According to predictions, the Earth will spin even faster in the future.
The Earth’s rotational velocity at the equatorial plane is quite high – approximately, 465.10 metres per second, or 1674.4 kilometers per hour. This, in fact, exceeds the speed of sound in dry air. Naturally, the length of the day is tightly related to this planetary parameter.
And, according to the latest observations, this speed is growing in magnitude: there were 28 shortest days in 2020 since 1960.
The Earth. Image credit: Kevin Gill from Nashua, NH, United States via Flickr, CC BY 2.0
How do we know that?
The answer is quite simple. Modern atomic clocks are accurate enough to spot even the tiniest differences in the duration of astronomical processes, including variations in the length of mean solar day.
By the mid-2020, the Earth has achieved at least 28 shortest day records, with the shortest day on July 19. This day, the earth rotated 1.4602 millisecconds less than its usual time of 86,400 seconds. Scientists say these variations depend on several factors, including changes in motion of the Earth’s molten core, atmosphere, and oceans.
In 2021 we can expect to achieve even shorter days. Preliminary predictions tell that a further reduction in mean solar day duration of 0.05 ms is possible, with the shortest year in decades.