Question

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.

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 only the galaxies on the surface of the ball will increase.
B.
The distances between all the galaxies will increase throughout the ball.
C.
The distances between the galaxies near the center of the ball will decrease.
D.
The distances between the galaxies will change randomly depending on the galaxies' motion.

Answer 1

B.

If the whole ball expands uniformly (the scale of space increases), every separation grows — distances between all galaxies increase proportionally, not just those on the surface.