Astronomers detect the slight anisotropy in the cosmic microwave background by making redshift measurements: wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter. This redshift is a
A) Doppler shift.
B) gravitational redshift.
C) cosmological redshift.
D) Doppler shift, gravitational redshift, or cosmological redshift since all three are one and the same thing.

Question

Quizplus · Accepted Answer

The redshift described is a result of the Doppler effect, which occurs when the source of a wave (in this case, parts of the cosmic microwave background) moves relative to an observer. The movement towards the observer results in a blueshift (shorter wavelengths), and movement away results in a redshift (longer wavelengths). This is distinct from gravitational redshift, which is caused by the influence of gravity on light escaping from a massive object, and cosmological redshift, which is due to the expansion of the universe.

Astronomers Detect the Slight Anisotropy in the Cosmic Microwave Background