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Days are getting shorter than 24 hours

The earth recorded the shortest day since record-keeping began on 19 July 2020 — when the day was 1.4602 milliseconds shorter than 24 hours

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Days are getting shorter than 24 hours

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

Making this startling revelation, scientists said that the earth’s rotation is faster than normal due to which the length of a day is currently “ever-so-slightly” shorter than the normal 24 hours, media reported.

The year 2020 included 28 shortest days since 1960 and 2021 is predicted to be even shorter.

According to Time and Date, on average, with respect to the Sun, the earth rotates once every 86,400 seconds, which equals 24 hours, or one mean solar day.

Scientists believe that 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 days length since the 1960s — will have accumulated a lag of about 19 milliseconds, they said.

A report in the Live Science said, “The 28 fastest days on record (since 1960) all occurred in 2020, with the earth completing its revolutions around its axis milliseconds quicker than average.”

According to atomic clocks, the earth has taken slightly less than 24 hours (86,400 seconds) to complete one rotation for the past 50 years.

The earth recorded the shortest day (since records began) on 19 July 2020 — when the day was 1.4602 milliseconds shorter than 24 hours.

Before 2020, the shortest days occurred in 2005. However, this record has been broken 28 times in the last 12 months.

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.

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, the report said.

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 the earth, which is irregular.

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 the 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, the report added.

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.

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 the earth’s rotation.

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.

According to the report, 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.

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