Re: Is a fact something that has been proven?


David Ewan Kahana wrote:
ave1 wrote:
Steven J. wrote:
ave1 wrote:
Oxidized wrote:
ave1 wrote:
Oxidized wrote:

ave1 wrote:
So it's your contention that the electrons go through the slits as
particles instead of a wave because an observer saps energy from the
electrons? How does observing sap energy?

Here's an easy example. A solar observatory captures light from
the sun. The shadow of the observatory saps energy which would
otherwise heat the ground "behind" the observatory, now in shadow.


So exactly what does this have to do with someone knowing something
about the path the electrons are taking?

You don't know about the path of the electron until you sap
some energy from it.

Why is it that energy *doesn't* get sapped when the person who would
otherwise gain the knowledge is purposely prevented from gaining it,
but the detectors are still "on"?

What is it about these photons or waves of light that can distinguish
whether or not a nearby person's thought is/willbe of the electron
pathway or something other than that (maybe last night's dinner)?

Unless you have a cite from the _Journal of Clairvoyance in Applied
Particle Physics_ to prove me wrong, I'm going to maintain that you
can't determine anything about the path of an electron merely by
thinking about it.

Well, then you are denying the facts revealed about quantum theory via
experimentation over the past 70 years.


No, he's got the facts exactly right.

It's in the knowing that the light's form is determined. He's denying
that, so he's wrong.

You have to use an actual physical instrument to
make an actual physical measurement -- which interferes with the
properties of the phenomenon being measured.

If you actually read the second chapter of the website in my sig, you'd
know that they already ruled out interference of the measuring
instruments as a factor in the results.


This claim is not supported by the website that you have in
your signature. `Interference' of the measuring instruments
is always the decisive factor.

I will present a good bit of evidence below which demonstrates that you
are wrong.

The problem is that the discussion at the website you are
referencing has been written in a deliberately deceptive
manner,

Sounds like a bald assertion to me.

in order to support the incorrect, and insupportable
description and interpretation of the double slit experiment
that is given there, and which you are trying to propagate
here: that the behaviour of electrons depends upon some
thinking observers *knowledge* of the electron's paths
through the experimental apparatus rather than just
upon the interactions of the electrons with the experimental
apparatus. Indeed it is precisely those interactions that
provide the experimenters with their knowledge.

.. . . but the propagation of light as a wave occurs when it goes
through the slits (with the detectors turned on) when human knowledge
is lacking about of the path of the electrons, and the propagation of
light as particles occurs when it goes through the slits (with the
detectors on) when a human gains the knowledge.

So how can you say that?

It's not that the detectors being on is the deciding factor. It's the
knowledge that's the deciding factor. It's going to take persuasive
evidence to convince me otherwise.

The relevant part of the description begins here:

http://www.bottomlayer.com/bottom/reality/chap2.html#examine

(skip down to the question: Why?)

We would like to think that the particle detectors at the
slits are affecting the passage of the electron -- perhaps
deflecting it, or modifying it's path, or in some other way
influencing the experiment. We could accept such an
explanation.

In fact we *do* accept such an explanation. It is, and it
remains, the standard interpretation of the double slit
experiment with uncorrelated single electrons.

Persuade me then.

So it should be emphasized that the claim that Rhodes makes
next, as well as being startling, is false:

But that does not seem to be the case. A series of
experiments have been conducted to test just such a
hypothesis, and the results are uniformly negative. I will
quickly run through some of the more ingenious attempts to
isolate and remove any possible influence stemming from the
detectors located at the slits.[2]

Now the first thing to do, when reading a claim that some
experiment or experiments have been done that prove
something or other that someone wants to tell you is the
God's own truth, especially something with amazing
implications, is to chase down and read the descriptions of
the actual experiments by the people who did them in the
first place.

The author of the website kindly provided links to
descriptions of the experiments which supposedly support the
rest of his discussion, in his endnote [2], so that's where
one should go immediately. The first reference to the
literature given there is:

http://xxx.lanl.gov/pdf/quant-ph/9903047

Which was published in Phys. Rev. Lett. 84, 000001 (2000):

http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=PRLTAO&CURRENT=NO&ONLINE=YES&smode=strresults&sort=rel&maxdisp=25&threshold=0&allprl=1&pjournals=PLRAAN%2CPRBMDO%2CPRVCAN%2CPRVDAQ%2CPLEEE8%2CPRLTAO%2CRMPHAT%2CPRABFM%2CPHRVAI%2CPHRVAO%2CPRSTCR&pjournals=PRLTAO&possible1=quantum+eraser&possible1zone=multi&OUTLOG=NO&viewabs=PRLTAO&key=DISPLAY&docID=10&page=1&chapter=0

At either of these links one can find a paper entitled: `A
Delayed Choice Quantum Eraser.'

The abstract of the paper reads:

This paper reports a "delayed choice quantum eraser" experiment
proposed by Scully and Druehl in 1982. The experimental results
demonstrated the possibility of simultaneously observing both
particle-like and wave-like behaviour of a quantum via quantum
entanglement. The which path or both-path information of a quantum
can be erased or marked by its entangled twin even after the
registration of a quantum.

Well, that's a bit odd -- it seems that the paper is all about a
`quantum eraser' and `quantum entanglement,' and the
abstract is talking about a quantum and its quantum entangled
`twin'. There's nothing there at all about a double slit experiment
involving single electrons!

Until you demonstrate that the content of the entire article cannot
relate to double slit experiments, it's not "a bit odd".

In fact here's a statement from
http://www.benbest.com/science/quantum.html which indicates that the
experiment has a close correlation to the double slit experiment: "An
experiment involving circular diffraction, and the famous two-slit
experiment, illustrate the most perplexing behavior of subatomic
particles/waves."

And indeed, the description given of the experiment later on
in the paper is as follows:

Two atoms lableled by A and B are excited by a laser
pulse. A *PAIR* OF ENTANGLED PHOTONS, photon 1 and photon
2, is then emitted from either atom A or atom B by atomic
cascade decay. Photon 1, propagating to the right, is
registered by a photon counting detector D_0 which can be
scanned by a step motor along its x-axis for the
observation of interference fringes. Photon 2, propagating
to the left, is injected into a beamsplitter. If the pair
is generated in atom A, photon 2 will follow the A path
meeting BSA with 50% chance of being reflected or
transmitted. If the pair is generated in atom B, photon 2
will follow the B path meeting BSB with 50% chance of being
reflected or transmitted. Under the 50% chance of being
transmitted by either ...

[my emphasis]

Lo and behold!

The reference describes an experiment dealing with quantum
entangled photon *PAIRS*, not a double slit experiment
involving *SINGLE* uncorrelated electrons. The paper does
not contain any description or any interpretation of a double
slit experiment with uncorrelated electrons, much less of
any attempt to `remove any possible influence stemming
from the detectors located at the slits, in any such experiment.

Now an experiment dealing with uncorrelated electrons is an
entirely different matter from an experiment dealing with
correlated photon pairs.

A two-body wavefunction is NOT the same thing as a one-body
wavefunction.

It may not be the same thing, but there certainly can be close
correlations made.

The second reference given in endnote [2] is:

http://arxiv.org/pdf/quant-ph/0512207

This preprint, similarly, describes an experiment using
quantum entangled photon pairs, not a double slit experiment
with uncorrelated single electrons.

So when the author writes, in his endnote [2], that he
continues to use electrons as the quantum units under
discussion purely _for pedagogical purposes_, I suggest
that he is being rather disingenuous:

For pedagogical purposes, I have continued to use electrons
as the quantum units under discussion. With recent
successes in achieving entanglement among atoms, it seems
likely that these experiments may be repeated in the near
future with various quantum units of matter (if this has
not already been achieved). QM being what it is, there is
no question but that the results will be consistent with
those obtained with photons.

Now despite all of these rosy predictions above by Ross
Rhodes about what might be achieved in the future, his
discussion of the single electron double slit experiment is
not supported in any way by actual double slit experiments,
or by the experiments that he refers to, which deal with
quantum entangled photon pairs, where indeed, it is once
again the interference between the two photon wavefunction
and the experimental apparatus that matters, and NOT the
knowledge of the experimenters.

I don't see this as disingenuous at all. He sees as strong correlation
and has confidence in that correlation.

Let me continue to look at Rhodes' discussion, just for fun,
to see precisely where he goes wrong. Immediately following
the paragraph that I initially quoted, there occurs the
following discussion:

1.TURN OFF THE ELECTRON DETECTORS AT THE SLITS. Suppose we
take our modified double slit set up -- with electron
detectors at the slits -- and leave everything
intact. But, we will conduct the experiment with the
electron detectors at the slits turned off, so that we
will not actually detect any electrons at the slits.

_The result upon analysis_: an interference pattern at the
back wall. So it seems that mere passage through the
electron detectors at the slits does not affect the
electron, so long as those electron detectors are not
functioning.

So far this is correct. This is indeed what happens in an
actual double slit experiment performed with uncorrelated
electrons. With the electron detectors turned off, an
interference pattern is observed.

Then Rhodes continues:

2.LEAVE THE ELECTRON DETECTORS ON, BUT DON'T GATHER THE
INFORMATION. Suppose we take our modified double slit
set up -- with electron detectors at the slits -- and
still leave everything intact. And we will keep the
electron detectors at the slits turned on, so that they
will be doing whatever they do to detect electrons at
the slits. But, we will not actually look at the count
of electrons at the slits, nor will we record the count
at the slits in any way, so that we will not be able to
obtain any results from these fully-functioning electron
detectors.

_The result upon analysis_: an interference pattern at the
back wall. So it seems that the electron detectors
located at the slits do not themselves affect the
electron, even when the equipment is fully functioning
and detecting (in a mechanical sense) the electrons, so
long as we don't obtain the results of these
measurements.

But this is *completely* wrong.

This is *not* what happens in an actual double slit
experiment done with single electrons. In fact, in such an
experiment, it doesn't matter *at all* whether we actually
record the counts at the slits or don't record the counts at
the slits, or whether we obtain any results at all from the
detectors at the slits.

If you are correct, then why does the Keith Mayes at
http://www.thekeyboard.org.uk/Quantum%20mechanics.htm (I found this
link here:http://en.wikipedia.org/wiki/Double-slit_experiment ) state
this:

"If we repeat the experiment, this time with only one hole open, the
individual photons behave themselves and all cluster round a point on
the detector screen behind the open hole, just as you would expect.
However, as soon as the second hole is opened they again immediately
start to form an interference pattern. An individual photon passing
through one of the holes is not only aware of the other hole, but also
aware of whether or not it is open!

We could try peeking, to see which hole the photon goes through, and to
see if it goes through both holes at once, or if half a photon goes
through each hole. When the experiment is carried out, and detectors
are placed at the holes to record the passage of electrons through each
of the holes, the result is even more bizarre. Imagine an arrangement
that records which hole a photon goes through but lets it pass on its
way to the detector screen. Now the photons behave like normal, self
respecting everyday particles. We always see a photon at one hole or
the other, never both at once, and now the pattern that builds up on
the detector screen is exactly equivalent to the pattern for bullets,
with no trace of interference. As if that was not bad enough, it gets
even worse! We do not need place detectors at both holes, we can get
the same result by watching just one hole. If a photon passes through a
hole that does not have a detector, it not only knows if the other hole
is open or not, it knows if the other hole is being observed! If there
is no detector at the other hole as well as the one it is passing
through, it will produce an interference pattern, otherwise it will act
as a particle. When we are watching the holes we can't catch out the
photon going through both at once, it will only go through one. When we
are not watching it will go through both at the same time! There is no
clearer example of the interaction of the observer with the experiment.
When we try to look at the spread-out photon wave, it collapses into a
definite particle, but when we are not looking it keeps its options
open."

Another good read is here:
http://www.lifesci.sussex.ac.uk/home/John_Gribbin/quantum.htm

Once you've read this, please reflect on why Ross Rhodes
(bottomlayer.com) has been persuaded to say what he has said about the
detectors not being central to quantum theories strange "measurement
effect". It's not the detectors that sway the outcome, but the
intelligent observers themselves having knowledge of that which
happened quantumly. Anyway, on to the write-up

"The archetypal example of the quantum mysteries is the "experiment
with two holes", where the measured position of a single electron that
passes through two holes in a screen can only be explained in terms of
the wave function travelling through both holes at once and interfering
with itself. But perhaps you've heard that one already, so here is a
rather sideways look at the whole business of collapsing wave
functions, a thought experiment which says that the lack of an
observation can make the wave function of a system collapse. This
wonderful example of the strangeness of the quantum world dates back to
the early 1950s, and is known as "Renninger's negative- result
experiment", after the German physicist Mauritius Renninger who first
thought of it. It is one of the easiest examples of quantum strangeness
to understand -- but not to explain.

Imagine that we have a source which will emit a single quantum particle
in a random direction (ordinary radioactive nuclei do exactly this, so
there is nothing special about the source). This source is in the
middle of a large hollow sphere, and the inner surface of the sphere is
lined with material that will give a flash at the point where the
particle hits it. The accepted quantum description of what happens when
the source emits a particle is that a quantum probability wave spreads
out evenly in all directions around the source, since there is an equal
probability for the particle being emitted in any direction. When the
probability wave reaches the inner surface of the spherical shell,
there is just one flash of light as the wave collapses to a single
point. The particle is only "real" when it is being observed -- when it
makes the flash of light -- not while it is travelling from the source
to the sphere.

So far, simple enough. But now imagine that half way between the source
and the sphere there is a hemispherical shield, which blocks off
exactly half of the outer sphere from the field of view of the source.
Like the outer sphere, this inner hemispherical shell is lined with
scintillating material that will flash when it is struck by a particle
from the source. Now what happens when the source emits a particle? We
are not interested in exactly where on the outer or inner spheres the
particle makes a flash of light, only in which of the two spheres it
strikes. Either the particle strikes the inner sphere and makes it
flash, or it strikes the outer sphere and makes it flash. There is an
equal probability of either outcome of the experiment. Now, suppose
that the source is once again triggered into emitting a particle. Once
again, standard quantum theory describes this as an expanding spherical
shell of probability, moving out evenly in all directions. We wait for
a time longer than the time needed for it to reach the inner
hemisphere, but too short for it to have reached the outer sphere, and
see no flash on the inner sphere. So we know that the final state of
the experiment will involve a flash on the outer sphere -- the particle
must have been emitted in the wrong direction to strike the inner
hemisphere. From a 50:50 probability of the flash occurring either on
the hemisphere or on the outer sphere, the quantum wave function has
collapsed into a 100 per cent certainty that the flash will occur on
the outer sphere. But this has happened without the observer actually
"observing" anything at all! It is purely a result of a change in the
observer's knowledge about what is going on in the experiment. It
requires an observer intelligent enough to infer what is happening, and
what would have happened if the particle had been heading towards the
inner hemisphere (so a cat, for example, clearly would not be
intelligent enough to cause this particular collapse of a wave
function). Under these circumstances, the absence of an observation can
collapse the quantum wave function as effectively as an actual
observation can. At least, so says the Copenhagen interpretation.

This central role for the observer -- not just any observer, but an
intelligent observer -- lies at the heart of the standard Copenhagen
interpretation of quantum mechanics."

So, what we have here is an explanation of the Copenhaen interpretation
and it depends on intelligent beings having knowledge of an occurance.


Ross Rhodes didn't invent the Copenhagen interpretation of quantum
mechanics, but he certainly knows much about it.

In NO case is an interference pattern formed at the back
wall when the electron detectors are on. That's because
the electron detector influences the motion of the electron.

So you assert.

No interference pattern is ever observed when there is even
the *possibility* of the experimenters measuring the path
that the electrons actually follow through the experimental
apparatus.

Do you have evidence that this is true?

It doesn't matter at all what the experimenters actually know about those paths.

But who set up the detectors? Those people with intent to measure
quantum things which happened, and they could always peak at the data
somewhere down the road.

The experiment done with single electrons in fact differs
critically from the experiments done with two quantum
entangled photons.

It differs in the following obvious way: there are two
photons involved, and these have initially, a common,
correlated two-body wavefunction. The detection of one of
the two photons at some later point in time in the `quantum
eraser' type experiments can thus be used to *deduce*
information about what has to have happened to the other of
the two photons, without necessarily destroying an
interference pattern.

This means that an entirely different analysis is required
for such experiments.

But there are definitely correlations which relate to the double slit
experiments. Here's another excerpt from
http://www.lifesci.sussex.ac.uk/home/John_Gribbin/quantum.htm

"But then Chiao and his colleagues ran the same experiment with
polarising filters in front of each of the two slits. Any photon going
one way would become "labelled" with left-handed circular polarization,
while any photon going through the other slit is labelled with
right-handed circular polarization. In this version of the experiment,
it is possible in principle to tell which slit any particular photon
arriving at the second screen went through. Sure enough, the
interference pattern vanishes -- even though nobody ever actually looks
to see which photon went through which slit.

Now comes the new trick -- the eraser. A third polarising filter is
placed between the two slits and the second screen, to scramble up (or
erase) the information about which photon went through which hole. Now,
once again, it is impossible to tell which path any particular photon
arriving at the second screen took through the experiment. And, sure
enough, the interference pattern reappears! "

This represents a close correlation to the double slit experiments when
it comes to the measurement effect. I don't know how you're getting
that it's unrelated.

We shall need to theoretically
describe the interactions of both photons with the
experimental apparatus to say what will happen in various
configurations.

I don't see what the problem is, though, when it comes to the
measurement effect and how it works similarly in both experiments. And
that is the heart of what Ross Rhodes is writing about at his website.

But it remains the case that all that is important in the
theoretical analysis is the interactions of the pair of
photons with the experimental apparatus itself. The state of
knowledge of the thinking observers is completely irrelevant
to the results of the experiment.

Then I suppose the Copenhagen interpretation of quantum theory is just
nonscience then. . . *rolls eyes*

We do not need to take into account the thoughts of the
experimenters when we do experiments in quantum mechanics.

I am not sure you've looked deep enough into this, because you don't
seem to understand the implications.

You can be thinking about
last night's dinner, as long as you use the instruments to make the
measurement.

-- [snip]

-- Steven J.

Call me crazy, but maybe you want to actually back up what your saying
about the measuring devices interfering with the results with something
that seems persuasive (other than assertions).



If I were you, and I wished to preserve my credibility, I
would modify my signature.

The signature stands. At this point, the credibility problem is with
you.

Did mind come before matter in the universe or matter come before mind?
Chapters 1 and 2 have your answer:
http://www.bottomlayer.com/bottom/reality/Intro.html


There's no answer to the question posed to be found on that
website. Instead there is a farrago of error and deception.

David

Or maybe you just don't like the implications of quantum theory. . .

Steve
---
Did mind come before matter in the universe or matter come before mind?
Chapters 1 and 2 have your answer:
http://www.bottomlayer.com/bottom/reality/Intro.html

.

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