The portrayal of extraterrestrials in movies and popular fiction strikes some scientists as unrealistic. Should any real visitors — or conquerors — from space come to our planet, the scientific odds strongly suggest the aliens will be completely artificial forms of life.

When considering the prospect of alien life, humankind should prepare for the worst, according to a new study: Either we're alone, or any aliens out there are acquisitive and resource-hungry, just like us.

Experts who, like Hawking, have devoted their careers to thoughtful exploration of the possibilities of alien contact say that we have little reason to be concerned that extraterrestrial civilizations are planning to invade Earth.

The chances of earth being detected by alien life forms are disappearing because the digital revolution has decreased analogue transmissions from television, radio and radar, a leading space scientist has claimed.

Richard Carrigan, Jr., a physicist at the Fermi National Accelerator Laboratory warns that scientiststs should think about decontaminating potential SETI signals to reduce the risk that the signals could carry harmful information similar to a computer virus.

Walter Simmons, a physicist at the University of Hawaii, together with his colleague, Professor Sandip Pakvasa, have come up with a clever scheme that would allow interstellar broadcasters to keep the coordinates of their home planet secret by taking advantage of advances in quantum cryptography.

According to Harrison, a Professor of Psychology at the University of California at Davis, if we detect a signal from advanced extraterrestrials, there?s a good chance that the basic principles of democracy play a role in their society.

A SETI Institute survey on people?s beliefs about etraterrestrials found, not surprisingly, that respondents projected characteristics on E.T. based on how they view their own life. For example, the study found that people who feel like the world is cold and cruel are more likely than other people to imagine extraterrestrials as being cold and cruel as well.

Researchers are debating the existence of life elsewhere in the universe -- and how meeting up with aliens might affect the Earth.

Seth Shostak explains why any extraterrestrials we come into contact with will almost certainly be more technologically advanced than we are.