Russian meteor strike injures hundreds, points to greater danger.

http://www.cnn.com/video/?hpt=hp_t1#/video/tech/2013/02/15/point-bill-nye-meteor.cnn

Hundreds of Russians injured by this meteor strike! Most of them by flying glass, some of them perhaps by the pressure wave from the airburst explosion of  meteor fragments.

In evaluating the potential danger to humans of meteor strikes, it is important to understand the actual PHYSICS of such an event. As Bill Nye explains in the video, meteors that enter the earth's atmosphere heat up instantly, because their speed is so high. Even in the thin gases of the upper atmosphere, an object traveling at such extreme speed has such friction with the air that it superheats, breaks into fragments, and may even explode or vaporize in an "airburst" before it hits the ground. In some respects this may resemble the explosion of a nuclear device, but with the important difference that there is zero radiation released. The purely Kinetic explosion can create a pressure wave strong enough to break bones, knock down trees, and generate immense heat, as happened in the "Tunguska event" of 1908, in an area of Siberia that was at the time almost devoid of humans.

Of course, if the meteor happens to be so large that it actually makes it to a ground or ocean impact, things could be much much worse. A large meteor of perhaps a hundred yards in diameter would indeed imitate a nuclear bomb detonation in terms of destruction if struck the land or the ocean of our planet. How about a meteor a mile in diameter? Wow, immeasurably worse. Such things have happened many times over the billions of years of earth history, and the results are far from pretty. Tidal waves result from ocean impacts. Land hits throw enormous amounts of superheated dirt and rock into the sky, risking a short term global cooling effect that can last for years as sunlight is blocked out by a murky dust filled sky. This kind of event can cause a massive die off of living things across the entire planet, primarily from cold and starvation (because when plants receive no light from a darkened sky, they die, and living animals then have nothing to eat.)

You may remember the two popular movies of a while back- "Deep impact" and  Armageddon".  In Deep Impact, Tea Leoni and company had a long period of waiting, then a colossal series of meteor hits that killed most of the film's characters, but not all. This unfortunately is probably how such an event would actually play out in the real world. Armageddon differed in that the human race came up with a daring plan to get rid of the meteor bysending up Bruce Willis, Ben Affleck, and company, to explode it harmlessly in space. Sounds great, but the actual technology to carry out such an effort of landing on a meteor in space and vaporizing it before it can hit the Earth, well, sorry, it does not yet exist.

In the Big Picture, it could be worth it for the human race to devise tools and strategies to actually prevent massive meteor strikes. These events are very rare- millions of years go by between such events- but when they happen, you are going to have a Very Bad Day.  But when we look at the current human race- busily squabbling over arbitrary national boundaries, unable to actually come to terms with global challenges such as population growth and climate change- it does not give much hope of re-directing human efforts away from self-destruction and towards self-preservation. But fear not, most likely we have many millenia to grow up in before we have to come up with the plan, the tools,  and the guts to deal with this mess.

Finally, something to be thankful for.