http://conversationamongfriends.org/taxonomy/term/117 Comments for "Apophis" en http://conversationamongfriends.org/13-year-olds-calcs#comment-354 <p> <strong>2008-Jul-10:<br /> </strong>An equivalent way of describing the problem of computing an impact probability for Apophis is that the true 2029 &quot;keyhole&quot; leading to a 2036 impact -- as distinct from the theoretical keyhole derived from the Standard Dynamical Model -- is not known in the absence of knowledge of the complete dynamics. The problem is acute enough for Apophis that, IF impact hasn&#39;t been previously excluded, AND there hasn&#39;t been a through physical characterization, it can&#39;t be known for certain it will impact until during or after the 2029 encounter, even if a spacecraft is accompanying Apophis and providing position measurements good to 2 meters. That is, the keyhole could be determined only retrospectively, after passage through it. <br />   </p> <p> From the NASA web site. </p> Wed, 23 Jul 2008 08:43:35 -0400 Joey comment 354 at http://conversationamongfriends.org http://conversationamongfriends.org/13-year-olds-calcs#comment-352 <p> That&#39;s good material for your college application: &quot;at age 13 corrected NASA&#39;s calculations about the Apophis asteroid&quot; </p> <p> 1 in 450 is getting too close for comfort  </p> Wed, 16 Apr 2008 08:16:23 -0400 Jonathan comment 352 at http://conversationamongfriends.org