Actually, there is really no doubt about the existence of Alien life.

The question, then, is not whether they exist or not. The big question is: how safe are they?

And would they allow us to exist?

The physicist Stephen Hawking is very pessimistic about it. He seems to be convinced that the Aliens share the universe with humans. However, he is also convinced that they are hostile and dangerous, and would not let us live on. He makes a strong claim in 'Favorite Places,' which is a virtual journey across the universe. "Beware responding to signals from far-off stars," he says. "After all, we do not know who is out there, and what kind of feeling they harbour towards us. They might just decide to "fire up their interstellar artillery and take us out."

That warning may be well-intentioned, but the communication with aliens doesn't seem to be happening soon. So is it too early to worry about the possibility of aliens being hostile if do we contact them?

No, "It's a bit late to worry about that," said Seth Shostak, American astronomer and Director, Center of searches for extraterrestrial intelligence (SETI). If there are indeed extra-terrestrials in outer space, they would already have taken note of the signals we sent. 

However, they may be much more ahead of us - maybe by a billion years. They "may not see us as any more valuable than we see bacteria" he said. Perhaps that is why they are not contacting us?

Soshtak splits a few hairs about the deportment and character of Aliens. He said that it might turn out that the extra-terrestrials live in a utopian, idealistic world. But then again it might not. "In any Darwinian system, there's always a benefit to aggression by some. So maybe a warning is warranted. Who would want to make their mark as the person who triggered the destruction of Earth in a misguided attempt to start an interspecies conversation?" he said.

Suppose the ETs do manage to capture some signals from space, it is possible that many people would want to establish contact and if they do, then Hawking is right in worrying about them. "Lay low," he advises.

However, the Earth has been beaming television, high-frequency radio, and radar into the heavens, not for "either entertaining or notifying aliens," but merely to send off radio transmissions into space.

Being millions of light years away, the Aliens would "require far better hardware." Hence, both travel and warfare would call for a lot more advancement.

"Yes, anything's possible. But that doesn't mean that everything's plausible. Sure, Martians could mount an attack on Earth in the near future. But that's one worry that won't keep me awake at night. Nor should it trouble you.

"If Hawking is really concerned, perhaps he should make sure his online movie isn't broadcast."

The message is very clear then. While we have loads of worries, the least should be about how dangerous the aliens are. It is possible for humans to connect them - and we will. There would be time enough to fret about being destroyed at that time.