Monday, January 18, 2010

Impact!

Cameras are every damn where these days, a consequence of the long, slow march we’ve made toward eliminating the basic concept of privacy. Still, they’ve got their moments. Take this, for example:



That’s a meteor burning up in the atmosphere, so brilliant that it washes out the camera entirely. This particular one was probably no more than a foot or so across and wasn’t moving particularly fast, so it disintegrated without actually impacting anything. There’s another video out there where a cop stops his car short after seeing the meteor through his front windshield. You have to wonder what he thought as his patrol was interrupted by the heavens.

This, on the other hand, is a meteor that is decidedly more than a foot across. Its speed is unmentioned but, at this scale, irrelevant.



Wha-bam! Now, doesn’t that make you feel secure? This is a rather extreme example of a meteor impact – I’m fairly certain that evil-looking rock is moon-sized – and the fact that the Earth’s crust is peeled like a big blue apple is probably an exaggeration of the real thing, but the basic point is that meteors are bad news, kids.

How bad? Observe this handy chart:


Friends, that is the Torino Scale, a device for classifying space objects according to their danger to us. Essentially, the larger an object is, and the more likely it is to hit the Earth, the higher rating it gets. Therefore, a very small object with a high chance to hit the Earth gets the same rating as a very large object with very little chance to hit Earth*. In this case, that rating would be “1”; it’s not a big deal, we should probably keep monitoring it, but there’s not all that much to worry about.

*Why aren’t we entirely certain of an asteroid’s exact path? You try working out the calculations needed to predict where a 20-meter long space rock will be thirty years from now. Remember to include every possible gravitational effect it could experience in those thirty years. Math is hard.

Everything above that, however, gets progressively worse.

Certain collisions are rated in on the right-most part of the graph, in red. An object around twenty meters across would, upon impact with the Earth, release up to one megaton of energy. By comparison, the bomb released over Hiroshima had a yield of 15 kilotons. As our theoretical space rock finally terminated its long orbit by smashing headlong into our planet, it would produce roughly the energy equivalent of 66.67* early nuclear bombs.


*Oooooh. Spooky! If only we didn’t round off repeating numbers, this would be biblical.

Bear in mind, that’s the low end of the scale.

The largest nuclear weapon ever developed is the “Tsar Bomba”. One of the more interesting relics of the Cold War, the Tsar Bomba has a theoretical yield of 100 megatons, dwarfing our 20 meter asteroid’s output significantly. Here’s a video of its first and only test, a 50-megaton blast.



I suspect that camera was rather far from the blast site. Consult the following map, stolen blatantly from Wikipedia and then hackishly edited by a man with no visual intelligence.


This fucking thing is kind of a circular argument against the continued justification of our existence. The only reason it was never introduced into active service is that the fireball alone was almost five miles wide and almost destroyed the plane that released it. We* made a weapon so powerful that it would kill whoever used it, which is all that a nuke is anyways, so the irony kind' of lines up.

*By “we”, I mean “humanity as a whole, considered as a single species with immense capability for self-destruction”. Not “America”.

Anyways, the Tsar Bomba is at the low end of the nine scale. A meteor 100 meters across could accomplish an equivalent level of devastation.

You can see, then, that even the smallest meteors, because of their velocity upon impacting the Earth, would cause substantial damage—wiping out a city, for starters. They’re why you should never be entirely comfortable looking up at the night sky, and why it’s important that we research both asteroid-detection and –deflection strategies*. Our entire existence might depend on it.

*I bet you think the only thing we can do is blow up an oncoming asteroid, eh? If so, thanks for reading The Toy Cannon, Michael Bay! There are actually several much more elegant solutions we could implement, not limited to the following: parking a satellite next to it so the extra gravitational force alters the asteroid’s path very slightly; attaching a solar sail to the asteroid; attaching a mining robot to the asteroid to eject material from it into space, propelling it in that manner, and so on. Given our general attitude as a species, however, we’ll probably just try to hammer the thing with as many nukes as possible.

The problem with that, however, is that as Carl Sagan pointed out, any method that can deflect an asteroid away from us can be used to deflect it toward us. We’re obviously a ways away from being able to do this with any degree of accuracy, but if you think your average government wouldn’t want such a destructive and unstoppable weapon, then you didn’t watch that Tsar Bomba video above. We are capable of great empathy and grace, but if you gave us a chance to go back to our caveman roots and once again throw rocks at our enemies, we’d do so in a half a second.

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Now.

One aspect of this that I haven’t brought up yet is how it proves that every science fiction movie you’ve ever watched has lied to you.

We’ve already seen that a small meteor can come down on the Earth like a hammer. Such asteroids are moving at a very high rate of speed – say, 20 kilometers per second. Anyone who’s ever played baseball from childhood can tell you that the same ball moving at 30 miles per hour hurts a lot more when it’s humming in there at 80 miles per hour.

Let’s take that same meteor and accelerate it to a slightly higher rate of speed. Say … 20 km/second to a little bit slower than 300,000 km/second (which is, not coincidentally, the speed of light). How big do you think it would have to be to do the same amount of damage as an asteroid at the small end of the Torino Scale?



About that big.

Nothing in the universe moves that fast, obviously (except for light itself), so we’re in the clear for now.

If we ever encounter another sentient species, however, we’d be in for a spot of bother. Most science-fiction universes begin with the concept that faster-than-light travel has been discovered and is commonplace. That stretches believability as-is, but the real question is this; why even bother to have a Death Star or anything of the sort? If you want to destroy a planet, all you really need to do is strap a big-enough engine to a big-enough asteroid, point it at where your target will be by the time your asteroid gets there, and turn it on. Boom! No more planet. Because the asteroid (by now known as a relativistic kill vehicle, or RKV) is ostensibly moving at or past the speed of light, it’ll actually be impossible to track; you won’t be able to see it until it hits you. Nothing we know of now or can even conceive of would be able to track or deflect such a monstrous device.

Given what we know of the history of first contact between two peoples of vastly different technological levels, I wouldn’t bet on our first meeting with an alien species being peaceful. Rather, it might come in the form of thousands of super-fast bullets, blasting the Earth to pieces before we even know what’s happened.

It might be best to put off meeting the neighbors for a while.


At least until we’ve got bigger rocks.

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