Earth is the third planet from the Sun in our solar system and the only place known in the universe where life has originated and found habitability. This process took billions of years and helped the planet turn into an ocean world. But there was a time in Earth's turbulent history when everything almost slowed to a standstill. A new study on this period - known as the 'boring billion' - has been published in Nature Geoscience and describes that the tectonic activity eased and biological evolution was limited.
The 'boring billion' saw a typical day on Earth lasting for 19 hours due to a delicate balance of opposing forces in our planet's distant past.
"Over time, the Moon has stolen Earth's rotational energy to boost it into a higher orbit farther from Earth," Ross Mitchell of the Chinese Academy of Sciences and Uwe Kirscher of Curtin University in Australia said about the research.
The two physicists analysed the geological data that has emerged in recent years to better understand the Earth, including the rhythmic changes in the planet's climate driven by astronomical forces, including its wobble and axial tilt.
"We realised that it was finally time to test a kind of fringe, but completely reasonable, alternative idea about Earth's paleorotation," Mr Mitchell was quoted as saying by Science Alert.
Mitchell and Kirscher delved into the annals of Earth's tumultuous past in search of the factors that could have ushered our planet into a phase of relative equilibrium.
According to their hypothesis, the period of consistent day length on early Earth emerged following significant fluctuations in atmospheric conditions. Notably, the Great Oxidation Event, a time when oxygen levels surged, generating an ozone layer that later dissipated.
The researchers propose that the introduction of this additional ozone layer could have absorbed more sunlight than water vapour, triggering a phenomenon known as Earth's lesser-known solar tides. These solar tides reverberate through the atmosphere as it warms up during daylight hours.
Although solar atmospheric tides pale in comparison to the gravitational might of the Moon governing oceanic tides, the scenario was different in the past. When Earth spun at a faster pace, the Moon's gravitational pull would have been considerably weaker - only a quarter of its present strength.
If Mitchell and Kirscher's theory holds true and the injection of ozone and sunlight accelerated atmospheric tides, it might have counterbalanced the opposing forces. As a result, Earth could have settled into an extended period of stability with days lasting a steady 19 hours.
