Earth’s rotation is slowing down!

The early history of Earth suggests that it had a much faster rotation and days were much shorter. It was calculated that 600 million years ago the day on Earth lasted for only 21 hours. However, the slowing down in the rotation period of Earth through tidal friction by the gravitational pull of the Moon has been going on ever since. This implies that the average length of a day was increasing by 1.7 milliseconds a century.

Astronomers who, back then, reported the effects of the Moon on tides were not aware that Earth could have a slow process of its rotation. Today, using atomic clocks and astronomical observations, scientists have confirmed and accurately measured this slow deceleration of Earth’s spin.

A Process Based on Physics

The primary reason for this change is – friction on Earth’s surface between tides and the Earth’s surface due to gravitational interaction between Earth and the Moon. Since the Moon moves in its orbit around the Earth, its gravity creates bulges in Earth’s oceans due to tidal forces. Tidal bulges experience friction against the Earth’s surface, leading to dissipation of energy and transfer of angular momentum from Earth to the Moon. Thus, the Earth’s rotation slows and the orbit of the Moon moves further and further away from Earth – at present by about 3.8 cm per year.

Interesting facts!

·         Other than tidal interaction, other causes of changes to Earth’s rate of rotation include large-scale weather events and large-scale circulatory movement of Earth’s core.

·         If it were not for the Moon, the world would have had days of 21 hours in the beginning 600 million years ago.

A Paradigm System

Our understanding of Earth’s rotational dynamics allows us to see the interconnectedness of Earth’s physical systems. Its rotation is influenced not only by tidal friction but also by seismic activity, glacial movement, and even atmospheric shifts. While these factors cause slight day-to-day and seasonal fluctuations, the overall trend of a slowing rotation remains steady.

An Ongoing Study

Scientists continue to monitor Earth’s rotation and changes in day length by improving methods that include laser ranging and satellite data. This is refining the scientists’ understanding of Earth’s dynamic systems and the long-term evolution of the planet.

A Look Ahead

This slow and yet gradual deceleration of Earth’s rotation implies that in millions of years, days will be long. The 24-hour day we have now is only a transient balance!