Today we are used to a 24-hour day. But long before the first humans appeared on Earth, the length of a day was very different. According to a new study by scientists, a day 1-2 billion years ago was 19 hours long.
The researchers used cyclostratigraphy and geological data to test their alternative version of “paleo-rotation of the Earth. They hypothesized that for a long time the Earth had the same well-defined day as it does today, only shorter.
The cyclostratigraphy method is based on studying rhythmic layering of sedimentary rocks to record Milankovitch cycles. Using these cycles, scientists can investigate and explain changes in climate over ultra-long intervals in Earth’s history.
The new data sets helped establish that the day was shorter because the moon was closer. And at some point, the duration of the day stopped its steady increase and leveled off at 19 hours. This happened about two to one billion years ago-the middle Proterozoic-and remained so for about a billion years.
Scientists suggest that the accelerating momentum of atmospheric thermal tides from solar energy balanced the slowing momentum of lunar oceanic tides, temporarily stabilizing Earth’s rotation. This deceleration coincides with a period of relatively limited biological evolution known as the “dull billion.
According to the authors, in addition to the oceanic tides associated with the Moon, solar tides associated with the heating of the atmosphere during the day were also observed. The latter are weaker today, but then the Earth rotated faster, weakening the attraction of the Moon. Thus, the Moon influenced the attraction, slowing down the planet, and the Sun “pushed” the Earth, speeding it up. According to scientists, during the “boring billion,” these forces were equal to each other, creating a tidal resonance and establishing a stable day.
It is also important to note that the period of the 19-hour day lies between the two largest rises in atmospheric oxygen levels. This may confirm the other theory that it took until the 24-hour day did begin to rise again and come to 24 hours to increase oxygen levels. This is enough time for photosynthesis and the daily production of the right amount of O2.
Historical information shows that the Earth is constantly changing and evolving. In the past, the duration of the day was shorter, and it may change again in the future. Some scientists suggest that in the future, the day on Earth may last up to 27 hours.
“We know that the moon continues to move farther away from Earth, so in the future it will be farther away and cause less braking momentum. This should speed up the Earth and increase the length of the day,” says Ross Mitchell of the Institute of Geology and Geophysics at the Chinese Academy of Sciences.
Ultimately, the length of the day on Earth depends on many factors, including the location of the Moon and the Sun, atmospheric conditions and climate change. But one thing remains constant: the Earth is constantly changing and evolving.