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Recently read that Earth is rotating faster than earlier1. However so far it is understood that earth's rotation is slowing down and to conserve the angular momentum Moon is going away from the Earth. What is true?
1for example see answers and comments at What effect does climate change have on the Earth's rotation? in Earth Science SE, and the 2015 Smithsonian article Is Global Warming Changing How Fast the Earth Spins?
Earth's rotation is slowing down, but it's a little bit irregular, which is why leap seconds can't be predicted in advance. There's provision for negative leap seconds, but they've never been used.
You can get the current list of leap seconds, maintained by The Internet Engineering Task Force (IETF), at https://www.ietf.org/timezones/data/leap-seconds.list
The decision to insert a leap second is made by the International Earth Rotation and Reference Systems Service (IERS), who coordinate the operations that gather the actual Earth rotation data. There is a wealth of information on their very extensive website.
Measuring the irregularities of the Earth's rotation
The variability of the earth-rotation vector relative to the body of the planet or in inertial space is caused by the gravitational torque exerted by the Moon, Sun and planets, displacements of matter in different parts of the planet and other excitation mechanisms. The observed oscillations can be interpreted in terms of mantle elasticity, earth flattening, structure and properties of the core-mantle boundary, rheology of the core, underground water, oceanic variability, and atmospheric variability on time scales of weather or climate. The understanding of the coupling between the various layers of our planet is also a key aspect of this research.
Several space geodesy techniques contribute to the permanent monitoring of the earth's rotation by IERS. For all these techniques, the IERS applications are only one part of their contribution to the study of planet earth and of the rest of the universe.
The measurements of the earth's rotation are under the form of time series of the so-called Earth Orientation Parameters (EOP). Universal time (UT1), polar motion and the celestial motion of the pole (precession/nutation) are determined by VLBI. The satellite-geodesy techniques, GPS, SLR and DORIS, determine polar motion and the rapid variations of universal time.
The satellite-geodesy programs used in the IERS give access to the time variations of the earth's gravity field, reflecting the evolution of the earth's shape, as well as the redistribution of masses in the planet. They have also detected changes in the location of the centre of mass of the earth relative to the crust. This makes it possible to investigate global phenomena such as mass redistributions in the atmosphere, oceans and solid earth.
Universal time and polar motion are available daily with an accuracy of 0.5 mas [milliarcseconds] and celestial pole motion are available every five to seven days at the same level of accuracy - this estimation of accuracy includes both short term and long term noise. Sub-daily variations in Universal time and polar motion are also measured on a campaign basis. Past data, going back to the 17th century in some cases, are also available.
EOP series are provided by the IERS in bulletins and as permanently updated series (long term earth orientation data).
Also, from the Wikipedia article on DUT1:
the SI second (as now used for UTC) was already, when adopted, a little shorter than the current value of the second of mean solar time [a].
So even if the Earth's rotation speed were perfectly constant, we'd still need leap seconds to keep UTC in synch with mean solar time because of the size of the SI second.
Astronomer Steve Allen maintains an extensive website on leap seconds and related matters, eg the history of time scales.
No, the Earth is not going to keep spinning faster, and here's why
Unlike most things in the year 2020, the planet's rotation was relatively stable.
We've barely made it to the year 2021, and there are already claims that the next 365 days will "fly by" because the Earth is spinning faster than usual.
A series of articles were published this week warning of shorter days and our planet acting out of character.
However, the Earth periodically speeds up and slows down during its rotation around its axis.
So while the Earth has been a little speedier in the past few years, scientists say that it's business as usual for our home planet.
The Earth’s rotation is changing speed: should we be worried?
We define a day as 86,400 seconds, or 24 hours – the time it takes for Earth to rotate once. However, the Earth doesn’t rotate perfectly uniformly. Usually, the Earth’s rotation is actually slowing down so that the length of the day increases by about 1.8 milliseconds per century, on average. This means that 600 million years ago a day lasted only 21 hours.
The variation in day length is due to several factors, including the tidal effects of the Moon and Sun, core-mantle coupling inside the Earth, and the overall distribution of mass on the planet. Seismic activity, glaciation, the weather, the oceans and the Earth’s magnetic field may also affect the length of the day.
In 2020 scientists made a startling discovery. They found that, instead of slowing down, the Earth has started to spin faster. It is now spinning faster than at any time in the last 50 years. In fact, the shortest 28 days on record all occurred during 2020.
As yet, scientists are not entirely sure what is causing this increase in Earth’s rotation rate, but some have suggested it could be due to the melting of glaciers during the 20th Century, or the accumulation of large quantities of water in northern hemisphere reservoirs. However, experts predict that this speeding
up is a temporary effect and the Earth will start slowing down again in the future.
But, for now, should we be worried? Although it will have no effect on our daily lives, there could be serious implications for technology such as GPS satellites, smartphones, computers and communication networks, all of which rely on extremely accurate timing systems. But such problems are ultimately surmountable, perhaps simply by subtracting a leap second rather than adding one.
So no, we shouldn’t be worried – unless the shortening of the day is attributable to human activity.
Earth's Daily Rotation Slowing
Analyzing ancient Chinese accounts of solar eclipses up to nearly 4,000 years old, Jet Propulsion Laboratory researchers have determined to within few thousandths of second the rate at which the Earth's daily rotation has been gradually slowing down.
Analyzing ancient Chinese accounts of solar eclipses up to nearly 4,000 years old, Jet Propulsion Laboratory researchers have determined to within few thousandths of second the rate at which the Earth's daily rotation has been gradually slowing down.
Their results -- from examining Chinese reports of eclipses in the years 532 A.D., 899 B.C. and 1876 B.C. -- closely match previous studies.
They showed that the span of each day was shorter by about 22/1,000ths of second in 532 A.D., 42/1,000th second in 899 B.C. and 70/1,000th second in 1876 B.C.
The study, due for publication in the British journal Vistas in Astronomy, was authored by JPL astronomer Kevin D. Pang, Kevin Yau of the University of Durham, England, Hung-hsiang Chou of UCLA and Robert Wolff, former JPL staff member now with Apple Computer Inc.
Previously, other astronomers had analyzed accounts of solar eclipses from Arabian and Babylonian sources for historical evidence of the gradual slowing of the Earth's rotation.
The oldest of those Middle Eastern solar eclipse reports analyzed dated to about 700 B.C. Key gaps in the Arabian and Babylonian records occurred during the Middle Ages.
Dr. Pang and his colleagues turned to formidable 1.2-million-word collection of ancient Chinese astronomical records currently being prepared for publication by the Beijing Observatory.
The Chinese text contains records of thousands of eclipses extending back almost unbroken to the 19th century B.C.
In order for an eclipse record to be useful, Pang said, the time of the eclipse must be accurately known.
Since ancient accounts generally do not specificy time of day, Pang explained that he and his colleagues limited themselves to eclipses which occurred at sunrise or sunset. The time of sunrise or sunset can be computed retroactively.
One of the eclipses they focused on took place on November 13 of the year 532 A.D., when China was divided into separate northern and southern kingdoms. From historical records it appears that sunrise took place during solar eclipse as observed from Loyang, the capital of the then northern Wei kingdom.
A second eclipse studied by the team occurred on April 21 of 899 B.C., when historical accounts relate that the day "dawned twice" at the since-vanished city of Zheng. very similar "double sunrise" will occur over Helsinki, Finland, on July 22, 1990.
Finally, the researchers were able to extend their analysis back in time another 1,000 years -- far more ancient than any other eclipse study -- by examining records of solar eclipse which occurred on October 16 of 1876 B.C., according to another report published recently by Pang in the Journal of Hydrology.
Continued analysis of such ancient eclipse records is expected to refine our understanding of the history of rotation of the Earth, Pang said.
The JPL research is funded by NASA's Office of Space Science and Applications.
Earth's Rotation IS Slowing Down. But More Earthquakes? That's A Hypothesis, Not A Fact
A crack in the ground caused by an earthquake in Japan. If this new idea is correct, 2018 should see . [+] up to 30 earthquakes of magnitude 7.0 or greater.
Wikimedia Commons user Katorisi,
A new story based on a fascinating scientific paper is making headlines all over the news: the slowing rotation of the Earth may be causing synchronized earthquakes. Moreover, as the Earth's rotation has been experiencing this exact type of slowdown, we may be due for this exact uptick in earthquakes just next year. While media coverage, as always, is breathless, there are a number of more sober takes saying that we might not have more earthquakes next year after all. The important thing to take away is that:
- we have had periods over the last century where greater numbers of more powerful earthquakes have occurred,
- there is a relationship between these periods and the slowing rotation of the Earth,
- and we've been going through another period of slowing rotation.
Will there be more earthquakes next year? And if so, why? Let's look at the science to find out.
The layers of Earth's interior are well-defined and understood thanks to seismology and other . [+] geophysical observations. But how the changes to the Earth's interior affect our surface are still not fully understood.
Wikimedia Commons user Surachit
We think of the Earth as a spheroidal planet that doesn't change with time, but that's not exactly true. Inside our planet, we have multiple layers: the crust, the mantle, the (liquid) outer core, and the (solid) inner core. The inner core hasn't always been there, but formed relatively recently in geological terms, between 1 and 1.5 billion years ago, as the Earth has cooled. Deep inside the inner core, three big changes happen over time.
- Long-lived radioactive elements, like uranium and thorium, decay, releasing large amounts of energy in the form of heat.
- Gravitational contraction occurs, causing the core to release energy and slowly morph into a more stable, denser configuration.
- And the outer core at the boundary of the inner core slowly solidifies over time, where we expect that small, "frozen" sediments build up on the edge of the inner core over time.
In other words, the inner core is growing, becoming more dense and stable, and changing its arrangement.
A depiction of Earth's interior, showing the movement of molten rock, which makes up the mantle.
These small effects add up to have a big change on the Earth! Increasing the density of the core, particularly during rearrangement events, brings more of the Earth's mass closer to the center. Outside of the inner core, the liquid, metallic outer core spins around, creating Earth's magnetic field. As the outer core shrinks and the inner core grows, small but substantial changes occur in Earth's magnetic field, which eventually propagates to the mantle, and then the crust. As tensions in the mantle and crust grow and grow, they eventually break, which causes a planet-wide mass rearrangement, an earthquake, and a brief rise in Earth's rotational speed.
Tidal rhythmites, such as the Touchet formation shown here, can allow us to determine what the rate . [+] of Earth's rotation was in the past. During the time of the dinosaurs, our day was only 22.5 hours, not 24.
Wikimedia Commons user williamborg
Under normal circumstances, the changes in the core are small, and even though the Earth's rotation changes over time, it's the effects of the magnetic field that are more important for surface-level earthquakes. The Earth has many layers, and internal changes take significant amounts of time to propagate to the surface. If internal rearrangements have been happening in the inner core, causing magnetic field changes in the outer core, is it reasonable to expect that a few years later, we'll begin experiencing a slew of powerful earthquakes here on our crust?
When we examine when the most powerful earthquakes of all have struck, there appears to be no pattern it's essentially random. But if you look at how frequently earthquakes that are quite powerful — say, magnitude 7.0 or above — have occurred, you normally get between 15-20 of them in a given year. However, some years are significantly worse than average, having about an extra 10 powerful earthquakes above the average. If you look at the worse-than-average years, they appear to be periodic: every 32 years or so. As geologist Trevor Nace noted:
The team was puzzled as to the root cause of this cyclicity in earthquake rate. They compared it with a number of global historical datasets and found only one that showed a strong correlation with the uptick in earthquakes. That correlation was to the slowing down of Earth's rotation. Specifically, the team noted that around every 25-30 years Earth's rotation began to slow down and that slowdown happened just before the uptick in earthquakes. The slowing rotation historically has lasted for 5 years, with the last year triggering an increase in earthquakes.
A picture taken on November 15, 2017 shows Kouik village near to Sarpol-e Zahab, two days after a . [+] 7.3-magnitude earthquake struck Iran's western Kermanshah province near the border with Iraq. If this new theory is correct, we can expect many magnitude 7.0+ quakes in 2018. Image credit: ATTA KENARE/AFP/Getty Images.
This slowdown was observed in 2014, 2015, 2016, and now 2017. If 2018 is the 5th year of the slowdown, and if this pattern holds, we'll expect 2018 to be a year rife with a large number of significant earthquakes. If this hypothesis is correct, it would herald a momentous advance in the field of geology and geophysics, as the ability to predict earthquakes in any important way has eluded us for a very long time.
However, there are many reasons to be skeptical. The connection between the changes in the magnetic field and Earth's periodic slowing down appears to be correlative, but no causal link has been established. We are not certain that this mechanism is real. We've also only had approximately four years since 1900 that display this excess of earthquakes, and to predict that 2018 will be the fifth requires a rather large leap-of-faith. Finally, 2017 has only exhibited seven earthquakes of magnitude 7.0 or higher: well below the 15-20 average. Statistical fluctuations are large, and even if we get 25-30 earthquakes next year, that doesn't necessarily mean that the Earth's slowing rotation caused it.
A map showing the locations of earthquakes above magnitude 6 over the last 100 years.
Over long enough times, the Moon is the only dominant factor in slowing down the spinning Earth, as our 24 hour day is relatively recent, and won't be around forever. But the fact remains that we do have years that are more dangerous for earthquakes than others, and we don't have either a good explanation as to why or a good way to predict when those years will occur. If this new study is correct, not only will we have taken a giant leap towards doing both, but we'll have some substantial evidence to support this theory just 12 months from now. It's a tremendously exciting time for science.
NASA bombshell: Earth’s rotation is slowing - and it could cause major earthquakesLink copied
New Zealand: Geologist warns to prepare for 'huge' earthquake
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Earth&rsquos rotation is slowing as our planet uses energy to keep the tidal bulge ahead of the Moon&rsquos orbit. The Moon&rsquos gravity keeps Earth&rsquos rotation in check, and to do this the lunar satellite&rsquos orbit must be slightly ahead of Earth&rsquos. As the Moon attempts to regulate Earth&rsquos rotation and slow it down, the Moon moves slowly away.
According to Matthew Funke, solar system ambassador for NASA&rsquos Jet Propulsion Laboratory, who wrote on Q+A website Quora: &ldquoThe Moon&rsquos gravity creates a tidal bulge on the Earth. This bulge attempts to rotate at the same speed as the rest of the planet.
&ldquoAs it moves &lsquoahead&rsquo of the Moon, the Moon attempts to pull it back. This slows the Earth&rsquos rotation down.
&ldquoOne of the rules of the Universe is that &lsquoangular momentum&rsquo can&rsquot go anywhere &mdash even if individual pieces speed up, slow down, or change direction, the sum total of angular momentum cannot change.
&ldquoThe Earth loses angular momentum when the Moon slows it down, so the Moon has to gain it &mdash and it does, by moving further away in its orbit.
NASA bombshell: Earth&rsquos rotation is slowing - and it could cause major earthquakes (Image: GETTY)
&ldquoThe Moon is currently receding from the Earth by about one and a half inches per year.&rdquo
This could lead to major earthquakes down the line.
A slower rotating globe leads to stronger and more frequent earthquakes &ndash exactly why this is the case is unclear, but experts believe it could be down to changes in the Earth&rsquos core which ultimately has an effect on the surface.
Research from Roger Bilham of the University of Colorado in Boulder and Rebecca Bendick of the University of Montana in Missoula looked at earthquakes with a magnitude higher than seven since 1900.
The Moon is drifting away from Earth (Image: GETTY)
The duo found five years since the turn of the 20th century where there were significantly more magnitude 7.0-plus earthquakes &ndash all of which were years that earth&rsquos rotation speed had slowed down slightly.
Prof Bilham said: &ldquoIn these periods, there were between 25 to 30 intense earthquakes a year.
&ldquoThe rest of the time the average figure was around 15 major earthquakes a year.
&ldquoThe correlation between Earth&rsquos rotation and earthquake activity is strong" (Image: GETTY)
&ldquoThe correlation between Earth&rsquos rotation and earthquake activity is strong and suggests there is going to be an increase in numbers of intense earthquakes.&rdquo
However, this is not expected to happen for billions of years, according to Physicist Paul Walorski who explained on physics forum PhysLink: &ldquoThe slowing rotation of the Earth results in a longer day as well as a longer month.
&ldquoThat&rsquos been projected to happen once the day and month both equal about 47 (current) days, billions of years in the future.&rdquo
Is Earth's rotation Slowing down or Increasing - Astronomy
When was the Moon formed and how fast was the Earth spinning then? In a previous answer you said: "The Earth's rotation is slowing down because of this [the Moon pulling back on its tidal bulge]. One hundred years from now, the day will be 2 milliseconds longer than it is now." I've seen numbers for the Moon's formation from 4 to 4.6 billion years ago. At the rate you gave above, the Earth would have been making a rotation every couple hours in the first case, or actually spinning BACKWARDS in the latter. I understand that the rate is definitely not constant, but wouldn't the Moon pull harder, and thus lengthen the day faster, when it was closer, making the problem even worse?
In a previous answer you said: "The Earth's rotation is slowing down because of this [the Moon pulling back on its tidal bulge]. One hundred years from now, the day will be 2 milliseconds longer than it is now."
I've seen numbers for the Moon's formation from 4 to 4.6 billion years ago. At the rate you gave above, the Earth would have been making a rotation every couple hours in the first case, or actually spinning BACKWARDS in the latter. I understand that the rate is definitely not constant, but wouldn't the Moon pull harder, and thus lengthen the day faster, when it was closer, making the problem even worse?
Everything you've said is quite right! The missing piece of the puzzle is in the details how the Moon interacts with the Earth via tides.
The Moon does cause a small distortion in the Earth's shape, but as everyone knows, the major effect is tides on the ocean. The Moon's gravity is actually dragging most strongly on the tidal bulge raised on the oceans.
And as it happens, it takes about 12 hours for a big wave to slosh across the Pacific Ocean and back--just in time for its height to be reinforced by the next high tide. So because of the size of the Pacific Basin, the Moon is very effective at slowing the Earth's rotation right now. However, the size of the ocean changes due to contiental drift, so in the past, even though the Moon was closer, tidal friction was a much weaker effect. Unfortunately, it's very difficult to measure or calculate exactly how the positions of the continents have changed over time to the degree of precision that is necessary to work out the effect on tides, and we have just a few ways to measure the rotation of the Earth at different times in its history, so we do not have a complete history of how the Earth and Moon have interacted, and we are not sure exactly how far from the Earth the Moon was when it first formed, or how fast the Earth was rotating at that time.
This page was last updated on July 18, 2015.
About the Author
Britt studies the rings of Saturn. She got her PhD from Cornell in 2006 and is now a Professor at Beloit College in Wisconson.
Could the Earth’s Rotation Really Slow Down Like It Does in the New Novel The Age of Miracles?
In The Age of Miracles, Karen Thompson Walker’s newly released debut novel, the Earth apparently hasn’t received the same memo as most of its citizens: Instead of moving at a pace faster than ever, the planet’s rotation begins to slow.
At first, the days grow by about 56 minutes. Eventually, each rotation takes longer than 48 hours. The novel explores scientific and environmental implications of “the slowing,” while focusing primarily on changes in society, relationships, and humanity itself.
Walker describes the lengthening days in such realistic detail—professional baseball games are thwarted by gravity’s changes agriculture must rely on artificial light—that I found myself wondering how fantastical the premise really is. Could this actually happen?
The answer is yes. Well, kind of.
The Earth’s rotation is, in fact, slowing. But not at a rate that anyone would notice—unless one happens to be around in 150 million years.
A number of forces cause the slowing of the Earth’s rotation, but the strongest is tidal friction, a result of the moon’s gravity. The side of Earth closest to the moon feels its pull the strongest, the center of Earth—the point from which gravity is measured—is essentially neutral, and the side farthest from the moon feels its gravity less. That difference in gravitational pull stretches the Earth, which causes tides and tidal bulges.
Because they have mass—and thus, gravity—these bulges pull the moon forward or farther away from Earth by roughly four centimeters per year. But just as these bulges exert force on the moon, the moon exerts the opposite force on them, pulling them back toward it, creating friction and slowing down the planet’s rotation.
Using eclipse data from as far back as 2000 BC, scientists estimate that the Earth’s rotation is slowing at approximately 1.7 milliseconds per solar day per century. In other words, the Earth day has grown by roughly 0.07 seconds in the last 4,000 years.
This is where the atomic clock comes in. It measures time by atomic vibrations, rather than by the Earth’s rotation, which is what our clocks do. The Earth currently rotates every 86,400.002 seconds—and the 0.002 means that our clocks lose time relative to the atomic clock. (Similarly, in the novel, “clock” time doesn’t match up with “real” time as the days stretch longer and longer.) This is why scientists periodically add leap seconds to our standard time. (The BBC has a great, short video explanation.)
The deceleration of Earth’s rotation is irregular: From 1999-2005, there were no leap seconds, but since then, there have been two, with another scheduled for the end of this month (June 2012). Without leap seconds, we’d have a 25-hour day in roughly 140 million years.
If the Earth is still around billions of years in the future, tidal friction would be eliminated when the tidal bulges line up exactly between the center of the earth and the center of the moon, thus “locking” the Earth. One Earth rotation would equal one revolution of the moon around the Earth one month would be the same as one day (about 47 current days long). However, most scientists believe that long before this happens, the sun’s radiation will vaporize the oceans (in approximately 2.1 billion years) and that the sun’s evolution into a red giant will destroy Earth (in about 4.5 billion years).
Forces that sporadically speed up Earth’s rotation cause the irregularities in its rotational deceleration. Rapid tidal variations change the distribution of water on Earth, which can decrease the planet’s moment of inertia, or the inertia of its rotation. A common example of moment of inertia is a figure skater who pulls her arms tight into her body to spin faster. When the moment of inertia decreases, the Earth’s rotational speed increases. Post-glacial rebound, a phenomenon that occurs when land previously kept under huge ice sheets starts rising, also decreases Earth’s moment of inertia. Similarly, as the polar ice masses disappear, Earth’s mass moves closer to its axis, making Earth more elliptical and increasing its rotational speed. Natural disasters can also accelerate Earth’s rotation. The earthquakes that hit Japan in 2011 and Chile in 2010, for example, likely displaced enough mass to change the Earth’s moment of inertia (scientists are still refining their calculations). While these accelerative forces oppose the Earth’s rotational deceleration, they aren’t strong enough to offset it.*
In The Age of Miracles, many characters speculate that the “slowing” is related to climate change and other environmental degradation. But while the Earth’s rotation is indeed slowing and fluctuating, only impact with another planet, moon, or massive asteroid could wreak the kind of havoc described in the book. So we’re safe, for now.
Although I have to say, a 25-hour day sounds pretty good at times.
*June 28, 2012: This post has been updated to clarify the explanation of post-glacial rebound.
Joelle Renstrom lives in Boston, where she teaches and writes about all things geeky. Her blog, Could This Happen?, explores the relationship between science and science fiction.
How is Earth’s rotation slowing down overtime?
What exactly does the Moon do to Earth’s rotation in the first place?
Will there eventually be a time, billions and billions of years away, where the Earth will completely stop spinning as a result of this?
The effect is known as Tidal Acceleration which causes a gradual recession of a satellite in a prograde orbit away from its primary, and a corresponding slowdown of the primary's rotation.
The mass of the Moon is sufficiently large, and it is sufficiently close, to raise tides in the mass of Earth – primarily in the form of bulges of ocean water of the sides of the Earth facing and opposite the current position of the Moon.
Due to the Earth's rotation the mean position of the bulge nearest the Moon is offset ahead (east) of the Earth-Moon center line, slightly ahead of the Moon in the direction it orbits. The gravitational pull of this tidal bulge therefore exerts torque between Earth and the Moon, transferring energy and angular momentum from the rotation of Earth to the orbital motion of the Moon. Most of the energy lost by Earth is converted to heat by frictional losses in the oceans and their interaction with the solid Earth. What remains boosts the Moon in its orbit and slows the rotation of Earth such that total angular momentum in the system is conserved.
Insufficient time remains for the Earth-Moon system to ever enter a mutual tidally locked state.
As the moon recedes, its tidal effects weaken.
As the Sun evolves, its luminosity increases. This will likely cause evaporation of the oceans within 1-2 billion years. Without the oceans, the tidal effects are much weaker.
The Earth-Moon system will likely be destroyed entirely when the Sun becomes a Red giant 5+ billion years from now – too soon for the Earth's rotation to have become locked with the Moon's.
Eclipses show Earth is slowing
This article is about how the Earth’s spin is actually slowing down. Astronomers have been able to track the Earths rotation by looking at evidence of eclipses dating back to 720 B.C.E. By tracking eclipses it was found that certain dates didn’t line up with historical records of where the eclipse should have been visible from in places like ancient Greece, China and the Middle East. It was found that the Earths rotation has slowed by 6 hours in the past 2740 years which equates to one Earth day being lengthened by about 1.78 milliseconds. There were also smaller glitches found in the Earth’s spin, in a decade-by-decade study, that was found to be due to shifts between the Earths liquid outer core and the mantle that covers it.
This connects to our conceptual objective because this has to due with the rotation of the Earth. What we have learned about the Earth’s position and motion is that the stars and sun appear to move around an observers field of vision because the Earth spins on its axis and makes the celestial objects move across our sky. If the Earth is slowing down then that will connect to how long it takes the sun moves across the sky. It might be possible that over many thousand years Earth would eventually have longer days because the sun takes so long to rise over the horizon to setting back below the horizon, since the Earth is spinning slower.
I thought that the article was fairly interesting. I didn’t know that it was possible to track the Earth’s rotation by looking at the history of eclipses. That it amazing to me. I think it is interesting to consider that Earth is slowing. It makes me wonder if Earth would eventually get to a 25 hour long day because of how much it slows down. It is worrying at the same time though, because it makes me wonder if the Earth will ever slow down so much that it stops retaining the ability to harbor life on its surface. Now that I know how celestial bodies move across the sky I will have a better appreciation for the stars and their positions when I look at the night sky. I will be able to track constellations across the night sky now.