A new study reveals how the Earth’s spinning is 1,8 milliseconds slower every century, augmenting the duration of days.
A group of scientist from the Royal Society Publishing conducted the study. They explained how ancient astronomers, and their observations, are the reason for why the investigation could be a success. With the help of old astronomy records and data was collected thousands of years ago, the researchers could prove that, in fact, there is a new rotation speed.
According to the study published in the journal Proceedings of Royal Society A, researchers analyzed centuries of lunar and solar eclipses recordings, many of which were found in Babylonian clay tablets. A part of the data was also found while studying Chinese dynasties histories.
Duncan Agnew, a geophysicist at the University of California, San Diego, explained how the ancient astronomers helped enormously during the course of the investigation.
“There were a bunch of guys back in what is now Iraq 2,500 years ago putting things on clay tablets. They weren’t thinking that 2,500 years later somebody was going to be writing a paper about Earth rotation,” Agnew told LiveScience in an interview this Wednesday.
What does this discovery mean?
This group of modern researchers successfully proved that Earth is, in fact, rotating slower than in earlier years. The discovery shows that the planet’s spin on its axis is taking 1.8 milliseconds more, compared to every century record, which means that every year the Earth is 1.8 milliseconds slower. This might seem depreciable, but when that constant time variation in the last 2,700 years is added up, the result is a 7-hour discrepancy with the time we are familiar with.
On this matter, if humans were measuring time with an atomic clock since the year 700 BC when the first observation was recorded, the time at noon, just when the sun is above, would actually be 7 PM.
The first astronomers measured time using the position of celestial bodies in the sky as guidance, along with the observation of the rise and setting of the sun and the several moon shapes. This is known in the science world as Universal Time, a time measure that uses gravitational movements of the Earth, the sun, and the moon as a reference.
There is another way to measure time and is called Terrestrial Time. This method is completely independent of the laws of physics. Its primary standard is the atomic clock, which is the most exact instrument known when it comes to time measuring. According to this mechanism, the Earth rotation lasts exactly 86.400 seconds.
However, as it was shown in the study, the Earth rotation is not perfect. And because of this, both Universal Time and Terrestrial Time do not commonly line up.
In modern times, the ruling of the time is made by atomic clocks measurements. For this reason, every time the Universal Time seems to be out of synchronization with the Terrestrial Time, the first standard has to add one leap second. This addition is commonly produced on June 30 or the last day of the year.
What can affect Universal Time measurements?
Many factors could affect how this standard results. Atmospheric winds, depending on their strength, could produce the increase or decrease of Earth’s velocity by thousands of seconds. Also, big volcanoes and earthquakes could produce the same consequence, although this is a phenomenon that is hard to detect by scientists.
Back in 2011, a group of researchers from the Jet Propulsion Laboratory discovered that the Japan earthquake might have shortened the calendar year by 1.8 millionths of a second. This quake was of 9 on the Richter scale, one of the most significant earth movements ever recorded.
Also, the variations regarding the Earth’s poles could affect the rotation velocity. The amount of ice in these areas can change the Earth’s shape and cause a slower spin.
All of these factors were taken into consideration by the team of British researchers to explain the different variations of Earth speed rotation. To do this, the scientist had to gather all the information that the ancient astronomers observed since the year 700 BC. It was, without a doubt, a hard task.
The researchers had to compare the duration and location of both solar and lunar eclipses through ancient times to modern era. Then, the investigation team had to do computer models of the site and duration of the eclipses using as reference the actual rate of Earth’s rotation speed. When comparing both models, the scientists were able to define by how much these two sets of information agreed or not, and conclude the time difference.
One of the researchers talked about how the comparison of both sets of data helped define the discovery.
“Even though the observations are crude, we can see a consistent discrepancy between the calculations and where and when the eclipses were actually seen. It means the Earth has been varying in its state of rotation,” said Leslie Morrison, an astronomer on the team.
Source: The Guardian