Professor Stephen Hawking has repeated his warning that human survival depends on finding a new home beyond the Earth.
The search for other planets to colonise should start now, he believes.
Speaking in London at a press conference previewing the Starmus science and arts festival taking place in Norway next month, the professor said: "I strongly believe we should start seeking alternative planets for possible habitation.
"We are running out of space on Earth and we need to break through the technical limitations preventing us living elsewhere in the universe."
Professor Hawking was presented with a special gold watch from Omega, new sponsors of the Stephen Hawking medal for science communication.
Three of the medals, which recognise achievements in making science more accessible, will be presented at the Starmus festival in Trondheim.
Each winner will also receive one of the 18 carat gold watches. Prof Hawking will be a keynote speaker at the festival.
Starmus founder astrophysicist Dr Garik Israelian said: "Its fun and it's science and it's music.
"This festival is about artists and scientists. The two most important values we have on this planet are science and art."
Press Association
