rogerb@tekmdp.UUCP (Roger C. Bonzer) (07/12/83)
I probably got this question from some book or other, but I don't
recall that I ever got a satisfactory answer for it. Anyway...
Protons and electrons, having opposite electrical charges, are
supposed to attract one another and repel themselves [?]. If this is
so, why is it that all the protons of an atom are all bunched up in the
nucleus? Why is it that the electrons and protons don't just get their
act together and stick tight to each other, instead of having each group
staying far away from the particles it is attracted to and staying with
the group that it is repelled by? (Since if all the e's and p's in the
universe were to do this life as we know it would cease quite abruptly,
I am not disappointed that this phenomenon does not occur, merely
curious why it doesn't)
Obviously not a physician,
Roger Bonzercmsj@ihuxm.UUCP (07/13/83)
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
..!ihnp4!ihuxm!cmsjbernie@watarts.UUCP (07/14/83)
The reason protons stay all bunched up together in the nucleus is that they are held together by a different (non-electromagnetic) force, which is more powerful over short distances than em, but that drops off more quickly than 1/r^2; the whole idea behind fusion is to bang protons together so hard and fast that they come close together before the EM forces push them apart. Once they're really close, the other force takes over and they stay that way (in the process giving up a *lot* of energy). --Bernie Roehl ...decvax!watmath!watarts!bernie
rh@mit-eddie.UUCP (Randy Haskins) (07/16/83)
When I was taking quantum (and getting a D), I thought of a neat application of the uncertainty principle: The protons wants to pull the electrons into the nucleus. In order to do this, however, they must know where they and what they're doing. Once the protons get a fix on it's position, the electron is moving differently. The proton can't win... -- Randwulf (Randy Haskins) genrad!mit-eddie!rh or... rh@mit-ee (via mit-mc)
gwyn@brl-bmd@sri-unix.UUCP (07/18/83)
From: Doug Gwyn (VLD/VMB) <gwyn@brl-bmd> The fact that an atom does not collapse is explained by quantum physics. The coherence of the "parts" of a nucleus is supposed to be due to some agency other than Maxwell-style electromagnetism, usually called the "strong force". In other words, there is more to physics than just electromagnetism.