A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Others » UK Astronomy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Asteroid Collision



 
 
Thread Tools Display Modes
  #1  
Old September 2nd 03, 01:12 PM
Gavin Whittaker
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 02:36 PM
Stephen Tonkin
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 02:51 PM
Paul
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 04:27 PM
Brian Tung
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 04:51 PM
Martin Frey
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 07:25 PM
mike ring
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 07:43 PM
Paul Schlyter
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 08:31 PM
lal_truckee
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 08:34 PM
lal_truckee
external usenet poster
 
Posts: n/a
Default 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  
Old September 2nd 03, 10:13 PM
Brian Tung
external usenet poster
 
Posts: n/a
Default 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
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Space Calendar - July 28, 2004 Ron Astronomy Misc 0 July 28th 04 05:18 PM
Space Calendar - June 25, 2004 Ron Astronomy Misc 0 June 25th 04 04:37 PM
Space Calendar - May 28, 2004 Ron Astronomy Misc 0 May 28th 04 04:03 PM
Space Calendar - April 30, 2004 Ron Astronomy Misc 0 April 30th 04 03:55 PM
Space Calendar - March 26, 2004 Ron Astronomy Misc 0 March 26th 04 05:05 PM


All times are GMT +1. The time now is 01:56 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.