LONDON (Reuters) - The biggest mystery in the universe perplexing one of the world's best known scientists is -- women.

When New Scientist magazine asked "Brief History of Time" author Stephen Hawking what he thinks about most, the Cambridge University professor renowned for unraveling some of the most complex questions in modern physics answered: "Women. They are a complete mystery."

The wheelchair-bound Hawking, who only recently retired from a post once held by Isaac Newton, talked to the magazine in the run-up to celebrations for his 70th birthday about his biggest scientific blunder and his hopes for modern science.

Hawking is due to celebrate his 70th birthday on Sunday with a public symposium entitled "The State of the Universe" at the University of Cambridge's Centre for Theoretical Cosmology.

Hawking heads a list of speakers including British Astronomer Royal Martin Rees, Nobel Prize-winning physicist Saul Perlmutter and Kip Thorne, one of the world's leading theoretical physicists.