Time Perception and Daily Hours Through Geological Ages
3 April 2025 路 Uncategorized 路
Source: 路 https://www.cnr.cn/tech/techgsrw/20241014/t20241014_526938852.shtml
Isn't there supposed to be exactly 24 hours in one day? The answer is not as straightforward as we might think. Recently, research led by Dr. He Huang and Professor Chao Ma from Chengdu University of Technology's Big Data Sedimentary Research Team, along with the international astronomy team headed by Jacques Laskar, has for the first time reconstructed Earth鈥檚 deceleration in rotation speed through geological records between 700 million years ago to 200 million years ago. This study published in *Proceedings of the National Academy of Sciences* (PNAS) garnered significant attention.
One reviewer of this paper, geologist Ross Mitchell, told China Youth Daily and its website that it was long believed Earth鈥檚 deceleration trend had been monotonous and stable; however, with these groundbreaking findings, authors have questioned such assumptions by presenting substantial data indicating interruptions in the planet's prolonged rotational slowdown.
According to Chao Ma, their team discovered a stepwise evolutionary pattern of "deceleration-stability-deceleration-stability" for Earth鈥檚 rotation speed over time. Around 700 million years ago, there was an acceleration in deceleration; around 540 million years ago, the rotational velocity stabilized again until about 340 million years ago when it started to slow down once more and reached a stable state approximately 250 million years ago. He noted that roughly 700 million years ago, one Earth rotation or day lasted for only around twenty hours; whereas by 200 million years ago, this had extended to about twenty-three hours.
These findings are derived from the "stories" told through rocks on our planet. Chao Ma explained how movements of the earth affect climate changes which in turn leave physical and chemical traces recorded within sedimentary layers under water鈥攁kin to chapters in a book that can be read back into Earth鈥檚 history.
What causes this deceleration?
The evolution of Earth has been influenced by universal gravitation, with one major reason being tidal dissipation鈥攖he interaction between the earth-moon system. Simply put, lunar gravity stretches terrestrial waters causing tides which then erode coastlines and dissipate energy from our planet's rotation over time.
Interestingly enough, Chao Ma pointed out that two significant geological events correspond to these changes in deceleration rates: The Cambrian Explosion of 540 million years ago when complex life forms flourished; and the Permian-Triassic mass extinction event around 250 million years ago where about ninety percent of species vanished. He added, however, that further research is needed for a definitive cause-and-effect relationship.
During this period from seven hundred to two hundred million years back鈥攚hen days were twenty hours long鈥攖he seas thrived with carefree single-celled organisms until the Cambrian Explosion brought forth complex life forms like anomalocaridids. Following the Permian-Triassic extinction, Earth saw a resurgence of biodiversity leading up to dinosaur dominance.
However, it seems that what primarily causes this deceleration isn't constant over time. Chao Ma explained how tidal dissipation's energy loss is transferred into lunar orbital motion due to conservation laws in angular momentum within the earth-moon system; thus causing gradual weakening as moon drifts away from Earth by about 4 meters every hundred years, totaling an increase of around twenty thousand kilometers since seven hundred million years ago. Around fifty million years ago, internal mass distribution changes became a significant factor influencing deceleration.
While it remains unclear how ocean and continental structures during this period contributed to the pause in rotational slowdowns, Mitchell noted that these findings enhance our understanding of Earth's ancient rotation history significantly.
So what are some impacts brought about by such slowing down? Are we currently experiencing another phase or stable one?
Chao Ma explained that current deceleration primarily affects day length and light exposure duration/frequency which can influence weather patterns leading to climate changes impacting plant growth. Further research is needed for specific effects though.
It's important to note the geological timescale involved here, typically measured in millions of years. Chao Ma stated we are currently within a stable phase with no expected turning points over the next million years (Zhang Qian).
One reviewer of this paper, geologist Ross Mitchell, told China Youth Daily and its website that it was long believed Earth鈥檚 deceleration trend had been monotonous and stable; however, with these groundbreaking findings, authors have questioned such assumptions by presenting substantial data indicating interruptions in the planet's prolonged rotational slowdown.
According to Chao Ma, their team discovered a stepwise evolutionary pattern of "deceleration-stability-deceleration-stability" for Earth鈥檚 rotation speed over time. Around 700 million years ago, there was an acceleration in deceleration; around 540 million years ago, the rotational velocity stabilized again until about 340 million years ago when it started to slow down once more and reached a stable state approximately 250 million years ago. He noted that roughly 700 million years ago, one Earth rotation or day lasted for only around twenty hours; whereas by 200 million years ago, this had extended to about twenty-three hours.
These findings are derived from the "stories" told through rocks on our planet. Chao Ma explained how movements of the earth affect climate changes which in turn leave physical and chemical traces recorded within sedimentary layers under water鈥攁kin to chapters in a book that can be read back into Earth鈥檚 history.
What causes this deceleration?
The evolution of Earth has been influenced by universal gravitation, with one major reason being tidal dissipation鈥攖he interaction between the earth-moon system. Simply put, lunar gravity stretches terrestrial waters causing tides which then erode coastlines and dissipate energy from our planet's rotation over time.
Interestingly enough, Chao Ma pointed out that two significant geological events correspond to these changes in deceleration rates: The Cambrian Explosion of 540 million years ago when complex life forms flourished; and the Permian-Triassic mass extinction event around 250 million years ago where about ninety percent of species vanished. He added, however, that further research is needed for a definitive cause-and-effect relationship.
During this period from seven hundred to two hundred million years back鈥攚hen days were twenty hours long鈥攖he seas thrived with carefree single-celled organisms until the Cambrian Explosion brought forth complex life forms like anomalocaridids. Following the Permian-Triassic extinction, Earth saw a resurgence of biodiversity leading up to dinosaur dominance.
However, it seems that what primarily causes this deceleration isn't constant over time. Chao Ma explained how tidal dissipation's energy loss is transferred into lunar orbital motion due to conservation laws in angular momentum within the earth-moon system; thus causing gradual weakening as moon drifts away from Earth by about 4 meters every hundred years, totaling an increase of around twenty thousand kilometers since seven hundred million years ago. Around fifty million years ago, internal mass distribution changes became a significant factor influencing deceleration.
While it remains unclear how ocean and continental structures during this period contributed to the pause in rotational slowdowns, Mitchell noted that these findings enhance our understanding of Earth's ancient rotation history significantly.
So what are some impacts brought about by such slowing down? Are we currently experiencing another phase or stable one?
Chao Ma explained that current deceleration primarily affects day length and light exposure duration/frequency which can influence weather patterns leading to climate changes impacting plant growth. Further research is needed for specific effects though.
It's important to note the geological timescale involved here, typically measured in millions of years. Chao Ma stated we are currently within a stable phase with no expected turning points over the next million years (Zhang Qian).