Sitting by the beach and listening to the tide come in is one of my favorite things to do. But if you stop and think about what causes the tide and how our world is so connected, it’s fascinating.

Tides are the regular rise and fall of sea levels caused by the gravitational pull of the moon and the sun on Earth’s oceans. As the moon orbits our planet, its gravity pulls on the water, creating a bulge, or high tide, on the side of Earth facing the moon. At the same time, a second high tide forms on the opposite side of the Earth due to the inertia of the water. Between these bulges, the ocean level drops, resulting in low tide. Most coastal areas experience two high tides and two low tides every 24 hours and 50 minutes.

While the moon has the greatest influence on tides, the sun also plays a role. When the sun, moon, and Earth align during full and new moons, we experience spring tides. These are extra-high high tides and lower-than-normal low tides. Conversely, when the sun and moon form a right angle with Earth, during the first and third quarters of the moon, neap tides occur, with more moderate tidal ranges.

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Then there are king tides, which are in a league of their own. They are the most extreme version of a spring tide. King tides happen when a full or new moon occurs at the same time the moon is closest to Earth in its elliptical orbit (a point called perigee). This alignment amplifies the gravitational pull even more, resulting in especially high tides. While king tides are natural and predictable, they often cause flooding in low-lying coastal areas.

Tides aren’t the same everywhere. Local geography, water depth, and ocean floor shape can all affect how dramatically tides rise and fall. In some places, the difference between high and low tide might be only a foot or two, while in others—like the Bay of Fundy in Canada—it can exceed 50 feet. Tides are also essential to many ecosystems, shaping coastal environments and influencing marine life. And for humans, they play a crucial role in navigation, fishing, and even renewable energy.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.