From the University of Liverpool , something I found interesting because a few years ago, former State Climatologist Jame Goodridge said he saw correlations between length of day and other atmospheric processes.
Research reveals Earth’s core affects length of day
Research at the University of Liverpool has found that variations in the length of day over periods of between one and 10 years are caused by processes in the Earth’s core.
The Earth rotates once per day, but the length of this day varies. A yeas, 300million years ago, lasted about 450 days and a day would last about 21 hours. As a result of the slowing down of the Earth’s rotation the length of day has increased.
The rotation of the earth on its axis, however, is affected by a number of other factors – for example, the force of the wind against mountain ranges changes the length of the day by plus or minus a millisecond over a period of a year.
Professor Richard Holme, from the School of Environmental Sciences, studied the variations and fluctuations in the length of day over a one to 10 year period between 1962 and 2012. The study took account of the effects on the Earth’s rotation of atmospheric and oceanic processes to produce a model of the variations in the length of day on time scales longer than a year.
Professor Holme said: “The model shows well-known variations on decadal time scales, but importantly resolves changes over periods between one and 10 years. Previously these changes were poorly characterised; the study shows they can be explained by just two key signals, a steady 5.9 year oscillation and episodic jumps which occur at the same time as abrupt changes in the Earth’s magnetic field, generated in the Earth’s core.
He added: “This study changes fundamentally our understanding of short-period dynamics of the Earth’s fluid core. It leads us to conclude that the Earth’s lower mantle, which sits above the Earth’s outer core, is a poor conductor of electricity giving us new insight into the chemistry and mineralogy of the Earth’s deep interior.”
The research was conducted in partnership with the Université Paris Diderot and is published in Nature.
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geran says:
July 14, 2013 at 11:16 am
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Well geran, surely you will admit that the people on the outside of the racetrack will see both sides of the horse, so that to maintain your stance you must agree that your definition of rotation is one of special perspective. A camera on the inside of the track does not see the dark side of a dark horse. A camera on the outside, trained constantly on the lead horse, sees the horse at all angles, so to that camera man it appears that the horse is rotating. He has the equivalent of a sidereal reference frame, an inertial perspective. I suppose you’re just having fun but I’ve seen better arguments for a flat earth. –AGF
Ian Wilson: and I should never say never.
Bart: truce.
–AGF
Retired Engineer John says:
July 14, 2013 at 8:38 am
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Oops, you probably knew what I meant but make that “LOD GAINS 2.3ms/century irreversibly…”
–AGF
agfosterjr says:
July 14, 2013 at 12:08 pm
???
Are you somehow trying to somewhat agree with me, or just confused?
Where did you ever get the idea that I have defined “rotation”? I have been using the term “rotates on its axis”.
Hope that helps.
???
“Diurnal Time Variations” sounds more scientific to me.
“Length of Day Variations” is that measured in miles or kilometres? (LOL)
geran says:
July 14, 2013 at 1:43 pm
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Well do you know about some kind of rotation that doesn’t involve spinning? About an axis?? All astronomers agree that the moon rotates about its axis. This was accepted even before
Copernicus. If you seriously don’t believe this there’s a flat earth society waiting for your membership.
How about this: does a ship sailing clear around the globe so a somersault? –AGF
Consensus will elect a prom king/queen.
and let’s see—is the flat earth society about continuing to believe things that can be so easily disproved??
Definitions certainly are a matter of consensus. You can’t make up your own. If you have a private philosophy consisting of idiosyncratic definitions you will have a hard time communicating. Wheels rotate/spin/revolve about an axle/axis. Whether a wheel has an axle or not, it does have an axis, a center of rotation, which is motionless relative to a perspective stationary relative to the (circumference of) the spinning object (if it is round). A bicycle wheel has an axis of rotation whether it’s spinning over the ground or in a bike shop. A motorcycle wheel has an axis of rotation anywhere it goes, including inside a circus cage cylinder. Assume two gears of equal size, one fastened to a table top, the second spinning around it. Does the second gear rotate or not? Does it revolve or not. Does it not rotate around its center? Does not the moon?
I pause for reply. –AGF
I know I have won the debate when they go off on rambling tangents….
Geran (1116): “…as you moved around the orange, you were turning the pencil, not rotating it on its axis. This is just the same as the race horse of race car. ”
So the moon doesn’t rotate, it turns? It doesn’t rotate on its axis, it turns on its axis?
You’ll have to be patient with all us of inferior intellect, lest you lose your audience. –AGF
agfosterjr says:
July 14, 2013 at 9:27 pm
So the moon doesn’t rotate, it turns?
>>>>>
There appears to be some progress!
Yes, the Moon is turning in its orbit, just as the race horse on an oval track. It is NOT rotating on its axis. There are two different motions here. For example, walk in a circle (orbit). Someone standing inside the orbit would see the same side of you. Next try walking the same orbit, while spinning on your axis. The person standing inside the orbit would then see different sides of you. That is why the Moon “rotating on its axis” is easily disproved.
And, as long as I see some progress, I will be patient. (That is why you do not receive any derisive slurs from me.)
Well by your criteria nothing rotates; all turns. The earth spins while it revolves around the earth/moon barycenter, while the barycenter revolves around the sun, while the sun revolves around the galaxy, while the galaxies move apart. So all you have done is repudiated generally the phrase “rotate around its axis.” You have defined the word “rotate” out of existence, in all but an Aristotelian universe. Not even a bicycle wheel can “rotate” by your definition, even in the bike shop, in a Copernican universe. –AGF
Let me try again. You use “turn” in the sense of revolve, and use “rotate” in the special sense of internal, central perspective. According to which, as I already noted, you ignore the external perspective as would be the case of a cameraman outside the race track, who definitely would see the horse “rotate.” So I repeat, you have invented your own definition of “rotate,” one which has nothing to do with an inertial reference frame but has only to do with special perspective: if the object appears to any observer in the universe not to be spinning, then it is not spinning–or “rotating,” all other observers be damned. –AGF
AGF– You have finally plumbed the depths (?) of G’s thought process. He reserves the phrase “rotates on its axis” for situations in which the axis itself is completely stationary. Like Humpty Dumpty, the phrase means only what he wants it to mean “neither more nor less”. But, of course, nothing in the universe is completely stationary– everything being subject to multiple simultaneous motions — therefore his use of the phrase is completely arbitrary.
skorrenet 1, right you are. Of course he would say our definitions are arbitrary. But while you posted I was writing too, and I’ll post it anyway:
Here’s another angle. If an object spins, does not every point on the object spin? Suppose you you stand in the middle of a merry-go-round and see children holding on near the perimeter. If you stand still you don’t have to turn your head to watch them steadily, while you would have to turn your head to look at someone standing on the ground. Now you might think it redundant to say the children are both revolving and rotating, but you must admit that you and they are rotating together, while the children experience centrifugal force which you do not because they are also “revolving” at some distance from the center. Does that make sense?
Maybe not. We could just as well say the centrifugal force was due to the rotation, in which case it is in fact redundant to say every point on the disc except the center both spins and revolves. OK, I think I see your point now. But the fact remains that every point on the disc does revolve around the center, and does rotate relative to the non-disc universe. So you would say that the fact that the moon experiences day and night over a synodic month follows from its revolution, not some separate rotation apart from its revolution.
But this just gets us back to convention and consensus. Since Newton, physicists have defined rotation according to a sidereal or inertial reference frame. And you must admit that for the moon to experience phases–day and night–it must rotate relative to the sun. And if it rotates relative to the sun it must do so about an axis of rotation. The moon must have a north and south pole from which the sun appears to revolve around the horizon, just like on earth. And we don’t care if it wobbles–the earth’s axis wobbles too.
So if you want to eliminate one or the other of the two terms ‘revolve’ or ‘rotate’ –or in your parlance, ‘turn’ or ‘rotate’ –you would have to get rid of ‘turn’ or ‘revolve’ (relative to a center), not ‘rotate’ (relative to the stars). But ever since we got rid of the celestial spheres we have needed both. The moon really does revolve around the earth/moon center of gravity. And it really does rotate relative to the sun and stars, if not relative to the earth. And your special terra-centric perspective really is a relic of the Aristotelian universe and has not place in modern science. Nor are you entitled to your own definition of terms. So give it up. –AGF
skorrent1 says:
July 15, 2013 at 8:09 am
You may need to try the “orange/pencil” experiment again.
agfosterjr says:
July 15, 2013 at 8:47 am
No amount of rhetoric can replace the facts.
The Moon does NOT rotate on its axis. (See “orange/pencil” experiment.)