"greysky" wrote in message
t...

Begin Part One

In chapter one, book three, of "The Feynman Lectures On Physics",
Professor
Richard Feynman had this to say about the double slit experiment:

======================================

I must object, strenuously - to the following.

"We choose to examine a phenomenon which is impossible, absolutely
impossible, to explain in any classical way, and which has in it the heart
of quantum mechanics. In reality, it contains the only mystery. We
cannot
make the mystery go away by explaining how it works. We will just tell you
how it works. In telling you how it works we will have told you about the
basic peculiarities of all quantum mechanics."


======================================


This single experiment forms the foundation of quantum mechanics. I
contend
it is also the most misunderstood. Clearly, quantum mechanics as a whole
is
a very successful description of how physical reality operates. Yet, how
much more successful, more powerful, would it be if we understood it
better?
The thing that limits us from a more complete understanding of the theory
is
not a limitation in our ability to think up complex experiments to test
our
hypothesis upon, but in our ability to transform what the experiments are
telling us into concrete visualizations our human brains can grasp.

This is precisely what Professor Feynman is talking about when he starts
off
his book on quantum mechanics with the double slit experiment. See, he can
and does describe the physical setup of his experiment, and also goes into
much detail explaining the results, and how they differ from what would be
expected if, say, you replaced the electrons with bullets shot from a gun.

It is a common practice in physics to solve a complex problem by breaking
it
up into many smaller pieces and then solving each piece separately. It
would seem that in order to apply this process to the double slit
experiment, it is necessary to first begin with but a single slit. This
is
about as simple as you can get - even the good professor doesn't devote
too
much time discussing the travails of a particle and its interaction with
just one slit. This is unfortunate. It turns out there is much to be
learned
from this most humble and simplest of all experiments in quantum action.

The single slit experiment turns out to be a tiger masquerading as a
pussycat. Properly understanding what happens to the electron in this
experiment will go a long way toward clearing up any confusion about its
more complex brethren, experiments where N, the number of slits, is some
number other than one.

At first glance, it seems only too simple. You have a setup where you have
an electron emitter which is able to shoot a single electron at a time
through a slit which can be arbitrarily open or closed, and detectors of
some type able to register an electron hit (or miss) on the far side of
the
slit (the target). There are two solutions possible:

1) Slit open. The electron passes through the slit and a detection event
is
registered on the detector at the target.
or,
2) Slit closed. The electron is stopped by the slit material and no
detection event is registered at the target.

An important thing to keep in mind for both these solutions is that the
total probability of action along the path for the electron is 100%. In
other words, if the electron is stopped at the slit, then it didn't make
it
to the target. A percentage below 100 indicates electrons missing and a
percentage above 100 indicates you have an electron both stopped by the
slit
and detected at the target. This leads to a simple statement about
probability: It is a conserved quantity.

If you put the electron emitter on a movable track such that it moves
parallel to the slit material, you could control how successful the
electron will be in hitting the detector at the target by moving the
electron emitter along the track.. At some point directly in line with
the
slit material, the probability that an electron will pass through the open
slit to be detected at the target is 100%, while at some other point along
the track the probability of passing through the slit decreases to 0%.
Please note how probability is always conserved in these examples:

For an arbitrary position where the electron has, say, a 40% chance of
passing through the slit, there is a corresponding 60% chance that it will
not. If the total probability, P(t), is the sum of the path probabilities
where P(s) = the probability where the electron is stopped at the slit
and
P(d) = the probability where the electron is detected at the target.

P (t) = P (s) + P (d) = 100


======================================

"probability is conserved"

It may seem inane, but knowing that probability is conserved in all cases
and under all conditions will become an important fact when thinking about
the double slit experiment later on.

======================================

End Part One

At this point I invite the curious to browse my web site, where I have
much
more to say concerning the foundations of QM, and where we went wrong in
interpreting what the universe has to tell us.


Greysky

www.allocations.cc
Learn how to build a FTL radio.