Wendy measures a recession velocity for two distant galaxies, well outside our Local Group of galaxies. Galaxy A has a recession velocity of 35,000 km/s and Galaxy B has a recession velocity of 70,000 km/s. What can she say about the distances to those galaxies?
A) She can't say anything about the distances to Galaxy A or B.
B) Galaxy A is twice as far as Galaxy B.
C) Galaxy A is four times as far as Galaxy B.
D) Galaxy B is four times as far as Galaxy A.
E) Galaxy B is twice as far as Galaxy A.

Question

Quizplus · Accepted Answer

According to Hubble's Law, the recession velocity of a galaxy is directly proportional to its distance from us. Therefore, if Galaxy B has twice the recession velocity of Galaxy A, it is twice as far away.

Wendy Measures a Recession Velocity for Two Distant Galaxies, Well