We want 2020 to finish as quickly as possible.

And it seems our Earth feels the same way, as it has been spinning unusually fast lately. 2020 included the 28 shortest days since 1960.

Earth rotates at irregular speed
The Earth rotates once every 86,400 seconds – or 24 hours, or one solar day.

But its speed is irregular and the length of a day can vary by milliseconds (1 millisecond equals 0.001 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.

Shortest day on record in 2020
Before 2020, the shortest day was July 5, 2005, with an Earth’s rotation lasting 1.0516 milliseconds less than 86,400 seconds.

But on July 19, 2020, the Earth completed its rotation in 1.4602 milliseconds less than 86,400 seconds, beating the previous record.

When was the shortest day on record?

Earth rotation is going quicker

If the Earth’s rotation gets too far out of sync with the super-steady beat of atomic clocks, a positive or negative leap second can be used to bring them back into alignment.

Since the system of leap seconds was introduced in 1972, there have been 27 leap seconds, and they have all been positive. In other words, they have all added an extra second to our clocks, enabling the Earth to catch up.

Recently, however, the Earth has been getting quicker, and no leap second has been required since 2016. If the Earth’s rotation continues to quicken, we may at some point require a negative leap second. If this happens, our clocks would skip a second, in order to keep up with the hurrying Earth.

How we measure that Earth is speeding up?

According to Time and date, to determine the true length of a day, IERS scientists determine the exact speed of the Earth’s rotation by measuring the precise moments a fixed star passes a certain location in the sky each day, expressed as Universal Time (UT1).

Then the UT1 is compared to International Atomic Time (TAI). The true length of a day is expressed by the deviation of UT1 from TAI over 24 hours.

Meaning for earthquakes and eruptions

Back in November 2017, I wrote an article about a possible link found between earth rotation speed and earthquake activity.

Scientists indeed concluded that a slowdown of the Earth’s rotation would actually increase the potential of big earthquakes, after finding roughly every 32 years there was an uptick in the number of significant earthquakes worldwide.

Specifically, the team noted that around every 25-30 years Earth’s rotation began to slow down and that slowdown happened just before the uptick in earthquakes. The slowing rotation historically has lasted for 5 years, with the last year triggering an increase in earthquakes.

Meanwhile, a very recent scientific paper shows a clear but complex mutual cause-and-effect interactions between the energies involved in the Length of Day (LOD) variations, the crustal deformation rate, seismic energy release and volcanic eruption on a global scale.

The scientists found a significant correlation between the occurrences of major volcanic eruptions and the LOD pattern since AD 1750. On a multiyear scale, eruption frequency worldwide increases with LOD changes.

Moreover, the injection of sulphur gases into the atmosphere during major eruptions is accompanied by significant inter-annual LOD variations.

In conclusion, stress changes induced by multiyear variations in Earth’s spin may affect climactic volcanic activity; also, the atmosphere’s dynamic response to volcanic plumes may result in global changes of wind circulation and climate, with consequent LOD variations.

 

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