If earths rotation stoped, the moon would be released.

[D H]

Though I knew this was happening, it only just now occurred to me that the drift must be accelerating, even if only at the tiniest rate.

In the long term, the rate is decreasing, not increasing. Tidal force is roughly a 1/r³ force. As the Moon recedes from the Earth the tidal forces on the Earth decrease (and decrease quickly thanks to that 1/r³ form). It is these tidal forces that drive the transfer of angular momentum from the Earth's rotation to the Moon's orbit.

The growing consensus is that the Moon formed at about 4 to 6 Earth radii from the center of the Earth from the remnants of a collision between the proto-Earth and a Mars-sized body. That early Moon receded rather quickly from that initial orbit thanks to the huge tidal forces at such short distances.

 

[Nik_2213]

Tidal Friction, really...

According to Wiki (YMMV)...
http://en.wikipedia.org/wiki/Tidal_acceleration

"The rotational angular momentum of the Earth decreases and consequently the length of the day increases. The net tide raised on Earth by the Moon is dragged ahead of the Moon by Earth's much faster rotation. Tidal friction is required to drag and maintain the bulge ahead of the Moon, and it dissipates the excess energy of the exchange of rotational and orbital energy between the Earth and Moon as heat. If the friction and heat dissipation were not present, the Moon's gravitational force on the tidal bulge would rapidly (within two days) bring the tide back into synchronization with the Moon, and the Moon would no longer recede. Most of the dissipation occurs in a turbulent bottom boundary layer in shallow seas such as the European shelf around the British Isles, the Patagonian shelf off Argentina, and the Bering Sea.[10]

"The dissipation of energy by tidal friction averages about 3.75 terawatts, of which 2.5 terawatts are from the principal M2 lunar component and the remainder from other components, both lunar and solar.[11]"

And... http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html

"The tidal braking in the Earth's rotation is actually caused primarily by friction in the oceans, where ``friction'' may refer to any number of physical mechanisms which have yet to be determined definitively. For example, bottom friction, induced by tidal currents flowing across the seabed, various kinds of wave breaking, and scattering of tidal waves into oceanic internal waves are all thought to play a role. For a recent overview of this subject, look up Walter Munk's paper ``Once again: once again--tidal friction,'' published in Progress in Oceanography, vol. 40, pp. 7-36, 1997."

Unfortunately, the link to that paper is broken, but Google found...
http://champs.cecs.ucf.edu/Library/Journal_Articles/pdfs/Once%20again,%20once%20again%20-%20tidal%20friction.pdf

 

[D H]

No. They are trading energy back and forth, changing rotations and orbital altitudes, but the the system is not losing any energy to some external recipient.

Sure it is.

While angular momentum is conserved here, mechanical energy is not. As mentioned in the previous post, it is the lossiness of the system that ultimately is the cause of the recession of the Moon and the slowing of the Earth's rotation rate.

 

[DaveC426913]

Sure it is.

While angular momentum is conserved here, mechanical energy is not. As mentioned in the previous post, it is the lossiness of the system that ultimately is the cause of the recession of the Moon and the slowing of the Earth's rotation rate.

All the energy of which is conserved in the Earth-Moon system.

 

[D H]

All the energy of which is conserved in the Earth-Moon system.

No, it is not.

Write the equations for angular momentum and mechanical energy. One is conserved, the other is not. The lost mechanical energy is transformed to heat, and that heat radiates away.

 

[DaveC426913]

No, it is not.

Write the equations for angular momentum and mechanical energy. One is conserved, the other is not. The lost mechanical energy is transformed to heat, and that heat radiates away.

Ah. OK. I was about to ask you how the energy escapes the system.

 

[narrator]

No, it is not.

Write the equations for angular momentum and mechanical energy. One is conserved, the other is not. The lost mechanical energy is transformed to heat, and that heat radiates away.

That's what I was wondering. If any system creates heat, it's generally energy lost to that system, unless that heat energy can be converted to something else. Heat energy must be one of the most inefficient forms, in any localized sense.

What percentage or proportion of the total energy in the Earth-Moon system would be heat energy? I imagine it would have to be tiny. Can it be computed from the displacement of the Moon's movement away from the Earth? Lay questions, so please excuse if I'm wildly off track.

 

[Nik_2213]

From my post above...

"The dissipation of energy by tidal friction averages about 3.75 terawatts, of which 2.5 terawatts are from the principal M2 lunar component and the remainder from other components, both lunar and solar.[11]"

 

[narrator]

From my post above...

"The dissipation of energy by tidal friction averages about 3.75 terawatts, of which 2.5 terawatts are from the principal M2 lunar component and the remainder from other components, both lunar and solar.[11]"

And the total energy in the Earth-Moon system is... ?

 

[ttown_okie]

If the Earth stopped spinning, then the Earth's magnetic field has also stopped. One of two things would happen. The moon would go out to a more distant orbit or it would come crashing to Earth do to the magnetic lock with Earth being affected by the lose of Earths Magnetic field.

 

[zhermes]

If the Earth stopped spinning, then the Earth's magnetic field has also stopped. One of two things would happen. The moon would go out to a more distant orbit or it would come crashing to Earth do to the magnetic lock with Earth being affected by the lose of Earths Magnetic field.

NO! Don't make things up!

 

[JaredJames]

If the Earth stopped spinning, then the Earth's magnetic field has also stopped. One of two things would happen. The moon would go out to a more distant orbit or it would come crashing to Earth do to the magnetic lock with Earth being affected by the lose of Earths Magnetic field.

This is the second thread in a row you've posted nonsense in.

I recommend you do a bit of reading before posting further because the above is complete and utter rubbish.

 

[ttown_okie]

This is the second thread in a row you've posted nonsense in.

I recommend you do a bit of reading before posting further because the above is complete and utter rubbish.

It is not rubbish, if you understood why the Earth has spin and the reason the moon is orbiting the Earth with one face always facing Earth to begin with you might then be able to better understand what would happen to the moon if the Earth were to suddenly stop which is what this topic asked.

 

[JaredJames]

It is not rubbish, if you understood why the Earth has spin and the reason the moon is orbiting the Earth with one face always facing Earth to begin with you might then be able to better understand what would happen to the moon if the Earth were to suddenly stop which is what this topic asked.

Nothing in your post has any scientific value.

Spinning or not, the Earth's gravitational attraction on the moon is the same. It is only the tidal issue that will have an effect.

Nothing to do with magnetic fields.

Bear in mind the magnetic field can barely move the needle on a compass, and its power drops off at the square of the distance. It really isn't that strong.

 

[sophiecentaur]

If the Earth stopped spinning, then the Earth's magnetic field has also stopped. One of two things would happen. The moon would go out to a more distant orbit or it would come crashing to Earth do to the magnetic lock with Earth being affected by the lose of Earths Magnetic field.

This is such nonsense. Have you no conception of conservation of angular momentum or the relative magnitudes of the fields involved? Why do you write such stuff with absolutely no basis in fact? Physics is not just a set of fairytales that someone made up, you know.

 

[ttown_okie]

Nothing in your post has any scientific value.

Spinning or not, the Earth's gravitational attraction on the moon is the same. It is only the tidal issue that will have an effect.

Nothing to do with magnetic fields.

Bear in mind the magnetic field can barely move the needle on a compass, and its power drops off at the square of the distance. It really isn't that strong.

You can not separate electricity and magnetic fields and you probably can not separate gravity from electromagnets either. In fact the a popular current theory is that north and south poles are holding together all matter itself, see quarks and string theory.

The compass aligns itself with the stream of magnetic particles flowing out of the south and north poles back around to the other pole and through the core of the Earth. When you have two highly concentrated streams of currents flowing in opposite directions along magnetic field lines you will generate a force perpendicular to the magnetic field lines and there is a rotation to it because the streams are going in opposite direction and as they pass twist around each other in a screwlike fashion. You can see this yourself by generating plasma along the outside of a wire and observing the currents twist around each other in a spin. If you understand how electricity is generated you would know this.

To say that if Earths magnetic field were to go away that it would have an impact on the moons movement is not nonsense. Stop ridiculing my posts just because you do not agree or understand. I think all of the fundamental forces are working together in this problem that the OP asked but when I bring up the electro-magnetic some of you get upset.

 

[JaredJames]

You can not separate electricity and magnetic fields

No one said you can. Moot point.

and you probably can not separate gravity from electromagnets either.

Uh, what? Are you saying that gravity on Mars is different because it has an incredicbly weak magnetic field?

In fact the a popular current theory is that north and south poles are holding together all matter itself, see quarks and string theory.

The guy who couldn't grasp reference points in the other thread is lecturing on string theory?

The compass aligns itself with the stream of magnetic particles flowing out of the south and north poles back around to the other pole and through the core of the Earth.

Magnetic particles?

When you have two highly concentrated streams of currents flowing in opposite directions along magnetic field lines you will generate a force perpendicular to the magnetic field lines and there is a rotation to it because the streams are going in opposite direction and as they pass twist around each other in a screwlike fashion. You can see this yourself by generating plasma along the outside of a wire and observing the currents twist around each other in a spin. If you understand how electricity is generated you would know this.

And this has what to do with your point?

To say that if Earths magnetic field were to go away that it would have an impact on the moons movement is not nonsense.

Have you calculated the strength of the Earths magnetic field on the moon?

Stop ridiculing my posts just because you do not agree or understand. I think all of the fundamental forces are working together in this problem that the OP asked but when I bring up the electro-magnetic some of you get upset.

What you think is irrelevant. What does the strong and weak nuclear force have to do with anything here, let alone the electromagnetic force? Science just doesn't agree with you.

Of course, you could prove everyone here wrong and start producing citations to published papers to back up what you're claiming...

 

[DaveC426913]

Stop ridiculing my posts just because you do not agree or understand.

They are not ridiculing them; they are pointing out that they are factually incorrect in many places, showing a dramatic lack of understanding of the physics involved.

Thread reported, in prep for rolling back [strike]nonsense[/strike] factual errors.

 

[ttown_okie]

They are not ridiculing them; they are pointing out that they are factually incorrect in many places, showing a dramatic lack of understanding of the physics involved.

Thread reported, in prep for rolling back [strike]nonsense[/strike] factual errors.

You claim factual error but yet offer no evidence, just ridicule. This thread is to discuss what would happen to the moon if the Earth were to stop rotating, let's stick to the topic.

 

[DaveC426913]

You claim factual error but yet offer no evidence, just ridicule. This thread is to discuss what would happen to the moon if the Earth were to stop rotating, let's stick to the topic.

Let's stick to known science.

You do not offer science, the onus is not on me (or any of us) to refute it.



Write short posts. This thread has been reported for review and cleansing of misinformation.

 

[JaredJames]

You claim factual error but yet offer no evidence, just ridicule. This thread is to discuss what would happen to the moon if the Earth were to stop rotating, let's stick to the topic.

Your claims are supported by no evidence - you need to provide it. It is not up to us to disprove you. It is down to the claimant to support their statements with evidence.

 

[narrator]

You claim factual error but yet offer no evidence, just ridicule. This thread is to discuss what would happen to the moon if the Earth were to stop rotating, let's stick to the topic.

ttown okie, this is a science forum, and the people who have responded to you, who have attempted to correct you, are well versed in these topics (not laymen). Rather than complain, you would do better to learn from them. Even as a layman myself, I can see where you are mistaken. There is nothing wrong with mistakes, as long as you allow yourself to be corrected.

Back to my question in post #39, if the dissipation of energy by tidal friction averages about 3.75 terawatts, what's the total energy in the Earth Moon system?

 

[Borek]

Back to my question in post #39, if the dissipation of energy by tidal friction averages about 3.75 terawatts, what's the total energy in the Earth Moon system?

I doubt total energy can be calculated from this data. I would start from known masses, radii, distance and speeds. Simple high school physics.

The only problem is - I am not sure what to include, as it depends on the definition of "total". Does the motion around Sun counts, or not?

 

[sophiecentaur]

I think the Energy to go for would just be the energy that could be transferred by the inter-planetary effects. If the Solar orbit of the c.m. of the Moon-Earth didn't change then the energy of the orbit round the Sun wouldn't be relevant in this respect. You could see what a small change in this orbit would represent in the form of 'extra' energy but any tidal locking of the Moon-earth to the Sun would probably be very small, considering the geometry. Suck it and see?

 

[narrator]

Interesting problem. And back to what I asked earlier, about proportion. "What percentage or proportion of the total energy in the Earth-Moon system would be heat energy?"

This is purely a guess, so please excuse. Given the masses of Earth and Moon, and excluding other influences (Sun et al) I'm thinking that the total energy between the two would be some hundreds times more than that given over to friction.

Having been a mechanical engineer in my distant past, I'm looking at it as being something like the efficiency of two well oiled gears or cogs, with one difference being that gravity is like energy normally delivered through the shaft (which I guess is where the analogy breaks down), but in engineering terms, I would expect something like 98% efficiency. And with celestial bodies suffering no physical friction or atmospheric friction, I would expect something like 99.99% efficiency.

Am I looking at this right?

 

[Janus]

Interesting problem. And back to what I asked earlier, about proportion. "What percentage or proportion of the total energy in the Earth-Moon system would be heat energy?"

This is purely a guess, so please excuse. Given the masses of Earth and Moon, and excluding other influences (Sun et al) I'm thinking that the total energy between the two would be some hundreds times more than that given over to friction.

Having been a mechanical engineer in my distant past, I'm looking at it as being something like the efficiency of two well oiled gears or cogs, with one difference being that gravity is like energy normally delivered through the shaft (which I guess is where the analogy breaks down), but in engineering terms, I would expect something like 98% efficiency. And with celestial bodies suffering no physical friction or atmospheric friction, I would expect something like 99.99% efficiency.

Am I looking at this right?

It's pretty easy to figure out. The moon is receding by 3.8 cm per year.

It's orbital energy is found by:

E = -\frac{G M_{earth}M_{moon}}{2a}

with 'a' being the average Earth-Moon distance.

In the process, it lengthens the Earth's rotation period by 1.5 milliseconds/century.

The Rotational energy of the Earth is found by:

E= \frac{r^2 \omega^2M}{5}

Where r, \omega and M are the radius, angular velocity( in rads/sec) and mass of the Earth.

So, find the energy gained by the Moon when it climbs 3.8 meters further out and compare it to the amount of rotational energy the Earth loses by lengthening its rotation by 1.5 ms.

Compare the two and you have your answer. (you might be surprised.)

 

[shashankac655]

So , the earth-moon system is constantly losing it's energy in the form of heat energy.Will the system lose energy like this even after the tidal locking??...if yes that means the system will continuously lose energy, but for how long? it can't lose energy forever right? ,the system must come to an end some way,how?? (just assume that the sun is not going to be a red giant and interfere with the system)

 

[ttmark]

Your friend is correct. We do not know if mass creates gravity. As you are aware many things can make you experience a different gravity constant than mass itself such as changes in velocity, centrifugal force, magnetics, etc. Current physics does not understand what actually commutes gravity between points but we can observe that mass is proportional to gravity in some cases but since even this mass of planetary objects is "proven" by it's gravitational effects, one should be careful in accepting this circular reasoning.

 

[JaredJames]

As you are aware many things can make you experience a different gravity constant than mass itself such as changes in velocity, centrifugal force, magnetics, etc.

Don't confuse feeling a different force to changing gravity. There is a big difference between simulated gravity (accelerating at 1g in a spaceship) and real gravity (standing on Earth).

Whilst accelerating upwards, you experience a greater downwards force than gravity alone, but gravity itself is constant. The only way to alter the force of gravity on you is to increase either your own, or the objects mass.

There is no circular reasoning, it is observe and report. Your misunderstanding is not an excuse to attack scientific theory.

I'll leave the rest of your post to someone with more subject knowledge than myself.

 

[ttmark]

There is no attack here. A person on the moon certainly experiences different gravity than a person on Earth, or on any other planetary object. The effect of gravity is the summation of all the forces acting towards the systems center of mass. To describe a gravity constant you must pick a frame of reference somewhere, this is typically done at the center of mass of the system in question. To an object at rest within this system it is accepted to call that force a gravity constant and it is measured by the acceleration of that body if in free fall in a vacuum. We are able to measure a gravity constant for objects near Earth but Physics does not know what caused the gravity effect to begin with.