Send any replies to this to me by private mail, please. Let's take this
off the list.

On Mon, 3 Nov 1997 22:29:40 -0500 (EST), Adam Conover
<dconover@garnet.acns.fsu.edu> wrote:

Actually, to the best of -my- knowledge (it's not like I've taken any
college physics yet or anything), HUP (or is that the HUT?)

We're not sure. :p

states that
you cannot judge the mass of an -electron- without changing its position,
and vice versa. This is -expanded-, however, to put doubt into the
existence of measurements in the world at all. >;)

Anyone care to correct me on this?

Yup.

Heisenberg's uncertainty principle says that it is impossible to measure
both the position and momentum of any particle (an electron is just one
example) with arbitrary precision. More precisely, that the product of
the uncertainties in the two measurements has to be at least a certain
amount.

There is a similar uncertainty relation for time and energy.

Does it "put doubt into the existence of measurements in the world at
all"? Not exactly. The quantum theory (not the uncertainty principle
specifically) changes the way in which we talk about things that can be
measured. In classical theory we talk about position, momentum, etc. as
definite quantities. Quantum theory says that all these things do not
have definite values, only probability distributions, until they are
measured.

It's like the old question about whether a tree falling makes a sound if
no one is there to hear it. Classical physics would say "yes". Quantum
physics would say you can't ask such a question, all you can talk about
are probabilities for what you might hear if you *did* listen. That
doesn't mean that measurements don't exist; it means that measurements
have to be *done* before the quantities they represent have definite
values.

Again, if anyone has questions on this, please E-mail me privately.
Let's take it off the list, OK?

 /\
/()\   Fnord.
/    \
------ 

Does Mike Loader know you borrowed his sig? ;-)



Gary Kleppe, Ph. D. in physics University of Florida (Gainesville) 1991
http://www.execpc.com/~kleppe/comics