Question

The distance to the Andromeda Galaxy is about 2.50 million light years. What was happening on Earth when light from stars in the Andromeda Galaxy left their on its way toward Earth?

Answer 1

Since light had to travel 2.5 million light years, that means we will need to look back 2.5 million years ago to figure out what was happening when the light left. Which means that when the light left the andromeda galaxy, earth was in the cenozoic era, when dinosaurs and other reptiles roamed the earth.