CAMBRIDGE, ENGLAND (AP) - Renowned physicist Stephen Hawking is celebrating his 70th birthday in typically ambitious fashion _ with a wide-ranging discussion of the nature of the universe.
The celebrity scientist is at the center of a daylong conference on cosmology being hosted at England's Cambridge University.
An expert on black holes, Hawking gained wide acclaim for popularizing the work of theoretical astrophysicists in best-selling books such as "A Brief History of Time" and "The Universe in a Nutshell."
Other speakers Sunday include Astronomer Royal Martin Rees, Nobel Prize-winning physicist Saul Perlmutter, and Hawking's longtime collaborator Kip Thorne. Among the topics due to be discussed are supernovae, black holes, and dark matter.