The earth spinning unusually fast lately

 

Time and Date  23-Dec-2020

Many of us wish we could get through this difficult year as quickly as possible. Seems the Earth feels the same way — it has been spinning unusually fast lately. 2020 included the 28 shortest days since 1960.

Atomic Clocks Expose Earth's Irregular Speed

The Earth is an excellent timekeeper: on average, with respect to the Sun, it rotates once every 86,400 seconds, which equals 24 hours, or one mean solar day.

But it is not perfect. When highly accurate atomic clocks were developed in the 1960s, they showed that the length of a mean solar day can vary by milliseconds (1 millisecond equals 0.001 seconds). These differences are obtained by measuring the Earth's rotation with respect to distant astronomical objects, and using a mathematical formula to calculate the mean solar day.

2020 Had Shortest Days on Record

Before this year began, the shortest day since 1973 was July 5, 2005, when the Earth's rotation took 1.0516 milliseconds less than 86,400 seconds.

But in the middle of 2020, the Earth beat that record no less than 28 times. The shortest day of all came on July 19, when the Earth completed its rotation in 1.4602 milliseconds less than 86,400 seconds.

The speed of the Earth's rotation varies constantly because of the complex motion of its molten core, oceans and atmosphere, plus other effects. 

2021 Is Predicted to Be Even Shorter

Scientists monitoring the Earth's rotational speed expect the trend of having shorter days to follow us into 2021 as well.

According to their calculations, an average day in 2021 will be 0.05 ms shorter than 86,400 seconds. Over the course of the entire year, atomic clocks will have accumulated a lag of about 19 ms. For comparison: in past years, they ran fast by a few hundred milliseconds per year. See yearly averages since 1973

In fact, the year 2021 is predicted to be the shortest in decades. The last time that an average day was less than 86,400 seconds across a full year was in 1937.