Does gravitational time dilation change the speed of light in outer space?

[Gardiananj]

I don't think there's a "corrected value", because the speed of light is always $c$. You may find that the coordinate speed varies, but that would depend on your coordinate system (it's one possible interpretation of Shapiro delay, for example).

What measurement did you have in mind?

ooops...the speed of light in an absolute vacuum is c, that can only be calculated, never measured because there is no place in this universe that is an absolute vacuum. The speed of light is dependent on the permitivity of the substance it is traveling through and even extragalactic space is not empty. Einstein always was careful to say "near light speed". As an aside...in an absolute vacuum there would be no electromagnetic waves, i.e. no light from which to calculate it's speed. Please correct me if I am wrong.

 

[Ibix]

ooops...the speed of light in an absolute vacuum is c, that can only be calculated, never measured because there is no place in this universe that is an absolute vacuum.

$c$ is a defined quantity these days, so it can't be measured even in principle. You are welcome to calculate the effect of a hydrogen ion per cubic meter on the propagation of light if you wish. You will need a lot of decimal places, and it has nothing to do with time dilation which is what the OP asked about.

in an absolute vacuum there would be no electromagnetic waves,

Unless you are defining space that contains only an electromagnetic wave as not an absolute vacuum because it contains an electromagnetic wave then your statement is not correct. Electromagnetic waves do not require a medium in which to travel.

 

[PeterDonis]

This thread has run its course and is now closed.