Science Common Sense

1571 - What causes the periodic change in the tides under the influence of the Earth-Sun-Moon system.

The change in tides is caused by the gravitational pull of the Moon and the Sun on the Earth's oceans. Here's how it works:

1. The Moon's gravity pulls on the ocean, creating a "bulge" in the water on the side closest to the Moon.
2. The Sun also pulls on the ocean, creating another bulge.
3. When the Sun and Moon are aligned (at new moon or full moon), their gravitational pulls work together, creating even bigger bulges and higher tides (called spring tides).
4. When the Sun and Moon are at right angles to each other (at quarter moon), their gravitational pulls cancel each other out, resulting in lower tides (called neap tides).

This alignment of the Earth, Sun, and Moon changes as the Moon orbits the Earth, causing the periodic change in tides.