How long are the days? Detailed answer

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How long are the days? Detailed answer

Big encyclopedia for children and adults

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Did you know?

How long are the days?

Depends on the circumstances.

A day is a period of time during which the Earth makes one rotation around its axis. And it's never exactly twenty-four hours.

Amazingly, this indicator can fluctuate in one direction or another for as much as fifty seconds! This is because the speed of the Earth's rotation changes all the time - due to friction caused by synoptic situations, tides, and geological events.

On an average year, a day is a fraction of a second shorter than twenty-four hours.

When these discrepancies were revealed with the help of atomic clocks, it was decided to redefine the second as a fixed fraction of a "solar" day, - more precisely, one million six hundred and forty thousandth.

The new second came into use in 1967 and is defined as "a time interval equal to 9 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-192 atom in the absence of perturbation by external fields." You can’t say more precisely - it’s just too dreary to pronounce all this at the end of a long day.

The new definition of the second means that the solar day gradually shifts in relation to the atomic. As a result, scientists had to introduce the so-called "leap second" (or "jump second") into the atomic year in order to align the atomic year with the solar year.

The last "leap second" (already the seventh since the establishment of Coordinated Universal Time - UTC in 1972) was added on December 31, 2005 at the direction of the International Service for Estimating the Parameters of the Rotation and Coordinates of the Earth, based at the Paris Observatory.

Good news for astronomers and those of us who love clocks to keep pace with the Earth's movement around the Sun, but a headache for computer programs and all the hardware that runs on space satellites.

The idea of introducing a "leap second" met with a strong rebuff from the International Telecommunication Union, which even made a formal proposal to completely abolish it by December 2007.

Of course, a compromise is possible: wait until the difference between Coordinated Universal Time (UTC) and Greenwich Mean Time (GMT) reaches exactly one hour (somewhere in 400 years) and even then put everything in order. In the meantime, the debate around what counts as "real" time continues.

Author: John Lloyd, John Mitchinson

Random interesting fact from the Great Encyclopedia:

Which producer publicly asked viewers not to watch his just-made film?

Released in 1987, the film "Leonard the Sixth", a parody of movies about spies, turned out to be very bad. Bill Cosby, who produced, co-wrote and starred in the film, was himself so disappointed that he publicly asked viewers not to spend money and watch it. At the same time, Cosby laid the blame for the failure on Paul Weiland, who first became the director of a full-length picture.

Test your knowledge! Did you know...

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