If Aliens Invaded the Earth, Which Weapons Could We Use Against Them?

Do we want to fight the aliens? No. They have ability to cross the depths of space and and probably comparable destructive abilities (but possibly not). We have to fight them with the technology that we have, despite its limitations.

So let's ask ourselves: what can we field now -- or in the near future -- that could be used to good effect against a spaceborne invasion? Foreign Policy magazine has several proposals now being frantically examined by DARPA. Among them is a missile defense laser system that can be mounted on fighter jets:

From studying footage of TIE-fighters and Cylon Raiders, we know that small alien craft may have the upper hand on even our most advanced jets when it comes to maneuverability. So when our flyboys or flygirls have alien fighters bearing down on their six, let's hope they're outfitted with this under-development project from DARPA that aims to "improve the performance of high energy lasers on tactical aircraft against targets" -- such as an incoming missile -- "in the aft field of regard." It might not win the dogfight, but it can buy us enough time for the cavalry to arrive.

Link -via Glenn Reynolds | Image: DARPA

We've already fought the aliens before. British, Spanish, French had no problem slaughtering them.

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Yup. We nearly have the technology to push any of the thousands of city-sized rocks that pass by us onto any spot we want. Nuclear missiles are obsolete if you can obliterate the life off a continent without all that nasty radioactive fallout and for less cost than refining scarce plutonium.

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They wouldn't even have to use any fancy energy weapons. Just drop a couple of big-enough asteroids in the Atlantic and Pacific Oceans and let the resulting tsunamis do the rest.

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ID4's Apple virus!

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Any aliens with the tech to get here would probably just kill us with an area energy or radiation weapon beamed from space. They don't even have to land.
Neil Degrasse Tyson best explained the futility of alien contact: 5% of DNA makes the difference between a chimpanzee and Mozart. If aliens have 5% on us, we'll just be quacking ducks to them.