While the theoretical physicist will not speak in person – he'll appear via a live video link from the University of Cambridge – his daughter, Lucy Hawking, will be on stage at the Opera House for the event.

Professor Hawking is one of the few scientists in the world to gain celebrity status, friend and fellow physicist Paul Davies says.

"The appeal of Stephen Hawking is that he addresses the sorts of things people love to discuss at dinner parties: how did the universe come to exist, what is human destiny, what are the laws of nature?" said Professor Davies, who will introduce the Opera House talk.

"Everybody is captivated by those big questions."

Professor Hawking's scientific work has been highly influential, including his research on black holes, general relativity and quantum mechanics.

"He revitalised a field that was really a backwater in the 1960s, taking Einstein's theory of relativity and combining it with the other great contribution to 20th century physics, quantum mechanics," Professor Davies said.

In 1974, he released his theoretical argument that black holes emit radiation – now referred to as Hawking radiation – one of the greatest achievements of theoretical physics in the 20th century.

However, Professor Hawking is perhaps better known to the public for his popular science writing. His international bestseller, A Brief History of Time, remained on the British Sunday Times best-seller list for a record-breaking 237 weeks. More recently, he has co-written a series of children's adventure books with his daughter.

Shortly after his 21st birthday, Professor Hawking was diagnosed with amyotrophic lateral sclerosis, ALS, a type of motor neurone disease. He has spent most of his adult life in a wheelchair, using a computerised voice system to communicate.

People with ALS are often diagnosed later in life but only about 5 per cent of patients survive more than 20 years. Professor Hawking, now 73, has defied doctors' expectations.

Last year, his life was portrayed in the popular film, The Theory of Everything. Actor Eddie Redmayne won both the Academy Award for Best Actor and the Golden Globe for his performance as the theoretical physicist.

Ann Mossop, the head of talks and ideas at the Opera House, said it was an honour to present one of the world's most extraordinary thinkers.

The talk is an initiative of the Big Questions Institute at UNSW, which was co-founded by Professor Hawking to tackle some of the fundamental questions in science.

Director John Webb said science was for everyone and one of the purposes of the institute was to form the bridge between fundamental science and the general public.

An Evening with Stephen Hawking is on at the Sydney Opera House on Sunday, April 26. Tickets start at $69.

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