Message text written by David Higgon >why you don't get an eclipse of the sun every month<
You are right it is because the earth moon and sun are not in the same plane but it is also a consequence of the three objects interacting as a three body problem. The motion of the moon (just as with the well known office toy where a ball moves erratically between three magnets) is very complicated. The shadow of the moon on the earth is in fact very small and the chances for any misalignment to prevent an eclipse being observed are also high. >how many eclipses the earth gets in a year< Meeus states: The least possible number of eclipses per calendar year (Jan -Dec not just in a 12 month) is four, 2 of the sun and 2 of the moon The greatest number of eclipses per calendar year is 7of which between 2 and 5 can be solar ones. Hope this is helpful. PS Yes, you should get your friend a copy of Meeus' Mathematical Astronomy Morsels 1997 - it is an excellent read. Patrick
