Will your watch ever be an hour behind? Will the sun set later and nights become longer in the future? It sounds like a story from a science fiction film, but scientific research is indicating something else. There is a very slow, but continuous change in the movement of the Earth. This change is so subtle that we cannot feel it in everyday life, but this process can make a day in future not 24 but 25 hours.

How stable is Earth’s 24-hour day?

The 24-hour day we consider normal is actually an average value. In scientific language it is called solar day, i.e. the time between the Sun appearing in the same position in the sky twice. But the rotation speed of the Earth is not completely constant. It changes very slowly with time and due to this the length of the day also keeps increasing and decreasing subtly.

Why is the Earth’s speed slowing down?

According to scientific studies, the Earth’s rotation is slowing down at the rate of a few milliseconds per century. This change shows its impact not in minutes or hours but over thousands and millions of years. Many natural factors have a combined effect on the movement of the Earth, in which the Moon is considered to play the most important role.

Moon’s gravity and tides

The Moon creates tides in the Earth’s oceans. These tides do not remain completely in line with the Earth, but lag behind a little due to friction. This imbalance has a brake-like effect on the Earth’s rotation. As a result, the rotational energy of the Earth gradually decreases. Due to this process, the Moon is moving away from the Earth by about 3.8 centimeters every year and the length of the day is increasing.

Climate change and melting ice

Reports from NASA and other international agencies show that the ice of Greenland and Antarctica is melting rapidly. Shrinking glaciers, rising sea levels and overexploitation of groundwater are changing the distribution of the Earth’s mass. When mass moves here and there on the Earth, it affects its rotation speed and the position of its axis. This increases the length of the day at the level of milliseconds.

Earth’s internal changes are also responsible

The Earth’s mantle and core are not completely stable. Movements within them, seismic activities and changes in internal structure also have a very subtle effect on the rotation. These effects are not directly visible, but in the long run their effect is recorded on the length of the day.

difference between solar day and sidereal day

Scientists measure the day in two ways. The solar day is measured based on the Sun, while the sidereal day is the time it takes for the Earth to complete one rotation relative to distant stars. The sidereal day is about four minutes shorter than the solar day. Slight fluctuations are recorded in both of these over time, which indicate changes in the Earth’s rotation speed.

How do scientists measure the length of the day?

With the help of modern geodesy techniques, scientists measure the movement of the Earth with utmost accuracy. It includes atomic clocks, satellite laser ranging, radio signals from distant quasars and more than 100 years of data. In recent years, these data have also been made more accurate through machine learning based analysis.

When will there be a 25 hour day?

This question is as exciting as it is related to the distant future. According to current scientific estimates, it may take about 200 million years for this level of change to occur in the Earth-Moon system. That means a 25-hour day will not be possible in our lifetime or that of many future generations, but in the very distant future.

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