> The phase is important because tidal forces are the sum of forces from both the Sun and the Moon. When the Moon is full, that is because the Moon is directly

> The phase is important because tidal forces are the sum of forces from both the Sun and the Moon. When the Moon is full, that is because the Moon is directly opposite the Sun. When the Moon is new, that is because it is directly in front of the Sun. This causes minimums and maximums in the tidal forces on the Earth. More pedantically, both those phases cause a spring tide (max tidal range). A neap tide (min tidal range) is when the sun and the moon are at right angles to the earth.