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Another Asteroid Close Call
james was one of a number of people that submitted the news that
the earth has had another near miss, this time with an asteroid. This particular one is thought to be about 300 meters in length, meaning that if it had struck the earth, it would have destroyed an area of say...South Africa. Not to mention the fall out. But
we don't need
a
better system
for watching the stars. Nope. Obviously not.
Easy. E=mv^2 IIRC. So take the mass of something that size, multiply by the square of the impact velocity, and that's the 'energy' released by the impact.
It's not _quite_ the same as a nuclear explosion, but if you get the energy level high enough, then the effects are similar enough that it doesnt matter.
A kiloton is define as 10^12 calories which is about 4 x 10 ^ 12 joules.
A 1000 tons of rock would have to hit the earth at about 1 kilometer per second to have a similar effect - which is quite a small speed if you are talking about relative speeds in space... (escape velocity is 7km/sec IIRC)
Don't know what the mass of that rock would have been, but a 300 metre sphere of rock is going to be _fairly_ heavy. Take some averages, and count a few fingers, and you start realising that several megatonnes of energy are comparatively easy to come by if you're hit by a big chunk of rock travelling at significant speeds.
(This is, assuming I can count of course.)
Actually, the formula is E = (1/2)*mv^2
Now you have: a 300 m sphere rock at about 3 grams/cm3, which is about 42.000.000 tons. Speeds are in the 10-70 km/sec range, let's take 30km/s, or 30.000 m/s
The total energy is (1/2)* 4,2*10^12 (grams) * 30.000^2 (m/s)
or 1,2* 10^22 joules (!)
if a kiloton is 4*10^12 joules, we have that this asteroid impact has an energy of about 3*10^9 kilotons, or 3 MILLION MEGATONS, all of them released on a single point.
I hope that my calculations are not too way off...
Nice theory.
Problem is that all the kinetic energy still ends up in our system. One big piece is bad. Split that one big piece into several smaller pieces, and it's even worse. But take things to an arbitrary limit, where you pulverize the entire asteroid down to dust.
Now all that dust impacts the atmosphere, heats to incandescence, and vaporizes. Do *you* want to be in the hemisphere where *that* happens? Imagine New York City under the glare of 70 trillion E-Z-Bake Ovens.
If the asteroid's big enough to have a significant negative impact on human civilization, breaking it up/pulverizing it will not help us. It must be diverted so that it doesn't intersect Earth at all.