Whoosh, I missed something… or it missed me?
I am totally failing at remembering the speaker, but I listened to a talk recently about the death of the universe, specifically the point at which all matter has vanished and the only things remaining are cold, slow photons. The argument noted that without matter there is no metric and thus the universe will have a size that is undefined. Somehow the speaker got from there to suggesting that “undefined” may as well mean “effectively but not quite zero”, at which point all those photons find themselves in a space with a diameter smaller than a Planck length, and they go “BANG!” in a new Big Bang.
It sounded to me like saying, “Since the universe no longer knows how big it is, it magically becomes almost zero”.
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Looking at it now I have no idea what I was thinking.
I probably wrote that when it was past bedtime and my brain was already on its way to sleep.
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We know that nothing magically happens in Nature. It
sounds to me that the speaker is trying to unite two different scenarios for the end of the universe, which does not appear to be plausible.
The first is the rebound, cyclical view, whereby the universe contracts back to the place of the singularity, and then repeats the process of the Big Bang. The big problem with this scenario is that scientists have determined that the universe does not have enough matter/energy to trigger this rebound. Thus we have the concept of dark matter and dark energy, which says that the mass/energy is there, but we cannot detect it.
The other says that the universe will continue to expand until it runs out of energy and dies a cold slow death. This is the scenario the speaker is working with. Both of the scenarios are speculative and have no real bearing on our lives, but the second is depressingly final unless we find a way to restart the universe as the speaker wants to do.
For me the formula E = mc squared is the key. It says no mass= no energy, so how can we have no matter and still have “slow photons.” The speed of light is a constant.
The Big Bang is not based cold, disbursed atoms. The singularity was composed of electrons, neutrons, and protons all packed together without the energy and space found in an atom. I believe that someone compared the amount of mass in an atom to a fly in a cathedral. One unit of Energy is equal to one unit of Mass times the speed of light squared,
We really do not know what happens when matter reaches Absolute 0. If no movement, that is, no heat, means no energy, then we would have fission, which should produce much energy.
Since neither matter or energy can be destroyed, (transformed? Yes) where does all the heat energy go? Where does all the light, photons, go?
These are some questions I would raise concerning the scenario the speaker is trying to construct.