Physics was the reason for the Big Bang, not God, according to scientist Stephen Hawking.

"Because there is a law such as gravity, the universe can and will create itself from nothing," the professor said in his new book, in a challenge to traditional religious beliefs.

"It is not necessary to invoke God to light the blue touch paper and set the universe going," he wrote in his book "The Grand Design," extracts of which are printed in London newspaper The Times.

The book, co-written by American physicist Leonard Mlodinow and published next week, sets out to contest Sir Isaac Newton's belief that the universe must have been designed by God as it could not have created out of chaos.

He cites the 1992 discovery of a planet orbiting a star other than the Sun.

"That makes the coincidences of our planetary conditions -- the single Sun, the lucky combination of Earth-Sun distance and solar mass -- far less remarkable, and far less compelling as evidence that the Earth was carefully designed just to please us human beings."

Professor Hawking had previously appeared to accept the role of God in the creation of the universe, writing in A Brief History Of Time in 1988.

"If we discover a complete theory, it would be the ultimate triumph of human reason -- for then we should know the mind of God," he wrote.

Until last year, the professor held the same post as Sir Isaac Newton, that of Lucasian Professor of Mathematics at Cambridge.

While other eminent scientists, such as leading atheist Richard Dawkins, will welcome Professor Hawking's views, others are still not convinced.

Professor George Ellis, emeritus professor at the University of Cape Town and President of the International Society for Science and Religion, says science may be the loser in this battle.

"My biggest problem with this is that it's presenting the public with a choice: science or religion.

"A lot of people will say, 'OK, I choose religion then' and it is science that will lose out."

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