[gem]

Halc I believe if you read back you attributing quotes to me from other members, therefore I cannot respond fairly.

[gem]

Especially as your disagreements with the points I was disagreeing with also.

[gem]

Ok apologies accepted even though it came with a but😀 you may like to review your post as some of the points raised are for others to address.
B/C, Halc says your reasonably patient rebuttals are wrong.
For example  when you stated.
The ground. That's my point.
The only thing the air can push is exactly the same ground that is the only thing it can brace itself against.

[Bored chemist]

All quotes above are from you in your post earlier today, the way you posted them.

The quote function sometimes screws up nested quotes so, so, for example, the text that says "Well  the only possible answer is "the ground" because that's the only thing it touches." is from me and that's not clear.

[Bored chemist]

B/C, Halc says your reasonably patient rebuttals are wrong.
For example  when you stated.
The ground. That's my point.
The only thing the air can push is exactly the same ground that is the only thing it can brace itself against.

There's a distinction between "the air" as a whole and "the air" referring to the bit of it hitting a windmill.
I'm sure that Halc agrees that, if you consider the air as a whole then the only thing it pushes against is the ground.
It should be easy enough to check.

Halc, Do you agree with my view that the idea of the atmosphere, as a whole, pushing the Earth is like the man standing  on the back of the truck trying to push it.?


Gem,
 even if he and I never come to agree about that, it doesn't detract from your basic rudeness in not answering my question.

Quote from: Bored chemist on 21/08/2020 11:04:44
Quote from: Bored chemist on 20/08/2020 19:37:09
But fundamentally, if you think the air is slowing the world down, you  still have to deal with this
Quote from: Bored chemist on Yesterday at 11:27:05
Quote from: Bored chemist on Yesterday at 10:36:19
Quote from: Bored chemist on Yesterday at 08:48:24

I'm still waiting for someone to explain how there's a change in angular momentum without a torque .
How do you get round this ?
Quote from: Bored chemist on 18/08/2020 18:12:27
The rate of change of angular  momentum is the torque divided by the moment of inertia.
If the torque is zero then the change in angular momentum is also zero.

Why not just admit that your view is at odds with the laws of physics, ad stop wasting everyone's time?

[Halc]

All quotes above are from you in your post earlier today, the way you posted them.

The quote function sometimes screws up nested quotes so, so, for example, the text that says "Well  the only possible answer is "the ground" because that's the only thing it touches." is from me and that's not clear.

It does nested quotes just fine for me, as evidenced above. The text is unclear what part is yours because again, gem refused to delimit your quote. He's the one repeatedly making it unclear whose words are whose, not even using quote marks like you had to add there.

I also don't recall saying that your patient rebuttals are wrong. The ground is the only thing it touches, and the only thing that could possibly transfer momentum to or from the atmosphere, but that seems unlikely since the sum total of the momentum transferred to the ground is essentially zero.

Halc, Do you agree with my view that the idea of the atmosphere, as a whole, pushing the Earth is like the man standing  on the back of the truck trying to push it.?

Yes, but I'm not sure gem ever figured out why that picture is funny.

Yes, gem, in refusing the repeated requests to identify a source of torque, seems to be taking the troll approach. If not, this would have been resolved about 120 posts ago.

[Bored chemist]

Yes, gem, in refusing the repeated requests to identify a source of torque, seems to be taking the troll approach. If not, this would have been resolved about 120 posts ago.

To be fair, in that regard he's just copying Alan (who seems to have gone rather quiet).

[gem]

So in regards to being rude, I don't believe I have, but will let others decide as to who's being rude.

Hal as far as the conditions set out in the original question how does your statement below not allow for a greater torque force favouring one direction to alter LOD

So for every eastbound gob of air, there is an equal and opposite westbound gob somewhere.  Each eventually hits a windmill or tree, and yes, that puts a bit of torque on the ground,

[Bored chemist]

So in regards to being rude, I don't believe I have, but will let others decide as to who's being rude.

Repeatedly refusing to answer a question is a breach of the rules of the site.
Most people would, I think, agree that signing up to the site rules, but not following them is rude.

So, once again...

Quote from: Bored chemist on 22/08/2020 11:06:53
Quote from: Bored chemist on 21/08/2020 11:04:44
Quote from: Bored chemist on 20/08/2020 19:37:09
But fundamentally, if you think the air is slowing the world down, you  still have to deal with this
Quote from: Bored chemist on Yesterday at 11:27:05
Quote from: Bored chemist on Yesterday at 10:36:19
Quote from: Bored chemist on Yesterday at 08:48:24

I'm still waiting for someone to explain how there's a change in angular momentum without a torque .
How do you get round this ?
Quote from: Bored chemist on 18/08/2020 18:12:27
The rate of change of angular  momentum is the torque divided by the moment of inertia.
If the torque is zero then the change in angular momentum is also zero.
Why not just admit that your view is at odds with the laws of physics, and stop wasting everyone's time?

[gem]

So Halc and BC I believe the question is answered accordingly following the logic of Halcs post, the kinetic energy that's driving the weather system and changing the energy it possesses due to its acceleration in motion and change in direction, and therefore change in velocity and therefore momentum.
which is the delta under discussion in regards as to what is moving air in relation to earths surface can apply a torque as it exchanges its kinetic energy gained from the solar input via frictional drag with wind turbine designed to favour one direction, by way of a reduction in kinetic energy of the atmosphere, as per the original question.
in an action/reaction pairing


Momentum = Mass X Velocity

https://en.wikipedia.org/wiki/Kinetic_energy#:~:text=In%20physics%2C%20the%20kinetic%20energy,energy%20unless%20its%20speed%20changes.

As to whether this would alter wind speed in one direction overall is your interpretation.

[Bored chemist]

It seems we need to sort out a few things.
Firstly, do you recognize that there are three conserved quantities and they are all conserved independently?

(1) Energy is conserved - but the Sun provides lots of it. The Earth isn't an isolated system.

(2) Angular momentum is conserved - To change this you need to supply an external torque (and it's  bit of semantics but you can do that by throwing something away from the Earth along a line that is not a radius)
(3) linear momentum is conserved. To change it you would need to apply a force to the Earth which is not compensated by some other force.

OK, once you get to grips with that, let's imagine one small bit of the Earth's surface getting heated by the Sun- don't worry, it's representative of the whole surface.

OK, let's say it is black tarmac and surrounded by fields.
So, when the Sun  heats it it gets hotter than the fields.
It warms the air above it. That warm air rises and is replaced by air coming in from all around it.
It is cylindrically symmetrical.
It can not generate a net force along a line tangential to the Earth's surface (though it does generate lift)
The air rises and cools http://apollo.lsc.vsc.edu/classes/met130/notes/chapter6/adiab_cool.html In effect, it exchanges thermal energy for gravitational potential energy.

And it's still cylindrically symmetrical.
The hot air that has risen and cools, spreads out because it is pushed away by the air underneath it.

And this cool air falls.
The whole thing now forms a convection cell.

It is still cylindrically symmetrical.

Now, I think the  mistake you are making is that, because a windmill near the tarmac will turn (pushed round by the air flowing into fill the "gap" left as the hot air rises), you think that will affect the momentum transfer.

At one level you are right- the sum of the angular momentum of the windmill and the rest of the planet is constant. if one spins one way, then the other spins the other way to compensate.
But that effect is small and not cumulative. When the windmill stops, the Earth goes back to its original axis and rate.
That's not going to extract energy from the spin of the planet.

Now there are two things you might mean by this phrase
"wind turbine designed to favour one direction"
It might be that you fix the axis of the windmill so it only ever spins when the wind blows along that axis.
Or you might put a brake of some sort on the mill so that, if the wind blows east, you let it turn, but if it blows west, you stall it.

It doesn't actually matter much which version you choose.

The wind, in the absence of the windmill doesn't get infinitely fast, even if the Sun keeps shining.
It reaches an equilibrium where the updraft dissipates as much energy by friction/ viscosity as it gains from the hot tarmac.
So we need to think about where that energy goes.
Well, it can't all go into heating the air by viscous drag.
If it heats that air, that just make it expand, and it rises faster. So the kinetic energy of the upward moving column is still in that column of air. And it's still symmetrical so it's not providing any torque on the Earth
It's not gone anywhere.
(Part of it goes into warming the air, but again, it's clear that it doesn't get hotter indefinitely. It's also irrelevant, since it is symmetrical)

The only place that it can dump energy is in frictional drag as the downgoing cold air hits the ground and travels across it. It can then dissipate energy as heat, a warming the ground.

OK, now imagine that you put your windmill in the way.
You extract energy from that air.
You also transfer momentum (though not angular momentum along any useful axis).
As far as I understand it, you are saying that the wind pushes the windmill and so the footings of the windmill push the ground and that provides a torque.
Well, yes it does.
(It would also do the same if it was a tree)

And here's the bit that you seem to ignore.
You slow down the bit of air that goes past the windmill.
So the bit of air that would have blown along the ground, pushing on it is not going so fast.
And- because of Newton's 3rd law, the extent to which the wind pushes on the windmill (or a tree) is exactly the same as the extent to which the mill (or tree) pushes back on the air.

And that "push" is no longer available to push on the ground, so there is a slightly smaller force acting on the ground in the lee of the windmill.
And, again, by Newton's 3rd law, that exactly compensates for the forces acting at the foot of the mill.
and it therefore exactly offsets the torque produced by the mill.

So the net effect of the mill is to provide zero torque on the Earth as a whole.

Now, given that the windmill's torques is exactly compensated by the lack of wind force acting on the ground,
(which Halc explained ages ago*)...

Will you please tell us what is providing the torque which you are saying changes the speed of the Earth?


*
He really did explain this; you just didn't pay attention.

Each eventually hits a windmill or tree, and yes, that puts a bit of torque on the ground, but torque is a vector quantity, and all those east and westbound torques add up to pretty much nothing, especially over time

[Bored chemist]

What baffles me was that you can show why the weather can't (permanently) affect the angular momentum of the Earth by giving a number of arguments
(1) simple symmetry
(2) analysis of the energy involved- if the rotation of the Earth was contributing more energy to the weather than the Sun, then we would see the change in rotation rate; Stonehenge wouldn't line up any more.
(3) The law of conservation of angular momentum says it's impossible without an external torque.
(4) the definition of angular momentum in terms of torque time and moment of inertia means that without a torque, the change in angular momentum (and thus rotational kinetic energy is zero.
(5) straightforward analogies in the form of "when the skater stops waving their arms about they are still spinning at the same rate as when they started and the man on the truck who thinks he's helping.

And, though nobody has in any way refuted those, they still don't actually accept a simple fact. The Sun drives the weather.

[Petrochemicals]

Stopping following this threeeeeeeead.   . Now

[Bored chemist]

Stopping following this threeeeeeeead.   . Now

No.

[gem]

Hi all, I believe we have already covered a lot of what is contained in your responses, however just to reiterate a couple of points, we may have misunderstood each other on.
Halc you stated in response to my statement
 

The weather is driven by solar energy, not kinetic energy.

In which I stated

the delta under discussion in regards as to what is moving air in relation to earths surface can apply a torque as it exchanges its kinetic energy gained from the solar input

so not sure where we disagree on that point. (that goes for BC also, as he stating disagreements about earth rotation generating the weather)

Halc you then went on to say.

That does change the kinetic energy of the atmosphere, but acceleration doesn't describe that since acceleration is a change in velocity, not a change in kinetic energy.

I believe that statement is incorrect as demonstrated by the following opening paragraph from the earlier link provided, which you dismissed as irrelevant

In physics, the kinetic energy (KE) of an object is the energy that it possesses due to its motion.[1] It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest
https://en.wikipedia.org/wiki/Kinetic_energy#:~:text=In%20physics%2C%20the%20kinetic%20energy,energy%20unless%20its%20speed%20changes.
You also stated

No turbine exerting force in one direction can have a significant effect on the momentum of the atmosphere since there is no way to isolate the air movement created from further friction with the ground. If the turbine pushes the ground eastward, then somewhere a tree pushes the ground westward.

which I don't disagree with, but in regards to the principle of the original question, by designing a turbine or retractable barrier as per your posting to favour one direction on what was originally a flat level surface will not only alter the amount of surface area the atmosphere comes into contact with, and the coefficient of friction at that point, it will therefore increase the amount of torque applied to that area, indeed when designing wind turbines the height above the ground is a key consideration, so a percentage of the air in question may not have been destined to contact the surface at all, which I believe addresses B/C point below

And that "push" is no longer available to push on the ground, so there is a slightly smaller force acting on the ground in the lee of the windmill.
And, again, by Newton's 3rd law, that exactly compensates for the forces acting at the foot of the mill.
and it therefore exactly offsets the torque produced by the mill.

Also BC I believe you seriously are mistaken in this statement regarding the atmosphere.

The only place that it can dump energy is in frictional drag

I believe the atmosphere is credited with approximate emission of energy back out to space of around 200 watts per metre square in the infrared spectrum.

quite windy today where i was

[Bored chemist]

so not sure where we disagree on that point.

I disagree with this because it's a breach of the conservation of angular momentum.

the delta under discussion in regards as to what is moving air in relation to earths surface can apply a torque as it exchanges its kinetic energy gained from the solar input

At least, I think it does.
It's impossible to be sure because it's too badly written.
It certainly appears to say "energy can change momentum" which is wrong.

I also think you have misunderstood Halc's  statement that "That does change the kinetic energy of the atmosphere, but acceleration doesn't describe that since acceleration is a change in velocity, not a change in kinetic energy."

You do not seem to grasp the fact that rotation is a change in velocity, and thus an acceleration, but without a change in speed and thus not a change in KE.

I believe the atmosphere is credited with approximate emission of energy back out to space of around 200 watts per metre square in the infrared spectrum.

I ignored that, because it's obviously irrelevant and the thread is long enough.
But since you seem to need me to point it out for you, that doesn't produce a torque.
It also doesn't produce any (meaningful) push. There's the tiny effect of radiation pressure, but it's symmetrical anyway so it has no net effect on an air parcel.

which I don't disagree with, but in regards to the principle of the original question, by designing a turbine or retractable barrier as per your posting to favour one direction on what was originally a flat level surface will not only alter the amount of surface area the atmosphere comes into contact with, and the coefficient of friction at that point, it will therefore increase the amount of torque applied to that area, indeed when designing wind turbines the height above the ground is a key consideration, so a percentage of the air in question may not have been destined to contact the surface at all, which I believe addresses B/C point below

You don't seem to realise that you just said you don't agree with Newton's 3rd law.
Is that what you intended to say?

Do you know what viscosity is?
It's the way that a layer of moving fluid transfers momentum to the layers adjacent to it, even if there is no material flux.
The high up air pushes the lower air and the lower air pushes that which is lower still and so on.
And eventually it reaches the ground.
Because there's nowhere else for it to go.

And, once again.
What provides the torque needed to change the angular momentum.
"energy" can't provide a torque (other than the effects of radiation pressure).

quite windy today where i was

It was here too.
But it has calmed done a lot now.
Presumably, you think the Earth must have stopped turning.

[gem]

Halc thanks for that response.
But think that grenade analogy only works from the centre of an isolated system.
I really struggle to visualise any scenario on Earth Or it’s atmosphere where this statement can be applied.
( This is why acceleration is not a change in kinetic energy.)

Just to use your grenade analogy, if we suspended a grenade at say 100m above the ground and chemical energy was converted to kinetic energy via an explosion (Similar to the solar input )
breaking the grenade shell in to two Identically equal parts initially going level in opposite directions (East/West) at equally high speeds, could you design a scenario where one piece transferred  more of its kinetic energy via a torque force applied to the Earths surface, and the other transfers more of its kinetic energy to heat.

[Bored chemist]

could you design a scenario where one piece transferred  more of its kinetic energy via a torque force applied to the Earths surface, and the other transfers more of its kinetic energy to heat.

No
Because you can't "transfer kinetic energy via torque" It's like trying to change the flavour of something by altering its position.
They are two different things.

You could get the   exploding grenade to change the rotation of the Earth- as long as one part of the grenade was thrown clear of the Earth- completely clear.  If it remained in orbit the angular momentum of the shrapnel/ Earth system would remain the same as before the bang.

But the problem you seem to have is that you think angular momentum can be "created" from energy.
It can't.

[Bored chemist]

I really struggle to visualise any scenario on Earth Or it’s atmosphere where this statement can be applied.
( This is why acceleration is not a change in kinetic energy.)

How do you find it difficult to visualise a rock tied to a string swinging round in a circle?

[Colin2B]

I really struggle to visualise any scenario on Earth Or it’s atmosphere where this statement can be applied.
( This is why acceleration is not a change in kinetic energy.)

How do you find it difficult to visualise a rock tied to a string swinging round in a circle?

Or the fairground big wheel or roundabout, lots and lots of visualisations - some real gems.