Is it true that you are never actually touching something?

[K^2]

It always occurs. Whatever we feel is ultimately just the electron field.

E-field can significantly extend past the electron density, though. Yes, I know the actual interactions are going to be much shorter range due to charges almost completely balancing, Van der Waals, etc., but the above seems like an over generalization.

 

[A. Neumaier]

E-field can significantly extend past the electron density, though. Yes, I know the actual interactions are going to be much shorter range due to charges almost completely balancing, Van der Waals, etc., but the above seems like an over generalization.

We have no sensors for the e/m field (except for vision), thus its longer range does not count.
All touching is based on contact, which is governed by the electron field.

 

[K^2]

Our touch receptors are sensitive enough to pick up minute movements caused by an E-field from charged object. It's much better picked up by hairs, but if you move your hand past a charged object, you should still be able to feel it.

But more importantly, the actual interaction of "touch" is an electrostatic interaction. You are still responding to an E field. Not to electron densities. Not directly.

 

[DiracPool]

But more importantly, the actual interaction of "touch" is an electrostatic interaction.

All this talk about electrostatic interactions involved in our sense perception I don't think advances an understanding of the OP's question. Why not just make the statement,"it all has to do with atoms." ALL sensory perception relates to electrostatic interactions. I don't think all of this discussion about electric fields, van der waal forces, etc. is advancing any insight into the psychophysiology of touch.

Touch receptors are mechanoreceptors in the deeper layers of the integument. They produce action potentials that travel toward the brain when they are "bent" or mechanically altered by a pressure on the superficial layers of skin. There can be a pressure there that is subliminal to conscious perception even though the mechanoreceptors are issuing pulses. Similarly, there can be pressure or contact on the skin that is insufficient to generate action potentials because the pressure is not great enough to deform the receptor in such a manner as to trigger action potentials.

That triggering is accomplished via the bending of the receptor allowing the transfer of Na+ and K+ ions to traverse the neuronal membrane triggering the potential. Yes, it is electrostratic, but then again, so is everything in human physiology.

 

[DiracPool]

I guess my point is that it seems to me the OP's question has already been answered--if you feel like you're touching something, then yes you are touching it. That could be a baseball you grip in your hand, a raindrop on your forearm, a laser beam pointed at your forehead, or a resistive magnetic force on a metal plate in your head when you're taking an MRI.

It seems to me that this discussion of the physics of overlapping electron clouds, etc., is now off-topic for this discussion. I just don't see the relevance. Maybe that conversation should be taken up in a new thread.

 

[Carlov]

No, it is entirely relevant. We're not discussing the sensation of touch per se (that would be more off-topic, if anything), we're discussing the physical definition - i.e. if we clasp two sponges together, are those sponges touching? Is there merely empty space between the atoms of those sponges? OP's question was probably raised in response to the popular notion brought up by certain physicists like Michio Kaku that say we're actually hovering over our chairs when we sit on them. Fortunately, the question in that context has been answered in this thread.

 

[DiracPool]

i.e. if we clasp two sponges together, are those sponges touching? Is there merely empty space between the atoms of those sponges?

Doesn't this get down to an epistemological question, though, at its foundation? I mean, if we continue to look deeper and deeper into the problem, don't we just come up with superpositions of states and wave functions? If these wave functions, as many do, extend out to infinity, albeit at negligible values for large radius's, how can we say where "contact" ends and inter-particle space begins? I think analysis at this level is qualitatively distinct from the psychophysics of sentient experience that seemed to be the OP's central concern.

 

[A. Neumaier]

All this talk about electrostatic interactions involved in our sense perception I don't think advances an understanding of the OP's question. Why not just make the statement,"it all has to do with atoms." ALL sensory perception relates to electrostatic interactions. I don't think all of this discussion about electric fields, van der waal forces, etc. is advancing any insight into the psychophysiology of touch.

Touch receptors are mechanoreceptors in the deeper layers of the integument.

It is this level that is addressed in question and answer. The question was not about how the receptors and the transmission work, but what causes the receptors to signal.

The signal is caused by a mechanical force on the skin, not by an electromagnetic one, since our skin is comnpletely insensitive to small electromagnetic fields unless these casue some mechanical or thermal effect first.

And the mechanical effect is a force caused by touching. Touching is the contact of electron clouds to an extent significant enough to change the macroscopic force field.