Alternating layers of white, red and blue-gray rocks, these changes implicit information on the Earth's precession cycle. Image source: Australian Dialogue magazine
Looking up at the moon in the night sky, probably no one would think that it is slowly moving away from the earth. In 1969, NASA's Apollo program installed reflector on the moon. Data shows that the moon is currently away from the Earth at a distance of 3.8 cm every year.
If you trace the moon's current far-distance speed, you will eventually infer that the Earth and the moon were together about 1.5 billion years ago. However, the moon was formed about 4.5 billion years ago, meaning the moon is currently away much faster than it used to be.
Utrecht University in the Netherlands and University of Geneva, Switzerland Researchers recently discovered a long history that reveals the moon's gradual "distance". This is not from the study of the moon itself, but from the reading of signals from ancient rock formations on Earth. Related research was published in the recent Proceedings of the National Academy of Sciences .
In the Australian Karigini National Park, some canyons contain stratified sediments from 2.5 billion years ago. These sediments consist of unique iron layers and silicon-rich minerals that were once widely deposited on the seabed and are now found in the oldest parts of the earth's crust. For example, the Cliff of Jofrey Falls shows the texture of reddish-brown iron layers and darker strips.
In 1972, Australian geologist A.F. Trendel proposed that the periodic patterns of these ancient rock formations may be related to past climate changes caused by the so-called "Milankovic cycle", which vary every 400,000 years, 100,000 years, 41,000 years and 21,000 years, affecting climate, animal and plant migration and evolution. The characteristics of these changes can be interpreted by periodic changes in sedimentary rocks .
The distance between the earth and the moon is directly related to the frequency of one of the Milankovic cycles, i.e. the climatic precession cycles. This period is caused by the oscillation of the Earth's rotation axis or the direction that changes over time. The current duration of this cycle is 21,000 years, but this cycle will be shorter when the moon was closer to Earth in the past.
Analysis of Australian band-like iron structures showed that these rocks contained cyclonic changes of multiple scales, repeated at intervals of approximately 10 cm and 85 cm. Combining these thicknesses with the deposition rate of the sediment, the researchers found that these periodic changes occur approximately every 11,000 years and 100,000 years.
Therefore, analysis shows that the 11,000 cycles observed in rocks may be related to climatic precession cycles, which are much shorter than the current 21,000 years. Using this -year-difference signal to calculate the distance between the Earth and the Moon 2.46 billion years ago, the researchers found that the moon was about 60,000 kilometers away from Earth at that time.
(Source: Science and Technology Daily)
