Ming measures a recession velocity of 2000 km/sec for a galaxy. About how far away is that galaxy if the Hubble constant is 20 km/sec/million light years? (Hint: be sure to check the units in your calculation.)
A)40 thousand light years
B)40 billion light years
C)100 million light years
D)100 light years

Question

Quizplus · Accepted Answer

We can use Hubble's law, which states that the recession velocity of a galaxy is directly proportional to its distance from us. We can use the equation v = H0*d, where v is the recession velocity, H0 is the Hubble constant, and d is the distance to the galaxy. Rearranging the equation to solve for d, we get d = v/H0. Plugging in the given values, we get d = (2000 km/sec)/(20 km/sec/million light years) = 100 million light years.

Ming Measures a Recession Velocity of 2000 Km/sec for a Galaxy