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Old 11 January 2007, 02:54 AM
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Morrigan Morrigan is offline
 
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Default Asteroid Threat Is Out There

"Friday the 13th of April 2029 could be a very unlucky day for planet Earth. At 4:36 am Greenwich Mean Time, a 25-million-ton, 820-ft.-wide asteroid called 99942 Apophis will slice across the orbit of the moon and barrel toward Earth at more than 28,000 mph. The huge pockmarked rock, two-thirds the size of Devils Tower in Wyoming, will pack the energy of 65,000 Hiroshima bombs -- enough to wipe out a small country or kick up an 800-ft. tsunami."

http://men.msn.com/articlepm.aspx?cp...28365&GT1=8991
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  #2  
Old 11 January 2007, 07:49 AM
Troberg Troberg is offline
 
 
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Oh my god, we're so screwed! Bruce Willis will be retired by then!
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  #3  
Old 11 January 2007, 07:59 AM
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ganzfeld ganzfeld is offline
 
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Oh my god, we're so screwed! Bruce Willis will be retired by then!
There's always Ben Afleck... Yup, we're screwed.
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  #4  
Old 11 January 2007, 02:38 PM
Der Jägermeister
 
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I can see it now: "Armageddon: the Next Generation." Aerosmith will still be touring with their cybernetic replacement bodies, so they can still sing the theme from the original.

--->Shane
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  #5  
Old 11 January 2007, 03:54 PM
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Am I missing something here? We have plenty of nuclear weapons and MOABs. Is there a technnological reason why, if we deem it a true danger, we couldn't launch a huge slew of nukes at this thing while it's still 100,000 miles away and break it up into chunks that will burn away in the atmosphere? It's only the size of a few city blocks.
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  #6  
Old 11 January 2007, 05:03 PM
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Keeper of the Mad Bunnies Keeper of the Mad Bunnies is offline
 
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Originally Posted by Grand Illusion View Post
Am I missing something here? We have plenty of nuclear weapons and MOABs. Is there a technnological reason why, if we deem it a true danger, we couldn't launch a huge slew of nukes at this thing while it's still 100,000 miles away and break it up into chunks that will burn away in the atmosphere? It's only the size of a few city blocks.
To my understanding, that only works in Hollywood.

Of course, we can always contact Jack O'Neill.

James Powell
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  #7  
Old 11 January 2007, 05:21 PM
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Originally Posted by Grand Illusion View Post
Am I missing something here? We have plenty of nuclear weapons and MOABs. Is there a technnological reason why, if we deem it a true danger, we couldn't launch a huge slew of nukes at this thing while it's still 100,000 miles away and break it up into chunks that will burn away in the atmosphere? It's only the size of a few city blocks.

Probbaly the speed of the astroid negaits the speeds and mass that our nukes have...

Just a guess though, I am not Billy Bob Thorton.
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  #8  
Old 11 January 2007, 05:39 PM
Troodon Troodon is offline
 
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Quote:
Originally Posted by Grand Illusion View Post
Am I missing something here? We have plenty of nuclear weapons and MOABs. Is there a technnological reason why, if we deem it a true danger, we couldn't launch a huge slew of nukes at this thing while it's still 100,000 miles away and break it up into chunks that will burn away in the atmosphere? It's only the size of a few city blocks.
Even if you reduce the asteroid to powder, that powder will still hit the earth while carrying the same kinetic energy that the unbroken asteroid did. The difference will be that you detonate 65,000 nuclear bombs in the upper atmosphere as opposed to a point on the surface. According to some estimates, that would actually have more harmful global consequences.
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  #9  
Old 11 January 2007, 06:01 PM
FloridaGirl
 
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(99942) Apophis (previously known by its provisional designation 2004 MN4) is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a relatively large probability that it would strike the Earth in 2029. However, additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However there remained a possibility that during the 2029 close encounter with Earth, Apophis would pass through a "gravitational keyhole", a precise region in space no more than about 400 meters across, that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale until August 2006.

http://en.wikipedia.org/wiki/99942_Apophis

There are lots of objects that are close to Earth. Yes, we have gotten hit. Yes, we will get hit again. As other have suggested, blowing up an asteroid/comet/any other assorted planetesimal could potentially make it worse. However,
Quote:
Even if you reduce the asteroid to powder, that powder will still hit the earth while carrying the same kinetic energy that the unbroken asteroid did. The difference will be that you detonate 65,000 nuclear bombs in the upper atmosphere as opposed to a point on the surface. According to some estimates, that would actually have more harmful global consequences.
power would just create a spectacular meteor shower. However, nukes cannot break up an asteroid that completely and uniformly. Now, this could still be true, but only we blew it up below our atmosphere. The Tunguska event shows just how devastating an exploding ateroid can be.

It's things like this that make me miss my astronomy book.
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  #10  
Old 11 January 2007, 06:09 PM
Troodon Troodon is offline
 
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Originally Posted by FloridaGirl View Post
However,

power would just create a spectacular meteor shower. However, nukes cannot break up an asteroid that completely and uniformly. Now, this could still be true, but only we blew it up below our atmosphere. The Tunguska event shows just how devastating an exploding ateroid can be.

It's things like this that make me miss my astronomy book.
You are right that nuclear weapons would not effectively reduce the asteroid to powder, but if they did, I do think that the powder would be more destructive than you say. Consider than even in the case of powder, it is still tons and tons of material going very, very fast and being stopped completely by the earth - all that energy has to go somewhere.
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  #11  
Old 11 January 2007, 06:24 PM
iskinner
 
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Originally Posted by Troodon View Post
You are right that nuclear weapons would not effectively reduce the asteroid to powder, but if they did, I do think that the powder would be more destructive than you say. Consider than even in the case of powder, it is still tons and tons of material going very, very fast and being stopped completely by the earth - all that energy has to go somewhere.
Yes, but it is going to be greatly slowed down by the impact on the atmosphere first and all that energy is going to go into creating one hell of a display of burning rocks and minerals. If if was possible to reduce an asteroid to small uniform fragments, I doubt many would survive this inferno to reach the surface of the earth.

But, of course, the trouble is that the pieces would most likely be large enough not burn up in the air and to hit the earth and instead of one large collision we are now dealing with thousands of medium collisions over a even larger area.
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  #12  
Old 11 January 2007, 06:29 PM
FloridaGirl
 
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Originally Posted by iskinner View Post
Yes, but it is going to be greatly slowed down by the impact on the atmosphere first and all that energy is going to go into creating one hell of a display of burning rocks and minerals. If if was possible to reduce an asteroid to small uniform fragments, I doubt many would survive this inferno to reach the surface of the earth.

But, of course, the trouble is that the pieces would most likely be large enough not burn up in the air and to hit the earth and instead of one large collision we are now dealing with thousands of medium collisions over a even larger area.
Exactly. To me, powder is very small particles. So perhaps Trooden and I merely disagree on what "powder" means.
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  #13  
Old 11 January 2007, 06:41 PM
Troodon Troodon is offline
 
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By "powder", I do mean particles that are all small enough to burn up in the atmosphere. They still would not be harmless, because that "display of burning rocks and minerals" could still release enough energy to temporarily change the climate.
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  #14  
Old 11 January 2007, 06:46 PM
iskinner
 
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Quote:
Originally Posted by FloridaGirl View Post
Exactly. To me, powder is very small particles. So perhaps Trooden and I merely disagree on what "powder" means.
OK, I'm not sure what you are agreeing or disagreeing with. But the bright meteor displays regularly occurring in our sky is small particles burning up from impact with the earth's atmosphere. So if the dust particles where sufficiently small, sand grain size - maybe a touch larger, the material would not survive the impact with the atmosphere.

If larger, say baseball size or bigger, then it should easily survive the transition through the atmosphere depending of the material of the asteroid. I'm not sure where between sand and baseball is the burn up/impact threshold. I suspect it depends on whether the material is metallic or more fragile rock.

But I would say reasonable "powder" sized particles would burn up.
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  #15  
Old 11 January 2007, 06:49 PM
Doug4.7
 
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There is nothing we can do about. Therefore, don't worry, be happy.

But spend all your savings by then....

Our nuclear weapons sound big, but in astronomical terms, they are a fart in a hurricane.
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  #16  
Old 11 January 2007, 06:53 PM
Troodon Troodon is offline
 
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One of my more unlikely "goals in life" is to live in a bunker somewhere in the wilderness, so that I could survive almost any catastrophe. It's part of my "If I really were the last man on earth then any surviving women would like me." theory.
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  #17  
Old 11 January 2007, 07:33 PM
jason13
 
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Quote:
Originally Posted by Grand Illusion View Post
Am I missing something here? We have plenty of nuclear weapons and MOABs. Is there a technnological reason why, if we deem it a true danger, we couldn't launch a huge slew of nukes at this thing while it's still 100,000 miles away and break it up into chunks that will burn away in the atmosphere? It's only the size of a few city blocks.
A few years ago, I read an article (I think on BBC News) where a group of researchers ran a a series of computer simulations where they tried to determine how many nuclear explosions it took to aim an asteroid at a particular place on earth (like a large city or small country). They determined it would take an average of 3 explosions with a few taking up to 5 to hit an area the size of England.

I'm sure the same sort of research can determine if it is possible to deflect an asteroid away from earth or to an unpopulated area.
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  #18  
Old 11 January 2007, 07:40 PM
Doug4.7
 
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Originally Posted by jason13 View Post
I'm sure the same sort of research can determine if it is possible to deflect an asteroid away from earth or to an unpopulated area.
It would have to be "away from the Earth" as a major impact ANYWHERE would be devastating.
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  #19  
Old 11 January 2007, 07:45 PM
Nick Theodorakis Nick Theodorakis is offline
 
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Quote:
Originally Posted by Troodon View Post
You are right that nuclear weapons would not effectively reduce the asteroid to powder, but if they did, I do think that the powder would be more destructive than you say. Consider than even in the case of powder, it is still tons and tons of material going very, very fast and being stopped completely by the earth - all that energy has to go somewhere.

Yes , it all goes to heat the atmosphere. You can calculate how much, if you know the kinetic energy of the asteroid, the mass of the atmosphere, and the specific heat of air, using this relationship:

Quote:
The equation relating heat energy to specific heat capacity, where the unit quantity is in terms of mass is:
Q = m c ΔT

where Q is the heat energy put into or taken out of the substance, m is the mass of the substance, c is the specific heat capacity, and ΔT is the temperature differential.
From the above reference, the approximate heat capacity for air is 1 Joule per gram per degree Kelvin.

From the OP:

Quote:
Originally Posted by Morrigan View Post
"Friday the 13th of April 2029 could be a very unlucky day for planet Earth. At 4:36 am Greenwich Mean Time, a 25-million-ton, 820-ft.-wide asteroid called 99942 Apophis will slice across the orbit of the moon and barrel toward Earth at more than 28,000 mph. The huge pockmarked rock, two-thirds the size of Devils Tower in Wyoming, will pack the energy of 65,000 Hiroshima bombs -- enough to wipe out a small country or kick up an 800-ft. tsunami."

http://men.msn.com/articlepm.aspx?cp...28365&GT1=8991
The mass of the asteroid is about 25 X 10^9 kg, and its velocity is about 125000 m/sec, so its kinetic energy, given by

K.E. = 1/2 m v^2


is about 2 x 10^18 Joules. Sounds like a lot. However, the mass of the atmosphere is about 5 x 10^21 g, according to wikipedia..

So putting those into the equation above:
Q = m c ΔT

and solving for ΔT, I get that it would raise the temperature of teh atmosphere by 0.0004 degrees.

I think we can handle that.

Nick
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  #20  
Old 11 January 2007, 07:59 PM
Troodon Troodon is offline
 
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I remember reading that even if an asteroid were to be broken up burn up in the atmosphere, it would still cause damage. IIRC, those calculations were using the mass of the asteroid that killed of the dinosaurs, which I think was significantly larger than this one. Also, there may be effects aside from direct temperature increases (including 25 million tons of dust in the atmosphere).

Of course, I may just be wrong. This isn't my field.
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