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Been seeing all this stuff about asteroids and how an asteroid that is a quarter to half a mile wide can destroy the world. They said that a rock the size of a football field could wipe out a continent.

don't understand this. I know these things would generate a large explosion but if you look at their size relative to the planet it is relatively very small.

Foe example, if you are looking at a map of the US that is say, 36 inches wide, a 100 yd asteroid would not even talke up the size of a pinhead relative to the size of the map. Just very hard to comprehend how this much destructive energy can be created by an object so small.

Anybody know how to explain this so that it seems reasonable??
 

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Probably depends upon how much of it makes it through the atmosphere.

If someone stood on the moon and shot the earth with a 10mm, we'd all be in trouble.

Hoping our resident physicist devildog comes along to fill in the gaps of knowledge :)
 

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BLR
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Kinetic Energy.

If you take a train traveling at 60 MPH we all know what it will do if it hits a truck or a car. Now take that same train and increase it's speed to 10,000 MPH and imagine what it would do. That is essentially what will happen if a large asteroid hits the earth. It's not the mass itself but mass and speed.

I'm sure devildog can give a better answer but that's the gist of it.
 

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Smartass Pilot
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Been seeing all this stuff about asteroids and how an asteroid that is a quarter to half a mile wide can destroy the world. They said that a rock the size of a football field could wipe out a continent.
It's not really that it could destroy the world or even a continent, but rather it could make the environment so hostile to life that we would have a hard time surviving in it. The Earth itself would hardly be affected at all by such an impact.

Imagine the Indian Ocean tsunami as seen from space. From our point of view it was devastating. From orbit, you probably wouldn't even be able to see it with the aid of instruments.
 

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Speed+mass=energy(?) One of the physics guys will correct this. That 1/4 mile asteroid is moving at thousands of miles per hour and easily weighs tens of thousands of tons. Try to imagine the energy at work when that thing comes to a stop. It has to go somewhere.

Either way, look up Kinetic Bombing. It is essentialy the same principle.
 

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Speed+mass=energy(?) One of the physics guys will correct this. That 1/4 mile asteroid is moving at thousands of miles per hour and easily weighs tens of thousands of tons. Try to imagine the energy at work when that thing comes to a stop. It has to go somewhere.

Either way, look up Kinetic Bombing. It is essentialy the same principle.
The relative velocity of an asteroid/meteorite impact is usually in the tens of thousands of mph. The meteorite that impacted in Arizona, was roughly the size of a schoolbus, travelling at approx 70,000 mph and left a crater a mile wide and 1000 feet deep.
 

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l'Italia s'è desta
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And don't forget, the atmosphere is fragile. Mess that up, and we can only hold our breath for so long. Probably not long enough for it to regenerate.
 

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Urine Idiot
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I ain't skeered of no asteroid.
 

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Tread Lightly
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Foe example, if you are looking at a map of the US that is say, 36 inches wide, a 100 yd asteroid would not even talke up the size of a pinhead relative to the size of the map. Just very hard to comprehend how this much destructive energy can be created by an object so small.

Anybody know how to explain this so that it seems reasonable??

A meteor half that size caused Barringer crater in AZ. Google it and check pics. Equivalent of ten megaton nuke groundburst. You wouldnt want to have been within 50 miles of it hitting.

Almost a mile across. Can be seen from space.
 

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The Bombdiggity
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To understand things like this you have to understand scale.

Imagine throwing a golf ball sized rock in a smooth calm lake, a big one. You will be able to detect that ripple for a very long way, miles even (assuming no weather) Now imagine being on that water and being much much smaller than a grain of sand. Even a small ripple would be a mighty wall of water.

When something hits the Earth going 30-100 thousand miles an hour, the Earth, as solid as it seems, will act more like a liquid. From the outside looking in (a G-d like view, or a space view) the ground "rippling" 10 feet high for hundreds of miles wouldn't seem like anything....for anything on the ground, it will be annihilated.

The next issue is all that crap getting put into the atmosphere. Even a large volcano erupting can and does effect the global weather for years. Airliners must change their flight plans for huge areas around volcanos. Imagine 10,000 large volcanos. Like very muddy water, it will block out the sun for a long time and everything left could die off.
 

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The Bombdiggity
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Wave propagation

[ame="http://www.youtube.com/watch?v=Qf0FxDOjCg0"]Slow Motion Shooting into Water - YouTube[/ame]

With this. Again, think scale. Toward the end when you see the wave expanding, if you were the size of a human cell, that wall of water would be hundreds of miles high. If that pond was big enough, even a half mile away the faintest ripple would be hundreds of feet high. Go outside and imagine a wall of water as tall as a skyscraper coming at you at a thousand miles an hour. It would destroy everything.

Also keep in mind, a bullet travels between 700 and 2500 miles per hour. The speed of impact from an asteroid or comet would be 30,000 to millions of miles per hour.
 

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Speed+mass=energy(?) One of the physics guys will correct this. That 1/4 mile asteroid is moving at thousands of miles per hour and easily weighs tens of thousands of tons. Try to imagine the energy at work when that thing comes to a stop. It has to go somewhere.

Either way, look up Kinetic Bombing. It is essentialy the same principle.
Kinetic Energy = 1/2 x mass x velocity squared.

Thousands of tons of mass travelling 10,000 or more mph results in a **** ton of energy, almost equal to an Underwood 10mm round.
 

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Boat Life ©
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It also depends on what the astroid is made of...
 

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Speed. Think of a .223 into a watermelon. Throwing that bullet does little, but when you get it up around 2000 fps.... Asteroids are much much faster.
 

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It also depends on what the astroid is made of...
Yup.
If it is just plain rock, there is a higher chance of it blowing up into dust when it hits the atmosphere. It if is dense(like iron), it has a higher chance of going through the atmosphere and actually hitting the earth.
 

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Boat Life ©
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Yup.
If it is just plain rock, there is a higher chance of it blowing up into dust when it hits the atmosphere. It if is dense(like iron), it has a higher chance of going through the atmosphere and actually hitting the earth.
Yup.

In my most serious voice -- I stand by my quote above.

Composition could make the difference b/t a neat fireworks show vs. the fate of humanity.
 

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The Bombdiggity
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Yup.

In my most serious voice -- I stand by my quote above.

Composition could make the difference b/t a neat fireworks show vs. the fate of humanity.
Not really. Tanguska was at best, 700 feet in diameter and it flattened an area over twice as large as all of New York city.

Even the meteor that blew up over Russia this year, was about 50 feet in diameter, it blew up at almost 15 miles high and damage 7000 buildings. People on the ground could feel the heat. Mach 60 will do that.....the dust lingered in the atmosphere for months.

http://www.space.com/22396-russian-meteor-explosion-dust-cloud.html

If you get a sand ball that is a mile wide, it isnt going to be just a fireworks show. It is going to shatter the ground for hundreds of miles and dust up the air for years.

If it is a metal meteor, it might end us.

I dont think people really understand what speed will do.
 
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