Quote:
Originally Posted by Nereid
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That photons, as pure energy, "actually [have] a gravitational component" is already built in to GR, and (as Ken G points out), the early universe (in the concordance model) did comprise 'pure energy'.
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Here it is stated that the universe began as "pure energy" yet when I try to nail down an elemental entity from which all of matter is derived posters like
Celestial Mechanic adamantly state that matter can not be derived from photons (due to considerations of spin, charge, etc.).
Quote:
Originally Posted by Nereid
I think you can start with the GR equations, and explicitly plug in 'only photons' ... it gets a little hairy to also include the Standard Model (of particle physics) in such a way that no matter (or anti-matter) gets created, but as long as the universe remains radiation dominated, I guess you could remove the matter and watch what happens ... (you'd also, probably, have to turn off the weak and strong force; while photon-photon collision cross-sections are small, they are not zero, and so, by the ergodic principle ...)
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Here the mention of "
photon-photon" collisions are invoked to explain the creation of matter from photons but then no explanation of how the momentum changed from expanding purely radial photons (no collision possible) to a momentum state that allows such photon-photon collisions to occur. (remember my
Big Bang Momentum thread?)
It would be nice if these things were tied together cohesively to allow one to understand all these seemingly contradictory conditions.