How round is the earth compared to the sun?

1 ANSWERS

1. amomipais82
   

   Hi,
   first of all, moon's orbit is tilted. So the moon crosses the earth-sun plane at two places on his orbit, they are called the two nodes of the moon's orbit.
   
   Now imagine the earth is riding in a year around the sun, and the moon rides every month around the earth. For an eclipse, the moon and earth and sun must stand in one straight line. So this is only possible when the moon just stands in one of his two nodes.
   
   Now you may think that exactly every half year a straight line of earth, moon and sun must be possible. Here you must know there is an other effect! The moon's orbit itself drifts around in 18 years time. Or you can say that the two nodes displace themselves. This makes that the main period between eclipses rather is 'a half year minus some days' instead of 'exactly a half year'.
   
   Of course, a solar eclipse can be followed by a lunar eclipse a half month later, or otherwise.
   
   Or it is even possible that 2 solar eclipses appear after each other, so a month between them. Just the same for 2 lunar eclipses. But these events are mostly not both total eclipses, they rather are two partial solar eclipses or two penumbral lunar eclipses.

   Report (0) (0)  |   12 years, 9 month(s) ago