We never really touch anything?

  • #1
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?
 
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  • #2
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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.
 
  • #3
DrChinese
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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.
 
  • #4
HallsofIvy
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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".
 
  • #5
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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
 
  • #6
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
 
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  • #7
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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.
 
  • #8
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bondinthesand said:
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.
 
  • #9
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QMysterious said:
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:smile:)
 
  • #10
negitron
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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.
 
  • #11
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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?
 
  • #12
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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.
 
  • #13
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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
 
  • #14
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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.
 
  • #15
then if we are only feeling the electromagnetic pulses, than how do we manage to pick something up?/
 
  • #16
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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.
 
  • #17
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 with out hands, there's not actually anything touching. Keep in mind that the seperation 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).
 
  • #18
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...You are familiar with a situation where the atomic nuclei of two atoms actually do touch... a nuclear bomb...

Touch, or fuse?
 
  • #19
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).
 
  • #20
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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?
 
  • #21
D H
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Keep in mind that the seperation 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.
 
  • #22
Dale
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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"?
 
  • #23
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.
 
  • #24
D H
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That wasn't my question.
 
  • #25
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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
 

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