The look-back time is numerically equal to the distance to a galaxy in light-years.

Question

Quizplus · Accepted Answer

Look-back time is defined as the amount of time it takes for the light from a galaxy to reach us. This is directly related to the distance to the galaxy, since light travels at a finite speed (the speed of light), which limits how far away we can see. Therefore, the look-back time can be used as a measure of distance, and is indeed numerically equal to the distance to a galaxy in light-years.

The Look-Back Time Is Numerically Equal to the Distance to a Galaxy