Do We Ever Truly Touch Anything?

[bondinthesand]

i was watching this show on the science channel called the known universe it stated that we never really touch anything because our skin is made up of atoms which have electrons and since the things we touch have the same we never actually come in contact with anything? if that is true how do we "feel" anything?

 

[xepma]

How does the sensation of "feeling" arise? Because there is a force acting on the nervous system. What causes this force? The Coulomb repulsion caused by the electrons, mostly.

 

[DrChinese]

As an extension of xepma's post: what we call "matter" is quite nearly a perfect vacuum. The entire Milky Way once fit into a space much smaller than a human cell. Most interactions are due to the fields generated by the gravitational and the electromagnetic forces associated with atoms. Rarely do the atoms in your body actually come into direct contact with other atoms.

 

[HallsofIvy]

Of course, whether we really "touch" something depends on what you mean by "touch"! I would consider the effect described by xepma and Dr. Chinese to be "touching".

 

[Naty1]

Touch, as noted, is rather subjective. on the other hand, even solid metals are 99.9999 percent ( I arbitrarily stopped typing 9's) "empty" space...feeling arises via information transfer...evolutionary based sensory perception

 

[maverick_starstrider]

i was watching this show on the science channel called the known universe it stated that we never really touch anything because our skin is made up of atoms which have electrons and since the things we touch have the same we never actually come in contact with anything? if that is true how do we "feel" anything?

Even though things never "touch" as my finger, for example, gets closer to hitting a key the electrostatic repulsion as I get closer causes the surface of my finger to deform. Our brains/bodies have evolved to attach a sensation with a deformation of the skin. Think about a windy day, when the day is calm we don't feel air impacting on us but we know that it is and then a strong gust comes along and suddely feel like we're being pushed by a strong force. We were always being pushed around by air, our body's nerve just didn't really have the sensitivity to detect it before. Sensation is in the head.

P.S. in the future you should probably post something like this in the General Physics forum

 

[sokrates]

As an extension of xepma's post: what we call "matter" is quite nearly a perfect vacuum. The entire Milky Way once fit into a space much smaller than a human cell. Most interactions are due to the fields generated by the gravitational and the electromagnetic forces associated with atoms. Rarely do the atoms in your body actually come into direct contact with other atoms.

Great post Dr. Chinese. Interesting topic OP brought up, I think touching would also be somehow related to the physiology of our nervous system.

It's an electrical sensor after all, so there's no mechanical touching in the conventional sense.

 

[WaveJumper]

i was watching this show on the science channel called the known universe it stated that we never really touch anything because our skin is made up of atoms which have electrons and since the things we touch have the same we never actually come in contact with anything?

Yes, literally speaking we never touch anything. Electrons in the outer shells of atoms repel each other at 10^-8 metres.(yes, you aren't really sitting on a chair, but hovering/flying slightly above it at 10^-8m.)

if that is true how do we "feel" anything?

Buried in the skin, there are nerve cells, which have extra electrons they can release when acted on by a force from outside. These electrons flow along the nerves, atom to atom, eventually reaching the brain, where other cells interpret this electrical signal as 'pain'. At no time do any atoms or electrons actually touch each other; the only 'contact' is the electromagnetic force ( positive and negative) between particles.

 

[WaveJumper]

Couldn't one say that the "electric charge" that fills the 10^-8 meter space is really apart of you, so yes you are really touching, just not the atoms?

Sure, but that would be a totally new way of defining 'touch', as far as our perception of solid structures goes. Our perception doesn't reveal that when are having sex, we are actually merely exchanging photons with no physical touch between the atoms of...(don't tell your wife i told you this)

 

[negitron]

Buried in the skin, there are nerve cells, which have extra electrons they can release when acted on by a force from outside. These electrons flow along the nerves, atom to atom, eventually reaching the brain, where other cells interpret this electrical signal as 'pain'.

[Morbo]NERVES DO NOT WORK THAT WAY! GOODNIGHT![/Morbo]


Well, he's right, they don't. It's much, much more complex than that; suffice to say it's a combination of electrical and chemical signals that propagates along the nerve in stepwise fashion. Between nerves, across gaps called synapses, chemicals called neurotransmitters carry the message from one nerve cell to another. Most of the electrical signals aren't carried by electrons, anyway, but by ions, principally calcium and potassium.

 

[jobyts]

Yes, literally speaking we never touch anything. Electrons in the outer shells of atoms repel each other at 10^-8 metres.(yes, you aren't really sitting on a chair, but hovering/flying slightly above it at 10^-8m.)

Is it only electron repulsion, or there is proton repulsion too? If you push someone, and if he falls down, the whole atoms moved.

Why a touch doesn't cause an momentarily electric current?

 

[n!kofeyn]

This sounds like Zeno's paradox all over. :)

Touch is not just in the mind, in my opinion. I think when any two objects come into any type of meaningful contact, they are touching. I also would consider electric field repulsions to be touching, since they need a medium to be transmitted through. We create our own electric fields, which interact in "close" proximity with objects around us, i.e. we touch.

 

[daisey]

boninthesand

Here is a thread I started earlier that you might be interested in reading.

https://www.physicsforums.com/showthread.php?t=301495

I'm no scientist, but from what I've read in books recently, and from very smart people on this forum, I believe Dr. Chinese said it best above. All you are "feeling" are the electromagnetic forces of electrons in the hammer repelling the electrons in the rock. And the electromagnetic force is extremely strong.

Daisey

 

[pallidin]

Yeah, this subject reminds me of two magnets in a repulsive arrangement.
Of course, the issue here does not involve pure magnetism. Still, it reminds me of that.

 

[bondinthesand]

then if we are only feeling the electromagnetic pulses, than how do we manage to pick something up?/

 

[Lambda3]

then if we are only feeling the electromagnetic pulses, than how do we manage to pick something up?/

We can pick stuff up because of the friction between an object and our hands.

 

[maverick_starstrider]

then if we are only feeling the electromagnetic pulses, than how do we manage to pick something up?/

As has been pointed out, the source of friction is coulombic forces (i.e. electromagnetic interaction) and, just as we are discussing here, when a block or something slides across something else, like without hands, there's not actually anything touching. Keep in mind that the separation between surfaces are on the atomic order so the distance would be about 1/100,000's the width of a human hair. So it's not like you can squint your eyes and see the seperation. You are familiar with a situation where the atomic nuclei of two atoms actually do touch... a nuclear bomb.

P.S. Completely incorrect use of electromagnetic pulse btw (an EMP is a type of weapon/ phenomena following a nuclear explosion in atmosphere).

 

[daisey]

...You are familiar with a situation where the atomic nuclei of two atoms actually do touch... a nuclear bomb...

Touch, or fuse?

 

[maverick_starstrider]

Touch, or fuse?

Uhh... potentially neither, fiss? Is that a word? Depending on the energy level involved and the nucleus under consideration this is either a fission event (like the original bomb where the atom "splits"), a fusion event (where the nuclei fuse), or simply isotope creation (where a neutron simply "joins" the nuclei).

 

[daisey]

Interesting. Actually I was really wondering when two nuclei actually do "touch", does that always lead to a nuclear explosion. I'm guessing your going to answer by saying that two nuclei would only touch in situations where tremendous forces were added to make them touch, and that would inevitably lead to a nuclear explosion. And I guess it would follow that nuclei would never naturally (in nature) touch (unless the nuclei lived inside a star). Correct?

 

[D H]

Keep in mind that the separation between surfaces are on the atomic order so the distance would be about 1/100,000's the width of a human hair. So it's not like you can squint your eyes and see the seperation.

Petty squabble: That is less than a nanometer. Isn't that about an order of magnitude too small?

The contact forces die off quickly with distance; much, much faster than an inverse square law. They are pretty much non-existent at a hundred nanometers to a micrometer separation. One simple way around this imbroglio is to define "touching" at the macro level as a separation distance at which contact forces are non-negligible.

 

[Dale]

I thought that everything (including matter) was viewed as fields in modern QFT etc. So if everything is a field and if the fields are overlapping then in what sense are they not "touching"?

 

[maverick_starstrider]

Petty squabble: That is less than a nanometer. Isn't that about an order of magnitude too small?

The contact forces die off quickly with distance; much, much faster than an inverse square law. They are pretty much non-existent at a hundred nanometers to a micrometer separation. One simple way around this imbroglio is to define "touching" at the macro level as a separation distance at which contact forces are non-negligible.

I was going for the order of angstroms so on the order of 0.1 nanometers.

As for your question on what happens with a nuclear "explosion". When making a fission bomb (one where the atoms "split") what happens is that you get a rogue neutron with tremendous force to actually "smash" into a nucleus. This neutron then becomes "captured" by the nucleus. What happens next depends on what kind of nucleus it was. For heavy nuclei (like uranium or plutonium isotopes) this added neutron causes it to be come unstable and it decays producing multiple smaller nuclei and most importantly another neutron PLUS ENERGY. This new neutron released can then be captured by another nucleus and so on such that you get a CHAIN REACTION. The key is to choose the right starting nuclei such that it easily decays into something + a rogue neutron that can then collide with its neighbours. This runaway reaction of neutrons and energy results in... well... boom. Although we gotten quite off topic at this point.

 

[D H]

That wasn't my question.

 

[daisey]

Although we gotten quite off topic at this point.

Well, kinda. The topic concerns touching matter, and I wasn't looking for an explanation of how a nuc-bomb works. Just trying to verify your saying that anytime two nuclei "touch" it results in a nuc explosion. But thanks for the info in any event.

Dailsey

 

[Razzor7]

Do electrons ever touch?

 

[daisey]

Do electrons ever touch?

No. From what I'v read, I don't think it's possible for ANY matter to touch (in the way most people think of touching) since all fundamental particles (which an electron is) have no physical extension. There is nothing there to "touch"! Really hard to get my mind around that. Kinda spooky!

Daisey

 

[bondinthesand]

heres another question.. when we jump into water and we have water dripping off of you.. is the water actually touching you or do we have a "force field" around us in the water??

 

[Dale]

Is he a dot, or is he a speck?
When he's underwater does he get wet?
Or does the water get him instead?
Nobody knows, Particle man

-They Might Be Giants

 

[daisey]

heres another question.. when we jump into water and we have water dripping off of you.. is the water actually touching you or do we have a "force field" around us in the water??

In my opinion, the difficulty with your question lies with the term 'touching'. It is theorized that everything in our universe - rocks, hammers, cars, atoms, people - are all just waves of energy. So, keeping that in mind, how would you answer the question "do waves of energy 'touch'"? Just remember, that based on the aforementioned theory, matter is not solid, so nothing can 'touch' anything, at least not in the way I believe you (and most people) define the word 'touch'.

 

[vin300]

Two electrons cannot touch. At the point is infinite potential

 

[daisey]

I thought that everything (including matter) was viewed as fields in modern QFT etc. So if everything is a field and if the fields are overlapping then in what sense are they not "touching"?

DaleSpam,

Someone please correct me if I am wrong, but I believe the fields you refer to consist of waves of possibility. No two waves are exactly the same - in other words if one were to square the wave amplitudes and compute the location of these particles based on probabilities, one would never find the locations to be overlapping - i.e. "touching".

 

[Dale]

Someone please correct me if I am wrong, but I believe the fields you refer to consist of waves of possibility. No two waves are exactly the same - in other words if one were to square the wave amplitudes and compute the location of these particles based on probabilities, one would never find the locations to be overlapping - i.e. "touching".

No, the joint probability density function would, in general, be non-zero. In other words, given any finite region there will be a non-zero probablity of finding both particles there. That is why I disagree with this idea that we never touch.

 

[daisey]

No, the joint probability density function would, in general, be non-zero. In other words, given any finite region there will be a non-zero probablity of finding both particles there.

Yes, you are right. Technically I have read that based on the probability density function of an electron, there is a chance that particle could be found inside the nucleus of an atom. A VERY SMALL chance, but non-zero. I guess that anything that is physically possible can happen. But some are very unlikely.

 

[daisey]

Dale Spam,

Did some re-reading last night on this subject. I would like to take this opportunity to summarize what I believe to be true regarding your earlier question about matter touching (this is an exciting subject, isn't it! )...

1. Dynamic attributes are contextual. While, as you stated, probability waves (fields) of two particles might be overlapping, their dynamic attributes (in this case, location) do not exist until measured. Until measured, they are just waves of probability. And once measured, the result of that measurement (again, location in this case) is dependent on the similar attributes of nearby particles (ie. being contextual). Therefore, based on this contextual manifestation, while the potential for two individual particles having the same location according to their wave functions might be non-zero, the chance of them naturally occupying the same space when measured (or observed) is zero.

2. Matter consists of electrons and quarks (and force carriers - bosons). And these are defined as having no spatial content (point particles - ZERO size). While these particles may have a mathematically calculated location in space-time when observed, there is nothing there to "touch" (using the common definition of that term), even if the location of two particles were identical. Now, there are consequences when two particles are fused (having the same location, yes - but not "touching"). But I do not believe that happening outside a star is a natural occurrence.

Daisey

 

[Dale]

1. Dynamic attributes are contextual. While, as you stated, probability waves (fields) of two particles might be overlapping, their dynamic attributes (in this case, location) do not exist until measured. Until measured, they are just waves of probability. And once measured, the result of that measurement (again, location in this case) is dependent on the similar attributes of nearby particles (ie. being contextual). Therefore, based on this contextual manifestation, while the potential for two individual particles having the same location according to their wave functions might be non-zero, the chance of them naturally occupying the same space when measured (or observed) is zero.

I am not completely certain what you are saying here. Phrases like "dynamic attributes are contextual" are not clear to me.

However, the remainder of what you say seems like a restatement of a basic property of continuous probablility distributions. The probability of a continuous random variable (CRV) to assume any specific value is 0. So you never speak of the probability of a CRV taking a specific value, but instead always speak of the probability of it taking a value within some range. It is only ranges of values that have meaning in a CRV. So again, for any range of values, however small, there is a non-zero probability of finding both particles there.

2. Matter consists of electrons and quarks (and force carriers - bosons). And these are defined as having no spatial content (point particles - ZERO size). While these particles may have a mathematically calculated location in space-time when observed, there is nothing there to "touch" (using the common definition of that term), even if the location of two particles were identical. Now, there are consequences when two particles are fused (having the same location, yes - but not "touching"). But I do not believe that happening outside a star is a natural occurrence.

What does it mean that a particle is a point particle? Experimentally it means that the highest wavelengths we can generate scatter off of it in a specific fashion. Since that highest wavelength is finite we return to my above comments on ranges of values.

However, there is a more basic point that I was trying to make earlier that really has nothing to do with probabilities. Any fundamental fermion (point particle) is a quantized excitation of a fermionic field, and this field has some spatial extent. When the fermionic fields from two fermions are overlapping then I think it makes sense to say that they are "touching". They are certainly spatially "together" in some sense and interacting with each other, so to me that qualifies as "touching".

 

[daisey]

Hello again, DaleSpam. I am really enjoying this discussion!

I am not completely certain what you are saying here. Phrases like "dynamic attributes are contextual" are not clear to me.

What I mean by that statement is the value of a dynamic attribute is determined by the context by which it is measured. If you measure that one attribute one way, it has one value. If you measure that same attribute a second way, it has a second value. And I understand that not only does the method of measurement have an impact on the outcome, but other particles in the same system also contribute to the outcome of the measurement (see next point regarding this)

It is only ranges of values that have meaning in a CRV. So again, for any range of values, however small, there is a non-zero probability of finding both particles there.

I'm not sure that just because two different particles have a similar range of values for single dynamic attribute (location, in this case), that it is possible they could both ever have the same value for location when observed concurrently. I say that because of the contextual nature of dynamic attributes, such as location (see above).

However, there is a more basic point that I was trying to make earlier that really has nothing to do with probabilities. Any fundamental fermion (point particle) is a quantized excitation of a fermionic field, and this field has some spatial extent. When the fermionic fields from two fermions are overlapping then I think it makes sense to say that they are "touching". They are certainly spatially "together" in some sense and interacting with each other, so to me that qualifies as "touching".

I did not know that all fermions were considered point particles. In any case, I really struggle defining the word "touch" (at least in its most commonly used meaning in our macro world) with fields of energy. According to orthodox ontology, when not measured all particles are waves of energy. And just because two of these waves mathematically overlap in their spatial extent, I do not consider this "touching". Analogy - When two rainbows appear to overlap, do you consider them "touching"? Their mathematical location as computed from you location of observance, and their appearance certainly overlap, but they are not really there in the physical sense.

Respectfully, Daisey

Edit: http://en.wikipedia.org/wiki/Fermion"

"Fermions can be elementary, like the electron, or composite, like the proton." Emphasis added

 

[Dale]

And just because two of these waves mathematically overlap in their spatial extent, I do not consider this "touching".

Why not? Especially considering they interact with each other (unlike rainbows).

"Fermions can be elementary, like the electron, or composite, like the proton." Emphasis added

Yes, that is why I specified fundamental fermions in my post above.

 

[daisey]

DaleSpam,


I can see your point. I guess it really comes down to the definition of the verb "touch". It is my humble opinion that waves of energy (or probability) are not able to "touch". Only "matter" can do this. But that is my opinion, and I can appreciate your arguement.

Daisey

 

[JimmyJones]

This works quite well with the ladies...

I bet I can kiss you without touching you.

 

[ManDay]

Oh, I've a good one: If everyone agrees that by that definition of "touch", we never touch anything...

...do we ever come in touch with ourselves then?

Someone answer that! :D

 

[KnowPhysics]

ok all, when you say we are not touching anything because of the electrons ripple we feel the pressure that we assume as touch. what about magnetized material which attracts each other how will you define that?

 

[Dale]

I can see your point. I guess it really comes down to the definition of the verb "touch".

You are right, the argument appears purely semantic and therefore not very interesting.

It is my humble opinion that waves of energy (or probability) are not able to "touch". Only "matter" can do this.

I guess my point is that from a QM perspective there is not really much difference between waves of energy and "matter". They are all consistently described as quantized excitations of fields in QM. I just think any physical definition of "touch" should be formulated in such a way as to reflect that.

 

[daisey]

...the argument appears purely semantic and therefore not very interesting.

Not sure I would agree there. This has been one of the most interesting arguments I've been involved with in a long time. But then again, as a mother of small children, I get into a lot of pointless arguments.

I guess my point is that from a QM perspective there is not really much difference between waves of energy and "matter". They are all consistently described as quantized excitations of fields in QM. I just think any physical definition of "touch" should be formulated in such a way as to reflect that.

I guess you could say I define "touch" as coming into physical contact with something. And it is my understanding that waves you refer to are fields of energy and of probability. I just can't get my mind around how fields of energy could touch, at least as how I define it.

 

[bondinthesand]

jesus! i haven't been on in a while and i was reading all your posts.. there great they do help but another question is if we don't touch anything then how come when we rude our feet on a carpet then touch the door knob it "shocks" us.. doesn't that require friction?

 

[Dale]

if we don't touch anything then how come ...

I still disagree with the premise. daisey and I have different definitions of "touch". Using hers nothing touches and using mine everything touches. But the argument is purely semantic.

 

[szekely]

I've been reading this thread and i just thought of something. If all atoms repel each other, then what keeps objects together? I know it doesn't happen but i would think that everything would fall apart into a "soup" of atoms. I bet there is a really simple answer to this but then again I'm 13... Thanks for the replies in advance.

 

[Dale]

If all atoms repel each other, then what keeps objects together?

Not all atoms repel each other, particularly not when they are sharing electrons.

 

[xavierkress]

So, if we don't truly "touch" anything, why do different types of foot pads work differently? Like the Gecko vs Elephant, or Lizard vs human foot or hand. Why do Gecko feet have nano-hairs that effectively help it run up vertical and upside down surfaces with minimal effort? It would seem if we don't actually touch anything (except for sensory perception) then having hair like structures vs ribbed skin wouldn't matter unless they give off different charges? Or how would that work?

 

[Dale]

Again, I think that the "no touching" premise is wrong. We do touch things, so it should be no surprise that different foot pads make a difference.