ASTRON 1F03 Lecture Notes - Lecture 22: Heinrich Wilhelm Matthias Olbers, Cosmic Microwave Background, Elliptical Galaxy
18 Dec 2015
School
Department
Course
Professor
Document Summary
Expanding gas cools: due to expansion, light red shifted, and temperatures dropped. If we rewind to the beginning, temperatures must heave been very high. If all matter in the observable universe is in a small volume, it means conditions were very hot. Prediction: a blackbody spectrum uniformly red shifted by the expansion of the universe to a temperature of about 5 10 kelvin. Form: a blackbody spectrum with a temperature of about 3 k. The sky faintly flows in microwaves: cosmic microwave background (cmb) radiation. Microwaves are from when the universe was hot and ionized. At several hundred thousand years, the temperature cooled so protons and electrons could form neutral h atoms: recombination. Then, light was no longer blocked from its travel by all of the matter. The light could travel freely, and cooled by a factor of about 1,000 to about 2. 77 k, as confirmed by satellite data.
