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 > >
