If it [the universe] was expanding fairly slowly, the force of gravity would cause it eventually to stop expanding and then to start contracting. However, if it was expanding at more than a certain critical rate, gravity would never be strong enough to stop it, and the universe would continue to expand forever.
Stephen W. Hawking (2003). “The Illustrated Theory of Everything: The Origin and Fate of the Universe”, New Millenium
![If it [the universe] was expanding fairly slowly, the force of gravity would cause it eventually to stop expanding and then to start contracting. However, if it was expanding at more than a certain critical rate,](http://cdn.quoteddaily.com/images/stephen-hawking/if-it-the-universe-was-expanding-fairly-slowly-the-force-of-gravity-would-cause-it-eventually-to-stop-expanding-and.jpg)