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Asteroid Collision
In uk.sci.astronomy Gareth Slee writted:
: Million to One chance of a collision apparently. : http://news.bbc.co.uk/1/hi/uk/3200019.stm from which: "The chances of a catastrophe are likely to become even slimmer once more measurements of the asteroid's orbit have been made." If this is true, shouldn't astronomers increase the number of measurements? If we look REALLY hard, we might be able to push it into Jupiter. Schrodinger had nothing on this one... ATB, Gavin |
#2
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Asteroid Collision
Pete Lawrence wrote:
Schrodinger had nothing on this one... I'm uncertain about this Gavin. Make up your mind, Pete - he either did or he didn't. Best, Stephen -- + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books + + (N51.162 E0.995) | http://www.astunit.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |
#3
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Asteroid Collision
It might be that each time we take a measurement it either will hit the
Earth or it will miss it. Therefore we should stop anyone taking any more measurments when we have one that states it won't hit the earth. Just looking at it could spell doom. Paul "Gavin Whittaker" wrote in message ... In uk.sci.astronomy Gareth Slee writted: : Million to One chance of a collision apparently. : http://news.bbc.co.uk/1/hi/uk/3200019.stm from which: "The chances of a catastrophe are likely to become even slimmer once more measurements of the asteroid's orbit have been made." If this is true, shouldn't astronomers increase the number of measurements? If we look REALLY hard, we might be able to push it into Jupiter. Schrodinger had nothing on this one... ATB, Gavin |
#4
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Asteroid Collision
Gavin Whittaker wrote:
In uk.sci.astronomy Gareth Slee writted: : Million to One chance of a collision apparently. : http://news.bbc.co.uk/1/hi/uk/3200019.stm from which: "The chances of a catastrophe are likely to become even slimmer once more measurements of the asteroid's orbit have been made." If this is true, shouldn't astronomers increase the number of measurements? If we look REALLY hard, we might be able to push it into Jupiter. A possible interpretation: The current odds are 1 in a million, based on very tentative measurements. Once better measurements are recorded, it turns out that the odds will become either 1. One in a billion, since the reduced error in measurements are now significantly less than the predicted "miss"; or 2. Around 99.9 percent, since the predicted "miss" is essentially zero. If we think there's a one in a million chance of outcome 2, and the rest of the time, outcome 1 happens, then our best estimate of the odds right now is (999,999/1,000,000)*(1/1,000,000,000) + (1/1,000,000)*(999/1,000) which is very close to one in a million. Note that it is very likely that the odds of a collision will drop a lot, but that is balanced by a tiny probability that it will become a virtual certainty. Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt |
#5
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Asteroid Collision
Gavin Whittaker wrote:
Schrodinger had nothing on ... What a truly appalling thought. Cheers Martin -------------- Martin Frey N 51 02 E 0 47 -------------- |
#6
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Asteroid Collision
Stephen Tonkin wrote in
: Pete Lawrence wrote: Schrodinger had nothing on this one... I'm uncertain about this Gavin. Make up your mind, Pete - he either did or he didn't. Not yet, mike (I used to be indecisive but now I'm not so sure) r |
#7
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Asteroid Collision
In article ,
Gavin Whittaker wrote: In uk.sci.astronomy Gareth Slee writted: : Million to One chance of a collision apparently. : http://news.bbc.co.uk/1/hi/uk/3200019.stm from which: "The chances of a catastrophe are likely to become even slimmer once more measurements of the asteroid's orbit have been made." If this is true, shouldn't astronomers increase the number of measurements? WELL, WHAT DO YOU THINK THEY'RE DOING? Do you think they'll never ever make another observation of this object? Duh! However, to be as useful as possible, the observation needs to be as much separated in time as possible. And there are two ways to accomplish this: 1. Make further observations of the object during a long time. 2. Identify the object in images on films or plates taken a long time ago. 2. is much faster than 1. ..... If we look REALLY hard, we might be able to push it into Jupiter. :-) .....no! The uncertaintly of the orbit isn't quite THAT large.... Schrodinger had nothing on this one... ATB, Gavin -- ---------------------------------------------------------------- Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN e-mail: pausch at stockholm dot bostream dot se WWW: http://www.stjarnhimlen.se/ http://home.tiscali.se/pausch/ |
#8
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Asteroid Collision
Stephen Tonkin wrote:
Pete Lawrence wrote: Schrodinger had nothing on this one... I'm uncertain about this Gavin. Make up your mind, Pete - he either did or he didn't. Not yet he either did or he didn't. Someone open the box and let's take a peek ... |
#9
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Asteroid Collision
Brian Tung wrote:
Gavin Whittaker wrote: In uk.sci.astronomy Gareth Slee writted: : Million to One chance of a collision apparently. : http://news.bbc.co.uk/1/hi/uk/3200019.stm from which: "The chances of a catastrophe are likely to become even slimmer once more measurements of the asteroid's orbit have been made." If this is true, shouldn't astronomers increase the number of measurements? If we look REALLY hard, we might be able to push it into Jupiter. A possible interpretation: The current odds are 1 in a million, based on very tentative measurements. Once better measurements are recorded, it turns out that the odds will become either 1. One in a billion, since the reduced error in measurements are now significantly less than the predicted "miss"; or 2. Around 99.9 percent, since the predicted "miss" is essentially zero. If we think there's a one in a million chance of outcome 2, and the rest of the time, outcome 1 happens, then our best estimate of the odds right now is (999,999/1,000,000)*(1/1,000,000,000) + (1/1,000,000)*(999/1,000) which is very close to one in a million. Note that it is very likely that the odds of a collision will drop a lot, but that is balanced by a tiny probability that it will become a virtual certainty. I believe the proper way to calculate impact odds is cross-sectional area of the earth divided by the cross-sectional area of the error-bounded predicted location of the asteroid at closest approach, adjusted for statistical density distribution within the error-bounded predicted location. |
#10
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Asteroid Collision
lal_truckee wrote:
I believe the proper way to calculate impact odds is cross-sectional area of the earth divided by the cross-sectional area of the error-bounded predicted location of the asteroid at closest approach, adjusted for statistical density distribution within the error-bounded predicted location. That's true, but a separate question. The original poster seemed to be asking not how is the probability calculated, but why that probability is "likely" to drop once better elements are obtained for the asteroid. In particular, if it always drops, why isn't the initial probability lower than it might be? The answer is that it only drops *most* of the time. A tiny fraction of the time, the Earth is still within an error's breadth of the recomputed path, and since the error is smaller, the probability of impact is correspondingly larger. As an analogy, consider the rock thrown at my head. Initially, I only know the point of impact to within, say, 10 m, and if I'm within that 10 m radius circle, there is a probability of impact with my head, although that probability is small. Once the point of impact is known to an accuracy of 1 m, the chances that my head is still in the circle is small, so the probability of impact drops to near zero in 99 percent of the cases. One percent of the time, though, my head is still within the circle, and since the circle is smaller, the probability of impact is larger. Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt |
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