Our timekeeping system consists of 24 hours in a day, where each hour is divided into 60 minutes and then into 60 seconds. This complex and interesting calculation dates back to ancient civilizations, in particular the Egyptians, who divided daytime into 10 hours and added an hour at the beginning and end of daylight. Nighttime was divided into 12 hours based on star observations. Interestingly, the length of day and night time in this system was not the same and varied depending on the season. Thus, despite the fact that modern methods of measuring time are more accurate and convenient, the tradition of a 24-hour day has survived due to its historical and cultural roots. But everything is not so simple, because the number of hours measured directly depends on the speed of the Earth's rotation, which is known to be slowing down. As the results of a recently published study have shown, in 200 million years a day on our planet will last 25 hours. But why and how did scientists come to this conclusion? Let's figure it out!
There are 24 hours in a day. But why exactly that many and could this change in the future? Image: media.licdn.com
Contents
- 1 The Earth's Rotation
- 1.1 How is it studied?
- 2 The planet rotates more slowly
- 3 A day on Earth will last 25 hours
- 4 The history of timekeeping
The Earth's Rotation
Our planet rotates on its axis, an imaginary line that runs from the North Pole to the South Pole, and this is how we experience the repeating cycle of day and night. The rotation is counterclockwise when viewed from the North Pole, and it takes approximately 24 hours to complete a full rotation.
The reason the Earth rotates is because of its origins – about 4.6 billion years ago, clouds of gas and dust came together under the influence of gravity and began to rotate. The physical principle of conservation of angular momentum states that the Earth continues to rotate unless acted upon by an external force.
A fundamental aspect of our planet's existence, combining aspects of astronomy, physics and geology, is rotation. Image: media.cnn.com
The division of the Earth into 24 time zones is also related to its rotation. Each zone is an area that contains a certain hour of the day, which corresponds to the position of the Sun in the sky. However, this was not always the case. In the time of the dinosaurs, for example, the day lasted not 24 hours, but 23. In fact, for over 1 billion years, the length of the Earth's day was, to be precise, approximately 19.5 hours. This is due to the fact that in the past, the planet rotated faster, and the gravitational force exerted on it by the Moon was weaker. Consequently, the days were shorter.
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How is it studied?
To study the Earth's rotation, scientists use a variety of astronomical instruments to track the positions of stars and other celestial bodies and to accurately measure the speed and changes in the planet's rotation. Another important tool is satellites equipped with advanced sensors – these instruments can detect subtle changes in the speed of rotation and the orientation of the Earth's axis. Geological data, such as sedimentary rock layers, also provide insight into historical changes in the Earth's rotation, helping scientists understand how the rotation has changed over millions of years.
The planet's rotation also affects climate and weather patterns. Image: epod.usra.edu
Thus, the Earth's rotation is a dynamic process that has a profound effect on the planet. It shapes our everyday perception of time, affects weather and climate patterns, and plays a key role in how the world functions.
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The planet is rotating more slowly
Recently, scientists from the Technical University of Munich (TUM) discovered that the length of the day on Earth could eventually increase to 25 hours. This study marks a major advance in our understanding of the planet's rotation dynamics. Yes, contrary to popular belief, the Earth's rotation does not follow a precise 24-hour cycle. This discrepancy is due to the Earth's heterogeneous composition – a mixture of different solids and liquids, each of which influences the planet's rotation speed.
Rotation oscillations are not only important for astronomy, they are also essential for creating accurate climate models and for better understanding weather phenomena such as El Niño. And the more accurate the data, the more accurate the forecasts, explains Ulrich Schreiber, project leader at the TUM observatory.
The TUM researchers' breakthrough is based on an improvement in the ring laser– a sophisticated device capable of measuring the Earth's rotation with astonishing accuracy. The laser, housed at the Wetzell Geodetic Observatory, operates in a specially designed sealed chamber 6 meters underground and consists of a laser ring gyroscope and a “treadmill” that are carefully calibrated to minimize the effects of external factors.
Ring laser allows us to measure the Earth's rotation at a speed never seen before. Image: i0.wp.com
«The two laser beams in the device propagate in opposite directions along a closed loop – if the loop rotates, the beams will have different frequencies,« the researchers explain. Thanks to this difference, it is possible to determine the exact differences in the speed of the Earth's rotation – the greater they are, the faster the rotation speed. In addition to the device, the scientists developed a theoretical model to account for the asymmetry of the beams and correct for the error.
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A day on Earth will last 25 hours
So, the length of the Earth's day is gradually increasing. In the era of dinosaurs, as mentioned above, the day lasted 23 hours, and 1.4 billion years ago only 18 hours and 41 minutes. Now scientists have reported that according to forecasts, in 200 million years the length of the day will increase to 25 hours. But why will this happen?
The answer, as is often the case, lies in our planet's satellite, which is constantly moving away from Earth, thereby slowing its gravitational pull on the planet (and making the days longer). The results of the study, published in National Geographic magazine, represent a significant step forward in understanding the rotation of our planet.
In the distant future, a day on our planet will last 25 hours. Image: services.meteored.com
Recall that the exact time it takes for Earth to complete a rotation can vary by small fractions of a millisecond each year due to a variety of factors, such as the movement of tectonic plates, changes in the rotation of the inner core, or the gravitational pull of the Moon. And their initial speed depends on the force with which dust, rocks, and gas orbiting the Sun collided to form our planet.
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But what will be the consequences of this event for the Earth and living beings? It is impossible to say for sure, since the predicted changes will occur on a geologically significant time scale. The only thing we know for sure is that all living organisms on Earth are closely connected to the 24-hour cycle. Therefore, the presence of 25-hour days can theoretically affect biological processes. The same applies to weather conditions. The main thing is that in 200 million years there will be someone to take measurements and calculate the passage of time.
History of time calculation
To determine the time, the Egyptians used a sundial – a special device for determining the time by changing the length of the shadow of the gnomon (the most ancient astronomical instrument) and its movement across the dial. Day and night time, based on observations, were divided into 12 parts and added up to 24 hours. The number 12 is also associated with the phases of the Moon and the movement of the stars, which made it convenient for astronomical observations. Later, the ancient Romans adopted this system.
But dividing hours and minutes by 60 comes from the ancient Babylonians, who preferred to use numbers with a base of 60. For example, III II (using slightly different strokes) meant three times 60 plus two, or 182.
The history of time goes back to ancient civilizations and observations of celestial objects. Image: www.militarytime.us
We also inherited from them the division of a circle into 360 parts or degrees. Astronomer Nick Lomb from the Sydney Observatory believes that the number 360 interested the Babylonians because this is how they estimated the number of days in a year.
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Interestingly, ancient China used a dual time system in which the day was divided into 12 so-called “double hours”, with the first double hour originally falling at midnight. They also had a separate system in which the day was divided into 100 equal parts, called “ke”. This system, however, was quite complex, which is why in 1628 the number of “ke” per day was reduced to 96.
The Egyptians Invented the Calendar by Watching the Movement of Celestial Bodies. Image: historicaleve.com
While many cultures had their own calendars, there seems to be no evidence of equivalent methods of keeping track of time. For example, the Mayan calendar gives no information about how they divided the day or counted time. However, the same is true for the Australian Aborigines, who had seasonal calendars to mark the seasons, but not time.