Date: Mon, 10 Mar 2003 17:51:28 +0000
Subject: Re: Shooting at Slits (rather than Iraqis.)


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on 8/3/03 3:28 pm, Anthony Crifasi at crifasi-AT-hotmail.com wrote speaking of
the famous two-slit experiment:

> Now, let's repeat the above with only ONE electron at a time, instead of a
> stream (electron guns can be slowed down to that extent). Open only one slit
> for them to go through. What's the impact pattern you expect after many
> single shots? The first pattern - one dense spot directly behind the slit,
> gradually spreading out the farther away from that spot you get. That's what
> you get. Everything's normal, right? Now, open TWO slits and allow only one
> electron at a time through, and the mystery begins. What's the pattern you
> expect? After all, there is only one electron emitted at a time, so there
> are not electrons going through both holes emerging and interfering with
> each other before impact, so you wouldn't expect an interference pattern at
> impact. So you would expect the first pattern behind each slit - one dense
> spot behind each slit, gradually spreading out the farther away from each
> spot you get. BUT THAT'S NOT WHAT YOU GET. You get the wave interference
> pattern, EVEN THOUGH THERE IS NOT MORE THAN ONE ELECTRON EMITTED AT ANY
> TIME, and therefore no "interference," since that would require one electron
> interfering with another one.
> 
> That's why the two-slit impact pattern cannot be explained through any
> normal notion of interference, since interference is by definition
> interference on one thing by another, so you would need at least two
> electrons, or at least you would need something affecting the electron gun.
> But there are not two electrons at any time (since only one is emitted at a
> time), nor is anything affect the electron gun because ALL YOU HAVE TO DO IS
> OPEN TWO HOLES IN THE BARRIOR, without even touching the gun. That is why it
> is mysterious and cannot be explained by previous physical principles, and
> is indeed quite mysterious.

The electron (or any -on) is neither a wave, nor a particle, nor a wavicle,
nor a wave-packet, nor... it will none of these pictures. As Bachelard
suggested, the apparatuses of modern physics are best represented as
'materialised theories'; they confine the natural within certain
problematics. The electron is (thatness and whatness) what shows itself in
experiments and observations as some being corresponding within the limits
of the apparatuses employed to display such; it is as it were, set up to
reflect the set-up it is made to appear in. If an experimental/observational
set-up is set up to measure/observe/trace an 'electron' in terms of
'particle' properties, then it shall be seen to be particular and have
momenta and positions, etc. If the apparatus is set up to display wave
properties then frequencies and interference fringes will be observed to be
properties of the 'electron'. What kills me in the two-slit experiment is
the notion that one knows that 'the' 'electron' was 'moving' towards the two
slits, 'one at a time': for this to be established, the 'electron' must have
been stopped or deflected in its tracks by another part of the universe, and
whilst it is entirely possible for the 'electron' to have been identified as
something particular (i.e., having a distinct identity and position in space
and travelling at a specific velocity, etc) at the time of the collision,
after such an 'observation' one can know nothing of the 'electron' for
certain. When, later, another observation is made vis-a-vis the two slits,
the 'electron' is made over as wavelike, because at that point in the career
of the 'electron' it was confronted with another part of the universe
designed to display wavelike properties (i.e., interference fringes, etc).
What is truly mysterious and mystifying in this saga is that we assume we
know the 'electron' post-quantum-theory, when quantum theory (at least in
the hands of Heisenberg) has surely questioned the very being of the
'electron' -- and not the results of the two-slit experiment.

Regards

michaelP 

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HTML VERSION:

> Now, let's repeat the above with only ONE electron at a time, instead of a
> stream (electron guns can be slowed down to that extent). Open only one slit
> for them to go through. What's the impact pattern you expect after many
> single shots? The first pattern - one dense spot directly behind the slit,
> gradually spreading out the farther away from that spot you get. That's what
> you get. Everything's normal, right? Now, open TWO slits and allow only one
> electron at a time through, and the mystery begins. What's the pattern you
> expect? After all, there is only one electron emitted at a time, so there
> are not electrons going through both holes emerging and interfering with
> each other before impact, so you wouldn't expect an interference pattern at
> impact. So you would expect the first pattern behind each slit - one dense
> spot behind each slit, gradually spreading out the farther away from each
> spot you get. BUT THAT'S NOT WHAT YOU GET. You get the wave interference
> pattern, EVEN THOUGH THERE IS NOT MORE THAN ONE ELECTRON EMITTED AT ANY
> TIME, and therefore no "interference," since that would require one electron
> interfering with another one.
>
> That's why the two-slit impact pattern cannot be explained through any
> normal notion of interference, since interference is by definition
> interference on one thing by another, so you would need at least two
> electrons, or at least you would need something affecting the electron gun.
> But there are not two electrons at any time (since only one is emitted at a
> time), nor is anything affect the electron gun because ALL YOU HAVE TO DO IS
> OPEN TWO HOLES IN THE BARRIOR, without even touching the gun. That is why it
> is mysterious and cannot be explained by previous physical principles, and
> is indeed quite mysterious.