LONDON (PTI): In what appears to be something straight out of a Hollywood science fiction, a leading astronomer has claimed that aliens might be "staring us in the face" in a form we are unable to recognise.

The startling remark was made by Lord Martin Rees, the president of Britain's Royal Society and astronomer to the Queen.

Rees, who last month hosted the National Science Academy's first conference on the possibility of alien life, said he believes the existence of extra terrestrial life may be beyond human understanding.

"They could be staring us in the face and we just don't recognise them. The problem is that we're looking for something very much like us, assuming that they at least have something like the same mathematics and technology.

"I suspect there could be life and intelligence out there in forms we can't conceive. Just as a chimpanzee can't understand quantum theory, it could be there as aspects of reality that are beyond the capacity of our brains."

During the conference entitled 'The Detection of Extra-terrestrial Life and the Consequences for Science and Society', Rees asked whether the discovery of aliens would cause terror or delight on earth, the Telegraph reported.

He told Prospect magazine that improved telescopes made the chance of finding extra-terrestrial life "better than ever".

However, Dr Frank Drake, known as the world's leading "ET hunter", told the conference that satellite TV and the "digital revolution" was making humanity invisible to aliens by cutting the transmission of TV and radio signals into space.

The earth is currently surrounded by a 50 light year-wide "shell" of radiation from analogue TV, radio and radar transmissions.

But although the signals have spread far enough to reach many nearby star systems, they are rapidly vanishing in the wake of digital technology, said Dr Drake, who founded the Search for Extra-terrestrial Intelligence organisation in the US.

According to him, digital TV signals would look like noise to a race of observing aliens.