The discussion revolves around the behavior of light beams in the context of the universe's expansion from the present to the time of the Big Bang. Participants explore concepts related to the convergence of light, the nature of the universe's beginning, and the implications of cosmic expansion on the paths of photons.
There is disagreement regarding the nature of light beam convergence and the implications of cosmic expansion on photon paths. Some participants hold differing views on the concept of a "single point" at the universe's beginning and the effects of expansion on light behavior.
Participants express various assumptions about the nature of light and cosmic expansion, with some relying on interpretations of geometry and others on physical models. The discussion includes unresolved questions about the implications of these concepts.
No, there was no "single point". This is a pop-science misconception that has no bearing on reality as far as we know. The "singularity" does not mean "point" it means "the place where our math model gives un-physical results and we don't know what was really going on."eugene pletcher said:Regarding expansion, from the present to the past: Do light beams (generally) converge to a single point, in the remote past, as geometry and matter was also condensed to a single point, prior to the big bang?
Thank you.
phinds said:No, there was no "single point". This is a pop-science misconception that has no bearing on reality as far as we know. The "singularity" does not mean "point" it means "the place where our math model gives un-physical results and we don't know what was really going on."
The beginning of the universe as we understand it was not a point and may in fact have been infinite in extent.
By the way, don't feel bad that you got sucked in by that mis-information. There are many dozens, probably hundreds, of posts here with people asking questions based on exactly that misunderstanding.
Yes, and if you go back far enough there were no galaxies.eugene pletcher said:Appreciated. Was the distance between galaxies not smaller in the past?
No, light is emitted from celestial objects, generally, radially and the angle between any two rays doesn't change as you get closer to the source.If so, does that not imply light beams were closer then they are now?
phinds said:Yes, and if you go back far enough there were no galaxies.No, light is emitted from celestial objects, generally, radially and the angle between any two rays doesn't change as you get closer to the source.
The photons that were emitted billions of years ago were closer to their source of origin than they are now, but so what? The photons that leave our sun are all within one solar diameter of each other when they leave and they get farther apart, but "converging" is the wrong way to think about that process in reverse.eugene pletcher said:Again thanks. Even when viewing several billion light years away, the light paths (travelling toward Earth) are not converging in the remote past?
I think in the sense that you mean (and I may be misinterpreting you) then of course they do because it's all just geometry. Mass has nothing to do with it.eugene pletcher said:May I ask just one more question? Does expansion separate individual photons, which are massless? I'm not referring to geodesics, or curved space. I'm interested to know if expansion itself can cause two, almost parallel, photons to separate. I suspect that the answer is no.
Thanks :)