Do you think that you had a long day today? Literally, you may be right! This is because on average the days on earth are getting longer as our planet's rotation is slowing down.

A group of British scientist from the Royal Society A from their the research finding came up with the best estimate of how much slower the time had gotten.
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![world-227747_1280.jpg](https://steemitimages.com/DQmPXWey1h4VWz2TQKMMyBuv5bsA5fCnCKWj1W89Qb8mRk3/world-227747_1280.jpg)
<sup>[Source](https://pixabay.com/en/world-globe-earth-astronomical-227747/)</sup>
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#### Going Back in Time
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Using records from around 720 BCE (about 2700 years ago) with no telescopes invented then but the olden day scientist could easily notice the Sun or Moon going dark during an eclipse which they write down. Those records, albeit crude, are enough to calculate the length of days thousands of years ago.
<div class="pull-right"><center><img src="![telescope-2826470_640.jpg](https://steemitimages.com/DQmXy2US5dqBa86m6FVZx492a8Sy2VQAaQ6bnYG7QWTabMr/telescope-2826470_640.jpg)" /><br/><em><a href="https://pixabay.com/en/telescope-astrology-astronomy-2826470/">Source: pixabay</a></em></center></div>

In the early 17th Century,1620, the astronomers now owns a telescope so they could keep records of the time the star disappeared behind the moon. The kept records of the time the star disappeared behind the moon for each day. This is a better accuracy of measurement of the day compared to the sun or moon eclipse method.



Shortly after 1962, the atomic clock was born which gives us a perfect measurement of time which had given us perfect record of time for the past 50+ years.


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The researchers from the UK collated all these data and run presented it graphically.
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https://steemitimages.com/DQmdSyEQSY25C7DsCzKUUAhPxYCnQo2m4etF5yTfE2KrprL/pic.png
<sup>[Source](http://rspa.royalsocietypublishing.org/content/472/2196/20160404.figures-only)</sup>

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#### Result
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The collated data shows that each day has been getting longer by 1.8 milliseconds every century. This was previously calculated to be 1.7 milliseconds in a previous paper published in 1995 per century which is a tiny difference but still important.

The days are getting longer due to pull of the moon's gravity shifts around the earth's insides creating bulges. This same phenomenon creates tides.
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<center>![tidal bulge.gif](https://steemitimages.com/DQmZDBd53Qsua6YFMrV69jDzGN4hecPS5SFoM4iVf1N7Reb/tidal%20bulge.gif)</center>
<sup>[Source](https://userscontent2.emaze.com/images/4d93b224-e346-4022-8ad8-2395e24ad260/a852a1eb-5930-44f9-ae75-f3e4fd36adb7.gif): Tidal bulge</sup>
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The Earth rotates and the bulges move away from the Moon. The Moon pulls back on it. This slows the Earth's rotation.
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<center>![moon_24.gif](https://steemitimages.com/DQmfDY6221rycLKFiemVDk6J2nzW2TLiN5u1ywNWkJQ6aFs/moon_24.gif)</center>
<sup>[Source](http://www.das.uchile.cl/~mhamuy/moon.html): Tidal Braking of The Earth's Rotation</sup>
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Mathemathmatically, the calculated Moon's gravitational force on Earth should even slow the Earth more; making a day longer by up to 2.3 milliseconds every century. But the day only gets slowed by 1.8 milliseconds (which is faster than the calculated 2.3 milliseconds) every century.
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#### What is Speeding the Earth's Rotation to make up for this Difference?
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1. Ice age is one of the factors contributing to this faster rotation of the earth. The weight of the ice pushing down on the poles and now with the ice gone.This makes the Earth's Mass be closer to the pole, making the Earth spin faster.
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2. Another factor is the way the core of the planets interacts with another layer, the mantle. The details of these interactions are still a subject of further research.
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So if you had a really long day just know you may probably be right, the days are getting longer <3

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Ref: [1](http://rspa.royalsocietypublishing.org/content/472/2196/20160404.figures-only),[2](http://www.das.uchile.cl/~mhamuy/moon.html),[3](https://www.sciencealert.com/astronomers-find-a-day-on-earth-is-getting-longer-each-century).