How many high tides do seashores have in a week?

The rhythmic rise and fall of ocean water, known as tides, are primarily orchestrated by the gravitational dance between Earth and its Moon. The Moon's powerful pull creates a bulge of water on the side of Earth directly facing it, resulting in one high tide. However, an equally significant high tide occurs simultaneously on the opposite side of the planet. This second bulge isn't due to a push from the Moon, but rather a combination of the Earth itself being pulled towards the Moon, leaving the water on the far side to bulge outwards due to inertia, and the centrifugal force generated by the Earth-Moon system revolving around their common center of mass.

As our planet spins on its axis, a specific seashore rotates through both of these watery bulges approximately once every 12 hours and 25 minutes. This means that within a single lunar day, which is slightly longer than our 24-hour solar day, any given coastal location will experience two distinct high tides and two corresponding low tides. Multiplying this daily occurrence by seven days reveals that seashores typically encounter 14 high tides in a standard week.

While the Moon is the main conductor of this oceanic symphony, the Sun also plays a role, though its influence is about half that of our lunar neighbor. When the Sun, Moon, and Earth align, their gravitational forces combine to create unusually strong "spring tides." Conversely, when they are at right angles to each other, their pulls partially cancel out, resulting in weaker "neap tides." This constant interplay of celestial mechanics ensures the continuous ebb and flow that shapes our coastlines.