Researchers have shown that the Earth is gradually losing speed in its rotation, which may eventually lead to 25-hour days. Although Earth’s rotation is slowing down extremely gradually (over millions of years), scientists argue that Earth’s rotation is slowing and it has not remained the same speed since the early formation of the planet. This process of slowing down, called rotational deceleration, happens for a variety of natural reasons including tidal friction, earthquakes, and alterations in the planet’s core.
The Earth currently completes one complete spin approximately every 24 hours. However, tides that result from the gravitational relationship between Earth and the Moon cause friction that results in slowing down the spinning of the planet. According to geophysicists, the day of Earth increases by around 1.7 milliseconds per century. That sounds insignificant at first glance, however, over long geological history time that action accumulates.
For example, 1.4 billion years ago, a day on Earth was only around 18 hours long. These historical claims have been verified through the study of rock layers in ancient sedimentary rock and growth rings of corals for example which are naturally and functionally linked over time.
Will There Actually Be 25-Hour Days?
Yes, eventually—but not in our lifetime. By scientific estimates, it would take about 200 million years for Earth’s day length to increase by an hour. While this is an incomprehensible length of time for any human being or any civilization we have ever imagined, considering the 25-hour days that some have envisioned starts to make sense, and even sparks discussion for scientists and futurists on how life might evolve (and how updated days, weeks, and months would accommodate that evolution).
Moreover, some believe if Earth’s rotation continues to decrease that future societies will have to be clever in their definition of “days” relative to the calendar or time measurements.
While the gradual deceleration of the Earth is not expected to have any acute or significant effects on daily life, it may influence long-term average patterns of climate, sea level changes, and the timing of leap seconds—i.e. the occasional addition of seconds to our system of timekeeping to enable our clocks to stay synchronized to Earth’s rotation.
For now, scientists will continue to track the spinning of the planet using everything from atomic clocks to satellite data monitoring Earth’s movement to grasp more clearly how the dynamics of the Earth build over time.
The Earth might have longer days—just not for millions of sunrises and sunsets.
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