How come eclipses do not happen every month?

Answer 1

We don't get a lunar eclipse (earth obscuring the sun to the moon) or a solar eclipse (moon obscuring the sun to earth) every month, since the alignment of the sun, moon and Earth is not exact enough. The moon sun and earth are not on the exact same plane, so most of the time when the moon passes in front of the sun, it is either too low or too high to cause a solar eclipse. The new moon passes `below` the sun or 'above' it rather than directly in front of it.

Its a similar story with a lunar eclipse, there is a higher chance of a lunar eclipse as the earth is larger than the moon, giving a larger target, but even with this in mind, the earth seen from the moon will either pass below the moon or above it most of the time.

Answer 2

There is not an eclipse every month because the moon's orbit is tilted with respect to the earth's orbit around the sun. therefore, the shadow of the moon may fall into empty space and not cross the earth.

Answer 3

The plane of the Earth's orbit about the Sun , is inclined by about 5 degrees to the plane of the Moon's orbit about the Earth.

They are NOT co-planar. These two planes intercept at two points which vary according to the Earth/Moon orbit about the Sun .

As a consequence, not every NEW/FULL Moon is directly in line with the Earth & Sun. So eclipses are not seen every month.

Answer 4

Eclipse are only happening when The sun, moon and earth aligned in a strait line which is rare and doesn't happen every month.