Is it true that you are never actually touching something?

[physicsnoob12]

is it true that you are never actually touching something? i keep hearing that this is true but why is it that we can feel the texture of things?

 

[Vanadium 50]

This depends entirely on the definition of "actually touching something". Probably also "you", since the outermost layer of skin is dead. But this will end up being an argument about semantics, not science.

 

[NobodySpecial]

i think the point is that two pieces of matter never touch - the force you feel is the electrostatic repulsion from the charges in the material

 

[Vanadium 50]

But there is also the fact that chemical bonds form between the two objects touching. If they are connected, how can one say they are not touching? And we're right back arguing about semantics.

 

[OmCheeto]

i think the point is that two pieces of matter never touch - the force you feel is the electrostatic repulsion from the charges in the material

And that's why I called Mr. Capra a crackpot the other day.

https://www.physicsforums.com/showthread.php?t=455290

There was a mention of that in his http://video.google.com/videoplay?docid=9107401959308808776#" .

53:40 thru 58:+

I'm a layman, and like to think about everything too much.

But really, I know nothing.

 

[DaveC426913]

is it true that you are never actually touching something? i keep hearing that this is true but why is it that we can feel the texture of things?

The summed answer to your question is:

At the atomic level, physical objects do not have clear, hard boundaries. Physical objects are made of atoms, which contain electrons, which have repulsive forces.

It is these forces that interact when physical objects come into contact with each other.

We can feel texture because texture is a macroscopic property of objects, far, far larger in scale than the individual atoms.


Think of this: say I'm standing in a forest, at night, wearing a pair of boxing gloves. OK, sure I can't touch small things, such as grass or pine needles, but would I be able to feel my way through the forest that's filled with foot thick trees? Of couse I can. Think of trees as the "texture" of the forest. As long as the texture is much bigger than my boxing gloves, I'll be fine.

 

[jfy4]

But there is also the fact that chemical bonds form between the two objects touching. If they are connected, how can one say they are not touching? And we're right back arguing about semantics.

Chemical bonds are the constant exchange of photons between charged particles. And I think this is what OP is getting at. But I do agree with you about the semantics. Like The matrix! Touch is really just a cascade of photons between electrons in your body. So can you really touch something? for sure, it's exactly what you just described.

You might mean, do two things touch in the naive sense, that they are contiguous? As far as physics knows, interaction only takes place when two objects are "local"... that is, an electron and a photon only interact when their world lines intersect. Do two electron's ever interact... no... it has never been observed, only the interaction between photons and electrons has been observed, Hence the QED vertex.

 

[DaveC426913]

Chemical bonds are the constant exchange of photons between charged particles.

This is not true.

 

[jfy4]

This is not true.

Please tell me what really happens then... Because I was under the strong impression that it was...

 

[Delta2]

What have been said may cover what happens in our daily life, but what happens when a neutron finds its way in the nucleus and causes nuclear fission or in the high energy collisions at particle accelerators. Do we have particles in contact then?

 

[Maui]

is it true that you are never actually touching something? i keep hearing that this is true but why is it that we can feel the texture of things?

http://www.worsleyschool.net/science/files/touch/touch.html

but why is it that we can feel the texture of things?

The repulsion is taking place between 'somethings' that are a matter of interpretation (aka personal opinion and/or belief). There are a few subtle differences between matter and force, but in this particular situation you are justified to think approximately of the 'touching' of macro surfaces as interactions of force fields.

 

[Maui]

At the atomic level, physical objects do not have clear, hard boundaries.

Then they are not 'physical' and qm is not physics per se, but a statistical mathematical tool.

 

[cbetanco]

Please tell me what really happens then... Because I was under the strong impression that it was...

I thought the same way also...

 

[Calrik]

Well yes and no obviously. Touch is a biological sensation it has pretty much nothing to do with physics which is about something beyond biological concerns. Essentially this isn't a physics question it's merely a question of psychology and biology.

Nothing touches in physics either, it just influences another field or particle. The term touch is entirely inappropriate to any science but biology.

 

[DaveC426913]

Well yes and no obviously. Touch is a biological sensation it has pretty much nothing to do with physics which is about something beyond biological concerns. Essentially this isn't a physics question it's merely a question of psychology and biology.

Nothing touches in physics either, it just influences another field or particle. The term touch is entirely inappropriate to any science but biology.

His question is equally applicable if he were asking how a ruler could touch a rock. No biology involved.

 

[alxm]

Please tell me what really happens then... Because I was under the strong impression that it was...

The electromagnetic force is mediated by photons. That says nothing at all about chemical bonding, because electrons on two atoms near each other (as well as within the atoms) will exchange photons and experience repulsion completely regardless of whether or not they're bonding. Knowing that the electromagnetic force is mediated by photons does nothing to explain chemical bonding. You don't even remotely need QED to explain chemical bonding; a 'classical' Coulomb gauge with instantaneous attraction/repulsion works fine.

Saying that chemical bonding is because of electromagnetic repulsion/attraction is like saying a turbulent vortex in a stream forms because water has viscosity. It's an inherently dynamical effect. On top of that, electrostatic forces are not sufficient to explain chemical bonding or any electronic properties, even when you take into account dynamics, since the Pauli principle and exchange energy plays a quite important role.

I am certain that nowhere, jfy4's imagination, has a chemical bond ever been defined as "the constant exchange of photons between charged particles". It's a ridiculous remark that says absolutely nothing other than "electrons repel". In what ways would "electrons repel" describe what a chemical bond is? And more relevantly, in what way does it explain why some atoms will form a bond, and others do not. They all have electrons around them, don't they? So why will two neutral hydrogen atoms form a bond, but not two neutral helium atoms? Explain yourself, jfy4.

 

[DaveC426913]

I am certain that nowhere, jfy4's imagination, has a chemical bond ever been defined as "the constant exchange of photons between charged particles". It's a ridiculous remark that says absolutely nothing other than "electrons repel"
...
Explain yourself, jfy4.

Let's just dial back the aggression please. There are ways of disagreeing and correcting without having to get insulting.

 

[cbetanco]

The electromagnetic force is mediated by photons. That says nothing at all about chemical bonding, because electrons on two atoms near each other (as well as within the atoms) will exchange photons and experience repulsion completely regardless of whether or not they're bonding.

Aren't chemical bonds an electromagnetic phenomena? Doesn't it have to due with how electrons in the outer shells of the atoms interact? The only way I know of two electrons interacting is through the exchange of virtual photons, but maybe I am missing something...

 

[Calrik]

His question is equally applicable if he were asking how a ruler could touch a rock. No biology involved.

Exactly, but then he did not ask that; define the experiment before you can expect the results, no?

We cannot use macroscopic descriptions to describe nanoscopic phenomena to do so means abandoning any limits to reason and of course the laws of physics as we currently understand them.

"If a tree falls in the woods and no one is around to hear it what colour is it?"

Monkey Island 4.

 

[DaveC426913]

Exactly, but then he did not ask that

He did. He asked about touching. A ruler can touch a rock. This a general case of touching. In the absence of specificity, any answer that can apply is valid.

But an answer that attempts to exclude valid answers because it imposes its own assumption is not a valid answer, such as your introduction of a narrow definition of 'touching' as being a limited to the senses.

"If a tree falls in the woods and no one is around to hear it what colour is it?"

Attempts to claim that there's no logic here won't work. We won't fall for this kind of verbal smoke and mirrors.

 

[Calrik]

He did. He asked about touching. A ruler can touch a rock. This a general case of touching. In the absence of specificity, any answer that can apply is valid.

But an answer that attempts to exclude valid answers because it imposes its own assumption is not a valid answer, such as your introduction of a narrow definition of 'touching' as being a limited to the senses.Attempts to claim that there's no logic here won't work. We won't fall for this kind of verbal smoke and mirrors.

Ok your not getting the point not sure if that is my problem or yours. Basically to ask a pertinent question you need to ask a pertinent question about something that is defined or at least knowable experimentally.

I'm not getting into an argument here just being specific.

I never said there was no logic just that there is no point in asking a question without logic.

A ruler can touch a rock, but can it touch god?

 

[DaveC426913]

Ok your not getting the point not sure if that is my problem or yours. Basically to ask a pertinent question you need to ask a pertinent question about something that is defined or at least knowable experimentally.

His question makes perfect sense as-is. I don't see where you're missing it.

Certainly, there are interesting facets to the question, such as yours, but the central question is simply:

Is it true that two things are never really touching?

That question can be answered independently of all the facets.

 

[Calrik]

His question makes perfect sense as-is. I don't see where you're missing it.

Certainly, there are interesting facets to the question, such as yours, but the central question is simply:

Is it true that two things are never really touching?

That question can be answered independently of all the facets.

Ok then we are agreed his question needed to be refined but if you take it at face value it doesn't. Doesn't mean something didn't need to be said about it though.

is it true that you are never actually touching something? i keep hearing that this is true but why is it that we can feel the texture of things?

I disagree the question made any sense you don't. So?

Of course you are never touching something if touch isn't an issue, the response is therefore implied.

 

[jfy4]

Aren't chemical bonds an electromagnetic phenomena? Doesn't it have to due with how electrons in the outer shells of the atoms interact? The only way I know of two electrons interacting is through the exchange of virtual photons, but maybe I am missing something...

Exactly. My knowledge on the subject of bonds is that they are entirely electromagnetic in nature, and as far as physicists know, the electromagnetic interaction is entirely mediated by photons... Hence, I'm glad we are on the same page.

As for others who have objected, please teach me! if it is not that way, i'd love to here a more correct view.

 

[Nick666]

Maybe the only place where stuff touches other stuff is at the center of a black hole .

 

[DaveC426913]

Maybe the only place where stuff touches other stuff is at the center of a black hole .

Neutron star - the lightweight little brother of a BH - where the force is enough to crush the electrons and the protons together till they're all just neutrons shoulder-to-shoulder.

 

[DaveC426913]

As for others who have objected, please teach me! if it is not that way, i'd love to here a more correct view.

I realize I do not actually have an answer. I too am hoping an expert in the field will weigh in.

 

[jfy4]

I realize I do not actually have an answer. I too am hoping an expert in the field will weigh in.

Unless there was some sort of logical inconsistency in my statement from before, how could you have known I was incorrect then...?

I am open to learning new information. But QED is is fairly clear in its explanation of electromagnetic phenomena. To be frank, I do not believe to be wrong in this matter, unless I can see a clear explanation of how bonds work besides the explanation I have provided. I was trying to help OP, not lead him astray.

 

[DaveC426913]

I am open to learning new information. But QED is is fairly clear in its explanation of electromagnetic phenomena. To be frank, I do not believe to be wrong in this matter,

I am certainly willing to be corrected. Can you show a reference where it says that chemical bonds are the constant exchange of photons between charged particles.

Are these virtual photons?

 

[jfy4]

I am certainly willing to be corrected. Can you show a reference where it says that chemical bonds are the constant exchange of photons between charged particles.

Are these virtual photons?

I'm not even sure anyone needs to be corrected, I don't think I have been shown wrong. Yes, I mean virtual photons. And yes, a quick internet search will show that electromagnetic phenomena of any kind (including chemical bonds) are mediated by photons (virtual and radiative).

With your "go-ahead" I will consider my response concerning chemical bonds still ok. Thank you for your dialogue.