British cosmologist Stephen Hawking launched Monday the biggest-ever search for intelligent extraterrestrial life in a 10-year, $100-million (92-million-euro) project to scan the heavens. Russian Silicon Valley entrepreneur Yuri Milner, who is funding the Breakthrough Listen initiative, said it would be the most intensive scientific search ever undertaken for signs of extra-terrestrial intelligent life.

"In an infinite universe, there must be other occurrences of life. Somewhere in the cosmos, perhaps, intelligent life may be watching," Hawking said at the launch event at the Royal Society science academy in London.

"Either way, there is no bigger question. It's time to commit to finding the answer, to search for life beyond Earth. We must know."

The project will use some of the biggest telescopes on Earth, searching far deeper into the universe than before for radio spectrum and laser signals.

"We are launching the most comprehensive search programme ever," said Milner. "Breakthrough Listen takes the search for intelligent life in the universe to a completely new level."

He said the scan would collect more data in one day than a year of any previous search, tracking the million closest stars, the centre of the Milky Way and the 100 closest galaxies.

Earth's telescopes would be able to detect a signal from similarly-advanced technology sent from the centre of the Milky Way.