With films like Star Trek and 2001: A Space Odyssey and millions of sci-fi books, man has always believed in aliens.
But the chances of finding extraterrestrial beings is growing unlikely even though we are discovering more planets.
Astronomers fear we could be alone in the universe and doubt there are planets with intelligent life close enough to Earth for us to make contact.
Hopes were raised by Nasa two weeks ago when it announced the discovery of a rocky sphere with a diameter of 1.4 times that of our own planet.
It orbits a star named Kepler-10 and lies 560 light years from Earth. Nasa scientists hailed it as a 'planetary missing link.'
But they then admitted the surface temperature is a searing 1,3000c, blasted by radiation from its sun which is just a few million miles away.
No life could exist in this hostile environment. An the bad news is that most of the 500 planets found so far around other stars have extreme conditions.
They are either scaldingly hot or frozen and have big temperature swings.
Professor Howard Smith, a senior astrophysicist at Harvard University, told the Sunday Times: 'The new information we are getting suggests we could effectively be alone in the universe.
Poppycock. They're already here on Earth, flying around in our skies. Professor Smith needs to open his eyes and look. To read the rest of the article, click here.