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Originally Posted by Ken G
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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 ...
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Indeed, there is an extended early phase of the Big Bang that is radiation dominated (and note that all relativistic particles behave the same way as light), so this is not a hypothetical question. The GR equations are actually the easiest in this situation, and you get a decelerating expansion but nothing that is "gravitationally bound" in the way mugaliens seems to be imagining. Indeed, were it not so, we would not be here now. |
mugaliens, would you mind clarifying your OP please?
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'.
What do you mean by "
gravitation component would have been strong enough to hold in everything, including light (energy)"? The universe
is everything, and the "gravitation component" of its (mass-)energy content is what determines its history.