Excerpted from here ➥ The Ocean's Tides Explained
As the Earth spins on its own axis, ocean water
is kept at equal levels around the planet by the Earth's gravity pulling inward and centrifugal force pushing outward.
However, the Moon's gravitational forces are strong enough to disrupt this balance by accelerating the water
towards the Moon. This causes the water to 'bulge.' As the Moon orbits our planet and as the Earth rotates, the bulge also moves. The areas of the Earth where the bulging occurs experience high tide, and the other areas are subject to a low tide.
The same forces are at play as the Earth revolves around the Sun. The Sun's gravity pulls ocean water toward the Sun, but at the same time, the centrifugal force of the combined Earth-Sun revolution causes water on the opposite side of Earth to bulge away from the Sun. However, the effect is smaller than the Moon, even given the greater mass of the Sun (greater mass means greater gravitational force). Why? Simply because The Sun is so far away — over 380 times farther away from the Earth than the Moon.
Because the tides are influenced by both the Moon and the Sun, it's easy to see that when the Sun lines up with the Moon and the Earth, as during a New Moon or Full Moon (a configuration also called "syzygy"), the tidal effect is increased. These are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal.
On the other hand, if the Sun and the Moon are 90 degrees apart in relation to an observer on Earth as during the First Quarter Moon or Third Quarter Moon (sometimes called half moons), then high tides are not as high as they normally would be. This is because despite its greater distance, the Sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the Moon's pull. This phenomenon of lower high tides is called a neap tide.