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I'm absolutely not an expert, but I believe there wasn't any mass at first; it was all energy. It had to slow down to become mass, at which point it was spread
by DougWebb 8y ago
I'm absolutely not an expert, but I believe there wasn't any mass at first; it was all energy. It had to slow down to become mass, at which point it was spread out enough. Or something along those lines.
Another possibility is that black holes are places where lots of mass accumulates in the same place in space, while the big bang was a rapid expansion of space itself. Even if there was enough mass in one spot to be what we'd consider a black hole, the space it occupied expanded, dragged the mass along with it, and ripped the black hole apart.
- twiceaday 8y agoDoesnt E=mc^2 form an equivalence? I would expect energy to warp space-time just as mass does.
- waterhouse 8y agoI believe it does. If you have a bottle full of chemicals with potential energy, and then you make them react and get the energy from them (via, I dunno, heat), while all the particles remain in the bottle, then I think the bottle weighs less afterwards—though probably by an undetectably small amount. I think I read that the change in mass is detectable after, say, nuclear fission.
- pdonis 8y ago> I would expect energy to warp space-time just as mass does. It does. So do pressure and stresses. The full "source" of gravity in General Relativity is the stress-energy tensor, which includes all of these things.
- mygo 8y ago> it was all energy. It had to slow down to become mass If there was no mass then what made the energy slow down? For example a photon will travel at the speed of light in a vacuum indefinitely. In what scenario does energy just slow down without interacting with matter?
- InclinedPlane 8y ago"Mass" is just another name for "rest-energy". A single photon cannot have mass because it has zero energy in the reference frame where it is at rest (zero net momentum). But a pair of non-parallel photons can have rest-mass, and indeed the mass of the photons inside a star is considerable, for example.
- pdonis 8y ago> "Mass" is just another name for "rest-energy". Not if you're talking about what the source of gravity (spacetime curvature) is. Massless particles still have energy and still cause spacetime curvature.
- InclinedPlane 8y agoThe "source" of gravity is the stress-energy tensor. "Mass" (rest-energy) is a simplification that is useful for approximations and conceptualizations.
- pdonis 8y ago> "Mass" (rest-energy) is a simplification that is useful for approximations and conceptualizations. Yes, but not in a context where radiation is present, since radiation can have energy but has no rest mass (rest energy).
- pdonis 8y ago> A single photon cannot have mass because it has zero energy in the reference frame where it is at rest (zero net momentum) I didn't catch this before, but it is not correct. There is no such thing as a frame in which a photon is at rest.
- flukus 8y agoYou can make black holes with massless particles: https://en.wikipedia.org/wiki/Kugelblitz_%28astrophysics%29 https://en.wikipedia.org/wiki/Kugelblitz_%28astrophysics%29
- pdonis 8y ago> I believe there wasn't any mass at first; it was all energy. It had to slow down to become mass This is partly true. During inflation, the universe was vacuum; all of the energy was in the "false vacuum" state of whatever field caused inflation (it's usually called the "inflaton" field, which IMO is a very confusing name). When inflation ended, all of that energy got transferred to the Standard Model fields, forming matter and radiation at very high temperature and expanding very rapidly. So the "all energy at first" part is true; but the "had to slow down to become mass" part is not. The matter and radiation was there as soon as inflation ended; it didn't have to slow down first.