30 (AAA) How come a lunar eclipse doesn't happen on every full moon?

30 (AAA) How come a lunar eclipse doesn't happen on every full moon?

The wobble in the moon

Another explanation

If the Moon's orbit around the Earth were in the same plane as the Earth's around the Sun (the ecliptic,) we would indeed have a monthly eclipse. However, the Moon's orbit is inclined about 5 degrees to the Earth's orbit. The Moon passes through the ecliptic only twice a month at a pair of points called the nodes. The rest of the time the Moon is either above or below the plane of the Earth's orbit and does not pass directly through the Earth's shadow.

A revolving line that doesn't spin around itself in an orbital plane will align with the orbital diameter or radius twice in each revolution.

The line that connects earth and moon when they are both in the orbital plane of the earth is one such line.

The moon and earth are on this line twice a month. Once going down and once going up

is when this line aligns with the diameter of the earths orbital circle. It happens twice a year.