ignore me, i just realized the error in my mental model. On Fri, Feb 15, 2013 at 3:08 PM, Alexander Hollins < alexander.holl...@gmail.com> wrote:
> The Moon makes about 13 revolutions in the course of a year. > > revolutions around what? > > On Fri, Feb 15, 2013 at 3:05 PM, Harry Veeder <hveeder...@gmail.com>wrote: > >> 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 >> >> >
