What Causes the Tides?
Tides are not just water moving in and out—they are actually waves, the largest on Earth. These waves make the sea rise and fall along coastlines across the world. The driving force behind tides is the gravitational pull of the Moon and the Sun. Because the Moon is much closer to Earth, it has a stronger effect than the Sun, making it the primary influence on tides.
The Role of the Moon
The Moon’s gravity pulls water toward it, creating a bulge on the side of Earth closest to the Moon. At the same time, another bulge forms on the opposite side of the planet. This happens because of the centrifugal force from the Earth-Moon system orbiting around a common center of mass. Centrifugal force is the same effect that pushes riders against the outer wall of a spinning carnival ride.
As Earth rotates, its surface moves underneath these two bulges. Any single location on Earth passes through both bulges and both low areas once each day. This results in two high tides and two low tides every 24 hours. However, because the Moon is also moving in its orbit, it takes an extra 50 minutes for Earth to realign with the Moon. That’s why high and low tide times shift slightly each day.
The Role of the Sun
Although the Moon has the strongest influence, the Sun also affects tides. When the Sun and Moon align on the same side of Earth, or on opposite sides, their gravitational forces combine to create especially high and low tides known as spring tides. These are not related to the season “spring,” but rather to the idea of water springing higher than usual.
On the other hand, when the Sun and Moon form a right angle relative to Earth, their pulls partially cancel out. This produces weaker tides called neap tides, when the difference between high and low tide is smaller than normal.
Why Tides Matter
Tides are essential for marine ecosystems and coastal environments. They affect where fish feed, how sediments move, and the daily lives of communities living along the shore. Understanding the science behind tides not only helps predict ocean behavior but also supports navigation, fishing, and coastal management.
