Is Earth spinning faster than it has in decades? Planet recorded 28 fastest days in 2020, here's what it means
Researchers who monitor the Earth's rotational speed also predict that 2021 could be even shorter
2020 was shorter than previous years, though it may not have felt that way. The reason: Earth was spinning quicker last year, more than at any other time in several years, according to scientists.
The Earth’s 28 fastest days on record since 1960 took place in 2020, with the planet completing its revolutions around its axis milliseconds quicker than average. Those 28 days broke the previous record for the shortest day ever documented: July 5, 2005, which lasted 1.0516 milliseconds less than the standard 86,400 seconds.
“Before this year (2020) 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,” reveals a blog published by TimeandDate.com.
This is not abnormal or alarming because days on Earth can be slightly longer or shorter than average due to the activity of the planet’s molten core, ocean currents and atmosphere. But so many faster days in 2020 could be a sign that Earth’s rotation is accelerating overall, say experts.
“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),” explains the article. It adds, “The speed of the Earth's rotation varies constantly because of the complex motion of its molten core, oceans, and atmosphere, plus other effects.
Previous research has also explained this phenomenon. According to scientists, because of Earth’s dynamic climate, winds and atmospheric pressure systems experience constant change. These fluctuations may affect how our planet rotates on its axis, stated the 2003 NASA-funded study that used wind and satellite data.
“Changes in the atmosphere, specifically atmospheric pressure around the world, and the motions of the winds that may be related to such climate signals as El Niño are strong enough that their effect is observed in the Earth’s rotation signal,” wrote David A Salstein, an atmospheric scientist in the paper.
From year to year, winds and air pressure patterns change, causing different forces to act on the solid Earth. During El Niño years, for example, the rotation of the Earth may slow ever so slightly because of stronger winds, increasing the length of a day by a fraction of a millisecond, explained experts.
Researchers who monitor the Earth's rotational speed also predict that 2021 could be even shorter. The average day is expected to last .05 milliseconds less than 86,400 seconds, and individual days could last 1.5 milliseconds less. “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. 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,” write authors.
Since the Earth’s rotation varies very slightly all the time, “leap seconds” are occasionally added at the end of June or December, so that the clocks are synchronized to the Earth’s rotation speed as accurately as possible.
“In every-day life, this extra second has practically no importance. However, in every field where exact time is needed (such as astronomy, navigation, spaceflight, computer networks for stock markets or energy supply) this second is of great importance,” Wolfgang Dick, a spokesman for the IERS, told USA Today in 2015.
According to the National Institute of Standards and Technology (NIST), US Department of Commerce, “leap seconds and leap years are both implemented to keep our time in accordance with the position of Earth.” However, leap seconds are added when needed, based on measurements, and leap years are regularly occurring events based on set rules, it explains.
The Earth’s rotation has been a “bit sluggish” since leap seconds were introduced in 1972, says TimeandDate.com, adding that overall 27 leap seconds have been added and all have been positive. This implies that all of them gave an “extra second to our clocks, enabling the Earth to catch up.”
“It’s quite possible that a negative leap second will be needed if Earth’s rotation rate increases further. There are also international discussions taking place about the future of leap seconds, and it’s also possible that the need for a negative leap second might push the decision towards ending leap seconds for good,” Peter Whibberley, a senior research scientist with Britain’s National Physical Laboratory, recently told The Daily Telegraph.
The International Earth Rotation and Reference Systems Service (IERS) in Paris is responsible for maintaining global time. While the last leap second was added on December 31, 2016, no new leap second is scheduled to be added, reveals the IERS’s Earth Orientation Center.