![a dark grey moon above a blue and white planet](https://cdn.mos.cms.futurecdn.net/PncSR3kS2vJ2erkbTcM6eU-320-80.jpg)
Earth's days once got more than two hours longer, thanks to the moon drifting thousands of miles farther away in its orbit over two periods, researchers have discovered.
The extra hours of sunlight, in turn, may have led to oxygenation events that ushered in a period when life's complexity exploded on Earth, the study researchers say.
"Daylength changes may influence the distribution of solar energy and temperature gradients, potentially impacting weather systems and atmospheric dynamics," the researchers wrote in the new study, published Aug. 6 in the journal PNAS.
Nowadays, the moon orbits at an average of 238,855 miles (384,400 kilometers) from Earth. But our satellite hasn't always been where it is now.
Earth's days are currently around 24 hours long, but that wasn't always the case. Over time, the moon tugs on our planet. As it does so, it migrates away from Earth, siphoning away its kinetic energy. As a result, our planet's spin around its axis slows, thus lengthening Earth's days, according to the study.
Modeling changes in how Earth wobbles as it spins can give a rough picture of this slowdown over the planet's history. But this estimate is clearly flawed, because it leads to a prediction that Earth and the moon would have collided around 1.5 billion years ago, the study authors noted.
In the new study, a team led by geologist He Huang from the Chengdu University of Technology in China, tried to clarify Earth's spin history by looking at eight datasets that captured rock layers from marine environments dating to roughly between 700 million and 200 million years ago. These tidalites, as they're called, can record the strength of the tides over time, in part because they reveal the ocean's thickness. The team combined these datasets with models of the tidal forces acting between the moon and Earth to map how quickly Earth spun around its axis over the half-billion-year study period.
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The researchers found that there was a "staircase" pattern in Earth's spin, with two periods where the planet's rotation quickly and dramatically changed, followed by periods of stability. Over the study period, days got 2.2 hours longer. The moon, during this period, also got an average of 12,000 miles (20,000 km) farther away.
One of these time periods, roughly 650 million to 500 million years ago, encompassed the Cambrian explosion, a period when life diversified dramatically and radiated into new niches. The second "step" in the staircase of Earth's spin occurred roughly 340 million to 280 million years ago, which corresponded to a period when massive glaciers covered the planet.
The study suggests that by increasing the day length — and, therefore, sun exposure — the moon may have triggered great oxygenation events that led to life's diversification. However, those results "need to be interpreted with care," the authors wrote in the study.
The study also casts doubt on another theory: that a period when glaciers rapidly covered Earth, leading to a mass extinction, had a big effect on Earth's spin. Rather, most of the slowdown is caused directly by tidal forces, they suggested.
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Tia is the assistant managing editor and was previously a senior writer for Live Science, a Space.com sister site. Her work has appeared in Scientific American, Wired.com and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.
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Unclear Engineer I am wondering if the study got the timing of the day lengthening events properly associated the climate events.Reply
The tidal forces of the Earth's oceans on the Moon's orbit, which tend to accelerate the Moon's velocity while decreasing the Earth's rotation rate, should be influenced by how much water is in the oceans. So, it makes sense that during warm periods of Earth's climate, with most of the water in equatorial oceans, the effects would be strongest, while during periods of global ice sheets with reduced liquid water in the oceans near the equator, the effects would be weakest.
But, this article puts one day-lengthening step in a hot climate period and the other in a cold climate period.
So, that makes me wonder if the ages of the steps and the climates were derived from different types f data and may not be adequately correlated. -
ChrisA When you see a step function, you want to know the cause. The cause of the Moon's slow drifting away is well known and why would there be steps in the drift rate? I think freak planetary alignments. It's not a one-time alignment but a long series of them. It would be interesting to simulate the Solar System 600 million years ago. But I think we may not be able to predict planetary motion over such a long time span.Reply
In any case, a possible cause of the steps would need to be known before this theory would be widely accepted
This is not unlike our understanding of Darwinism in biology. A first even Darwin himself thought the changes would be more or less uniform but now we think biological evolution moves in "jumps" and the rate of change is not so constant over time. Although these are unrelated fields the causes of the steps need to be understood before they can be widely accepted. -
Classical Motion Maybe the moon’s distance from earth sets our climate. Everything else seems too.Reply
The moon might be responsible for all extinctions.
Life on earth at the moon’s whim. We are totally innocent. A true moon child.
Supposition can go anywhere. How long has the moon been locked? Who has the key?
How does one verify the motion exchanged between the earth and the moon? We would have to make a quick change in distance to see what true effect it has. And what earth’s reaction to it is.
I certainly wouldn’t trust the math of it. I don’t believe we understand gravity.
I’ll bet our understanding of this pair is incomplete. And when found out surprising.
Does the moon’s distance have an analog effect or a quantum effect on earth’s response? An analog scale or a rotational resonance scale? Strictly an analog distance scale or a quantum period scale.
How do we know? Could we move a smaller moon and see what happens? How about binary asteroids? Let’s adjust one and check our gravity math. A locked one would be better. I hear locked moons are common. Interesting. Kinda quantum. In a way.
This is the kind of solar system work and experiments we should be doing. Real space mechanics.
We might even learn to mathematically simulate these motions. After we learn the true motion. 3D motion. -
ChrisA We only need to "understand gravity" to the level that Isaac Newton did to understand why the Moon is drifting away. We certainly do not need General Relativity or some yet-to-be-discovered theory of quantum gravity. Undergraduate-level classical physics is enough.Reply
Your argument uses an equivocation of terms. such arguments are always invalid because "gravity in one use of the word is different from "gravity" in another use.
Just ignore the quantum mechanics, this a very obviously a macro-level problem. And even more, only weak (<1G) gravity is involved so we can also ignore general relativity -
Classical Motion The past two time periods mentioned.Reply
One about ~800 and one at ~250 million years ago. Didn’t say how long the moon was out there on these excursions, or the force that moved it out or brought it back.
They are deciphering patterns found here on earth. -
billslugg The article says during the 500 million year study period, day length increased by 2.2 hours.Reply
There were two step increases.
The Moon suddenly moved further out each time.
So, what caused the Moon to jump out?
To move the Moon outward we must add energy.
This is done by a tidal bulge on Earth pulling the Moon from "off centerline".
Why did the tidal bulge suddenly get bigger?
Possibly from an alignment of continents that allowed free flow all the way around the Earth's equator, forming a giant bulge.
Just a thought. -
Classical Motion Does the moon need to be locked to get the tides we do? Has our moon ever been not locked?Reply
Can the moon change it’s orbital distance in a locked state? Does a locked moon have the same kind of motion transfer as an unlocked moon?
Can a locked moon reflect the motion back? A yo-yo exchange. A harmonic.
Does the moon torque back and forth a little? -
billslugg The Moon would raise exactly the same tides if its rotation was not tidally locked to Earth.Reply
Being tidally locked is irrelevant. We have tides on the side of the Earth facing the Moon because the Moon pulls the water towards it. The Moon raises tides on the far side of the Earth because the Moon pulls the Earth towards it, leaving the water behind, thus it bulges out.
The fact the Earth spins is essential. It is the spinning Earth moves the bulge of water to the east which puts the bulge's center of mass to the east of a line connecting Earth and Moon. It is this off center vector that pulls the Moon to a 4" higher orbit every year.
It is the friction of the tidal waters that slows the Earth down. The energy from the slowing Earth is transferred to the Moon so it can have a higher energy orbit. -
Classical Motion Our atmospheric molecules buzz. They buzz at a ~670 MPH velocity and is omnidirectional.Reply
It’s a charge free mechanical buzz. An inertia buzz. We can not hear that buzz, but we can hear the change in that pressure buzz. And we call that change sound. A change in the buzz will propagate thru that buzz with the direction and velocity of that buzz. The buzz is a carrier.
We have a similar buzz in space. However the space buzz has no charge but it does have orphan EM field buzz. And this buzz also has an omni-directional buzz, but a velocity of c, a c buzz. A constant c buzz and does not change it’s velocity like a pressure buzz can.
I wonder what all is carried by that buzz, or what could be carried by that buzz. It’s always there maybe we could use it. Maybe it is already used.
I often have wondered what could be a carrier medium for gravity. Omnidirectional with c velocity and inverse square loss. -
Unclear Engineer Bill, Good thought about how the changes in continent positions might affect the way the tidal bulges move and maybe explain the steps in the rate of change for Earth's day length.Reply
Here is a good visual display of how the continents have moved over time:
https://www.britannica.com/video/151108/Earth-Pangea-Proxima-locations-continents-inset
It starts only 650 million years ago, so misses the first of the 2 steps at 800 million years ago.
Looking at the changes in continent positions around 250 million years ago, there is a shift from Gondwana being a supercontinent located below the equator, with an open ocean to the north, becoming a more modern string of continent spanning from pole to pole, with a huge Panthalassic Ocean roughly where the Pacific is today. So there does seem to be some change in potential ocean tide currents about then, but I don't see something happening and then going away that would cause a shorter term step function in the Earth's rotation period rate of change.
Look at it yourself and tell us if you see anything that would explain a step. The best way to observe the video is to click on it so that it plays, then pause it and run the pause position back and forth as you want. If you let the whole video play to the end, the only way to repeat it is to go out of the Internet site and then come back in to start the video from the beginning, again.