Earth’s rotation sped up in 2020
As our planet orbits the sun, it rotates, completing one revolution in one day, or 24 hours (86,400 seconds).
However, the time it takes to complete that one complete revolution can vary slightly from day to day, the result of variations in the planet's atmospheric pressure, weather systems and associated winds (for example, El Nino), ocean currents, movement of the planet's core, and even, in one instance, as a result of a manmade development project (Google the Three Gorges Dam in China for more information).
The world's time clocks are synchronized to what is known as Coordinated Universal
Time (UTC). Established on Jan. 1, 1960, adopted in 1970, and implemented in 1972, UTC's function is to regulate and coordinate the ultra-accurate atomic clocks used around the world for astronomy, navigation, spaceflight, computer networks, and other time-specific purposes.
UTC is based on the mean solar time (one day or 24 hours) at zero degrees longitude (measured at midnight at the Royal Observatory in Greenwich, London, England; thus the former name of UTC was Greenwich Mean Time or GMT).
In 1972, the concept of leap seconds was introduced to simplify future time adjustments. When astronomical time (time measured in mean solar time units over 24 hours beginning at midnight of each civil day) deviates from UTC by more than 0.4 seconds, a leap second is added to the year in either June or December, thereby bringing all global atomic clocks back in sync with one another. The last leap second was added on New Year's Eve 2016 at 23 hours, 59 minutes, and 59 seconds.
Although records show that the Earth's rotation time has been slowing over the years since accurate measurements began in the late 1960s, it now appears that the rotation, at least for 2020, slightly increased.
A recent online Live Science article states in reference to the Earth's rotation period, "the 28 fastest days on record all occurred in 2020," with the end result being that an astronomical day in 2021 will be 0.05 milliseconds shorter on average (19 milliseconds for the year). July 19, 2020, was the shortest day measured for the year, with the Earth spinning 1.4602 milliseconds faster than the average 86,400 seconds (24 hours).
This has led some scientists to propose deleting a leap second from UTC at some point in the near future, although ongoing monitoring and measurement will be required before a decision is made. Some scientists are even proposing doing away with leap seconds altogether, citing issues with data-logging applications and telecommunications.
Fortunately, for most everyday purposes and functions, and us here on Earth, variations in the planet's rotational rate have no direct impact.
THIS WEEK’S SKY
Venus is currently too close to the sun to be seen, as are Jupiter and Saturn, leaving only Mars and Mercury visible in the evening sky this coming week.
Mars (magnitude +0.3) becomes visible high in the southeast sky around 5:35 p.m., reaching its highest elevation of 58 degrees above the southern horizon about an hour later. It remains visible until about 12:35 a.m. when it drops below 10 degrees above the western horizon.
Mercury (magnitude -0.7) reaches its greatest eastern (to the left) elongation of 19 degrees from the sun as dusk falls in the southwest sky on Jan. 23.
Until next week, clear skies.
EVENTS
• Jan. 20 — First quarter moon
• Jan. 21 — Moon at apogee (farthest from Earth)
• Jan. 23 — Mercury at greatest eastern elongation Correction: The photo cutline of the moon that ran with the Jan. 12 Atlantic Skies column was incorrect and mislabelled the stage of the moon shown in the image.