Professor Hawking: 'We will reach out to the stars'

"The danger is that either by accident or design, we create a virus that destroys us," he told the UK newspaper in an interview published on Tuesday.

"I don't think that the human race will survive the next thousand years, unless we spread into space.

"There are too many accidents that can befall life on a single planet," he said.

But Professor Hawking, Lucasian professor of mathematics at Cambridge University, said that he was optimistic that humanity would manage to reach out to the stars.

Book extracts

Biology, rather than physics, he says, presents the biggest challenge to the survival of the human race.

Nuclear weapons need large facilities, but genetic engineering can be done in a small lab

Stephen Hawking

"Although 11 September was horrible, it didn't threaten the survival of the human race, like nuclear weapons do.

"In the long term, I am more worried about biology. Nuclear weapons need large facilities, but genetic engineering can be done in a small lab," he told the paper.

"You can't regulate every lab in the world," he said.

The paper is serialising extracts from Professor Hawking's new book, The Universe In A Nutshell.