Earth Is Spinning Faster

Earth is Spinning Faster

Why in News?

• Time is flying quicker this year as Earth is spinning around faster than it has in a half-century.
• This means each day on the blue planet is now shorter than 24 hours, owing to the increase in the speed of earth’s rotation over the last 5 decades.

Time

• For most of the history of mankind, time has been marked by the 24-hour day/night cycle (with some alterations made for convenience as the seasons change).
• The cycle is governed by the speed at which the planet spins on its axis. Because of that, the length of a day has become the standard by which time is marked—each day lasts approximately 86,400 seconds.
• The day/night cycle is remarkably consistent despite the fact that it actually varies slightly on a regular basis.
• Scientists also noted that this past summer, on July 19, the shortest day ever was recorded—it was 1.4602 milliseconds shorter than the standard.

Factors Responsible

• There are many factors that have an impact on planetary spin—including the moon’s pull, snowfall levels and mountain erosion.
• They also have begun wondering if global warming might push the Earth to spin faster as the snow caps and high-altitude snows begin disappearing.
• Adding a negative leap second could lead to problems, so some have suggested shifting the world’s clocks from solar time to atomic time.

2021 TO BE SHORTER THAN 2020?

• The year 2020 included 28 shortest days since 1960 and 2021 is predicted to be even shorter.
• An average day in 2021 will be 0.05 milliseconds shorter than 86,400 seconds. Over the entire year, atomic clocks — which have been keeping ultra-precise records of day length since the 1960s — will have accumulated a lag of about 19 milliseconds.
• The 28 fastest days on record (since 1960) all occurred in 2020, with Earth completing its revolutions around its axis milliseconds quicker than average.

How We Know That Earth Is Speeding Up

• The International Earth Rotation and Reference Systems Service (IERS) officially measures the length of a day.
• To determine the actual length of a day, scientists at the IERS “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. This measurement is expressed as Universal Time (UT1), a type of solar time”.
• This UT1 is then compared to the International Atomic Time (TAI) — a highly precise time scale that combines the output of some 200 atomic clocks maintained in laboratories around the world.
• The length of a day is revealed by the deviation of UT1 from TAI over 24 hours.

 A NEGATIVE LEAP?

• If the Earth’s rotation gets 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.
• This has prompted scientists to call for the addition of a “negative leap second’, sparking a debate whether there’s a need to subtract a second from time to account for the change, and bring the precise passing of time back into line with the rotation of the Earth.

What Is A Leap Second?

• Leap seconds refer to adjustment of time, similar to leap years.
• The National Institute of Standards and Technology (NIST) describes a leap second as a second that is added to Coordinated Universal Time (UTC) in order to keep it synchronized with astronomical time.
• UTC is an atomic time scale, based on the performance of atomic clocks that are more stable than the Earth’s rotational rate.
• Astronomical time (UT1), or mean solar time, is based on the rotation of Earth, which is irregular.

How Often A Leap Second Has Been Added Or Substracted?

• While the addition of a ‘negative leap second’ has never been done before, a total of 27 ‘leap seconds’ have been added since the 1970s.
• This was done because Earth has taken slightly longer than 24 hours to complete a rotation over a decade. But since last year, the planet has been taking slightly less time.
• Since 1972, scientists have added leap seconds about every year-and-a-half, on average, according to the National Institute of Standards and Technology (NIST).
• The last addition came in 2016, when on New Year’s Eve at 23 hours, 59 minutes and 59 seconds, an extra “leap second” was added.

When Do Leap Seconds Occur?

• Leap seconds have always occurred at the end of December or the end of June.
• So far, there have only been positive leap seconds. There might be a provision for negative leap seconds if it becomes necessary due to changes in Earth’s rotation.

Pros and Cons

• According to the NIST, leap seconds are useful for making sure that astronomical observations are synced with clock time, however, they can be a hassle for some data-logging applications and telecommunications infrastructure, Live Science reported.
• Several scientists at the International Telecommunication Union suggested to let the gap between the astronomical and the atomic time widen until a “leap hour” is needed, which would minimize disruption to telecommunications.

India Today