Do Aliens Exist? If So, Will They Kill Us?

In a new Discovery Channel documentary "Into the Universe with Stephen Hawking", the world-famous physicist goes on the record about his concern for attracting the wrong kind of attention in our cosmic neighborhood.

We're an inquisitive lot, we humans. But could our inquisitiveness ultimately kill us?

In a new Discovery Channel documentary "Into the Universe with Stephen Hawking," the world's most recognized physicist speculates about different forms of alien life and explores efforts under way to search and communicate with intelligent extraterrestrial civilizations. However, he cautions that perhaps we shouldn't be advertising our location; perhaps we should just sit back and listen instead.

Earth Brand™ Life

So, Hawking takes us on a thrilling ride through some potential shapes aliens may take, but using life on Earth as the blueprint.

At one point in the documentary, Hawking describes how feet would be useful for any life form that has evolved on a solid surface. He also points out that eyes are handy too.

Eyes and feet have been optimized to function on our planet, so perhaps some variation will be found attached to a life form thriving on a distant world.

When speculating about alien life, it's open season; anything goes. But we only have experience of Earth Brand™ Life, so that's an obvious place to start.

We know (to the best of our ability) that the laws of physics are universal, it seems logical to assume life is too (apart from some variations in detail).

If there's life, there's the potential that in some world orbiting some star in some galaxy, an intelligent space-faring race may be as inquisitive as we are, pondering their place in the cosmos and looking for other civilizations like their own.

In an effort to find intelligent civilizations, we have to assume that they're a bit like us, so the first thing we look for are radio waves. The Search for Extraterrestrial Intelligence (SETI) has been doing this for 50 years, carefully listening for any ET call home. If humans communicate via radio waves, there's a good chance that another intelligent civilization has done the same.

Alas, apart from one isolated case, SETI has turned up zero evidence for the existence of extraterrestrial intelligence. This means we are either wrong to be listening out for ET's radio transmissions, we haven't given it enough time or (and this is the downer) there's no other intelligent life out there.

I strongly suspect that given the sheer scale of the universe, and the mind-boggling quantities of exoplanets orbiting countless stars in countless galaxies, there's intelligent life other than us. Granted, there's no evidence of ET, but as Hawking points out in his documentary, his mathematical brain cannot discount the possibility of alien intelligence when there are endless possibilities inside the hundreds of billions of galaxies we know are out there.

Attracting Too Much Attention?

So we continue to listen out for the signal from aliens through ever more ingenious methods. But we are transmitting too.

There have been numerous attempts at "Active SETI" or Messaging Extraterrestrial Intelligence (METI), where we transmit our presence to the cosmos. The most basic of these methods was to attach our information to the Voyager and Pioneer probes in the 1970s.

This space-age "message in a bottle" has a very limited probability of ending up in the hands of an alien species. However, more recent modes of communication have included beaming our own radio waves into space attempting to make contact.

It's also worth remembering that our planet started to get "radio noisy" when we started transmitting radio and television signals about 100 years ago. Some of these transmissions will have "leaked" into space.

Therefore, if anyone is looking for us within 100 light-years from Earth, they might have already heard us. However, 100 light-years is very small in cosmic distances. For a galaxy measuring 100,000 light-years across, our signal has only reached 0.1 percent of the Milky Way.

Okay, so what if we start blasting out signals advertising our presence? To assume alien civilizations will be friendly and welcome us with open arms seems grossly naïve. As Hawking points out, if there's one thing we've learned from our own evolution, although we might have the best of intentions, we've rarely "come in peace."

The Human Menace

Mankind is all about resources; imagine if a more advanced civilization sees Earth as a bountiful supply of sustenance and sees our civilization as nothing more than ants crawling over a big juicy apple. Wouldn't they just wash us off?

And so this is where Hawking leaves us, pondering our fascination with broadcasting our presence into space. Wouldn't it just be better for us to stay as quiet as we can, listening rather than shouting from the rooftops?

Personally, I think Hawking has a point. Although it might take hundreds, thousands or even millions of years for our signal to reach an intelligent "ear," if that ear isn't a friendly one, we've basically decided our future-Earth's fate.

If there are any human decedents beginning to spread beyond our planet, it would be a real downer for an aggressive alien invasion to suddenly appear in response to our ancient transmissions. I'm sure we'd look back at our idiotic past-selves with anger when we realize we are living in the backyard of a vastly superior alien race intent on eradicating the human infestation that's spreading down their garden path.

On the other hand, we might contact a race of "huggy" aliens who genuinely want to be our friends. But on the off chance that we might get eaten, I'm with Stephen Hawking. Let's be careful about how we advertise ourselves, shall we?

You don’t come in peace? We really regret sending you that map to our home world now.