```Date: Feb 19, 2013 2:52 PM
Author: Robert Clark
Subject: Re: Coincidence of meteor strike and close asteroid approach at same time.

On Feb 18, 8:46 am, Bjørn Sørheim <bsoer...@nixspam.online.no> wrote:> Here you made a MAJOR error. Your argument is way stronger, my friend.> You probably didn't do much probability computations?>> I just choose to accept your numbers for probability  of the two> phenomena, as they seem to on the right level.> So the probability of these two different phenomena occuring within> 24hours is found by multiplying their probability for each separate> incident. If the probability for the asteroid occuring is Pa, and the> meteor occuring is Pm, then the two on the same day is Pa times Pm. So> calculating the probability  is like this:> 1/30x365x30x365=1/119902500, that is 1 over 100 million!> So you have to start the discussion over again> with this imensly low probability in mind.>> CNN posted on Saturday an article where an astronomer from Yale came> to a very similar number. Unfortunately she shot her in the foot by> saying the two trajectories/orbits were incompatiable. She probably> bought  that statement from NASA.> Personally I think these two are connected, and the probability of> them occuring together is as shown imensly low if not the first is> producing the latter. So it questions why NASA, at least preliminary,> said they were not connected.>> Bjørn Sørheim>> On Sun, 17 Feb 2013 07:26:38 -0800 (PST), Robert Clark>>> <rgregorycl...@yahoo.com> wrote:> > I really don't like coincidences in science. Reports are asteroids> >the size of 2012 DA14  getting this close occur about once in 30> >years. And meteors the size of the Russian one enter our atmosphere> >about similar frequency. But the problem is their both occurring in> >the same 24 hour period. If you imagine the asteroid arriving on a> >particular day, the question to ask is what is the probability of the> >Russian meteor arriving on that same day? Once in 30 years, and then> >365 days in a year, means the chance of this happening is like 1 in> >10,000. That's disturbingly unlikely.> >On the other hand if this really is just coincidence, then it should> >be kept in mind that chances this low have been quoted in regards to> >large asteroids impacting Earth in our lifetime.> Here's the article by the Yale astronomer:A meteor and asteroid: 1 in 100 million odds.By Meg Urry, Special to CNNupdated 8:16 PM EST, Mon February 18, 2013http://www.cnn.com/2013/02/16/opinion/urry-meteor-asteroid/index.html She states the two have very different orbits so they should beunrelated, but acknowledges that the very low probability of theirboth occurring so close to each other in time is puzzling. In view of the very real dangers that would arise IF it is the casethey are related I think we should investigate some possible ways thiscould occur. What I mean by this is cases where we assume asteroidsthat make close approaches but do not impact, and therefore offer nothreat, still could have associated fragments that do impact. One way is mentioned in the comment section to this NASA blog whichshows the different orbits of the asteroid and the meteor:How Do We Know the Russian Meteor and 2012 DA14 Aren't Related?Posted on Feb 16, 2013 11:37:14 AM | William Cooke | 25 Comments    |http://blogs.nasa.gov/cm/blog/Watch%20the%20Skies/posts/post_1361037562855.html First though, note there are many ways a fragment could be separatedfrom the main asteroid. For instance some asteroids are "rubblepiles", loosely held together by gravity. In this case collisionsamong the individual fragments could send a fragment away from themain asteroid body. Another is the obvious way of a collision with another asteroid ormeteor. Still another would be outgassing of volatiles that provides anotherforce to separate a fragment from the asteroid. Then once the fragment is separated from the asteroid, over time,since it was given some initial boost away and the asteroid gravity isso small, it will travel further and further away from the asteroid,though still in the same or close orbit. But the key point isdepending on the direction the fragment is sent, once the asteroidcomes around to the Earth or Moon or other planet on a close approach,that fragment could be much closer to that large gravitating body thanthe asteroid and therefore be sent on a different orbit. Then on subsequent orbits it could impact the gravitating body.Indeed it could even be captured by the gravitating body, such as theEarth, depending on the speed it is traveling with respect to thebody. For instance asteroid 2012 DA14 was traveling at 18,641 mph,about 8.3 km/s on closest approach. At the distance it passed theEarth at 17,000 miles this is greater than escape velocity. But it'sless than escape velocity at the Earth's surface. So a fragment thathappened to be closer in to use on that closest approach could havebeen captured.   Bob Clark
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