[John H K]

For some reason people like to make fun of asteroid defense, though.

Mainly because it's never happened in recorded human history. But human history is pretty damn short.

Even the most fanatical small-government proponent would have to concede that one valid function of government is to do what it can to prevent civilization from ending.

There's a tiny chance of that but it's so bad it's worth devoting some money to.

[RightWhale]

human history is pretty damn short

Yes, it is. One might wonder why that is so, if there might be an external reason or if people essentially the same as us for 100,000 years didn't happen to think of keeping a diary until 6000 years ago.

Why is human history so short?

Did something happen back then?

[cogitator]

Mainly because it's never happened in recorded human history.

That's incorrect, and I only say that to correct a factual error, not to disagree with you. The Tunguska impact happened in 1908, and there have been some large airbursts recorded by satellites (and some ground video) since then. In 1997, a large meteor passed over (and may have landed on) Greenland.

Greenland Meteor

Meteor impact Greenland? (loads of links; note that the dark cloud shown in some of the satellite images probably wasn't related to the impact)

I looked and looked and finally found a page with a still from the surveillance video (below). The image of the incoming meteor is seen as bright trail reflected on the roof of the car in the image.

Greenland Meteorite