The year 2020 will be remembered for many things, most unpleasant, but it will also be remembered for being one of the fastest recorded, due to the accelerated rate of rotation of our planet. If this trend continues, it could lead to an unprecedented “second negative jump”.
Our clocks are out of sync, but instead of running slowly as they usually do, they start running a little fast. The reason for this has to do with the surprising number of short days lived last year, the result of the acceleration of the rotation of our planet tan slightly. As Time and Date reports, 2020 had the 28th shortest days since 1960.
It takes the Earth 24 hours, or 86,400 seconds, to make a complete rotation around its axis, which scientists refer to as an average solar day. However, the term “average” is key, as slight variations occur every day. This became evident in the 1960s with the development of the atomic chronicle. Atomic clocks measuring the rotation of the Earth relative to a distant astronomical object, typically a fixed star. Scientists learned that the duration of a single day can deviate a few milliseconds (ms), in which 1 ms equals 0.001 seconds.
The variability of our planet’s rotation has nothing to worry about, and you certainly don’t have to cling to the couch for fear of being thrown into space. The variability of the Earth’s rotational speed is a normal phenomenon and is influenced by factors such as the internal detachment of the planet’s outer core, oceans, winds and atmospheric pressure.
Tthat is, we are talking about very small numbers. Today, for example, is expected to last 24 hours, 0 minutes and 0.0792 ms, while yesterday it lasted 24 hours, 0 minutes and 0.2561 ms, seconds at the time and Data, a website run by journalists and researchers. It is a difference of 0.1769 ms, so yes, minuscule stuff. Some days may be out of an unusual degree, however, such as July 5, 2005, when the Earth’s rotation was 1.0516 ms lower than the average solar day.
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The year 2020 was quite extraordinary in this sense, surpassing the 2005 record no more and no less than 28 times. The shortest was on July 19, when the Earth’s rotation was 1.4602 ms below the average solar day.
Interestingly, we can expect more of the same in 2021. “[A]The average day in 2021 will be 0.05 ms less than 86,400 seconds ” reports Time and Data, which means that, throughout the year, “atomic clocks will have accumulated a delay of about 19 ms.”
Typically, these clocks run fast for a few hundred milliseconds each year and require a added a second jump to keep the clocks in sync.
“A second jump is a second added to Coordinated Universal Time (UTC) to keep it in sync with astronomical time,” seconds at the U.S. National Institute of Standards and Technology. “UTC is an atomic time scale, based on the performance of atomic clocks that are more stable than the Earth’s rotational speed.”
The last time it happened was in 2016. Normally, jump seconds are added at midnight on New Year’s Eve, so if it was held at that time i didn’t wait for an additional full second, it started 2017 a bit prematurely.
We didn’t have to invoke one second since 2016 and, given the acceleration of the Earth’s rotation, we may have to do something we had never done before, which is take away a full second. In other words, a second negative leap.
This action would have the same purpose as a positive jump second, which is to keep UTC at the same time as our atomic clocks. That said, the International Earth Rotation and Reference Systems Service, which decides on these matters, has at present without plans to do it.
It could happen, though. And in case we have to invoke a second negative jump at some future time, you can impress your friends by starting the new year exactly one second earlier than the rest. We welcome you.