Lights from decorating lamps on trees at University Ave.
My friend called me one day, and told me about his research. His study is about materials sending out heat due to friction during the absorption process to some black holes with masses of 1000 times of the mass of sun. Part of the heat is converted into light and escapes from black hole, what's the spectrum people on earth observe after general relativity? Here is the answer from an astronomy idiot.