If the distance of a galaxy at a redshift z = 0.5 is 1,800 Mpc, how many years back into the past are we looking when we observe this galaxy?
A) 500 million years
B) 2 billion years
C) 6 billion years
D) 9 billion years
E) 10 billion years

Question

Quizplus · Accepted Answer

The redshift z = 0.5 corresponds to looking back approximately 5 billion years. Given the distance of 1,800 Mpc, which is consistent with this redshift, the look-back time is about 6 billion years.

If the Distance of a Galaxy at a Redshift Z