Question

Q1. Why do planets and celestial bodies moving away from us cause a redshift in the electromagnetic spectrum and celestial bodies moving towards us cause a blueshift in the electromagnetic spectrum?
Q2. Why is the Andromeda galaxy moving towards us when literally every other galaxy and celestial body is moving away from us?

Answer 1

Explanation:

redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in frequency and energy, is known as a negative redshift, or blueshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum.