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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] san rr com> 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] nawaz org<<<<<<
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] ieee org says...
> Warp wrote:
> > Mueen Nawaz <m.n### [at] ieee org> 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. ;)
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else
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In article <48457419@news.povray.org>, dne### [at] san rr com 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.
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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] san rr com> 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] san rr com> 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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I simply had nothing new to add myself. I did not think I could add
anything that might help you understand each others point. I was clear
to me that everybody seemed intent to stick to their own
(mis)interpretation. So why bother?
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