Acclaimed physicist Stephen Hawking has said that humanity is finally getting close to understanding the origin of the universe.

Speaking at a lecture in Hong Kong, Hawking said that despite some theoretical advances in the past years, there are still mysteries as to how the universe began.

"Despite having had some great successes, not everything is solved. We do not yet have good theoretical understanding of the observation of the expansion of the universe," he told an audience of 2,500 at the Hong Kong University of Science and Technology.

"Without such understanding, we cannot be sure of the future of the universe.

"New observational results and theoretical advances are coming in rapidly; cosmology is a very exciting subject. We are getting close to answering these old questions: why are we here, where did we come from?"

The 64-year-old also said his unfulfilled ambitions, among many, were to find out what happens inside black holes, how the universe began and how the human race can survive in the next 100 years.

Above all, he joked, he wants to understand women.

On Tuesday Hawking said the human race should reach for the stars to survive as the Earth is at risk of being wiped out by a disaster.

He believes humans should settle in space, predicting a lunar settlement within 20 years and a Martian colony in 40.

Hawking, a Lucasian Professor of Mathematics at the University of Cambridge, speaks with a voice synthesiser and has been in a wheelchair since developing motor neurone disease.

During his Hong Kong visit he also revealed he is writing a children's book with his daughter about theoretical physics.

Hawking is the author of international best seller "A Brief History of Time", which attempted to explain a range of subjects in cosmology, including the Big Bang, black holes, light cones and superstring theory.

He is on a six-day visit to Hong Kong and will meet Chief Executive Donald Tsang Friday before heading to Beijing Saturday where he will give a lecture on string theory.