The Big Bang was strange -- and we still don't understand it, said Professor Stephen Hawking in his latest speech.
But whatever happened in the first seconds of creation, it didn't take God's help.
Our universe did not require the intervention of any divine being, he said.
"What was God doing before He made the world?" Hawking asked in his new address, delivered at the California Institute of Technology.
"Was He preparing Hell for people who asked such questions?"
At the speech, attended by a full house and another 1,000 people crammed on a lawn outside watching giant TV screens, the hugely respected scientist and author said that humanity should not seek to fill areas of its current ignorance with fantastical stories.
"There are two attitudes one can take," Hawking said.
"One is to that God chose how the universe began for reasons we could not understand. This was the view of Pope John Paul. At a conference on cosmology in the Vatican, the Pope told the delegates that it was OK to study the universe after it began, but they should not inquire into the beginning itself, because that was the moment of creation, and the work of God.
"I was glad he didn't realize I had presented a paper at the conference suggesting how the universe began. I didn't fancy the thought of being handed over to the Inquisition, like Galileo."
Hawking went on to discuss current theories for the creation and expansion of the universe, and outlined the areas he believes are most exciting for future study.
He finished with a plea to continue exploring the universe, and to keep searching for answers.
"We must continue to go into space for the future of humanity," he said - adding that humanity would not survive another 1,000 years if it did not.
After being diagnosed with a rare form of motor neurone disease in 1964 at the age of 22, Stephen Hawking was given just a few years to live.
Nearly half a century later, he celebrated his 70th birthday as one of the most brilliant and celebrated scientists of the modern age.
Despite his illness leaving him almost completely paralysed and unable to speak, Prof Hawking's countless scientific papers, best-selling books and numerous awards have earned him comparisons with Albert Einstein and Sir Isaac Newton.