Humans have less than 1000 years on Earth before we are wiped out in a mass extinction.

This grim outlook was delivered by Professor Stephen Hawking during a speech addressing the universe and the origins of humans at Oxford Union.

The leading theoretical physicist said the only way for humankind to avoid the very real possibility of extinction was to find another planet to inhabit.

"We must also continue to go into space for the future of humanity," he said.

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"I don't think we will survive another 1000 without escaping beyond our fragile planet."

This bleak outlook on the humanity is nothing new for the 74-year-old, who earlier this year predicted technology would lead Earth to a virtually inevitable global cataclysm.

"We face a number of threats to our survival from nuclear war, catastrophic global warming, and genetically engineered viruses," he said in January.

"The number is likely to increase in the future, with the development of new technologies, and new ways things can go wrong. Although the chance of a disaster to planet Earth in a given year may be quite low, it adds up over time."

Prof Hawking added that finding another planet was the only chance of survival.

"[We] have spread out into space, and to other stars, so a disaster on Earth would not mean the end of the human race," he said.

"However, we will not establish self-sustaining colonies in space for at least the next hundred years, so we have to be very careful in this period."

FILE - In this file photo dated Wednesday Aug. 29, 2012, British physicist, Professor Stephen Hawking speaks during the Opening Ceremony for the 2012 Paralympics in London, Wednesday Aug. 29, 2012. Ha
FILE - In this file photo dated Wednesday Aug. 29, 2012, British physicist, Professor Stephen Hawking speaks during the Opening Ceremony for the 2012 Paralympics in London, Wednesday Aug. 29, 2012. Ha

More recently, Prof Hawking voiced concern about the potential dangers of artificial intelligence.

"I believe there is no deep difference between what can be achieved by a biological brain and what can be achieved by a computer," he said.

"It therefore follows that computers can, in theory, emulate human intelligence - and exceed it."

While admitting AI could be the biggest event in the history of our civilisation, he said it wasn't without risks.

"[AI] could develop a will of its own - a will that is in conflict with ours," he said.

"In short, the rise of powerful AI will be either the best, or the worst thing, ever to happen to humanity."

Despite frequently suggesting the worst case scenario, the world famous cosmologist ended his most recent talk with a call for optimism and intellectual curiosity.

"Remember to look up at the stars and not down at your feet. Try to make sense of what you see, wonder about what makes the universe exist. Be curious," he said

"However difficult life may seem, there is always something you can do and succeed at. It matters that you don't just give up."

HOW CLOSE ARE WE TO FINDING ANOTHER PLANET?

Since 2009, NASA has been working to discover Earth-like planets in the habitable zone - the region around a star in which the surface temperature of an orbiting planet might support water.

The telescope has since confirmed the discovery of more than 1000 planets, with another 3000 "planet candidates" waiting to have their existence confirmed.

"The first exoplanet orbiting another star like our sun was discovered in 1995," NASA said in a statement.

"Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago.

"Today, and thousands of discoveries later, astronomers are on the cusp of finding something people have dreamt about for thousands of years."

In August, a team of astronomers announced the discovery of the nearest exoplanet to our own solar system.

Dubbed Proxima b, the planet orbits the star Proxima Centauriand and is only a little more than four light years away from our sun.

British researcher Nick Pope said the development was a game-changer.

"This game-changing discovery may help us answer the question of whether or not we're alone in the universe - one of the biggest and most profound questions we can ask," he said.

"Many people believe there are aliens out there and now it's possible that they're our galactic next door neighbours.

"Every effort should be made not just to find out more about this planet, but to look for evidence of life - and maybe even intelligent life."

Despite being Earth's closest neighbour, it would take 76,000 years to get reach using current rocket technology.

However, there is hope that new technology currently under development could allow us to send a robotic probe to the planet in about 25 years.

In the meantime we just have to hope Prof Hawking's prediction doesn't come to fruition.