LECTURE

Assuming that our part of the Universe was typical, Hubble’s discovery suggested that the entire Universe was expanding. As Belgian astronomer Georges Lemaître pointed out, this implied that in the distant past everything in the Universe must have been crushed into a single, tiny, dense hot point, a “primeval atom” as he called it. This meant that the entire Universe had a history. These ideas solved the problems posed by an in nite Universe, for an expanding Universe had to be nite, containing nite amounts of light and heat, and plenty of usable energy. The idea of an expanding Universe also tted Einstein’s recently formulated general theory of relativity, which appeared to show (though Einstein initially resisted this conclusion) that the Universe must be either expanding or contracting. The name “big bang” was coined by Fred Hoyle (1915–2001), who had worked with Gamow but would become a erce critic of the theory. He used the label derisively in a 1950 radio broadcast.

We have seen how, early in the 20th century, new evidence and new arguments accumulating over several centuries generated a new model of the Universe. This model suggested that the Universe had been created at a speci c date and had been expanding ever since. In other words, the Universe had a history!

Essential Reading

Supplementary Reading

Bryson, A Short History of Nearly Everything, chap. 8. Christian, Maps of Time, chap. 1.

Coles, Cosmology, chaps. 1, 4.