On Fri, Feb 15, 2013 at 3:50 PM, Alan Fletcher <a...@well.com> wrote: > At 12:14 PM 2/15/2013, you wrote: > > On Fri, Feb 15, 2013 at 2:22 PM, James Bowery <jabow...@gmail.com> wrote: >> Obvious question: >> Was the vector correlated with that of the earth approaching asteroid? > > No, they were almost perpendicular. Pure and delightful coincidence. > > > That was my first thought. > > < > http://www.washingtonpost.com/world/europe/meteorite-injures-more-than-900-in- > russian-city/2013/02/15/ff67c624-7770-11e2-aa12-e6cf1d31106b_story.html?wprss=r > ss_europe> > > Sergei Zakharov, regional branch chairman of the Russian Geographic > Society, told the Interfax news agency that three explosions occurred > as the meteor blew apart. > > “Judging by my observations, the fireball was flying from southeast to > northwest,” he said. “A bright flare of more than 2,500 degrees > [Celsius] happened before the three explosions. The first explosion was > the strongest.” > > - - - - - > > My quick take (partly copied from elsewhere) > > Consider a small object (in this case the meteor) orbiting a large > object (asteroid), as seen from above the orbit. > > If the orbital velocity of the meteor round the asteroid is small, > then the trajectory of the meteor will look like a sine wave around the > trajectory of the asteroid. > > (Similarly, the trajectory of the moon looks like a sine wave > superimposed on the orbit of the earth).
I thought so too 25 years ago, when my instructor in an introductory course on astronomy asked us what we thought the trajectory of the moon is around the sun. It is actually a curve which is always convex... http://www.math.nus.edu.sg/aslaksen/teaching/convex.html <<It is not a circle, but is close to a 12-gon with rounded corners. It is locally convex in the sense that it has no loops and the curvature never changes sign.>> harry
