How old is the light from the Triangulum Galaxy?

[FrankC]

Not to get off subject but, when I gaze at the Triangulum Galaxy how “Old” is the light I’m observing?

 

[Vanadium 50]

About 2.7 million years old.

 

[DrStupid]

Does it make sense to ask for the age of light?

 

[russ_watters]

Does it make sense to ask for the age of light?

Kind of.

 

[Dragrath]

Does it make sense to ask for the age of light?

If you know Relativity no as anything traveling at the speed of light does not experience "time". However you can validly ask "when was a photon of light emitted relative to our reference frame". For someone lacking an understanding of special or general relativity and used to our largely nonreletavistic everyday experiences where Galilean transformations produce close enough approximations to reality that those rules were only valid for speeds much less than the speed of light wouldn't be realized until Michelson and Morley's famous experiment showed the speed of light is a constant of nature and that no "Aether" exists.

 

[weirdoguy]

no as anything traveling at the speed of light does not experience "time".

That is a pop-science nonsense. There is no frame of reference in which light is at rest, so there is no meaningfull way to talk about what light "experiences".

 

[Dragrath]

That is a pop-science nonsense. There is no frame of reference in which light is at rest, so there is no meaningful way to talk about what light "experiences".

True that typical definition of time doesn't apply, hence why I said "time" not time, but it is a useful way to conceptualize a minkowski diagram as it will fall entierly along the spatial axes so it helps get the point across.