Totally Sciencing It Up: The Shot Heard 'Round the World

As if there was any doubt what explosion I'd talk about this week.  But, in case you missed it, there was an impressive meteor event in Russia last week, where a chunk of space rock came plummeting into our inner atmosphere and detonating over the Chelyabinsk region.  Since it actually flew over a fairly well-populated area in Russia, there have been dozens of videos of the event, which is pretty cool because things like this are rare enough on their own.  To give planetary scientists a chance to look at and study the event, though, was invaluable.

The event itself would have been cool enough if a big hunk of rock had simply fallen from the sky.  However, when the hunk of rock exploded in the atmosphere, well, that was something to write home about!  Here's a compilation of some of the best videos capturing the event, thanks to Russia Today's channel on the YouTube:

Pretty impressive, to say the least.  Unfortunately, thanks to the shockwave of the explosion shattering glass and throwing people to the ground, about a thousand folks sustained some kind of injury.  Fortunately, nothing seemed to be life-threatening.

So, why did this thing explode?  Well, we all know that when an object enters the Earth's atmosphere, it begins colliding with all the gas molecules that comprise our atmosphere.  The object giving us our close encounter is usually traveling at such a high rate of speed that it suffers millions of these interactions a second, and the brushing off of gas particles is enough to transfer heat via friction to the chunk of space rock.  This heats the object up until it starts to glow--think about the coils in your toaster, except imagine them traveling around 40,000 miles per hour!.  Since most space rocks have a fairly high content of iron in them, this analogy isn't too far off.  We've all seen pictures of forges and foundries where molten iron and steel are glowing hot.

The reason why iron (and most anything else that glows when heated) does that is because pumping heat into a system adds energy, and when you add energy, you excite the electrons surrounding the atom.  As the electrons get excited--like, literally quivering with anticipation--they jump, much like a corgi looking for a treat.  Unlike the corgi, the electrons have to travel into different shells surrounding the atom.  After jumping, the electrons aren't where they are supposed to be, they are excited, and they now want to go home where they are more comfortable.  The electron then falls back down to its original shell, and when it falls, it releases that energy in the form of light (and heat).  

But why the explosion?  Well, as you might expect, the heating of the space rock isn't uniform.  The composition of the rock isn't uniform, either, and so as it heats, some of the solids in the rock are vaporized--literally turned into gas form--and as we've learned, gasses expanding more rapidly than their container can withstand = explosion.  And explosions = awesome.

And what an explosion!  It was estimated that the Chelyabinsk blast was roughly equivalent to 20 atomic bombs going off at the same time!  Sensors from around the globe picked up on the shockwaves, which does, literally, make it a shot heard around the world.  Im. Press. Ive!

The difference between all these space rocks, also, involves where they are and their size.  Asteroids (literally, "star forms") are very large chunks of space rock, but they are smaller than planets, planetoids and moons, typically have no atmosphere, but they do have enough mass to exert gravitational pull on other objects.  Sometimes the definitions can get a little hinky.  Phobos and Deimos, Mars' moons, are technically captured asteroids from the asteroid belt.  Eventually, someday, they'll crash into the surface of Mars.  Talk about Fear and Dread!

Meteoroids are small chunks of space rock, like our friend who provided the spectacular aerial show over Chelyabinsk, that have not interacted with Earth's atmosphere (yet!).  Once they hit the upper atmosphere and start glowing, they are called meteors.  If, by chance, they make it to the surface of the Earth (which, despite its size, the Chelyabinsk meteor has yet to provide evidence of reaching the ground) they are called meteorites.  Or starmetal, if you're into D&D--which I'm not.  Seriously.  Stop looking at me like that.

Of course, it has to be mere coincidence that this whole thing happened but three days after the DVD release of Skyfall.  *nodding*  Well-played, MGM...well-played...