Alien Attack
© National Geographic

Pasadena, California. - What if there really ARE little green men out there in the vast universe who plan to plop their UFO in a cornfield in Nebraska? That's not just a question for science-fiction writers and 10-year-old boys, but for real scientists with alphabets after their names.

"It's my day job, of course, to look for them," says Dr. Seth Shostek, senior astronomer with the Search for Extraterrestrial Intelligence (SETI.) "And I can assure you that I wouldn't do that if I didn't think that there was a good chance for success because it is not that lucrative," he says.

Shostek and several other scientists are taking the matter seriously when the National Geographic Channel presents When Aliens Attack, premiering May 22.

"NASA has a Kepler satellite orbiting the Earth right now. Within 600 days you will know what fraction of stars have planets that are somewhat like the Earth. And the expectation is that the number will come out to between 10 and 50 billion in our galaxy," says Shostek.

"If you don't like our galaxy, there are 200 billion other galaxies we can see, and there's a vast amount of the universe we cannot see. So it comes down to this: if you say, 'No, I don't think that there are any aliens out there,' then you believe in miracles. Because that would be the miracle. The miracle is not that they would be there. The miracle is that they didn't exist. Whether they are here ... a third of the population believes they are here walking the streets abducting you for experiments your mom wouldn't approve of, very few scientists believe that."

So why are the aliens always on attack instead of being ambassadors of goodwill? Shostek says it stands to reason, as Homo sapiens has always reacted to strangers with aggression.

"If you look historically at what's happened here on Earth, the natives of the Americas did not meet your average Spaniard selling fish on the street, they met the aggressive guys. So there's a very strong filter. If they come to town they're probably aggressive. That's not a faulty assumption, I think."

John Ringo, who has written five best sellers on the topic of alien invasions, says that we should screw our courage to the sticking point, just in case. "One of the aspects is even when people come in peace and with the best of intentions, it has a tendency to damage or destroy cultures. So being prepared for this type of thing, there is no reason not to be prepared for a situation. Getting really upset about it, despite the fact that I write in that field, I wouldn't suggest that you worry about the sky falling today."

"It should be as statistical as human nature, for example, that there's going to be good guys and bad guys," says Dr. Travis Taylor, who's with the U.S. Space and Missile Command Department and has worked with the Department of Defense and NASA for 20 years.

"What we would hope is that the good guys show up first, and that would be really nice. But the point of this wasn't to debate whether they are or they aren't, it's what happens if they did. Do we have a plan? What type of plan should we put together, and how would we defend the planet?" Taylor has also written the handbook for harrying aliens, An Introduction to Planetary Defense.

"Being a scientist, looking up at the sky at night and seeing all the stars and then realizing how many stars there are. You know, in the universe there are so many stars that you can write the number one and 22 zeros after it. That's how many stars we think is in the universe. And we know that planets form around those stars. And so a lot of them are going to be Earth-like. Billions are going to be Earth-like. So it would be a big waste, to paraphrase that Carl Sagan movie, if there wasn't other life out there," says Taylor

Lt. Col. Brian De Toy, director of defense and strategic studies program at West Point, doesn't buy the premise. "I am a skeptical believer in miracles. So a year ago right now I was in Iraq, and I'm more worried about Iraq and Afghanistan right now and the aliens that I'm dealing with there. And so right now, I'm pretty skeptical about the others."

Ringo is a believer. "I personally think that there are probably more planets with life on them in this universe than all of the losses on Wall Street. However, whether we will ever be able to contact them, that is another question."