Physicist Stephen Hawking has described the idea of heaven as a 'fairy story'.
In an interview with the UK's Guardian newspaper, he says he regards the brain as a computer which will stop working when its components fail.
"There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark," he says.
Hawking set out his thoughts on the subject in 2010 in his book The Grand Design, in which he argued that there was no need to postulate a creator in order to explain the existence of the universe.
However, because he didn't specifically say that there was no God - and because he'd metaphorically referred to the 'mind of God' in A Brief History of Time, some hopefuls argued that he still might be a believer.
But in the Guardian interview, he makes his opinions clear, adding that he personally is not afraid of death.
Tomorrow, Hawking will address the Google Zeitgeist conference in London about how he believes the universe began.
"Science predicts that many different kinds of universe will be spontaneously created out of nothing," he says, explaining that matter originated through tiny quantum fluctuations in the very early universe.
He will discuss M-theory, which encompasses string theory and postulates a universe with 11 dimensions.