It's not often (perhaps never) that a breakup song uses imagery from astrophysics, but:
In case you, like me, needed a quick brush-up on the physics involved, a red shift is similar to the Doppler effect, only with electromagnetic radiation. The light of something moving readily away from you is shifted toward the red (lower frequency) end of the spectrum. Observed red shift is evidence of an expanding universe, and a broken heart.
Julia Nunes could sing the phone book and make it sound amazing. [Note to self: come up with new reference point for something dry and boring. There are no phone books any more.]