Understanding Ocean Tides: The Dance of the Moon and Sun

What Tides Are

Tides are the periodic rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of Earth. The primary cause is the difference in gravitational pull between the near side and far side of Earth as it orbits the Sun.

The most significant contributor to tides is the Moon due to its proximity to Earth; however, the Sun also plays a crucial role, especially during full and new moons.

Equilibrium Bulge Formation

When the gravitational forces of the Moon (and sometimes the Sun) act on Earth’s oceans, they create an equilibrium bulge. This bulge is not static but moves with the relative positions of Earth and the Moon or Sun.

The tidal force causes water to be pulled towards these points, creating a high tide where the bulge is present and a low tide in areas between two bulges.

Spring and Neap Tides

During spring tides, which occur at new and full moons, the Sun and Moon align with Earth, creating stronger tidal forces. This results in higher high tides (spring tides) and lower low tides.

Neap tides happen during first and last quarter moons when the Sun and Moon are perpendicular to each other relative to Earth, reducing their combined gravitational effect on the oceans.

Orbital Eccentricity and Axial Tilt

The shape of Earth’s orbit around the Sun (eccentricity) also affects tides. When Earth is closer to the Sun, its gravitational pull can slightly alter tidal patterns.

Earth's axial tilt further influences tides by changing the angle at which solar and lunar forces act on different parts of the planet throughout the year.

Frequently asked questions

Try it live

Everything above runs in your browser — open Ocean Tides from Moon and Sun: Equilibrium Bulge, Spring and Neap Cycle and a Live Tide Gauge and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.