Did the universe existed forever?

Before the 20th century nobody suggested the universe was expanding or contracting. It was accepted that either it had existed forever in an unchanging stare, or that It had been created at a finite time in the past. 

Olber's paradox

The difficulty is that in an infinite static universe nearly every line of sight would end on the surface of a star. Thus one would expect the whole sky to be as bright as the sun, even at night. Olber's counter argument was that the light from distant stars would be dimmed by absorption by intervening matter. However, if that happened the intervening matter would eventually heat up until it glowed as brightly as the stars. The only way of avoiding the conclusion that the whole of night sky should be as bright as the surface of the sun would be to assume that the stars had not been shining forever but had turned on at some finite time in the past. 

The argument of Kant for the thesis was: if the universe did not have a beginning, there would be an infinite period of time before any event, which he considered absurd. 

The argument for the antithesis was that if the universe had a beginning, there would be an infinite period of time before it, so why should the universe begin at any particular time?