Why don't eclipses occur during every full-moon or new moon phase?

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Answer 1 · 2016-12-11T08:46:08

See explanation

The Sun's (S) shadow cones ( umbras ) of the Moon (M) and the

Earth (E) are revolving, relatively.. When the Moon's umbra sweeps

the Earth's surface, it is solar eclipse. If the Earth's shadow sweeps

the surface of the Moon, it is lunar eclipse. These do not happen in

every New Moon and Full Moon. They happen, when the

#angleEMS#, during New Moon, and the #angleMES#. during Full

Moon, are very near #180^o#, for near-perfect alignment.

Solar eclipse alignment:

S----------------------------------------------------------M------------E

Lunar eclipse alignment:

S-------------------------------------------------------------------------E--------------M