Why is the moon more important than the sun for causing earth's ocean tides?

Tides on our planet are caused by the gravitational pull of the Moon and Sun. Earth's oceans "bulge out" because the Moon's gravity pulls a little harder on one side of our planet (the side closer to the Moon) than it does on the other. The Sun's gravity raises tides, too, but lunar tides are twice as big.

The Moon is way nearer to Earth than the Sun is. Although the Sun is much bigger than the Moon, the Moon has only twice more effect on the tides of the Earth. This may not sound a lot, but it definitely makes the Moon twice as important as the Sun.