ROMANIA
- august 11 -


General info on the eclipses

How the eclipses happen

If the orbit plane of the Moon coincides to the orbit plane of the Earth, in the "New Moon" phase a Sun eclipse will happen and in the "Full Moon" phase a Moon eclipse will happen - that means two eclipses per month; the fact that these eclipses don't happen shows that the two orbit planes do not coincid. They are delayed one from the other with 59', as it is shown in the next image.


That is why, most of the time, the shadow of the Moon in the "New Moon" phase doesn't reach the Earth and that of the Earth in the "Full Moon" phase doesn't reach the Moon, so there will be no eclipse.

The line that results from the intersection between the Moon's orbit and the Earth's orbit is called the line of nodes. If the Moon arrives in one of the nodes in the same time with the Sun a Sun eclipse will produce; if the Moon arrives in one of the nodes at the time the Sun arrives in the opposite node, a Moon eclipse will produce. This is why the yearly path of the Sun was called "the ecliptic".

Due to the changing of the orbit's plan of the Moon in space, the line of nodes makes a full rotation around the Earth in approximately 18.6 years. This is why, after this period of time (named the Saros cycle), the eclipses are generally repeating.




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