[Jaaanosik]

Just saying that under right conditions a windmill torques the Earth.

Under the right conditions maybe, but not due to locking precession around the tower axis. Go back to basic gyroscope theory and tell me why that is.

Are you saying there is no counter torque required to prevent the precession?
Video at 2:47.
Jano

[Colin2B]

Are you saying there is no counter torque required to prevent the precession?
Video at 2:47.
Jano

No, even more basic than that.

[Jaaanosik]

...

I am not sure what was changed and discussed.

Among other things , this:

There's also the change in angular velocity which takes place when I climb the stairs.
But that's reversed when I come back down again.

The question seemed to be about a cumulative effect- where a mill running for 2 days changed the speed of the Earth more than running it for 1 day.

Under right conditions 2 days effect can be bigger than 1 day effect.
The Sun heats the ground, the air, there is a wind caused by the external energy input.
If all is aligned well then yes, 2 days effect can be bigger than 1 day effect due to the external energy input.

Are you deliberately missing the point?
In your world, would the third day produce an even bigger effect and so on?

If the wind blows in a correct direction all the time.
The wind does not stop because it has a continuous energy input from the heat.
What is the problem?
The effect has to accumulate, no?

[Jaaanosik]

Are you saying there is no counter torque required to prevent the precession?
Video at 2:47.
Jano

No, even more basic than that.

I suggest an experiment.
Take the toy gyro, spin it, hold it between your fingers at one end/on one side and see if it takes any torque to prevent the precession.
Jano

[Colin2B]

Are you saying there is no counter torque required to prevent the precession?
Video at 2:47.
Jano

No, even more basic than that.

I suggest an experiment.
Take the toy gyro, spin it, hold it between your fingers at one end/on one side and see if it takes any torque to prevent the precession.
Jano

Been there, done that, got the faded tee shirt.
Read my post https://www.thenakedscientists.com/forum/index.php?topic=80399.msg614353#msg614353
See if it gives you a clue.
Think very, very basic

Sorry, think very, very, very basic

[Jaaanosik]

Are you saying there is no counter torque required to prevent the precession?
Video at 2:47.
Jano

No, even more basic than that.

I suggest an experiment.
Take the toy gyro, spin it, hold it between your fingers at one end/on one side and see if it takes any torque to prevent the precession.
Jano

Been there, done that, got the faded tee shirt.
Read my post https://www.thenakedscientists.com/forum/index.php?topic=80399.msg614353#msg614353
See if it gives you a clue.
Think very, very basic

Sorry, think very, very, very basic

Imagine 1kg weight on a table.
Is anything happening?
Nothing.
Imagine two Earth like planets  next to each other, no rotation, just being next to each other in an intergalactic space.
Are they going to start to crumble/collapse after some time?

The 1kg weight has an effect on the Earth just not the same as the other planet.
Holding the toy gyro in fingers and preventing the precession cannot be done without a counter torque.

[Bored chemist]

All the windmill can hope to do is (infinitesimally) change the axis of the Earth's rotation ( and only while it's running; the axis returns to where it was when the mill stops).
Making the windmill bigger doesn't help much. The effect is still temporary and tiny.

A bunch of windmills all round the Earth all facing West (or East or whatever) doesn't help- they cancel out.

[Bored chemist]

If the wind blows in a correct direction all the time.

Then it runs out of puff.

[Jaaanosik]

If the wind blows in a correct direction all the time.

Then it runs out of puff.

There is an external energy input from the Sun.
If we simplify the scenario and we assume the energy input goes only to generating the wind.
The wind passes energy to windmill rotation but it never stops because of more energy input from the Sun.
Question, what happens with all energy input assuming the energy cannot escape anywhere else, the energy just goes into rotating the windmill?

[Bored chemist]

There is an external energy input from the Sun.

Why do you keep saying that?
It's not as if anyone has disputed it.

Is it because you don't understand that conservation of energy is independent of the conservation of momentum and that both are independent of the conservation of angular momentum?

Question, what happens with all energy input assuming the energy cannot escape anywhere else, the energy just goes into rotating the windmill?

Who cares?
Did you read the OP:
It's about the real world.

Obviously the answer was that the windmill breaks long before it makes a measurable difference to the angular momentum of the rest of the Earth.
Why did you think that was worth asking?

[Jaaanosik]

There is an external energy input from the Sun.

Why do you keep saying that?
It's not as if anyone has disputed it.

Is it because you don't understand that conservation of energy is independent of the conservation of momentum and that both are independent of the conservation of angular momentum?

Question, what happens with all energy input assuming the energy cannot escape anywhere else, the energy just goes into rotating the windmill?

Who cares?
Did you read the OP:
It's about the real world.

Obviously the answer was that the windmill breaks long before it makes a measurable difference to the angular momentum of the rest of the Earth.
Why did you think that was worth asking?

Do you understand work energy principle and rigid bodies?
Do you understand Newton's second law?
An increase in kinetic energy will lead to an increase of momentum.
The momentum is conserved for a closed system.
I did not described a closed system.

The answer to the OP is yes.
No matter how small change it is if the wind is considered to be cause by the Sun's energy then the system is not closed.
Real life has other energy flows but this one is into the system.
Just look at Venus measurements.
Jano

[Bored chemist]

The momentum is conserved for a closed system.

I explained this earlier.
At least read the thread before you rehash the same errors.

It is, as you keep stressing the importance of the fact, an isolated system.
The atmosphere can't push the world for the same reason that the man on the truck bed can't push the truck.

You seem to be trying to elevate the terms isolated and closed to the status of holy writ.

It's not magical.
Classically:
(1) A system to which you can't add or remove stuff will not change mass
(2) A system to which you can't add or  remove energy will  change energy
(3)A system to which you can not apply a force will not change momentum.
(4) A system to which you can't apply a torque  will not change angular momentum.
Those are pretty much tautologically true.
Since Einstein's day the first pair of those are a bit more flexible, but only in a very clearly defined way.

Historically, in thermodynamics it was important to lump together some of those statements of the obvious.
If you have a system to which you can add or subtract matter then you can't sensibly define what it will do- because it depends on the matter you might add.The same goes for applying forces to it. Those forces just complicate the issue.
So, they invented the "closed system" where tautologies 1 and 3 apply.
 

Similarly, for some calculations, you want to prevent energy entering or leaving the system.
And that's why they invented the "isolated system"- as  a shorthand for a system where tautology 2 also applies.

If thermodynamics dealt with angular momentum they would have invented another term for systems where tautology 4 also applied. They didn't.

But, if they had done, the Earth would be on the list.


I'm still waiting for you to explain where the torque comes from.

[Jaaanosik]

The momentum is conserved for a closed system.

I explained this earlier.
At least read the thread before you rehash the same errors.
...

Please, check this video:

At around 8:20 the explanation starts to describe a small displacement of the disc.
So, if the Earth system is like the perfect disc, ...
but the first event is the air displacement from the Sun's input energy then there could be a cascade of events leading to big angular momentum changes.
The windmills could be part of the 'chain reaction', not important.

The point is that the Sun's heat can trigger big changes.
What is slowing down the Venus?
Jano

[gem]

So BC when I stated,

Quote

1, No change in momentum has occurred

2, The forces of the trade winds and polar winds 0-30 and 60-90 degree regions, are exactly matched by the prevailing winds in the 30-60 degree regions so LOD is maintained.

3, , The forces of the trade winds and polar winds 0-30 and 60-90 degree regions, that have frictional contact with the surface, are NOT exactly matched by the prevailing winds in the 30-60 degree regions, would require a external torque force. (ie the LOD is the earth's terminal velocity, balance between all frictional drag and external force)

These are separate explanations/options that the merits (truth) of each would have to be considered as to the sustainability of wind energy electrical generation for man's use long term.

on point 2 you stated

Congratulations on finally working out what Halc,others and I said ages ago, The torques all balance out.

You then contradict yourself

 

I focussed on the one that is correct.
Try posting the others on an anti-science forum.

So which scenario is correct in your view 1 or 2  as with point one there can be no torque


Colin given your statement about torque applied to the solid earth via a windmill,

Under the right conditions maybe,

what do you believe would be the outcome of placing windmills at 15 degrees north and south latitude given the north easterly and south easterly trade winds


https://commons.wikimedia.org/wiki/File:Earth_Global_Circulation_-_en.svg#/media/File:Earth_Global_Circulation_-_en.svg

[Bored chemist]

what do you believe would be the outcome of placing windmills at 15 degrees north and south latitude given the north easterly and south easterly trade winds

It would mean that rather than the trade winds spending their energy warming the air via viscosity against the ground, they would dissipate that energy via a windmill.
But the forces would be the same. Instead of pushing a windmill, they would push against the ground. Why are you asking this? I have already told you what the answer is.

And the change in net torque would be zero.
That's to say that it would change from zero  to zero.

[Bored chemist]

At around 8:20 the explanation starts to describe a small displacement of the disc.

And, at 4:30, he explains that it won't work with a sphere- like the Earth so... it's not going to be very relevant.
OK,
When does it show the mathematical falsification of Noether's theorem?

Because if it doesn't do that, it's not relevant.

[gem]

Hi all,
Noether”s theorem cannot apply to the dynamics of the earth’s atmosphere, whilst it is effected by the gravitational field and solar input, It’s conditional On meeting certain criteria to be applied. So not relevant.

So BC you’re plumping for scenario 2,

Which is the friction applied to earth’s surface, balances.
Therefore  let’s consider If we treat the earths surface as a anemometer 

https://en.m.wikipedia.org/wiki/Anemometer
The coefficient of friction will come into consideration to different latitudes.

[Colin2B]

Windmills do affect the Earth rotation.
Windmills are gyros and they are prevented from doing the precession therefore they torque the Earth.
Jano

I went by OP:

If all windmills on earth are designed to catch only eastward wind,  while westward wind can blow freely,  will it accelerate earth rotation?

I am not sure what was changed and discussed.

Apologies for slow response, out and about a lot with poor wifi, so priority is on spammers rather than following threads. Also, apologies if you’ve already covered this as I haven’t been following.

Firstly, congratulations on knowing about precession torque, many people don’t.
I didn’t say they don’t torque the earth, but perhaps being unfair in the interpretation of the OP you quote, perhaps winding you up a bit 

Let’s assume a single east facing windmill on the equator. The only way this will try to precess around the tower (as in the diagram on your post) is if the axis of rotor spin is torqued or rotated in the vertical plane. This will happen as the earth spins, giving a torque vector for the tower pointing out vertically from the earth centre (all very idealised), but 180° later this vector is pointed in the opposite direction so cancels out. So assuming random distribution of all windmills on earth then all those windmill’s towers are trying to torque on different axes and over all the earth will cancel out (apologies to BC if he’s already pointed this out, but short on time at moment).

However, here’s an alternative to consider (again apologies if you already have).
What if you put a single windmill on latitude 45°N 0°E what happens; then add another 45°N 180°E what happens; you can go on adding. Of course you still have to contend with halc’s point about what happens when the force is removed https://www.thenakedscientists.com/forum/index.php?topic=80136.msg609359#msg609359, so you are back to continuing discussion.

[Bored chemist]

Hi all,
Noether”s theorem cannot apply to the dynamics of the earth’s atmosphere, whilst it is effected by the gravitational field and solar input, It’s conditional On meeting certain criteria to be applied. So not relevant.

So BC you’re plumping for scenario 2,

Which is the friction applied to earth’s surface, balances.
Therefore  let’s consider If we treat the earths surface as a anemometer 

https://en.m.wikipedia.org/wiki/Anemometer
The coefficient of friction will come into consideration to different latitudes.

I'm lot looking at any of your scenarios in particular (except #1 by default).
I'm just pointing out the fact that angular momentum is a conserved quantity.

No torque implies no change in rotation.
There's nothing more to say.

[Jaaanosik]

At around 8:20 the explanation starts to describe a small displacement of the disc.

And, at 4:30, he explains that it won't work with a sphere- like the Earth so... it's not going to be very relevant.
OK,
When does it show the mathematical falsification of Noether's theorem?

Because if it doesn't do that, it's not relevant.

It is relevant, if you watch it till the end. It is being explained why.
A system is defined by boundaries.
The OP does not define any boundaries of the Earth rotation acceleration question.
It is OK to assume only the current axis of rotation is considered.
The video shows that rotation around one axis can be transformed to rotation around another axis.
The total angular momentum is the same, still individual axis of rotation have different angular momentum.
The answer to OP is yes, when one axis is considered without breaking the total angular momentum.

What is slowing down the rotation of the Venus anyway?
How is Noether's theorem holding there?
Jano