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

Energy and mass, equal in amount in the universe?

  1. Sep 14, 2013 #1
    Mass and energy are convertible to each other with E = mc^2. Cosmic background radiation average intensity roughly 2.725 K, and it's all over the place with very little variation. Suppose we add up all the energy in the universe, including the cosmic background radiation, the kinetic and gravitational energies of all the objects in the universe, all the electrical and heat energies, is it likely that the amount of mass and the amount of energy in the universe are equal to each other?
  2. jcsd
  3. Sep 15, 2013 #2


    User Avatar
    Science Advisor
    Gold Member

    I would have to say no, because matter can be converted into energy and back again in nuclear processes.

    If at some point in time, the amount of matter and energy in the universe were the same, the fusing of two hydrogens into helium-2 would convert a small amount of matter into energy, offsetting the balance.

    We do have good reason to believe that with [itex]E=mc^{2}[/itex], that energy-equivalent of matter plus the rest of the energy stays the same total value. In fact, modern theories say that matter is just a really incredibly compact form of energy, and that the real total energy remains constant.
  4. Sep 18, 2013 #3
    There's no reason for the equality between the entire energies combined and all mass (in your post you mean regular baryons).
    Any way it's proven that energy occupies most of the universe, but not our regular type of energy; it's the dark energy.
    Here are some numbers:
    Ordinairy matter (baryonic matter: neutrons, quarks etc...): 4.9% ( I believe that this takes into consideration the "regular" energy [photons] )
    Dark matter: 26.8%
    Dark energy: 68.3%
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook