They're body snatchers invading human bodies and taking over society; they're E.T. and The Man Who Fell to Earth trying desperately to get home. They're a malign new crustacean life form with multiple sets of acid-drooling jaws that uses our bodies as incubators, vessels to spread its population throughout the galaxy.

Since the early days of film, Hollywood has capitalized on our insatiable appetite for stories about aliens.

We've been enthralled with aliens since the beginning of civilization. The ancient Greek philosopher, Anaximander, speculated about the existence of worlds outside our own as far back as the 7th century BC. Every civilization, from ancient Babylon to the Incas of South America, had a sense of life existing somewhere besides here.

Newsweek's recent cover story was about the search for alien life. But what exactly is an alien life form if it doesn't look like the bug-eyed green men so often displayed in tabloid papers? What if it does not care about finding us, much less abducting us for experimentation?

Astrobiology Magazine spoke with the author of Newsweek's cover article this week, senior writer Aliens Exist Andrew Romano, about alien life, the movies, the Kepler Mission, and about our need to find out if there is anyone else out there.

Q: Do you have any theory about why we've needed or wanted to know whether there's life outside our planet since the beginning of time? Is it an existential problem? A problem of having an escape hatch once we've destroyed our own home planet?

A: I don't have any over-arching theory. It's certainly been a perennial topic for Hollywood for the past sixty years. No, I don't think of the search for life on other planets as a search for an escape hatch. It's more about anxiety over what we have going on here. Economic insecurity, our fear of outside forces acting on us in a destructive way. Think of "The Invasion of the Body Snatchers." It's the Cold War and everyone is turning into commies.

Q: So we need some sort of unifying metaphorical 'bad guy' enemy to deal with our economic and social insecurity?

A: Yes. In the new movie "District Nine," an alien spacecraft stalls over Johannesburg. The alien creatures are ghettoized. It's a thinly veiled metaphor for the racism in South Africa.

Q: Why is the Kepler mission so important? (Kepler is a space telescope launched in March. The lens is pointed at a portion of the galaxy where a group of 100,000 stars look to be promising suns for their orbiting planets. If they have the right atmosphere, if they are found to have water, the existence of inhabitable terrestrial planets becomes a real possibility.)

A: The Kepler mission is the single way we have of gathering empirical evidence that planets like Earth exist elsewhere in the galaxy. Clearly if intelligent life exists, the SETI project begs the question of whether they're looking for us. They're not. So we have to find them. And that entails more than just tuning a receiver in that direction.

Q: Basically what is Kepler looking for?

A: Water, mostly.

Q: What if there's a life form based on argon? Would we recognize it as 'life?'

A: All the evidence we have is what we've observed here. We can only draw analogies from what we already know. If we could broaden our definition of life, we'd have to find an exploratory pathway to go looking for it. We know the pathway to the life form we're looking for now. It's possible we could stumble upon something else.

Q: Things have changed a lot. I remember as a child asking my father - an ostensibly educated man - whether there were life on other planets. He shot down the idea and said that anyone who did believe it was probably a schizophrenic. Are things a whole lot different now?

A: Absolutely. For one thing, NASA makes it clear they're behind it by spending $600 million to search for it. But face it, there are always going to be people out there whose way of dealing with anything outside their existing worldview is either to deny it altogether, or to invent some elaborate, irrational justification for why something is the way it is. Conspiracy theorists are prime examples.

Q: Everything is a twisted version of what I think I already know, you mean.

A: Yes, better the elaborate fantasy than a rational explanation.

Q: What if this new life form simply moved through time differently from the way we do? What if its life span was geological, that is, it had the lifespan of your average rock? To us, it would be totally inanimate and inert, where really it might be alive.

A: It's an intriguing idea. But as I say, we can only follow the pathway we recognize if we want to find something we'll actually be able to identify as 'life.'