Why the Moon
minute, the Moon moves forward 38 miles (green arrow) and also falls 16
feet toward Earth (yellow arrow). The combination of forward motion and
gravity turns the Moon just the right amount to keep it circling Earth.
Causes Earth's Tides
Moon pulls every part of Earth toward its center, and pulls more
strongly on nearer parts. Water nearest the Moon is pulled more than
Earth's center, which is pulled more than water on the opposite side.
Water on the top side is pulled in a direction that's slightly down,
and water on the bottom is pulled slightly up. Thus we have two high
tides and two low tides each day. The Sun causes tides also, but with
half the effect of the Moon.