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Earth has recorded its shortest day since the 1960s

  • Category
    Geography
  • Published
    12th Aug, 2022

Context

On June 29th, the Earth completed one full spin in 1.59 milliseconds less than its routine 24 hours. It was the shortest day recorded since the 1960s.

Details:

  • The Earth has set the record for the shortest day ever recorded since scientists began using atomic clocks to measure its rotational speed.
  • In recent years, the Earth's rotation has accelerated, shortening some days by milliseconds. Since 2016 the Earth started to accelerate.

Background

The method

  • Scientists used precise atomic clocks to measure the Earth’s rotational speed.
  • This change was not witnessed since the beginning of precise radio astronomy in the 1970s
  • Scientists use a measurement scale called “length of day” to describe how fast or slow a planet is spinning.
  • The data from International Earth Rotation and Reference Systems Service (IERS) shows how the length of day measurement has been on a constant downward trend for a while.

The length of the day is the difference between the time the planet takes to complete one rotation on its axis or 86,400 seconds.

What factors are affecting the rate of Earth’s Spin?

  • Chandler wobble phenomenon: It is a phenomenon that refers to the small deviation in the movement of Earth’s geographical poles. The normal amplitude of the Chandler wobble is about three to four meters at Earth’s surface, but from 2017 to 2020 it disappeared.
  • Long-term tidal effects: It could just be long-term tidal effects working in parallel with other periodic processes to produce a temporary change in Earth’s rotation rate. The research attributed the larger trend of the Earth’s slower spin mostly to the gravitational pull of the Moon, which causes tidal friction and slows down the Earth’s rotations.
  • Climate change-induced surface variations: Melting ice sheets in Greenland and Antarctica Changes in ocean circulation.
  • Geomorphic factors: Movements in the planet’s inner molten core Seismic activity, Wind speed, and shifting atmospheric gases.
  • Other reasons: Activities that push mass towards the center of the Earth will hasten the planet’s rotation. Anything that pushes mass outwards will slow down the spin.

What can happen if the Earth continues to spin faster on a sustained basis?

  • Difficulty in Timekeeping: The changes brought to the speed of the rotation of the earth by any reason makes timekeeping a difficult job. If the Earth continues to spin faster and days subsequently become shorter, scientists may have to introduce the first ever ‘negative leap second,’ which involves subtraction of a second from clocks.

A negative leap second is a second that is subtracted from our clocks to keep them in sync with the Earth's rotation. It is the opposite of a positive leap second, which is a one-second addition to our clocks. The system of leap seconds was introduced in the early 1970s.

  • It involves one-second adjustments to Coordinated Universal Time (UTC), the time standard used to synchronize clocks around the world. Due to the long-term slowing in the planet’s spin, 27 leap seconds have been added to UTC.
  • As opposed to leap years, which have an extra day added, a negative leap second would mean clocks skip one second.

Coordinated Universal Time (UTC): Before 1972, this time was called Greenwich Mean Time (GMT) but is now referred to as Coordinated Universal Time or Universal Time Coordinated (UTC). It is a coordinated time scale, maintained by the Bureau International des Poids et Mesures (BIPM). It is also known as "Z time" or "Zulu Time"

  • The devastating effect on software: Since a negative leap second has never been tested on a large scale, “it could have a devastating effect on the software relying on timers or schedulers”. In the year 2012, the website Reddit was left inaccessible for 30-40 minutes due to the addition of leap second.

Is Earth spinning faster than it used to be?

  • The answer is “No”. While the Earth has been completing its rotations faster in recent years, when looked at over a much longer period of time, our planet is actually spinning slower.
  • Every century, the Earth takes a few milliseconds longer to complete one rotation — and on average, days are actually getting longer. So, 1.4 billion years ago, a day would have ended in less than 19 hours.

Conclusion:

Such oscillations can occur at any time and therefore do not point towards a one-way progression or regression in a period of time.

While there may be a reduction in the length or duration of a day, it is possible that in the future, there could be an increase that can compensate for the same.

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