I thought i understood a light year as a measure of distance.But i keep running into articles that say something like ...around Galaxy NCG 4921 there are a cluster of galaxies estimated to be 13+ billion years old at a distance of 320 light years from earth.How do you get that when you are...
What is the speed of light at 2.7 degrees K.If it`s less than C,you know what my next question is.
Empty space is not empty i am told, so we don`t have the classical definition of a vacuum so photons
are passing through something that should slow the photons down?
At cryogenic temperatures on...