Do We Ever Truly Touch Anything?

[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.

 

[Brad Hickman]

If we never touch anything why do we have fingerprints on things?

 

[Dale]

This thread is from 2009, I think it is time to close it.