To judge by some of the biggest blockbusters of the past few years -- and especially the past few weeks -- we're on the verge of an alien invasion.

Accounts of how they'll get here vary. Let's just focus on the movies of 2012. (Spoilers ahead!) If "The Avengers" is to be believed, the aliens will arrive via an interdimensional portal opened by a demigod named Loki using the power of a glowing blue cube called -- paging "A Wrinkle in Time" -- a tesseract. The aliens of "Battleship" -- like those of "Independence Day," "District 9" and countless others before them -- reach Earth in a gigantic, metal spacecraft. According to "Men in Black III," the aliens are already among us, posing in plain sight as extraordinary humans like Lady Gaga. And "Prometheus," being released Friday, claims we're the descendants of an alien race, although once we find that out, we're in for a serious battle.

With all these different routes open to them, the extraterrestrials should be here any minute. (If they aren't already here!) We have to be prepared. Someone -- at the Department of Defense or the United Nations or at least the SETI (Search for Extraterrestrial Intelligence) Institute -- must be working up contingency plans so we know what to do once they arrive. A real-life "Men in Black" of sorts. Right?

Probably not. At least officially.

Albert Harrison, who studies the idea of extraterrestrials at the University of California, Davis, told The Huffington Post that he participated in a privately funded mini think tank called the Contact Planning Group in 1999. He and other interested parties from science, science fiction and even government discussed possible human reactions to close encounters of the third kind. Harrison said that he was sworn to secrecy about the identities of the other panel members.

"It's a very low-probability thing in some ways, but I think it's something that we should be prepared for," said Harrison.

He added that it frustrated him to report that he had never heard of anything more official than that group.

Paul Davies, director of the Beyond Center for Fundamental Concepts in Science at Arizona State University, explained, "The United Nations has absolutely zero interest in SETI. And SETI itself is a completely open public enterprise. Whether or not the Department of Defense has some secret program dedicated to aliens, I can't be sure. I somehow very much doubt it. Their resources are limited, and they have to focus on credible threats."

Davies admitted to having seen some of the recent movies. Doesn't he realize that aliens are credible threats?

No? Well, John Rummel, chairman of the Panel on Planetary Protection at the Committee on Space Research for the International Council for Science, must. He filled the same role for years at NASA. And "planetary protection" sounds like a code phrase for alien fighting if we ever heard one!

"When the original 'Men in Black' movie came out, some people called us the 'real Men in Black.' But I had to disappoint them. There's really nothing like that as far as I know. If there were, I wouldn't have had such a hard time getting funding every year," Rummel said.

In truth, Rummel is much more likely to concoct a sanitation strategy than he is to propose tactics for an interstellar war. He explained that the main goal of "planetary protection" is to keep Earth's vehicles from accidentally tainting other astronomical bodies with terrestrial microbes.

All that leaves us with three possibilities:
A. Scientists and policymakers are keeping their alien invasion preparations on the DL.
B. Scientists and policymakers haven't seen enough alien invasion movies to grasp the gravity of the threat.
C. The alien invasion movies that Hollywood is producing aren't realistic.

Davies opted for choice C. He said that science fiction movies almost all get aliens completely wrong.

"Travel in the flesh in spacecraft between stars is completely infeasible and absurd," he said. "People just have no idea of the stupendous cost of moving hunks of metal across the universe."

Davies and Rummel also both noted that, given the 4.5 billion years Earth has been around, the chances of an alien civilization choosing to visit while we humans happen to be here are miniscule. What would they even have to gain? Fresh meat?

"The idea that somebody would come all this way to encounter humans just to eat them … it just doesn't seem very efficient," Rummel said.

Davies and Rummel suggested that, at some point, we might be able to communicate with alien life forms at a distance using something like lasers or radio waves. (That's the goal of SETI -- though Davies was bearish on its odds of success. Still, SETI does have a whole protocol in place in the event of a possible detection.)

They also floated the idea that we might someday encounter post-biological intelligence from another world, which we might or might not recognize as the traces of another life form. Think an all-silicon spacecraft, sent by ancient extraterrestrials as a sentient time capsule of their distant civilization.

But neither of those are exactly the makings of a popcorn flick. So suspend disbelief for a second, and imagine that somehow an alien race does discover a new law of physics or a new kind of propulsion that brings them to us in person. Err ... in alien. What then?

"For all intents and purposes, we'd look at them as if they were other persons," Harrison said. "If they've got a behavior that's widely condemned, we're going to hate them and fear them. If we see virtues, we're going to like them."

Kathryn Denning, an anthropologist who studies human thinking about extraterrestrials at York University in Toronto, compared what might happen to the 15th century encounter between the Old World and the New.

"When it comes to intercultural encounters, we have a very mixed record. It just depends on what's at stake," Denning said. "If there were a situation where people had something to fear from aliens … that doesn't usually go all that well."

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