Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2.In this case,
A)Galaxy 1 must be twice as big as Galaxy 2.
B)we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2.
C)we are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2.
D)Galaxy 2 must be twice as old as Galaxy 1.

Question

Quizplus · Accepted Answer

Since Galaxy 1 is twice as far away as Galaxy 2, it means that light from Galaxy 1 has taken twice as long to reach us as light from Galaxy 2. Therefore, we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2. This phenomenon is referred to as "lookback time". The distance of the galaxy does not necessarily relate to its size or age.

Suppose We Look at Two Distant Galaxies: Galaxy 1 Is