We mentioned earlier that the Earth’s rotation speed is not a perfect constant. Because this speed is affected by the mass distribution of the Moon and the planet. This means that days can be a few microseconds longer or shorter than 24 hours. The shortest day ever was a testament to that. But now the days are starting to get longer in an interesting way, and no one knows why.
The news that our days are getting longer contrasts with June 29, the shortest day since we gained the ability to measure day length precisely thanks to these atomic clocks and pulsars. But with the exception of June 29, on average, our days were getting shorter until 2020, and then they got longer.
This has come as a surprise to planetary scientists as it is the fastest change in 50 years in which we have the ability to measure days precisely.
Some of the forces that affect the length of days are well understood. The interaction between the Earth and the Moon is slowly reducing the system’s energy as the driving force behind the tides, causing the Earth to slow down. When dinosaurs dominated the Earth, Earth days were half an hour shorter, and we can say that this trend will continue in the long term. Many years from now, Earth’s days will be longer than Mars’ days of 24 hours 37 minutes and 22 seconds.
However, there are also shorter-term factors. Professor Matt King of the University of Tasmania and Dr. As Christopher Watson explains in The Conversation, the Earth works like an ice skater, which starts spinning faster when she pulls her arms towards her. You can achieve a similar feeling with a swivel chair and a few additional weights.
Since the end of the last Ice Age, the melting of ice floes has reduced the pressure at the poles. Reducing the pressure not only created an isostatic response, but also caused the Earth’s crust to spread from the equator to the poles. This creates a force that compensates for the slowing effect of the Moon, thus accelerating the planet’s rotation. Between 1972 and 2020, the average loss of days was about 3 milliseconds.
The distribution of planetary mass can occur much faster and in different ways with events such as earthquakes, creating a slowing or accelerating effect depending on its proximity to the equator or poles. Even the weather can have an effect on acceleration and deceleration. For example, King and Watson write that rain released by major storms near the equator slows the rate of return, while snow falling near the poles creates an accelerating effect. Of course, these effects are valid until the water returns to the sea.
However, when all the events that we know have an effect are examined together, they are not enough to explain the latest observations. So, there is another event that we don’t know yet, and scientists are trying to find it…
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