By studying distant galaxies in the 1920s, Hubble made the following important discovery that led us to conclude that the universe is expanding.
A) All galaxies contain billions of stars, and all galaxies have spiral shapes.
B) All galaxies were born at the same time, and all will die at the same time.
C) All galaxies outside the Local Group are moving away from us, and the farther away they are, the faster they're going.
D) All galaxies outside the Local Group are orbiting the Local Group.
E) All galaxies outside the Local Group are moving away from us, and all are moving away at nearly the same speed.

Question

Quizplus · Accepted Answer

Hubble observed that the light from distant galaxies was shifted towards longer (redder) wavelengths, which is known as redshift. He found that the amount of redshift increased with the distance of the galaxy, indicating that the galaxies were moving away from us. This led to the conclusion that the universe is expanding, and the farther away a galaxy is, the faster it is moving away from us. Option A is incorrect because not all galaxies have spiral shapes. Option B is incorrect because we know that galaxies have different ages and lifetimes. Option D is incorrect because not all galaxies outside the Local Group are orbiting it. Option E is incorrect because the speed at which galaxies are moving away from us increases with their distance.

By Studying Distant Galaxies in the 1920s, Hubble Made the Following