High and low tides happen mainly because of the Moon’s gravitational pull on the Earth’s oceans, with the Sun also having some influence. When the Moon’s gravity pulls on the water on the side of the Earth closest to it, it causes the water to bulge outwards. This bulge creates a high tide in that area since the water is being pulled away from the Earth’s surface.

On the opposite side of the Earth, another high tide occurs. This happens because, as the Moon pulls on the Earth, it creates an opposite effect on the water on the far side. The water there bulges out too, but for a different reason. It’s due to the Earth’s movement and the balance between the gravitational pull and the centrifugal force, which makes the water form another high tide. The areas between these two bulges experience low tides because the water is being pulled toward the high tide areas, leaving less water in these regions.

As the Earth spins on its axis, different parts of the world move through these bulges. This rotation, along with the Moon orbiting the Earth, leads to two high tides and two low tides in most coastal areas every day. The Sun’s gravity also affects the tides, but not as strongly as the Moon because the Sun is much farther away. The height and timing of the tides can also change based on the shape of the coastlines and the ocean floor, making some tides higher or lower than others.