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From: cmsj@ihuxm.UUCP
Newsgroups: net.physics
Subject: Re: opposites attract
Message-ID: <360@ihuxm.UUCP>
Date: Wed, 13-Jul-83 09:46:16 EDT
Article-I.D.: ihuxm.360
Posted: Wed Jul 13 09:46:16 1983
Date-Received: Thu, 14-Jul-83 21:31:18 EDT
References: <2075@tekmdp.UUCP>
Organization: BTL Naperville, Il.
Lines: 32

There are two parts to Roger's question and I'll try to answer
them:

First, why don't the electrons fall into the nucleus?  One of
the simplest ways of "explaining" this is via the Heisenberg
Uncertainty Principle (which comes out of Quantum Mechanics).
The principle states:

                delta_p * delta_x >= h/2*pi

where delta_p is the uncertainty in a particle's momentum
and delta_x is the uncertainty in its' position.  h is Planck's
constant.  Basically this inequality states that it is not
possible to know both the position and momentum of any particle
simultaneously to arbitrary precision.

Appllying this relation to an electron confined to nuclear (not atomic)
dimensions ( nuclear radii are roughly proportional to A ** (1/3) where
A is the atomic weight; the units of the radii are in Fermi (1 F = 10 **
(-15) meters)) results in an electron energy which is WAY too high for
the electron to remain where it is.  Hence no electrons in the nucleus.

The second question, how do protons stay together in the nucleus?
Well, it is true that protons repel each other via the electromagnetic
force.  However, at close enough range, another force (suitably named
the "strong" interaction) takes over and this force attracts the protons (and
neutrons) to each other.

Hope I remembered enough of my Physics...
                                     Chris Jachcinski
                                     BTL, Naperville, IL
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