Brief Answers to the Big Questions

by Stephen Hawking

Observational evidence to confirm the idea that the universe had a very dense beginning came in October 1965, a few months after my first singularity result, with the discovery of a faint background of microwaves throughout space. These microwaves are the same as those in your microwave oven, but very much less powerful. They would heat your pizza only to minus 270.4 degrees centigrade (minus 518.72 degrees Fahrenheit), not much good for defrosting the pizza, let alone cooking it. You can actually observe these microwaves yourself. Those of you who remember analogue televisions have almost certainly observed these microwaves. If you ever set your television to an empty channel, a few per cent of the snow you saw on the screen was caused by this background of microwaves. The only reasonable interpretation of the background is that it is radiation left over from an early very hot and dense state. As the universe expanded, the radiation would have cooled until it is just the faint remnant we observe today.