, and says that an electron is made up of nothing more than "energy", then I need to account not just the energy content of that electron (via E=mc^2), but also its charge and spin angular momentum. Note that "energy" as in a photon, for example, does not have a charge, and has a spin of 1, which is very different than a spin of 1/2 for the electron. I could add more photons to my strawman to try to come up with something that will resemble an electron, but I can't. So already saying an electron is made up of energy runs into trouble.

    But how does pair production occurs then? Here, the DETAILS are important. In pair production, not only does the photon needs a minimum energy to create the e-p pair (energy accounting), but it must also conserve linear momentum. It is why pair production always occurs near a massive particle, where the massive particle takes up the necessary momentum. We do this by shooting these gamma photons through a material such as beryllium film, and out comes electrons and positrons. With each of them carrying a spin of 1/2, a triplet configuration will allow for the conservation of spin with the original photon.

    So the "conversion" between matter and energy is not that easy. It isn't simply accounting for the energy conversion into mass. It has to abide by a lot more rules than that. With all that in mind, it isn't that easy to simply claim that matter is made up of energy ONLY.

  11. Sep 14, 2008 #10
    Note that, if you believe in Unruh temperature, an accelerating observer in empty space feels himself in a thermal bath, including electron-positron pairs.
  12. Jun 28, 2010 #11
    My own view is that matter is simply energy (photons) that are somehow traveling in a tight circle (orbital). There are numerous problems with this theory of course. We have pair production but this always seems to create matter/anti-matter. There does not seem to be any means by which matter can be created without the anti-matter.

    An equally interesting question is weather or not enery in transit (light) is massless. It has zero rest mass so we are told but what does this mean when there is no such thing as a photon at rest? If photons in transit do contribute gravity this would go a long way to bridge the so-called missing mass that would enable the conjecure of the big bang to eventually become the big crunch.

    On the other hand if photons do not exhibit gravity then this could help explain how a big bang (singularity disruption) could occur. All it would need is some critical point to be reached (string degeneracy?) whereby all matter was converted to energy. At which point the gravity would cease and out would come all the energy.

    Does anyone know what the current theory is on this and what if any experiments are being done to prove it. It occurs to be one might just be able to prove it with chirped lasers ....
  13. Jul 3, 2010 #12
    Because gravitation exceeds the ability of EM radiation to radiate linearly at a certain distance from a black hole, I would think that radiant energy gets bent into a closed-circuit at such high levels of gravitation. As such, I would expect this process to result in energy-matter conversion. Everywhere else in the universe, the momentum of EM radiation exceeds the ability of gravitation to bend it in on itself, right? If matter was created by energy approaching a black hole, though, I don't know what would cause that matter to exit the black hole. Can black holes divide and separate under the force of their own gravitation? In orbit around one another, could they produce a level of gravity that allows radiation to bend into a closed-circuit without falling into either black hole? Could the particles formed be driven away from the black holes by the gravity waves they generate in orbiting one another?
  14. Jul 7, 2010 #13
    I'd actually opt for the opposite. Matter falling into a singularity is probably converted to energy by being crushed. Any energy that falls in then just adds to it.

    For singularities to be comprised wholly or mostly of energy, the energy would have to exhibit gravity (which it is presumed to do although this is a question that to my knowledge, has yet to be proved).

    Either way there is no known mechanism for singularity disruption - except Hawkins radiation which would be absurdly slow for large black holes. And yet there is 'evidence' that singularities can be disrupted insofar as there is evidence of a big bang (Either the big bang did not happen or it was a singularity or cosmologists need to turn to theology)

    To add to my hypothesis that singularities are just photons orbiting each other, I would question the ability of matter to ever reach a singularity. The energy it would gain in collapsing to a point would either be infinite or at the very least many orders of magnitude greater than it's mass-energy equivalence. But is the matter was converted to energy this conundrum would not arise.....
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