Have you ever felt that your day was too short to accomplish what you wanted to do?Have you ever wondered how different your life would be if the day could be extended?You may be surprised, but the truth is that the length of the daylight on Earth is not set in stone, and it can change over time. And this change is not only related to the movement of the earth itself, but also closely related to our neighbor - the moon.
Did you know?100 million years ago, there were only 19 hours of daylight on Earth!It may sound hard to believe, but it's a surprising fact that scientists have discovered through a new geological approach. This method can measure the length of days in Earth's history, revealing a mysterious connection between the Earth and the Moon. Let's take a look at the content and implications of this study.
We all know that the Earth revolves around the Sun and also rotates on its own axis. The rotation of the earth determines our day-night cycle, and the rotation of the earth determines the change of our seasons. However, the rotation of the Earth is not constant, it changes due to the influence of the Moon and the Sun. The gravitational pull of the Moon and the Sun can have a tidal effect on the Earth, slowing down the Earth's rotation, which leads to an increase in the length of the day. According to scientists' estimates, every century, the Earth's daylight increases by about 17 ms. This means that if we go back in time, the days on Earth would be shorter than they are now. So, how short were the daylight days on Earth in the past?
To answer this question, some scientists have made use of a relatively new geological method to measure the length of the day in history. This technique is known as cyclic stratigraphy, and it focuses on changes in rock deposits. Cyclostratigraphy helps researchers identify "Milankovitch cycles" – changes in the Earth's orbit and rotation that affect the Earth's climate. By analyzing a large number of cyclic stratigraphic records, researchers were able to peer into the past and determine how long the Earth's daylight was at different times.
The results of this study are surprising. Scientists have found that between about 2 billion years ago and 1 billion years ago, there were five hours less time in a full day than there are now, that is, there were only 19 hours of daylight on Earth. This is because during that period, the Moon was very close to the Earth and had a strong tidal effect on the Earth, making the Earth's rotation very fast. Since then, the Earth's daylight has gradually become longer as the Moon moves away from our planet, slowing down the Earth's rotation. "Over time, the Moon has stolen the Earth's rotation energy, putting it into a higher, farther orbit," said Ross Mitchell, lead author of the study and a geophysicist at the Institute of Geology and Geophysics of the Chinese Academy of Sciences.
However, scientists have also discovered an even stranger phenomenon. During the Mesoproterozoic, between about 1.6 billion and 1 billion years ago, the length of the Earth's daylight suddenly stopped changing, remained at about 19 hours, and only began to lengthen again after 100 million years. Scientists call this period a "boring billion" because the Earth's tectonic activity, climate, and biological evolution are relatively stable and have not changed much. So, why does the length of the Earth's daylight stay the same during this time?
Scientists believe that this may be related to the tides that affect the Earth's rotation. The gravitational pull of the Moon controls the Earth's ocean tides, which slows down the Earth's rotation. However, the Sun also exerts a gravitational pull on the Earth in the form of "solar atmospheric tides", which accelerate the Earth's rotation speed when sunlight hits the Earth's surface. "Solar atmospheric tides" refer to the changes in atmospheric pressure that occur when sunlight hits the Earth's surface.
Currently, the Moon tides are twice as strong as the Sun's atmospheric tides, which means that they have a greater impact on the Earth's rotation speed. But in the "boring billion" year, the Earth rotated faster, suggesting that the Moon's gravitational pull was weaker than it is now, the study showed. Thus, during that time, the tidal forces of the Sun and Moon were more balanced, reaching a state of "tidal resonance". "Because of this, if in the past these two opposing forces were ever equal, this tidal resonance would cause the Earth's daylight length to stop changing and remain constant for a period of time," said Uwe Kirschel, a research co-author at Curtin University in Australia.
This long period of 19 hours of daylight coincided with a similar slowdown in the rise of oxygen in the Mesoproterozoic atmosphere, the study found. This may have led to a slowdown in the evolution of life on Earth, as oxygen is an essential component of life and a driver of biodiversity. The Mesoproterozoic was one of the slowest periods in the history of the earth in which life evolved, and it was not until the Neoproterozoic that life exploded and diversified. These radiation and diversification may be related to the re-change of the Earth's daylight length, because the change in the daylight length affects the Earth's climate, temperature, water cycle, and other factors, thus affecting the adaptation and evolution of life.