Days on Earth Are Getting Longer, Thanks to the Moon

Space.com ^ | June 5, 2018 | Samantha Mathewson, Space.com Contributor

[ETL]

Days on Earth are getting longer as the moon slowly moves farther away from us, new research shows. 

The moon is about 4.5 billion years old and resides some 239,000 miles (385,000 kilometers) away from Earth, on average. However, due to tidal forces between our planet and the moon, the natural satellite slowly spirals away from Earth at a rate of about 1.5 inches (3.82 centimeters) per year, causing our planet to rotate more slowly around its axis. 

Using a new statistical method called astrochronology, astronomers peered into Earth's deep geologic past and reconstructed the planet's history. This work revealed that, just 1.4 billion years ago, the moon was significantly closer to Earth, which made the planet spin faster. As a result, a day on Earth lasted just over 18 hours back then, according to a statement from the University of Wisconsin-Madison.

"As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out," study co-author Stephen Meyers, a professor of geoscience at UW-Madison, said in the statement. "One of our ambitions was to use astrochronology to tell time in the most distant past, to develop very ancient geological time scales. We want to be able to study rocks that are billions of years old in a way that is comparable to how we study modern geologic processes."

Astrochronology combines astronomical theory with geological observation, allowing researchers to reconstruct the history of the solar system and better understand ancient climate change as captured in the rock record, according to the statement. 

The moon and other bodies in the solar system largely influence Earth's rotation, creating orbital variations called Milankovitch cycles. These variations ultimately determine where sunlight is distributed on Earth, based on the planet’s rotation and tilt. 

Earth's climate rhythms are captured in the rock record, going back hundreds of millions of years. However, regarding our planet’s ancient past, which spans billions of years, this geological record is fairly limited, researchers said in the statement. 

This can lead to some uncertainty and confusion. For example, the current rate at which the moon is moving away from Earth suggests that "beyond about 1.5 billion years ago, the moon would have been close enough that its gravitational interactions with the Earth would have ripped the moon apart," Meyers said. 

Using their new statistical method, the researchers were able to compensate for the uncertainty across time. This approach was tested on two stratigraphic rock layers: The 1.4-billion-year-old Xiamaling Formation from northern China and a 55-million-year-old record from Walvis Ridge, in the southern Atlantic Ocean.  

Examining the geologic record captured in the rock layers and integrating the measure of uncertainty revealed changes in Earth's rotation, orbit and distance from the moon throughout history, as well as how the length of day on Earth has steadily increased.   

"The geologic record is an astronomical observatory for the early solar system," Meyers said in the statement. "We are looking at its pulsing rhythm, preserved in the rock and the history of life."

The new study was published Monday (June 4) in the journal Proceedings of the National Academy of Sciences.

[TigersEye]

Every million years the album will be re-released with an extra 15 second bonus track.

[Hugin]

Good. More time to sleep in.

[SES1066]

I’m a third grade dropout but doesn’t this mean that in the future, total solar eclipses will no longer be total?

The answer to this is yes, we live in a unique era when the 'visual diameter' of the Moon/Luna as seen from the Earth's surface matches the same 'visual diameter' of our sun, Sol. In earlier eras (pre-human), the eclipses would have lasted longer, been less spectacular and been more frequent with a closer Lunar Orbit (annular Lunar Eclipses would have been 'full').

Per this article from The Popular Mechanics website, the ending of total Solar Eclipses will be a comfortable 563 million years in the future, at a minimum.

[ExGeeEye]

Eventually it will be long enough to sync up with “Lawrence of Arabia”, to startlingly accurate effect!

[poconopundit]

Thank you, guys. This is all very interesting. Sorry for being skeptical. You made me believers in this technology and it’s fascinating to think about the computation it must take to calculate the Moon’s position relative to Earth and Sun.

You gave me a nice brief course in Physics... great.

[ETL]

Excellent info. You explained in detail what I only made a quip about.

Thanks, but that of course was a wikipedia piece.

[TigersEye]

Just about the time the sun goes red dwarf and fries the planet.

I guess an event like that deserves a good sound track.

[SunkenCiv]

Thanks ETL. The article is incoherent, but overall, yes, the Moon has a small influence on the Earth. There's a tidal transfer of momentum from Earth to Moon; this means that over time, the rotation rate of the Earth slows down and pushes the Moon away. There's also been a tidal transfer of momentum from the Moon to the Earth, but the lunar mass is only one percent that of the Earth, hence, its rotational momentum is depleted to the point that we see the same face of the Moon all the time. Eventually the Moon may recede enough to slip the surly bonds of Earth, and depending where on its orbit it is at the time, that could be one bad, crazy day. None of us will live to see it. :^)

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• When the Days Were Shorter [2004]
• Early Earth Likely Had Continents, Was Habitable, According To New Study [2005]
• Neptune Might Have Captured Triton [2006]
• Planets Around Planets? [2006]
• Moon Is Younger And More Earth-Like Than Thought [2007]
• Why is the Earth moving away from the sun? [2009]
• The Moon may have formed in a nuclear explosion [2010] [2010]

[Lonesome in Massachussets]

The secular slowing of the earth and recession of the moon is a well established fact. Ancient eclipses documented in cuneiform tablets show that the ratio of the time of day and the lunar cycle have changed over the centuries. Edmund Halley attributed the change to an acceleration of the moon in its orbit. Today, we know from a century of observations that the moon is receding, and it’s orbital period therefore increasing, but the Earth’s rotation period is increasing even faster.

This “secular” deceleration is what caused the moon to become tidally locked to the earth: It always keeps the same face pointing towards earth. If the solar system lasts long enough (it won’t) eventually, the earth would be tidally locked to the moon, with a period of about 48 days: The lunar month, currently about 29.53 days would be about 48 of our current days long, and the day would be about 48 times its current length.

Today, the average length of a solar day is about 86400.002 seconds, because the adopted length of the second (defined by the cesium atom) can be traced to the mean length of day in 1825. (The length of second is traceable to Simon Newcombe’s theory of the sun, which was based on observations during the period 1700-1900.)

*In orbital mechanics “secular” terms are long term trends, as opposed to cyclical terms, like the period of an orbit. Secular meaning, particular to a certain time and place. In theology secular authority, as opposed to ecclesiastic authority, which is permanent and applies to all places and ages.

[ETL]

The article is incoherent, but overall, yes, the Moon has a small influence on the Earth.

As far as I know, it is believed that the moon stabilizes Earth's tilt angle. Without it, the Earth will wobble uncontrollably (over long periods of time) as does Mars now, dramatically changing our familiar climatic zones.

[ETL]

“The moon has long been recognized as a significant stabilizer of Earth’s orbital axis.

Without it, astronomers have predicted that Earth’s tilt could vary as much as 85 degrees.

In such a scenario, the sun would swing from being directly over the equator to directly over the poles over the course of a few million years, a change which could result in dramatic climatic shifts.

Such shifts have the potential to impact the development of life.”

https://www.space.com/12464-earth-moon-unique-solar-system-universe.html

[SunkenCiv]

I believe that's a canard, one of those, "everything must have a purpose" kinds of just-so stories.

[SunkenCiv]

Thanks ETL.

[ETL]

You’re welcome.

Thanks for pinging the list.

[ETL]

Crocodile eats beloved terrier that had spent a decade taunting it

https://www.freerepublic.com/focus/f-chat/3661119/posts

[zeugma]

One of the greatest photographs ever. The one on the moon with the flag pointing towards it is just as good IMO.

[zeugma]

15 seconds every million years...I need to reset my clock!

Don't worry about it. They take care of that with leap seconds.

[zeugma]

One of the greatest albums ever made.

[Bellflower]

Of course the obligatory billions of years.

[Rebelbase]

I expect an article towards the first of July that indicates the days are getting shorter.