Today, we know that the Earth takes 24 hours to complete one rotation in its axis. However, in the has the Earth apparently only had 19 hrs in a day. A new study published in the journal Nature Geoscience revealed that Earth took only 19 hrs to make one rotation about its axis a billion years ago and hence, had only 19 hrs long days. In the mid-proterozoic era, Earth had 19 hours long days due to tidal phenomena. The Proterozoic era began 2.5 billion years ago and ended 543 million years ago.
As per the study, the Earth had 19 hrs long days because the moon was closer to Earth. Tidal resonance was behind the stalling of the length of days during the mid-proterozoic era. The new study has revealed that during the mid-proterozoic era, the torque of lunar oceanic tides was decelerative. This means that the Earth's rotation energy was drained by the tides and slowed the planet down.
On the other hand, the atmospheric thermal tides influenced by solar energy would fasten the rotation of the Earth. Together, the accelerative and decelerative torques temporarily stabilised Earth's rotation and stalled the day length.
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The mid-proterozoic era was also a time when biological evolution was relatively limited. In a statement released by the Chinese Academy of Sciences, Ross Mitchell, a geophysicist at the institute, and lead author on the paper said that over time, the moon has stolen Earth's rotational energy to boost it into a higher orbit farther from Earth.
This means that every time the Moon drains Earth's rotational energy, our planet would take longer to spin and the Moon moves higher up in its orbit.
