enter image description here

As far as I can understand, Hubble's law has the form of V(to)=HoDo at a close distance. The meaning of this equation is as follows. For example, when z=0.01, the emitted photons arrive at us and tell us the speed and distance measured at now. That is, the distance to this galaxy is a(to)X.

My question is as follows: When observing a distant galaxy, is its proper distane a(to)X or a(t)X? ( X is comoving distance)

As far as I understand, I think we should use a(to) because we see photons arriving now, whether it's a galaxy far away.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.