Why don't eclipses happen every month?
You probably know how eclipses happen – a solar eclipse happens when the Moon blocks the Sun by coming between the Earth and the Sun, and a lunar eclipse happens when the Earth is between the Moon and the Sun and sunlight is blocked from the Moon. This raises the question of why solar and lunar eclipses don’t happen every month. After all, the length of the lunar cycle is about one month, and the Moon is between the Earth and the Sun every time there is a New Moon. Similarly, the Earth is between the Moon and the Sun every time there is a Full Moon. Doesn’t this mean that we should experience solar and lunar eclipses every month when there is a New or a Full Moon? The reason why this doesn’t happen is because the Moon’s orbit around the Earth is tilted by about 5 degrees with respect to the ecliptic . The ecliptic is the straight line connecting the Earth and the Sun. The tilt of the Moon’s orbit causes the Moon to usually cross slightly above or below the Sun during a New Moon...