[net.physics] Millikan oil drops

rjs (02/24/83)

I just overheard a very brief conversation in which it was claimed
that Millikan found a few oil drops which contained integer multiples of
1/3 the currently accepted charge on an electron, but which did not contain
an integer multiple of the electron charge.  It was also claimed that
he suppressed these findings as experimental errors of some sort.
Has anyone else heard of this?  Has anyone heard of recent discoveries
of free particles with 1/3 the electron charge?  Would/Do these findings
have any significant effect on particle theories or are they already
predicted?

	Robert Snyder
	floyd!rjs

leichter (02/25/83)

Millikan found some oil drops that didn't give reasonable values, so he
threw them out.  He was pretty careful about justifying which ones he threw
out, I think.  What you may have heard being discussed was more recent attempts
to look for 1/3-charge particles, using a much more sensitive version of the
Millikan experiment.  (Instead of oil drops, the exprimenters use tiny niobium
spheres, cooled to super-conductivity and floated in a magnetic field.  They
have much tighter control over what's going on and can use a single ball for
hours (days?) on end, adding and removing charge, or letting cosmic rays do
their stuff.)  I seem to recall that someone looked back at Millikan's original
data and found some cases that were consistent with a 1/3 charge; however, it's
only if you are looking for this pattern that you'd notice these against the
other "noisy" data.

The current trend in particle physics is to believe that quarks really are
bound permanently inside leptons and baryons.  There is now some good reason
to believe the theories that exist require this.  If anyone actually found a
particle of charge 1/3, either quark theory would need rethinking, or it would
be of a whole new class, or both.
							-- Jerry
						decvax!yale-comix!leichter
PS - just to make it clear:  What I said about Millikan's 1/3 charge (and other
"inconsistent" results) is based on vague memory; if anyone can find a
reference & prove me wrong, I won't be too shocked.