When Hubble first calculated the recessional speeds of galaxies in the 1920s, he used
A) the Doppler shift relationship. This was an error, and the calculations had to be repeated using the cosmological redshift relationship.
B) the Doppler shift relationship. This was an error, and the calculations had to be repeated using the gravitational redshift relationship.
C) the Doppler shift relationship. This was correct because the nonrelativistic cosmological redshift relationship gives the same result.
D) the cosmological redshift relationship. This was an error, and the calculations had to be repeated using the Doppler shift relationship.

Question

Quizplus · Accepted Answer

Hubble used the Doppler shift relationship to calculate the recessional speeds of galaxies, which was correct for his observations. The nonrelativistic cosmological redshift relationship gives the same result as the Doppler shift for the velocities and distances Hubble was dealing with.

When Hubble First Calculated the Recessional Speeds of Galaxies in the 1920s