Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Warp wrote:
>>>   You are the one saying that wave interference somehow must imply that
>>> sometimes it cancels itself out. That's just not true. Basic math.
> 
>> Except there *are* spots in the interference pattern between two slits 
>> (if you place them properly) where no electron lands.
> 
>> The electron isn't interfering with itself (or other electrons) in the 
>> same way a wave interferes with itself.
> 
>   I honestly don't understand. It looks a lot to me like your two
> consecutive paragraphs are saying the exact opposite things.

A wave interferes with itself by being in multiple places at the same 
time, and it generates an interference pattern by having different 
magnitudes at different places.

An electron "interferes with itself" by modifying the probability of 
where it will be detected. It's always detected in a single place, and 
it always has the same intensity.

A polynomial "interferes with itself" by doubling the number of tangents 
of zero derivative when you convolve it with itself. A polynomial 
doesn't need a medium in which to wave either, and isn't a "wave" in any 
but the most informal sense of the word. But the same math applies to 
waves of water as applies to the sine function multiplied by itself.

You're confusing "the electron is a wave" with "the probability that the 
particle that is an electron is in a particular place is a wave." The 
electron isn't a wave any more than a molecule of water in the ocean is 
a wave. The wave describes where you'll find the molecules of water. 
That doesn't make the molecules of water waves.

Does that help?

>> And there's no medium to be waving.
> 
>   Medium? Are we back to the luminiferous aether era? I thought it was
> demonstrated almost a hundred years ago that waves don't necessarily
> need a medium.

No. It was demonstrated that wave-like effects (i.e., actions whose 
measures are isomorphic to waves mathematically speaking) can occur 
where there isn't a medium. *If* you think light is waves, then it 
doesn't need a medium. (More precisely, if it needs a medium, that 
medium will be undetectable by virtue of Lorenz contraction.)

If you mean "in some cases, the same math describes both waves and 
probabilities" when you say "the electron is a wave", then I'll agree 
with you, but point out that you're oversimplifying.

>> You're looking at a pattern of events, seeing that its mathematical 
>> equation matches in some ways the mathematical equation of the height of 
>> a wave, and you're saying "hence, the phenomenon must be a wave."
> 
>   Actually no. What I'm saying is "it behaves like a wave".

The *probability* behaves much like a wave. The individual eletrons 
don't. There's a resultant pattern of locations where the electrons land 
which is different based on how you measure their path. That density of 
electrons landing in a certain place is similar to the height a wave 
would be there, were there a wave. But the *electron* isn't a wave - the 
probability of it behaving in a particular way is wave-like.

-- 
   Darren New / San Diego, CA, USA (PST)
     "That's pretty. Where's that?"
          "It's the Age of Channelwood."
     "We should go there on vacation some time."

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Warp wrote:
> When I accuse you of making straw men, that never is the case.
> How convenient.

Well, to be a straw man, it has to be something I'm arguing against. 
Maybe it's some other fallacy, but it isn't a straw man.

> "In the path integral formulation, a particle such as a photon takes
> every possible path through space-time to get from point A to point B. In
> the double-slit experiment, point A might be the emitter, and point B the
> screen upon which the interference pattern appears, and a particle takes
> every possible path, including paths ***through both slits at once***, to
> get from A to B."

Yes. It also take paths that go in circles, thru both slits, backwards 
in time so it goes thru both slits multiple times at once, etc. It can 
also split into multiple virtual particles that go thru both slits and 
recombine into a single photon when it's done.

The "path integral formulation" is an infinite series of different ways 
something can happen. The different paths each have a complex number 
representing the likelihood of it happening. This number is based on 
surprisingly few parameters (six, two of which are universal constants, 
if I remember right). You get the probability of an event happening by 
doing the normal probability math (multiplication is "and" and addition 
is "or") on the complex numbers.

The math doesn't work (i.e., doesn't match experimental evidence) if you 
assume photons can go thru both slits but can't go back in time.

I'm not saying you're making it up. I'm saying electrons aren't waves. 
They don't go through both slits the same way a "wave" does. If they go 
through both slits, it's by either going around in a circle, or by going 
back in time (equivalent, turn into two virtual particles and then 
happen to run into each other and recombine on the other side) so they 
go thru each slit separately and then interact again. At no point are 
they waves in the "water" sense of the word.

> "When a detector is placed at one of the slits, ***the situation changes***,
> and we now have a different point B. Point B is now at the detector, and a
> new path proceeds from the detector to the screen. In this eventuality
> there is only empty space between (B =) A' and the new terminus B', no
> double slit in the way, and so an interference pattern no longer appears."

Right. You integrate the paths up to the detection event, and the 
probability is the magnitude of the square of the complex number. From 
then on, it's normal real-valued probability calculations. In other 
words, if you have event A is "electron leaves generator at time T1", 
event C is "electron hits wall at time T3", then you take all the 
possible ways that could happen, including the electron that is created 
at T1 actually going to T5 (after T3) turning into two particles that 
fly apart, bump into other particles, and smash back together again to 
turn back into an electron, then back to T0 (before T1) and then to T3, 
and add them together using complex addition. (That's the "path 
integral". You can see why the math is hard.) Then you take the 
magnitude of the square of the result, and that's the likelyhood that 
"Electron leaves generator at T1 and hits wall at T3."

If you stick a detector in there and say "Electron leaves generator at 
T1, is detected by the detector at T2, and hits wall at T3", then you 
build the path integral for generator->detector, then for 
detector->wall, and then you add up the magnitudes of the squares of the 
path integrals. I.e., you use normal probability when you're talking 
about "normal" events, rather than probability based on complex numbers.

Note that the retroactive quantum eraser has things like
   leaves generator at T0
   hits wall at T1
   decides which slits to go thru at T2

-- 
   Darren New / San Diego, CA, USA (PST)
     "That's pretty. Where's that?"
          "It's the Age of Channelwood."
     "We should go there on vacation some time."

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>   I'm not the only one who has this "mistaken" notion. From the very
> http://en.wikipedia.org/wiki/Double-slit_experiment article itself
> (emphasis mine):
> 
> "In the path integral formulation, a particle such as a photon takes
> every possible path through space-time to get from point A to point B. In
> the double-slit experiment, point A might be the emitter, and point B the
> screen upon which the interference pattern appears, and a particle takes
> every possible path, including paths ***through both slits at once***, to
> get from A to B."

And the preceding sentence is:

"(Feynman stresses that his formulation is merely a mathematical 
description, not an attempt to describe some "real" process that we 
cannot see.)"


-- 
On a clear disk you can seek forever.


                     /\  /\               /\  /
                    /  \/  \ u e e n     /  \/  a w a z
                        >>>>>>mue### [at] nawazorg<<<<<<
                                    anl

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Mueen Nawaz wrote:
> And the preceding sentence is:
> 
> "(Feynman stresses that his formulation is merely a mathematical 
> description, not an attempt to describe some "real" process that we 
> cannot see.)"

Yep. But Feynman says that about everything, including electrons.

Note that I'm not saying it's *really* time travel. I'm saying that 
claiming time-travel creates paradoxes is unsupported, and claiming that 
time travel is absurd is untrue.

For all we can tell, electrons get around by flapping their wings. 
That's unsupported too.

-- 
   Darren New / San Diego, CA, USA (PST)
     "That's pretty. Where's that?"
          "It's the Age of Channelwood."
     "We should go there on vacation some time."

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In article <48455450$1@news.povray.org>, m.n### [at] ieeeorg says...
> Warp wrote:
> > Mueen Nawaz <m.n### [at] ieeeorg> wrote:
> >>>>         And, AFAIK, that's the best explanation there is.
> >>>   Except that it's not an explanation at all. It's simply stating the
> >>> result of the experiment.
> > 
> >>         Isn't that what a theory is?
> > 
> >   No. A theory is a suggested explanation for a phenomenon, not just a
> > description of the phenomenon.
> 
> 	I'm not seeing a difference here. If a theory purports to explain what
 
> is going on, then an experiment has to be performed to verify that 
> mechanism (not the original experiment). And thus theories are 
> equivalent to predicting the results of experiments.
> 
> 	We have Newton's theory of gravitation. It didn't explain how gravity
 
> worked.
> 
> 	Einstein's special theory of relativity didn't explain much either - i
t 
> was just a framework that could duplicate some weird experimental 
> results - and predicted some more weird results. It didn't explain why 
> the speed of light is constant w.r.t. any observer, why it didn't need a
 
> medium to travel, and why you have length contraction as you go faster.
> 
> 	The difference between a good theory and just any theory is that last
 
> bit - not only can it match the result of known experiments, but it 
> suggests new experiments and predicts their results.
> 
> >>         Your claim that it passes through both slits is untestable. We
 can 
> >> never detect that it is doing this.
> > 
> >   There are many theories which are untestable in practice. For example
> > the existence of the so-called cosmic horizon is, by definition, untest
able.
> > (If we could go and see if the cosmic horizon indeed exists, it would n
ot
> > be a cosmic horizon anymore, by the very definition of cosmic horizon.)
> > That doesn't make the theory any less of a theory.
> 
> 	Many scientists think it does. Wikipedia definition (emphasis mine):
> 
> "In science a theory is a *testable* model of the manner of interaction
 
> of a set of natural phenomena, capable of predicting future occurrences
 
> or observations of the same kind, and capable of being *tested* through
 
> experiment or otherwise verified through empirical observation. "
> 
> 
Not to quibble too much, but Warp is talking "Hypothesis", not "Theory", 
and you are not really helping. A Theory has to be "supported by 
evidence", a hypothesis is merely a possible explanation, whether 
testable or not. Something doesn't become a "theory" until its not just 
been tested, but provisionally passed such a test. Its still only a 
hypothesis *until* you test it, and receive results that confirm that it 
*can be* called a theory. That is why gravity gets the pass, in that you 
can test "if" it exists and what it does, even if you don't have a 
theory that really says "why" it does so, while, "I have invisible pink 
unicorns  in my garden", can't go past being a hypothesis, there being 
no way to prove they exist, that they "do" anything, never mind why they 
are there.

Its a distinction that gets rehashed about once a month on 
scienceblogs.com when dealing with lay people and various alternate 
reality wackos that equate "theory" with "hypothesis", and both with 
"wild guess". If you want to talk the talk, lets not confuse the rubes 
(or embolden the loonies), by using their sloppy definitions. ;)

-- 
void main () {

    if version = "Vista" {
      call slow_by_half();
      call DRM_everything();
    }
    call functional_code();
  }
  else
    call crash_windows();
}

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In article <48457419@news.povray.org>, dne### [at] sanrrcom says...

You know, I had a thought. What if electrons have no "fixed" path as we 
would think of it. I.e., their position tends to fluctuate, similar to 
what you get with the cloud of them around an atom (hint, they don't 
form shells, its just a useful analogy). Then, if the slits are wide 
enough and at a distance "equal" to the effective maximum distance of 
displacement that can happen in these fluctuations, multiple electrons 
fired in close proximity "may" find themselves in situations where their 
positions must be logically coincidence with one of the slits, and they 
"would" interfere and generate a pattern. Even a single one may do so, 
since it "could" in such a state pass through "both" at the same time, 
or near enough that similar coincident effects could cause it to pass 
through one perfectly, vanish, then reappear too close to the other, 
perturbing its path slightly, only to have its next "bounce" happen off 
center of where it "should have" gone had it passed through both 
perfectly, or missed one completely. I.e., maybe electrons actually act 
like virtual particles in a vacuum. Something makes them more "stable" 
than those particles, but their position is inherently unstable, within 
the limits of their known path, due to fluctuations similar to those 
that cause virtual particles.

This would allow a particle to both "pass through" two slits at the same 
time, and yet, *not* have done so, but only if the slits where within a 
the maximum distance in which such fluctuations would allow the electron 
to fluctuate.

The only question is then, what about diffusion? Would diffusion be 
explained by an increase in the effective diameter of possible 
fluctuations, as velocity is lost, kind of like bullets wobble more as 
their spinning slows?

Just thinking about what explanation would "fit" the data, while giving 
a better explanation that, "well, it just goes through two slots." Kind 
of begs the question, "Ok, but how?" And, it provides a plausible source 
for quantum uncertainty. If all particles are, on some level, a form of 
virtual particle, but something about their energy state keeps making 
stable from moment to moment, unlike the more common ones. Well, its a 
creepy prospect, but it might explain some things about quantum physics 
and the whole Heisenberg Uncertainty mess.

-- 
void main () {

    if version = "Vista" {
      call slow_by_half();
      call DRM_everything();
    }
    call functional_code();
  }
  else
    call crash_windows();
}

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Patrick Elliott wrote:
> You know, I had a thought. What if electrons have no "fixed" path as we 
> would think of it. I.e., their position tends to fluctuate, similar to 
> what you get with the cloud of them around an atom (hint, they don't 
> form shells, its just a useful analogy).

Well, I'm not sure this is the right way of looking at it. Nobody knows 
what the electron is doing when you're not looking at it. Nobody knows 
if electrons have a fixed path or not. People only know that if there 
*is* a fixed path, you can't tell what it is without looking at it.

Nobody knows if electrons have a fixed position at any given time. 
Certainly every time you look, they do. Equally certainly, for the math 
to come out right, you have to assume they *might* be most anywhere.

> Then, if the slits are wide 
> enough and at a distance "equal" to the effective maximum distance of 
> displacement that can happen in these fluctuations,

There is no effective maximum distance. There are only "fluctuations" 
that are impossible, and "fluctuations" with very low probabilities. 
(It's the "impossible" bits that keep all the electrons from falling 
into the nucleus.)

> multiple electrons 
> fired in close proximity "may" find themselves in situations where their 
> positions must be logically coincidence with one of the slits, and they 
> "would" interfere and generate a pattern. Even a single one may do so, 
> since it "could" in such a state pass through "both" at the same time, 
> or near enough that similar coincident effects could cause it to pass 
> through one perfectly, vanish, then reappear too close to the other, 
> perturbing its path slightly, only to have its next "bounce" happen off 
> center of where it "should have" gone had it passed through both 
> perfectly, or missed one completely.

Yes, that's basically what the math says.

> I.e., maybe electrons actually act 
> like virtual particles in a vacuum. 

"Maybe"?

> Something makes them more "stable" 
> than those particles, but their position is inherently unstable, within 
> the limits of their known path, due to fluctuations similar to those 
> that cause virtual particles.

Yes.

> This would allow a particle to both "pass through" two slits at the same 
> time, and yet, *not* have done so, but only if the slits where within a 
> the maximum distance in which such fluctuations would allow the electron 
> to fluctuate.

I think you're looking at one experiment that gives very un-common-sense 
results, and trying to come up with a common-sense explanation based on 
popular understanding of what's known about how it works.

Any explanation you give for the "two slits" bit has to deal with 
quantum erasure and delayed quantum erasure, for example.

> The only question is then, what about diffusion? Would diffusion be 
> explained by an increase in the effective diameter of possible 
> fluctuations, as velocity is lost, kind of like bullets wobble more as 
> their spinning slows?

I'm not sure what you mean by "diffusion" here. Diffusion happens 
without wobble or loss of velocity, so you might be talking about 
something else.  There is no "effective diameter of possible 
fluctuations" if I understand what you mean by that properly.

-- 
   Darren New / San Diego, CA, USA (PST)
     "That's pretty. Where's that?"
          "It's the Age of Channelwood."
     "We should go there on vacation some time."

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Hmmm... No new posts on this thread from folks who were doing several 
posts a day for the last few days.  This seems to happen a lot, without 
any real closure.  I'm just curious, now.

1) I argue/discuss/debate in a way that pisses people off enough that 
they stop in disgust.

2) I seem too dense to consider what others have said, but it's not 
worth saying "I don't think we'll come to an agreement, so I'm stopping."

3) I explained sufficiently clearly to change your mind (for arbitrary 
values of "you"*), but you're either embarrassed or don't think it's 
worth mentioning "yes, that makes sense, we're done."

4) You explained enough and you think I'm just arguing because I refuse 
to admit I'm wrong?

5) You (for some "you") got tired of talking about it and just didn't 
bother to say "I'm tired of talking about it."

6) You (for some "you") got busy and didn't take the time to say "too 
busy to finish talking about this."

I'm curious why many of these discussions which seem to me lively and 
interesting also seem to just ... stop without coming to any sort of 
explicit closure.


[*] By which I mean, not specifically the people on this thread, but 
often times on this server.

-- 
   Darren New / San Diego, CA, USA (PST)
     "That's pretty. Where's that?"
          "It's the Age of Channelwood."
     "We should go there on vacation some time."

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Darren New <dne### [at] sanrrcom> wrote:
> I'm curious why many of these discussions which seem to me lively and 
> interesting also seem to just ... stop without coming to any sort of 
> explicit closure.

  When a conversation is going basically nowhere, and especially when
the tone of the text is not the most positive, people get tired of
arguing.

  People don't like being told in harsh words "that's not true, you
are wrong", even if that's the case. Being too blunt about someone's
error (especially if it's actually not completely clear if there *is*
an error) is usually not going to get very positive feedback. People
feel attacked. Sometimes someone may actually realise he's not
completely right, but he still may feel that he doesn't deserve such
a blunt response.

-- 
                                                          - Warp

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On Wed, 04 Jun 2008 13:13:44 -0400, Warp wrote:

> Darren New <dne### [at] sanrrcom> wrote:
>> I'm curious why many of these discussions which seem to me lively and
>> interesting also seem to just ... stop without coming to any sort of
>> explicit closure.
> 
>   When a conversation is going basically nowhere, and especially when
> the tone of the text is not the most positive, people get tired of
> arguing.
> 
>   People don't like being told in harsh words "that's not true, you
> are wrong", even if that's the case. Being too blunt about someone's
> error (especially if it's actually not completely clear if there *is* an
> error) is usually not going to get very positive feedback. People feel
> attacked. Sometimes someone may actually realise he's not completely
> right, but he still may feel that he doesn't deserve such a blunt
> response.

You're wrong.

<scnr>

Jim

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