Reason why the chair can support me

[nrqed]

What about before I sit onto the chair? Could you use the HUP to explain what prevents the electrons in the chair from completely collapsing into the nuclei (off couse I wouldn't know if the electrons did collapse because that would involve a measurement hence HUP would automatically come into it)?

As I mentioned in my other post, the HUP is obeyed by the wavefunction even before you make any measurement.
And yes, even before you sit on the chair the HUP can be invoked to explain why the chair does not collapse (or why your own body does not collapse!), no matter if you take a measurement or not.

Pat

 

[alfredblase]

Bah you guys call yourselves physicists and can't come up with an all round satisfactory answer to why you don't fall through a chair?! Let's us assume we have a diamond crystal large enough to sit on. This will be our chair. The question then becomes: why am I unable to compress a diamond crystal by sitting on it, by an amount noticeable to the naked eye? The answer of course is that diamond has a crystal structure that is resistant enough. This crystal structure is held together by the electro-magnetic forces exerted on each atom by each atom. And these atoms do not collapse because of Pauli's exclusion principle, the EM force and the quantized nature of electron orbitals. And what about the HUP? Well, yeah, that works too, but the HUP alone is not enough because we would not conserve atomic structure. And why do the nuclei not fall apart? Well that's because of the strong force, the quantized nature of nucleon orbitals (see the shell model) and Pauli's principle (again HUP is not enough on its own as we must conserve nuclear structure) . And why do the nucleons not tear apart? Well that's QCD for you. Nuff said... (dear oh dear).

 

[inha]

Bah you guys call yourselves physicists and can't come up with an all round satisfactory answer to why you don't fall through a chair?! Let's us assume we have a diamond crystal large enough to sit on. This will be our chair. The question then becomes: why am I unable to compress a diamond crystal by sitting on it, by an amount noticeable to the naked eye? The answer of course is that diamond has a crystal structure that is resistant enough. This crystal structure is held together by the electro-magnetic forces exerted on each carbon atom by the electrons in each carbon atom. And these carbon atoms do not collapse because of Pauli's exclusion principle. Nuff said... (dear oh dear)

Not all chairs are made out of crystalline materials.

 

[alfredblase]

Not all chairs are made out of crystalline materials.

That's obvious... I used the diamond chair example beacuse it was the simplest example I could think of. Skipping the carpintery, ironmongery, smithery, etc, etc step the arguments hold for all materials resistant enought to be made into a chair, meaning that plastics for example, without having a crystal structure, are still held together by the forces and principles mentioned in my previous post. Nuff said

P.S.I modified my previous post to make it more complete and satisfactory.

 

[Gokul43201]

Bah you guys call yourselves physicists and can't come up with an all round satisfactory answer to why you don't fall through a chair?!

That, sir, is your opinion.

Lets us assume we have a diamond crystal large enough to sit on. This will be our chair. The question then becomes: why am I unable to compress a diamond crystal by sitting on it, by an amount noticeable to the naked eye?

No, that is not the question. Nuff said !

 

[jhe1984]

The reason that the chair supports you is because angels are holding it up.

I think we can all agree on this.

 

[alfredblase]

No, that is not the question. Nuff said !

Hehehe. How is that not the question? I wish people would stop replying to my posts in this thread, with one sentenced answers lacking in depth.

In the case of a chair made form a block of material (e.g. a very large diamond crystal), the block undergoes compression when I sit on it. The fact that it does not compress too much means that it is a good chair. Hence if you engage your brain for more than a few seconds I think you will find that the answer given in my post before last, answers the original question in a satisfactory manner...

Edit: inha I would be grateful if you would update the quote you made of my first post as I wrote it in a hurry and have since changed it a lot. =)

 

[Gokul43201]

Blase : (for starters) What does noticeability "by the human eye" have anything to do with the problem being discussed ?

I find that I do not pass through my hammock !

 

[alfredblase]

Gokul,

you refuse to think...

The crystal lattice of the diamond will undergo a small amount of compression, but not enough compression so we will notice it... Please use your brain. All I was saying is that this qualifies it as a chair that can support me. It was a simple example of a chair. But you are being very pedantic over this. I repeat: the forces and principles mentioned in my first post allow a block of suitable material to support a person as a good chair is supposed to do. You can get into an even more trivial and pedantic argument over carpintery and come up with infinite examples of chairs but the general arguments I made hold for all of them. If you disagree with the physics behind my arguments please tell me exactly which part of my arguments you disagree with... [please refer to the latest version of my first post (post 52) as due to having originally written in it a hurry i updated it quite a lot to make it better]

 

[pivoxa15]

Gokul,

you refuse to think...

The crystal lattice of the diamond will undergo a small amount of compression, but not enough compression so we will notice it... Please use your brain. All I was saying is that this qualifies it as a chair that can support me. It was a simple example of a chair. But you are being very pedantic over this. I repeat: the forces and principles mentioned in my first post allow a block of suitable material to support a person as a good chair is supposed to do. You can get into an even more trivial and pedantic argument over carpintery and come up with infinite examples of chairs but the general arguments I made hold for all of them. If you disagree with the physics behind my arguments please tell me exactly which part of my arguments you disagree with... [please refer to the latest version of my first post (post 52) as due to having originally written in it a hurry i updated it quite a lot to make it better]

So you have basically reduced all of the variables a normal chair might have for breaking such as its geometry and considered a pure physical substance and answered why it would not break after a force is applied onto on the quantum level. It makes sense to me.

 

[Gokul43201]

Bah you guys call yourselves physicists and can't come up with an all round satisfactory answer to why you don't fall through a chair?! Let's us assume we have a diamond crystal large enough to sit on. This will be our chair. The question then becomes: why am I unable to compress a diamond crystal by sitting on it, by an amount noticeable to the naked eye? The answer of course is that diamond has a crystal structure that is resistant enough.

Q : Why can the chair resist my weight.
A: Because the material of the chair is resistant enough.

This crystal structure is held together by the electro-magnetic forces exerted on each atom by each atom.

This (the role of EM interactions between atoms) has been stated at least thrice in this thread before your "pioneering" post. Besides, a wooden chair has no crystal structure.

And these atoms do not collapse because of Pauli's exclusion principle, the EM force and the quantized nature of electron orbitals.

That's a complete non-answer (and the question has nothing to do with why an atom is stable, so everything from this point on is just fluff).

Secondly, you can't just throw words around and call it an explanation. I contend that the reason for the stability of the atom (of the chair under the forces it seees from your butt ) comes from time-dependent perturbation theory (applied to the eigenstates of the electrons), and can not be explained by the Exclusion Principle.

Thirdly - and this is pedantry -there is no mention of any kind of "force" in the QM description of an atom.

And what about the HUP? Well, yeah, that works too, but the HUP alone is not enough because we would not conserve atomic structure.

You are not saying anything physically meaningful with this sentence. What do you mean by "that works too" ?

And why do the nuclei not fall apart? Well that's because of the strong force, the quantized nature of nucleon orbitals (see the shell model) and Pauli's principle (again HUP is not enough on its own as we must conserve nuclear structure). And why do the nucleons not tear apart? Well that's QCD for you. Nuff said... (dear oh dear).

All you've done is show that you know some key words. Please, show me how QCD ensures the stability of the nucleon. I can't recall how asymptotic freedom arises out of the color of virtual gluons...

Blase : Your "explanation" is not explaining anything more than for instance, if I said : the reason the chair supports me is that this outcome corresponds to a local free energy minimum in the system whose activation energy is extremely large compared to thermal energies. This at least, is correct.

The only part of your post that goes towards answering the question, is the part that has been covered more than a few times before you joined this thread.

Edit: PS : Nuff said.