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Re: [Phys-l] Fields and touch?



I did not look at the footnote when I wrote the previous message. The
footnote has some big problems. It claims that normally electrons do not
"touch" protons, but the previous part of the web page does not say this.
Indeed if you realize that electrons and protons attract, you would say that
they should bond with each other and touch.

In the 1S wave state the electron has the maximimum probability at the
center of the atom, so one could say the proton and electron "touch", but
that is mixing QM with classical mechanics so touch does not exist as a
concept sub-microscopically.

So the footnote brings up even more complications and does not in any way
answer them. One needs to appeal to nuclear forces and to QM to understand
the process being presented. I really do not know of any simple way to
discuss why electrons do not combine spontaneously with protons to form
neutrons without going into some QM. And of course free neutrons decay
spontaneously, but not neutrons bonded into stable nuclei.

Making a simple explanation which has some accuracy is very difficult, and
you MUST avoid certain types of terminology such as layer of force. It is
also wise to leave out problematic concepts, or at least be more complete.
So the discussion of electron-proton interactions should at least say that
electrons normally bond to protons by the electric interactions and they
orbit in an electron cloud. But even when electrons bond to protons to form
neutrons, the concept of touch does not exist. And there is a third
particle involved in this nuclear interaction, a neutrino.

The big difficulty with this whole web page is that it never brings out the
idea that concepts which may exist in a macroscopic model do not exist in a
microscopic model. And sometimes the various models we use to understand
the concepts are actually contradictory.

Students are brought up to believe that science is absolute and that we have
the "TRUTH". But this is not so. We make up models to be able to explain
phenomena and when we see these models predict events correctly we often
call them true. But scientific truth is not absolute and is subject to
revision. Look at the arguing that happens on this list. Unfortunately I
also see this webpage as promoting "TRUTH".

Students below the age of 10 generally have difficulty with competing ideas
and tend to judge things according to just one factor. But at 10+ they can
develop formal operational reasoning which uses competing factors in making
judgments. The topic on this web page is an example of trying to force
students to think only with one idea. The idea that touch is not relevant
sub-microscopically but is a good concept macroscopically needs to be
brought out.

And actually when people kiss their lips actually bond rather than being
separated by a layer of force. The Vaseline model of force is very
misconcepted.

John M. Clement
Houston, TX

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of sridhar chitta
Sent: Tuesday, February 23, 2010 6:15 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Fields and touch?

Please visit the following webpage
http://www.worsleyschool.net/science/files/touch/touch.html
I hope this answers your question.

- Sridhar chitta
On Tue, Feb 23, 2010 at 7:14 AM, Tony <physixdude@comcast.net> wrote:

When my hand rests on the table, do I touch the table? ...Or do the
electric
fields between my hand and table leave a gap between the to objects?
Maybe
it comes down to how "touch" is defined?

-Tony

--
Tony Wayne
Albemarle High School
Physics Teacher
Science Department Chair
twayne@k12albemarle.org
http://www.mrwaynesclass.com
-
Those who can do.
Those who understand, teach.



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