Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Radiation condensing into matter?

  1. Jul 13, 2005 #1
    I've seen shows on the Science Channel and Discovery Channel that say at the Big Bang there could have been a lot of energy and this later condensed into matter, via [tex]E=mc^2[/tex]. Is this true? If so, exactly how would that work? Would it be by collisions between photons or something.. ? Surely light propagating through space doesn't just spontaeously condense the way radioactive elements can spontaneously transfer part of their mass into energy..
  2. jcsd
  3. Jul 13, 2005 #2


    User Avatar
    Science Advisor

    I think this is part of a complicated process called "reheating", which took place after inflation. At the end of inflation most of the energy of the inflaton is kinetic energy and the coupling to other fields leads to a transfer of energy and to particle creation with an increase of temperature.
  4. Jul 13, 2005 #3


    User Avatar
    Science Advisor

    But the mechanism you describe should have took place also, afterwards. The collision between two energetic photons or bosons (energy) may lead to the creation of fermions (matter), which may collide between them to form photons again. I am not sure whether during reheating the inflaton couples to bosons or also to fermions.
  5. Jul 13, 2005 #4


    User Avatar
    Gold Member

    Very plausible is perhaps a better description than true. What happened 14 billion years ago can probably never be known with certainty.

    There are certainly examples of photons spontaneously becoming matter. But, keep in mind that you need a very high energy photon to produce enough matter to create an electron and postiron pair, let alone a quark.
  6. Jul 13, 2005 #5


    User Avatar
    Science Advisor

    The photons after the big bang were largely high energy gamma rays. If they are energetic enough, a collision between gamma rays can result in a matter-antimatter pair being produced. A collision between a matter particle and its antimatter twin will produce two gamma rays. One of the unsolved problems of cosmology is the fact that we ended up with matter in excess. Qualitatively it is known that there are slight differences in transformations between matter particles and their antimatter twins. However, quantitatively the question is still open.
  7. Jul 13, 2005 #6
    I can answer this, it relates to Dark Energy, ie..before the Universe's light got switched on. Most of the Photons were constrained by the Density of Space, the energy of photons were infact still tied up[locked within the Electron Orbits, not external] within Electro-Magnetic Potentials due to the Quark Condensate.

    I can give the Reasons why DIRAC..PAULI and ZEEMAN pondered the potential of Casimir Scattering from within the deep structure of Atoms(Casimir force was unknown then, as were Quarks), let me finish what I am doing, I will dig out some paperwork I have that details the Quantized Space, and I will post it for a scrutiny by those interested.

    In order that you may understand, you may wish to brush up on Zeeman Effect, Casimir Effect, Pauli Exclusion Principle and Diracs Electro-Magnetic workins, but all will be revealed in simplistic easy to understand writing, with just the [tex]E=mc^2[/tex] equation you posted, the only equation in sight.
    Last edited: Jul 13, 2005
  8. Jul 15, 2005 #7
    Thanks for the replies, everyone. In terms of entropy, is matter or energy in a higher state of order? Or is it even meaningful to compare the two in terms of entropy? Does energy naturally tend toward "condensing" into matter, or must it be violently forced into a matter state? It seems to me that most matter must be forced into a state of energy, although radioactive elements are a bit of an exception.
  9. Mar 2, 2011 #8
    One of the holy grails of laser science far as I see it is achieving a sufficient flux to "boil the vacuum" by focusing two or more beams into as tight a point as possible. There is actually some studies being done on this now arXiv:hep-ph/0304139v1 " Boiling the Vacuum with an X-Ray Free Electron Laser" is an example which focuses on creating extremely short lived pieces of matter- what I would imagine are the easiest forms of matter to condense out of energy, odds are there is not going to be a isle of stability right at the start.

    How long until we have holodecks, replicators and transporters? That is prob just as hard a question to answer- but in a way you could say it is being worked on hehe.

    Far as I can figure two or more beams is needed to create pairs of patterns of energy that balance each other out until thrown out of equilibrium and back to energy.
  10. Mar 2, 2011 #9

    Ken G

    User Avatar
    Gold Member

    Entropy simply involves counting "how many ways" a certain process can happen, and noting that what happens is what has a higher number of ways to happen. When two very high energy gamma rays make two particles at an energy well above their rest energies, there's little difference, so not much in the way of an entropy hit. But when the energy is not a lot above the rest energy of the particles, there is a big entropy hit when kinetic energy is converted to rest energy, because there are fewer states available at lower momentum. So if you had a large number of photons and particles in equilibrium, there would be more photons than particles. I don't think there'd be any particles at all if not for the "entropy of mixing", whereby the identical nature of the photons mean you get a bit of an entropy advantage just by having something different in there, even if it is soaks up some kinetic energy into its rest mass.
  11. Mar 2, 2011 #10


    User Avatar
    Science Advisor
    Gold Member

    Getting matter from energy is as Ken described. Photons are essentially collisionless, like dark matter. So you need a huge concentration to trick a few into condensing. Fortunately, this was the state of the universe during the initial stages of the big bang. The matter/antimatter imbalance is still unresolved. Astrophysicists do the heavy lifting and leave the details for particle physicists to work out. They, of course, can't resist the urge to introduce complications.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook