why, if a big enough meteor hits the earth, is the impact like a nuclear bomb?
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Energy = Mass X Velocity^2 (that means squared)
Take a big rock traveling at 20,000 mph
20,000 X 20,000 X rock_mass = you don’t wanna be where the rock hits!
Total energy released can be a lot more than most nuclear weapons, depending of course on the speed and size of the rock.
The dinosaur killer makes the largest nuke ever tested look like nothing much to mention.
It’s different–and potentially much, much worse. A recent science story in the news claimed that the asteroid that hit what is now the Gulf of Mexico and killed off the dinosaurs sent a tsunami *one mile high* crashing into the surrounding land, and the tsunami effects actually struck the other side of the planet. No current nuclear bomb has even close to that kind of power.
It isn’t exactly like a nuke, but they’re similar simply because both release huge amounts of energy.
The Tsar Bomba, the largest nuclear weapon ever made by mankind, released about 50 megatons of energy (that is, it released as much energy as blowing up 50 million tons of TNT at once). An object hitting Earth from space necessarily hits Earth with at least Earth’s escape velocity of about 8 km/s, so if we use the formula for kinetic energy:
E = (1/2) m v^2
50 megatons TNT = 1/2 m (8 km/s)^2
we find that an object of mass m = about 3 billion kg would hit Earth with the same energy as was released by the Tsar Bomba. (In practice, since they’re usually going faster than this, you can get away with slightly smaller objects.) That sounds like a lot, but it’s roughly the mass of the Great Pyramid at Giza: big, but well within reach of even smaller objects in space.
A typical comet is about a thousand times that mass, meaning that it impacts with the energy of a thousand of mankind’s largest nukes going off at once.
EDIT: I had Earth’s escape velocity wrong – it’s ~12 km/s, not 8. But the broader idea stands.
When most people think about nuclear bombs they think “radiation”. But the point of a nuclear bomb is not to spread radiation (we describe _those_ bombs as “dirty bombs”). The point of a nuke is to *use* the radioactivity to create a bigger explosion. The point of a nuke is to make the biggest possible explosion.
So a meteor doesn’t have to release a bunch of radiation to be compared to a nuke. It just has to make a big explosion, which happens if you release a lot of energy quickly. And big rocks traveling at tens of thousands of kilometers per hour release *lots* of energy when they hit a planet (or even just when they hit the atmosphere).
Throw two apples at one another at a high speed. Then imagine you’re standing on one of those apples.
It’s the blast wave and thermal radiation of a nuke, but without the ionizing radiation. It can be like a large or small nuke depending on factors like size, mass and velocity. The more of all, the bigger the boom. Plus nukes tend to be air burst to maximize the effects, while an asteroid is ground burst, so it will be throwing a lot of stuff into the air that will eventually come back down and hit things.
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