When the aliens finally invade Earth, you may wish you had listened to Travis Taylor and Bob Boan.
And if the invasion follows the plot of a typical Hollywood blockbuster, they might also be the guys called in to save the day.
After all, they have written An Introduction to Planetary Defence, a primer on how humanity can defend itself if little green men wielding death rays show up.
And yes, they're serious.
"The probability really is there that aliens exist and are old enough to have technology to enable them to come here," said Taylor.
Taylor and Boan are hardly basement-dwelling paranoids obsessed with tinfoil hats and Area 51. Taylor holds advanced degrees in astronomy and physics, and is an associate at consulting firm Booz Allen Hamilton. He and Boan have done consulting work for the Defence Department and NASA.
Taylor said it is naive to assume that any beings advanced enough to master star travel will have evolved beyond war.
He and Boan started thinking about how to respond to an aggressive extraterrestrial attack during a 2001 discussion about defending against terrorist attacks.
"One thing that popped into my mind was that the only way Americans would be in an asymmetric war on the other side would be if we were attacked by aliens. Everyone chuckled, but then after a minute the comments started setting in," said Taylor. "Then we really got to talking about it and we thought, well, you know, we really might need this contingency plan anyway."
Failure to prepare may mean mankind will have to dig in and fight with improvised weapons and hit-and-run tactics, much the same way Islamic extremists have battled the US military in Iraq, Taylor said.
"You'd have to create an insurgency, a mujahideen-type resistance," Taylor said. "The insurgents know how to win this war against us. It also tells us that if we were attacked by aliens, this is our best defence."
Source: China Daily/agencies