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Just missed us
November 9, 2011 - Stephen Browne
Yesterday evening Nov. 8, we all had a close call when asteroid 2005 YU55 passed the earth about 201,700 miles away at 6:28 p.m. EST.
That might not seem very close but it's actually a bit closer than the moon, making it a near miss by cosmic standards.
The asteroid is about a quarter-mile wide and traveled past the earth at about eight miles per second.
If it had hit the earth the impact would have left a crater four miles across and 1,700 feet deep, according to Purdue University professor Jay Melosh. An ocean impact would have raised a 70-foot tsunami.
Other effects would have included dust clouds that would obscure the sun enough to plunge the earth into a years-long winter.
There are thought to be possibly thousands of these NEAs "near earth asteroids" and PHAs "potentially hazardous asteroids." It's hard to be sure, they're hard to detect because they are small and often dark colored.
Mostly they miss, because space is deep and the planets are comparatively small, so there's a lot of room to miss. But impacts have happened. The theory that an asteroid or comet impact led to the extinction of the dinosaurs, once science fiction speculation is now respectable science. There are also serious suggestions that the Gulf of Mexico is an ancient impact crater!
We have only to look at the surface of the moon, where the absence of weathering reveals a long history of impacts.
I draw two conclusions from this. One is a reminder that the universe is a dangerous place, prone to incredibly catastrophic events that make our worst fears seem incredibly petty.
The other is the absolute necessity of continuing the exploration and exploitation of space. Because if we ever find an asteroid that is heading straight for us, and astronomers agree it's only a matter of time, we are very close to having the capability of knocking it aside if detected early enough.
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