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

Imagine that the universe is a solid ball with galaxies scattered all through it from the center to the edge. Suppose the galaxies stay the same size, but the ball gets bigger. What will happen to the distance between the galaxies?
A.
The distances between the galaxies near the center of the ball will decrease.
B.
The distances between all the galaxies will increase throughout the ball.
C.
The distances between only the galaxies on the surface of the ball will increase.
D.
The distances between the galaxies will change randomly depending on the galaxies' motion.

Answer 1

The correct answer is:

B. The distances between all the galaxies will increase throughout the ball.

As the universe expands (represented by the solid ball getting bigger), the distances between the galaxies also increase, regardless of their position in the ball. This is analogous to the surface of an inflating balloon, where the dots on the surface move away from each other as the balloon expands.