Expedia's galaxy-wide website must be offering Earth at a major discount. In one movie after another, aliens decide to pass up competing Milky Way attractions -- including neutron stars, antimatter clouds, hot Jupiters, and a 4 billion-trillion-trillion-ton central black hole -- in favor of our planet. The small speck of rock we inhabit is more popular with tourists than Disneyland.

Even an abbreviated laundry list of invasion films will give you the idea: Independence Day, War of the Worlds, Superman II, Mars Attacks, The Day the Earth Stood Still, Killer Clowns from Outer Space ... They all share a common premise, namely that Earth is the bee's knees, cosmically speaking.

But really, you've got to wonder what would motivate creatures from other worlds to suffer a journey of hundreds of trillions of miles to visit our planet? It's a trip so relentlessly devoid of scenery, their spacecraft wouldn't need windows. Why bother?

I've been asked this question at least a half-dozen times by Hollywood writers, and the best answer I can muster is "I don't know."

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