Other galaxies observed by astronomers are almost all redshifted. This means that most galaxies are moving away from our galaxy. Since this is true in every direction, the galaxies are all moving away from each other.

Question

Suppose the galaxies in the image are moving in the directions indicated by the arrows. What would have been true at some point in the past?
All the galaxies were moving in the same direction.
All the galaxies were moving with the same velocity.
The galaxies all had the same mass.
The galaxies were closer together.

Answer 1

Given that galaxies are observed to be redshifted and moving away from each other, it's implied that the universe is expanding. At some point in the past, the galaxies would have been closer together before the expansion began.

Therefore, the correct statement is: The galaxies were closer together.

This aligns with the understanding of the Big Bang theory, where the universe has been expanding since its inception, causing galaxies to move away from each other over time.