Days lasted 19 hours in Earth’s distant past daily menu

Over the course of more than a billion years of Earth’s history, our days lasted just 19 hours, according to a new study based on discoveries from the stratiform annulare.

It is a geological method that uses rhythmic sedimentary layers To discover the “Milankovitch” astronomical cycles that reflect how changes in the Earth’s orbit and rotation affect climate.

The length of the day was shorter because the moon was closer. “Over time, the moon has stolen the energy of Earth’s rotation to propel it into a higher orbit, farther from Earth,” said Ross Mitchell, a geophysicist at the Institute of Geology and Geophysics of the Chinese Academy of Sciences and lead author of a new study published in the journal Science. in natural earth sciences.

“Most models of Earth’s rotation predict that the length of the day is getting shorter and shorter as you go back in time,” said Uwe Kircher, study co-author who is now a researcher at Curtin University in Australia.

But a slow but steady change in the length of a day that moves back in time is not what Mitchell and Kircher found.

How do researchers measure the length of an ancient day? In past decades, geologists have used special sedimentary rock records that preserved extremely fine stratification of tidal bogs. Calculate the number of layers of sediment per month caused by tidal fluctuations and you will know the number of hours in an ancient day.

But such tidal records are rare, and those that do survive are often disputed. The new research relies on cyclostratigraphy.

“Two Milankovitch cycles, precession and tilt, are associated with the wobble and tilt of Earth’s spin axis in space. Therefore, the faster rotation of the early Earth can be detected in shorter cycles of precession and deflection in the past,” explained study co-author Uwe Kirscher, now a researcher at Curtin University.

Mitchell and Kircher benefited from the recent proliferation of Milankovitch records, with more than half of the antiquity data generated in the past seven years.

“We realized it was finally time to try some sort of fringe, but totally sensible alternative idea about Earth decaying,” Mitchell said.

An unproven theory is that The length of the day could have remained constant at a fixed value in Earth’s distant past. In addition to the ocean tides associated with the pull of the Moon, the Earth also has solar tides associated with the warming of the atmosphere during the day.

Tides in the solar atmosphere are not as strong as tides in the lunar ocean, but this has not always been the case. When the Earth rotated faster in the past, the pull of the Moon was much weaker. Unlike the moon’s pull, the sun’s tide pushes on the earth. So while the moon slows down the earth’s rotation, the sun speeds it up.

“Because of this, if in the past these two opposing forces were equal to each other, such a tidal resonance would have caused the length of Earth’s day to stop changing and remain constant for some time,” Kircher said.

And this is exactly what the new data compilation showed.

The length of Earth’s day seems to have stopped increasing in the long run and Settled at about 19 hours from approximately 2 to 1 billion years ago: Known as the “boring” billion, Mitchell noted, the “billion years” in which Earth’s development has not undergone major changes.

Interestingly, stagnation time falls between the largest increases in oxygen. “It is surprising to think that the evolution of Earth’s rotation may have affected the evolution of the composition of the atmosphere,” said Timothy Lyons of the University of California, Riverside, who was not involved in the study.

Thus, the new study supports the idea that as Earth climbed to modern oxygen levels, it would have to wait days longer for photosynthetic bacteria to generate more oxygen each day.