“We were marching down the street, & we were at the head of the troops. We went on marching, & the troops went off to the left.” –Geoffrey Burbidge
It’s such a part of our cosmic and scientific history, that it’s difficult to remember that it’s only been for the past 50 years that the Big Bang has been the leading theory-and-model that describes our Universe.
Ever since the 1920s, when Edwin Hubble discovered the apparent expansion of our Universe, we’ve recognized that it’s a much bigger place than simply what’s in the Milky Way. But the Big Bang was hardly the only game in town. Yet the discovery of not only the Cosmic Microwave Background, but the detailed measurement of its temperature and spectrum, was able to rule out every single alternative as a non-viable model.