Astronomer A claims that the Hubble constant is 84 km/s per Mpc, while astronomer B claims that it is 63 km/s per Mpc. If, using the Hubble constant, astronomer A claims that a particular galaxy is 4 billion ly away, then astronomer B would claim that it is _____ billion ly away.
A) 3
B) 5.3
C) 6
D) 2

Question

Quizplus · Accepted Answer

The Hubble constant is used to estimate the distance of galaxies based on their velocity. If astronomer A, using a higher Hubble constant, estimates a galaxy to be 4 billion light-years away, astronomer B, using a lower Hubble constant, would estimate the galaxy to be further away. The relationship between the Hubble constant and distance is inversely proportional, so if the Hubble constant decreases from 84 to 63 (a factor of 84/63 = 4/3), the estimated distance would increase by the same factor (4 billion ly * 4/3 = 5.3 billion ly).

Astronomer a Claims That the Hubble Constant Is 84 Km/s