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Earths rotation.


Relative

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Yes, due to tidal interaction with the Moon, the length of Earth's rotational period increases by ~2 milliseconds per century.

That is in accordance with the entry in Wikipedia under Tidal acceleration:

 

From the observed change in the Moon's orbit, the corresponding change in the length of the day can be computed:

+2.3 ms/cy (cy is centuries).

However, from historical records over the past 2700 years the following average value is found:

+1.70 ± 0.05 ms/cy[24][25]
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Yes, due to tidal interaction with the Moon, the length of Earth's rotational period increases by ~2 milliseconds per century.

 

 

It's an acceleration, slowing by ~2 ms/day/century (Robbitybob1's quote agrees). The current rate of slowing is of order 1 millisecond/day, but it varies over the course of a year.

 

 

http://tycho.usno.navy.mil/leapsec.html

http://maia.usno.navy.mil/whatiseop.html

 

You can see that about a decade ago we had intervals when we were actually speeding up. That's why there were no leap second insertions from 1999 until June 2005 and the smaller average excess length of day is why we've only had a few since then, as opposed to eight in the decade preceding that "dead" interval.

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It's an acceleration, slowing by ~2 ms/day/century (Robbitybob1's quote agrees). The current rate of slowing is of order 1 millisecond/day, but it varies over the course of a year.

 

 

http://tycho.usno.navy.mil/leapsec.html

http://maia.usno.navy.mil/whatiseop.html

 

You can see that about a decade ago we had intervals when we were actually speeding up. That's why there were no leap second insertions from 1999 until June 2005 and the smaller average excess length of day is why we've only had a few since then, as opposed to eight in the decade preceding that "dead" interval.

I was finding that when one thinks of a period "slowing" a little confusing and I'd rather say lengthens or shortens. Do you see my point?

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The Earth spins, and I have heard the spin is slowing down.

 

 

Is this true?

 

 

 

Did you not bother to read the link?

 

 

but my question was what makes the spin

 

 

You need to complete your SF course in torque and moment before this second question can be answered

Edited by studiot
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Thank you for confirming the information is correct that I have read. What is the Physical process that makes the Earth spin?

 

The solar system was formed from a cloud of gas and dust that collapsed under its own gravity. As this cloud was not stationary, it ended up rotating as it collapsed. The rotation was transferred to the Sun and planets as they formed (because of conservation of angular momentum).

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Did you not bother to read the link?

 

 

You need to complete your SF course in torque and moment before this second question can be answered

I partly read the link , I will refer back to the link when I know some basics first about the moon, I am trying not to run before I can walk...

 

The solar system was formed from a cloud of gas and dust that collapsed under its own gravity. As this cloud was not stationary, it ended up rotating as it collapsed. The rotation was transferred to the Sun and planets as they formed (because of conservation of angular momentum).

Ok I thought that would be the answer, and initial inertia was the big bang.

 

Newtons first law is not been broken then by it been slowed down?

Edited by Relative
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Newtons first law is not been broken then by it been slowed down?

 

I don't think Newton's first law is relevant here as we are talking about rotation rather then motion in a straight line.

 

Speed of rotation can be changed without applying a force. You might have seen ice skaters change the speed of their spin by extending their arms or tucking them in. This is due to conservation of angular momentum.

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I don't think Newton's first law is relevant here as we are talking about rotation rather then motion in a straight line.

 

Speed of rotation can be changed without applying a force. You might have seen ice skaters change the speed of their spin by extending their arms or tucking them in. This is due to conservation of angular momentum.

I understand speed of a spin can be altered by aerodynamics on Earth in an atmosphere, but Newtons law states that an object in space that has momentum, whether it be linear or rotational should not slow unless an external acting force opposes it.

 

Ok , so what external force acts on the moon?

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No it doesn't.

Hmm. yes it does , ''An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.''

 

 

a spin is motion.

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Relative, on 13 Oct 2014 - 12:11 PM, said:

Hmm. yes it does , ''An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.''

 

 

a spin is motion.

 

Variations in Earth's rotation (defined in terms of length of day) arise from external tidal torques, or from an exchange of angular momentum between the solid Earth and its fluid components1. On short timescales (annual or shorter) the non-tidal component is dominated by the atmosphere, with small contributions from the ocean and hydrological system. On decadal timescales, the dominant contribution is from angular momentum exchange between the solid mantle and fluid outer core. Intradecadal periods have been less clear and have been characterized by signals with a wide range of periods and varying amplitudes, including a peak at about 6years (refs 2, 3, 4). Here, by working in the time domain rather than the frequency domain, we show a clear partition of the non-atmospheric component into only three components: a decadally varying trend, a 5.9-year period oscillation, and jumps at times contemporaneous with geomagnetic jerks. The nature of the jumps in length of day leads to a fundamental change in what class of phenomena may give rise to the jerks, and provides a strong constraint on electrical conductivity of the lower mantle, which can in turn constrain its structure and composition.

 

http://www.nature.com/nature/journal/v499/n7457/full/nature12282.html

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Relative, on 13 Oct 2014 - 12:11 PM, said:

Hmm. yes it does , ''An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.''

 

 

a spin is motion.

 

Variations in Earth's rotation (defined in terms of length of day) arise from external tidal torques, or from an exchange of angular momentum between the solid Earth and its fluid components1. On short timescales (annual or shorter) the non-tidal component is dominated by the atmosphere, with small contributions from the ocean and hydrological system. On decadal timescales, the dominant contribution is from angular momentum exchange between the solid mantle and fluid outer core. Intradecadal periods have been less clear and have been characterized by signals with a wide range of periods and varying amplitudes, including a peak at about 6 years (refs 2, 3, 4). Here, by working in the time domain rather than the frequency domain, we show a clear partition of the non-atmospheric component into only three components: a decadally varying trend, a 5.9-year period oscillation, and jumps at times contemporaneous with geomagnetic jerks. The nature of the jumps in length of day leads to a fundamental change in what class of phenomena may give rise to the jerks, and provides a strong constraint on electrical conductivity of the lower mantle, which can in turn constrain its structure and composition.

 

http://www.nature.com/nature/journal/v499/n7457/full/nature12282.html

 

Ok, thank you, so you are saying the Earth and the Moon are a couple and there is a torque involved?

 

Are you saying that forces with no linkage and based on a connection of forces, that there is an energy linkage that creates torque?

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Hmm. yes it does , ''An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.''

 

Where are you quoting that from? It is over-simplified.

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Relative, on 13 Oct 2014 - 12:24 PM, said:

Ok, thank you, so you are saying the Earth and the Moon are a couple and there is a torque involved?

 

Are you saying that forces with no linkage and based on a connection of forces, that there is an energy linkage that creates torque?

No, that reference was in relation to your question about the necessity for external forces changing the Earth's rate of rotation ...which it isn't. The changes can be caused internally.

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No, that reference was in relation to your question about the necessity for external forces changing the Earth's rate of rotation ...which it isn't. The changes can be caused internally.

Are you saying it is the electrostatics involved and the repulsion forces of electrostatics?

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Are you saying it is the electrostatics involved and the repulsion forces of electrostatics?

Nobody has come close to even hinting at that.

 

Mass distribution changes - snowfall in the north melts and the water moves to the equator - will change the rotation rate. Weather systems trade angular momentum with the rest of the earth. Droughts. Lots of different effects.

I was finding that when one thinks of a period "slowing" a little confusing and I'd rather say lengthens or shortens. Do you see my point?

 

Yes. The fact that the rotation rate is slower doesn't require an acceleration; the rotation could be constant, and a time difference would accrue - the day gets longer.

What is the Physical process that makes the Earth spin?

It was born that way. It was never not spinning.

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Nobody has come close to even hinting at that.

 

Mass distribution changes - snowfall in the north melts and the water moves to the equator - will change the rotation rate. Weather systems trade angular momentum with the rest of the earth. Droughts. Lots of different effects.

 

Yes. The fact that the rotation rate is slower doesn't require an acceleration; the rotation could be constant, and a time difference would accrue - the day gets longer.

 

It was born that way. It was never not spinning.

Thank you I think I understand, you are are saying the rotation slows down by internal means, meaning mass shift,

 

Is electro- motive force ever considered when considering the rotation?

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