Suppose that Hubble's constant were 20 kilometers per second per million light-years.How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is due only to Hubble's law. )
A)away from us at 200 km/s
B)toward us at 2,000 km/s
C)away from us at 2,000 km/s
D)away from us at 20,000 km/s

Question

Quizplus · Accepted Answer

According to Hubble's law, the recession velocity (or speed at which a galaxy is moving away from us) is proportional to its distance from us. The proportionality constant is Hubble's constant. So, using the given Hubble's constant value of 20 kilometers per second per million light-years, a galaxy 100 million light-years away would be expected to be moving away from us at a speed of (20 km/s) x 100 = 2000 km/s. Choice C is the closest option.

Suppose That Hubble's Constant Were 20 Kilometers Per Second Per