World News for Students of English

16-04-2025 07:00

In the 17th century, Isaac Newton explained that gravity causes tides.

The Moon pulls most strongly on the side of Earth closest to it, creating a tidal bulge. A second bulge forms on the opposite side because the Earth and Moon orbit a shared center of mass. As Earth spins, different places move into and out of these bulges, causing two high tides and two low tides every day.

The Sun also affects tides. When the Sun and Moon line up during a full or new moon, we get strong spring tides. When they are at right angles, we get weaker neap tides. Local geography affects how strong tides are – wide, shallow bays can make tides more extreme. Tidal forces are even stronger on other moons and planets. Jupiter’s moon Io has powerful tidal heating that causes volcanic activity. Over time, Earth will become tidally locked to the Moon, always showing the same face. But that won’t happen for billions of years, long after the Sun is gone.

Difficult words: tidal bulge (a rise in sea level caused by gravity), neap (a tide just after the first or third quarters of the moon when there is the least difference between high and low water).

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