Renowned theoretical physicist Stephen Hawking: Humans have only about 1,000 years left.

Stephen Hawking thinks our days are numbered — unless we find a new planet to live on.

During a talk at the Oxford Union debating society recently, the renowned theoretical physicist said humanity probably had only about 1,000 years left before going extinct.

Hawking, 74, has spoken several times of what he sees as our doomed fate, with the risk of things like nuclear war increasing as well as the threat of global climate change. He has also warned that the development of artificial intelligence could end mankind.

Our only hope of escaping these dangers, Hawking says, is by finding another habitable planet.

"We must also continue to go into space for the future of humanity," he said. "I don't think we will survive another 1,000 years without escaping beyond our fragile planet."

NASA launched its Kepler spacecraft in 2009 with a mission to do just that. It was designed to search the nearby region of our galaxy for Earth-size planets orbiting in the habitable zone of stars similar to our sun. This zone is called the "Goldilocks zone" because it is the range in which pressure and temperature are "just right" for liquid water to exist on a planet's surface.

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

This year, astronomers were excited by the discovery of Proxima B, an Earth-size planet orbiting in the star Proxima Centauri's Goldilocks zone. It also lies just 4.2 light-years away from us, which in space terms is pretty close. So far, Proxima B seems to be our best chance of escape.

Hawking's speech ended with his encouraging the students to stay curious, and he told them to remember to "look up to the stars and not down at your feet."

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