Day on Earth was much shorter: scientists discover traces of "boring billion" years
People who always feel like they don't have enough time in the day to get everything done would probably be even busier if they lived in ancient times when the length of the day was completely different. A new study has found that in ancient times, a day on Earth lasted only 19 hours.
The study, which revealed such a period, was published in the journal Nature Geoscience. The scientists came across the discovery while studying solar tides.
Nowadays, a day on Earth lasts 24 hours. During this time, the planet manages to make one revolution around its axis. The Moon orbits the Earth in 27 days, being at a distance of about 384 thousand km.
But, as scientists have discovered, for almost a billion years in a row during the Proterozoic era, the geological period of the Precambrian that lasted from 2.5 billion years to 541 million years ago, the average day length was about 19 hours. Scientists call this period in the history of the Earth the "boring billion".
This contradicts the previous theory that the length of the day increased gradually, since in this case it could not have been stable for a billion years.
At the same time, the Moon was orbiting much closer to the planet. In recent decades, geologists have been studying a special type of sedimentary rock that contains preserved layers from tidal mudflats. By counting the number of sedimentary layers caused by the fluctuations, they were able to determine what the length of a day was in previous geological periods.
However, the accuracy of the data obtained in this way has been controversial, so in the new study, the scientists used another method of estimating the length of the day, known as cyclostratigraphy.
This geological method studies rhythmic sedimentary layers that describe how changes in the eccentricity and tilt of the Earth's orbit have affected its climate over time.
The study allowed them to establish that the length of the day in the past may have remained constant over a long period of time, rather than gradually increasing. The key evidence was the "solar atmospheric tides" associated with the heating of our atmosphere during the day.
Traces of such tides can also be considered as traces of tides caused by the Moon's gravity.
Scientists explain that the more traces of "solar tides" were found, the faster the Earth's rotation was during this period, and therefore the day was shorter.
Earlier, OBOZREVATEL also talked about what will happen when the Earth's rotation accelerates.