Do the light that we see from stars/galaxies travel at the speed of light?

Asked Oct 18 '21 at 02:47

Active Oct 18 '21 at 05:18

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From my understanding, the speed of light is reduced when traveling in a medium. Also, space is the closest thing we have to a vacuum, but it is not a perfect vacuum.

So I wonder if the almost vacuum effect of space is meaningful enough to be taken into account when calculating the location of galaxies & stars billions of light-years away from us?

edited Oct 18 '21 at 05:18

Qmechanic

201,751

asked Oct 18 '21 at 02:47

Ilya Gazman

2,115

I believe that the density is so low that the refractive index is taken as one, but could not find by google any calculations. – anna v Oct 18 '21 at 04:01
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Does this answer your question? Is light actually faster than what our present measurements tell us? – John Rennie Oct 18 '21 at 04:19
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Yes you are right!! Space is the closest we have to a vacuum. It has 30 particles/$m^3$ and some voids in space have 4-5 particles/$m^3$. But according to me that does not effect the speed of light that much as these particles are too small to increase the optical density of space. – Oct 18 '21 at 04:25
Found this https://hypertextbook.com/facts/2000/DaWeiCai.shtmlvfor density in outer space. – anna v Oct 18 '21 at 04:35

Do the light that we see from stars/galaxies travel at the speed of light?

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