Things in space being “xxxx lightyears away”, therefore light from the object would take “xxxx years to reach us on earth”

Question

I don’t really understand it, could someone explain in basic terms?

Are we saying if a star is 120 million lightyears away, light from the star would take 120 million years to reach us? Meaning from the pov of time on earth, the light left the star when the earth was still in its Cretaceous period?

In: 292

Answer 1

Yes. That’s basically the definition of what a light year is – how far light travels in one year. If it set out from somewhere a light year away, and it’s just arriving, it started out a year ago. 20 light years away, it started out 20 years ago. 120 million light years away, it started out 120 million years ago.

Every time you look up at the stars in the night sky, you are literally looking years back in time.