The U.K.'s leading astronomer says the chance of finding life elsewhere in the universe is better than ever, though others say looking for E.T. is a waste of time.

Astronomers and other scientists have gathered in London for a two-day international conference on the search for extra-terrestrial life. The conference began Monday at the Royal Society, Britain's academy of science.

Martin Rees, president of the Royal Society and Britain's Astronomer Royal, says the chances of finding life in the cosmos have never been better.

"Technology has advanced so that for the very first time we can actually have the realistic hope of detecting planets no bigger than the Earth orbiting other stars," Rees told the conference.

He said it's now possible to learn about the atmospheres, oceans and even continents present on planets outside our solar system.

"Although it is a long shot to be able to learn more about any life on them ... it's tremendous progress to be able to get some sort of image of another planet, rather like the Earth, orbiting another star."

Rees said the discovery of extra-terrestrial life would change humanity's view of its place in the universe.

Separate biology

"Were we to find life — even the simplest life — elsewhere, that would clearly be one of the great discoveries of the 21st century," he said.

"I suspect there could be life and intelligence out there in forms that we can't conceive, and there could, of course, be forms of intelligence beyond human capacity, beyond us much as we are beyond a chimpanzee."

But Paul Davis, a physicist at Arizona State University, says scientists should give up on finding and communicating with life in space and concentrate on finding "alien" life on Earth.

Davies says finding life on Earth that is completely separate from the rest of the planet's biology — for instance, in extreme environments like volcanic vents or salt lakes — would suggest that life emerged more than once on this planet.

For example, geologist Felissa Wolfe-Simon of the U.S. Geological Survey is searching for exotic life forms in Mono Lake, a California lake with a large naturally occurring deposit of arsenic.

In her work, Wolfe-Simon is trying to find out if organisms there could use the arsenic in their biochemistry the same way more other life on the planet uses phosphorus.

Davies's talk at the conference focuses on the history of SETI, the search for extra-terrestrial intelligence, and the "eerie silence" that came after astronomers tried sending out messages into space.

In another talk at the conference, Simon Conway Morris, an evolutionary paleobiologist at Cambridge University, will predict what alien beings might be like. He says they probably would look very much like humans.

Conway Morris argues that evolution is highly predictable and intelligent life would likely come in a form similar to ours: with eyes, two legs, a body and limbs. That means the rubber masks that the aliens of Star Trek and Star Wars wore might not be too far from the truth.