How can light from the Big Bang still be traveling at this point in time?
How can it be that bright? If I stand at a point with a flashlight, how far can it be seen?
Asked
Active
Viewed 72 times
0
-
Why should it stop travelling? – PM 2Ring Dec 12 '23 at 07:24
-
1Does this answer your question? How is it possible that we see light from shortly after the big bang? – Miyase Dec 12 '23 at 07:25
-
@Miyase, actually, the answer you linked goes in the right direction but does not provide more than an analogy. – GiorgioP-DoomsdayClockIsAt-90 Dec 12 '23 at 09:26
-
2Note that the Big Bang did not happen at a point. The Big Bang happened everywhere in the universe at the same time so the light from the Big Bang is coming from all directions around us. – John Rennie Dec 12 '23 at 11:56
1 Answers
1
I think the better question is "why wouldn't it?". Light (the CMB) was emitted at the Big Bang, and, although some photons may have been deflected, or even absorbed by black holes. It has also been redshifted into microwave wavelengths, but that does not stop it from still traveling. Remember that there are countless photons but not many objects to stop them (space is quite empty), which also gets harder the longer the wavelength. Now, it's really not that bright, it's actually pretty dim and more of a "faint glow". I don't really see its correlation with a flashlight but, if you were to point it at the sky, excluding the atmosphere and other obstacles, it would technically travel forever, though being increasingly redshifted to invisibility, eventually (but after a REALLY long time).
Flamethrower
- 39
-
I do not think that "why wouldn't it?" is correct. And your argument does not address the main issue behind the question. In a Minkowsky spacetime, photons originating from a point will propagate on the light cone and, at each space point, are detectable at one time. – GiorgioP-DoomsdayClockIsAt-90 Dec 12 '23 at 09:21
-
"Absorbed by black holes," and by ordinary stars, and by planets, and by dust, and by molecular clouds, and by... – Solomon Slow Dec 12 '23 at 12:28