Before, days on Earth lasted 19 hours, not 24: research

In the billions of years of Earth's life, the planet has changed dramatically. Before, for example, the continents were united into one, Pangea, and other creatures inhabited the different ecosystems, such as dinosaurs, and the day was shorter too.

Now, and for a long time, the day lasts 24 hours, but in the past, a day was equivalent to 19 hours. This has been discovered by scientists from the Chinese Academy of Sciences (CAS), who have published their study in 'Nature Geoscience'.

The scientists used cyclostratigraphy, which analyzes the sedimentary layers of the sea, to detect "Milankovitch" astronomical cycles. These are able to reflect changes in the Earth's orbit and rotation and also affect the planet's climate.

"Two Milankovitch cycles, precession, and obliquity, are related to the wobble and tilt of the Earth's axis of rotation in space. Therefore, the faster rotation of the early Earth can be detected in shorter cycles of precession and obliquity in the past," explained Uwe Kirscher, co-author of the study, to CAS.

So the Earth was spinning faster in the past, and the Moon's pull on it was weaker. Therefore, it was not the pull of the Moon that pushed the Earth to move; but the tide of the Sun. Millions of years ago, it was the Moon that slowed down the terrestrial rotation.

"Because of this, if in the past these two opposing forces had been equal to each other, such a tidal resonance would have caused the length of the Earth's day to stop changing and remain constant for some time," Kirscher clarified.

So, roughly between two and a billion years ago, the length of the day on Earth stopped and stabilized at about 19 hours in length. Over time, and with the change in tension between the Earth and the Moon and its influence, this number has increased to the current 24, the research said.