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Warp wrote:
> Darren New <dne### [at] san rrcom> wrote:
>> Warp wrote:
>>> So when the electron hits the sensitive film *after* it has passed the
>>> slits, it goes back to the past and changes it so that it goes through
>>> only one of the slits after all?
>
>> No. It either interferes with itself or not. You're assuming the only
>> way it can interfere with itself is to go through both slits. There's no
>> evidence that's the case, and much evidence that it isn't.
>
> So why does it interfere with itself when there are two slits but not
> when there is only one? If it was just one regular physical macroscopical
> particle it wouldn't matter how many slits there are: If it goes through
> one of them, it just goes through one of them, that's it. It doesn't even
> "know" that there are other slits.
> However, when there are two slits, the electron passes through and starts
> interfering with itself, as if it has passed through both and changed
> direction in different ways.
>
> How else can this be explained? How does the electron "know" that there's
> another slit so that it "knows" to start interfering with itself, other than
> actually going through the other slit as well?
'It' knows that the second slit is there because an electron has an
infinite size. Part of the problem is that you use 'it', implying that
it is an identifiable object and it has a subconscious connotation of
something finite.
>
> (I believe this has something to do with wave-particle duality: In the
> double-slit experiment the wave nature of the electron shows up: The wave
> goes through both slits and starts interfering with itself.)
Both 'wave' and 'particle' are concepts from classical physics that
don't apply here.
In the double slit experiment you have a source of electrons, a double
slit and a screen. You know that you had an electron at the source and
you can compute the likelihood of the position on the screen that will
light up, enabling you to estimate the pattern if you use a large number
of electrons. Between the source and the screen, the electron passes
through ever point in the universe and you are not even sure that the
same electron hit the screen as the one you started with. Simply because
'same' is not defined here.
A basic rule of quantum mechanics: don't try to visualize what happens.
You can either visualize it or compute it, not both at the same time. ;)
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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>>> What the mathematical model *can* do is to give a distribution function
>>> which tells how the electron is distributed in space (a bit like a
>>> function which tells how the water is distributed, except that with
>>> the electron the "density" of the "water" is not constant).
>
>> No, actually, it tells you the likelihood of finding it at any
>> particular place, were you to look.
>
> Assuming the particle *is* at some specific location at any given time
> instead of being distributed in space.
>
>> Yes, it can actually hit the other side of the Earth. It can also hit a
>> week before you shoot it. Very unlikely, but possible.
>
> I don't believe in the time travelling.
Luckily you don't have to believe it in order for it to exist. BTW I
don't think what Darren proposes can actually happen, though it might be
possible to create a situation that is indistinguishable from it.
> As for the location, I assume
> the probability of it hitting the other side of the Earth is so small that
> some physical constant prevents it.
The only thing that prevents it is the number of electrons you have to
try it. Still even if it will never actually happen, yet the fact that
it could will influence the outcome anyway.
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Darren New wrote:
> Mueen Nawaz wrote:
>> Yes - wasn't that proven only recently?
>
> I heard about it recently, like in the last couple of years.
Actually, I found it - proven in 1990.
> Something like 10^50 cuts or something? I know it's on Wolfram's
> mathworld somewhere, but I don't remember the name of it, so it's hard
> to find.
http://en.wikipedia.org/wiki/Tarski%27s_circle-squaring_problem
--
The next war will determine not what is right, but what is left.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Warp wrote:
>> Indeed, a straight edge and compass. What more do you need?
>
> I assume that dividing the circle into an uncountable set of points.
I posted the link in another message. The set of regions it is cut into
is countably finite.
--
The next war will determine not what is right, but what is left.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Warp wrote:
> However, when there are two slits, the electron passes through and starts
> interfering with itself, as if it has passed through both and changed
> direction in different ways.
>
> How else can this be explained? How does the electron "know" that there's
> another slit so that it "knows" to start interfering with itself, other than
> actually going through the other slit as well?
Your questions are interesting, but the conclusions do not necessarily
follow. If you actually attempt to detect the electron passing through a
slit, you'll detect it passing through only one slit (and you won't get
an interference pattern). When you don't try to detect it, you get an
interference pattern.
You're concluding it passed through two slits when you don't try to
detect it? It knows before passing through the slit that you're trying
to detect it? Such a suggestion is about as weird as an electron
interfering with itself. It may be true, or it may not be. I don't
presume to know.
As you yourself stated elsewhere, you get an interference pattern even
when only one electron is shot at a time. However, the electron strikes
the screen in only one place at a time. Looking at where they struck
individually gives no evidence of any interference - it doesn't "weakly"
strike two places at once. Looking at the whole set of locations the
electron struck, though, does. One could simply explain this by saying
that the presence of two slits causes the electron to act in a
probabilistic manner - resulting in an interference pattern.
And, AFAIK, that's the best explanation there is. I have a formalism
that describes experimental results, and I don't have to resort to
thinking about electrons interfering with themselves.
The reason I don't want to declare self-interference is that there is
no way I can test it (or as Darren would say - any attempt to show this
fails). I can have two slits and put detectors at each slit. When you
detect an electron passing through a slit, interference ceases. Why? If
the electron can pass through both slits, why can't you actually detect
this?
>>> If there's "no evidence", what do you call the interference pattern?
>>> "Non-evidence"?
>
>> Interference.
>
> The interference can be explained with the electron passing through both
> slits at the same time. Ergo the interference is evidence of that happening.
> (Note that "evidence" is not the same thing as "proof".)
And detecting which slit an electron passes through is also evidence
that it isn't passing through both slits.
--
The next war will determine not what is right, but what is left.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Warp wrote:
>> There is a non-zero probability that this can happen.
>
> I bet the probability is so small that it hits the barrier of some
> physical constant (Planck maybe?)
I'm not sure what that means. Probability is a mathematical construct -
not beholden to physical constants. If the probability is 1e-100, you
can't use physics to conclude that it *won't* happen tomorrow.
--
The next war will determine not what is right, but what is left.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Darren New wrote:
> John VanSickle wrote:
>> I wouldn't say that it is truly random, but merely that predicting the
>> outcome of any interaction requires information that is presently not
>> available.
>
> You would be incorrect. Google on "Bell's Inequality".
>
>> For instance, the decay of unstable particles appears to happen
>> randomly, but at what appears to be a predictable rate for aggregate
>> amounts of like particles. What is likely is that the particles decay
>> when they encounter certain conditions (such as a gradient in the
>> electric or magnetic potential) that is high enough to overcome the
>> weak internal cohesiveness of the particle, causing it to come apart.
>
> That's the "hidden variable" theory. It has been disproven, multiple
> times and with hundreds of different experiments. Boggling, isn't it?
I question the assertion that it's been disproven. I think only a
certain class of hidden variables have been shown not to exist. (Local
vs non-local?)
--
The next war will determine not what is right, but what is left.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Mueen Nawaz wrote:
> http://en.wikipedia.org/wiki/Tarski%27s_circle-squaring_problem
Interestingly, following the links from there to
http://en.wikipedia.org/wiki/Non-measurable_subset give an example of
what might be a reality inconsistent with math:
"""
These sets are rich enough to include every conceivable definition of a
set that arises in standard mathematics, but they require a lot of
formalism to prove that sets are measurable.
"""
So if reality actually includes non-measurable sets (something that
wouldn't seem too impossible, given the definition, such as "space where
you can't pick any random position", i.e., quantum space), you already
have a serious problem.
--
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:
>> No, it only interferes with other electrons. The electrons it interferes
>> with are electrons from other times. There's always a possibility that
>> it lands at any particular place. Why is it any stranger that it
>> interferes with electrons in the future than it is it interferes with
>> itself?
>
> Because time travel doesn't exist?
At the quantum level, it most certainly does.
--
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:
> So why does it interfere with itself when there are two slits but not
> when there is only one?
I don't know, offhand. That's actually one of the burning questions of
quantum physics. Are you saying you've figured it out? :-)
Incidentally, it doesn't interfere with itself - I misspoke. It
interferes with other electrons. Sure, they only go through one at a
time. What was that about time travel?
> However, when there are two slits, the electron passes through and starts
> interfering with itself, as if it has passed through both and changed
> direction in different ways.
How do you know? Every time you measure whether it went through both
slits, the answer is "no, there was only one electron." You keep
asserting this, with no evidence other than "I can't think of any other
explanation", along with rejecting both evidence and other explanations.
> How else can this be explained? How does the electron "know" that there's
> another slit so that it "knows" to start interfering with itself, other than
> actually going through the other slit as well?
Your intuition is confusing you. How does it "know" there's a back
surface to the glass and therefore needs to reflect differently? How
does it "know" there's another electron already "on the way" to where
it's going and hence that position needs to be avoided?
Why is it a wave going through both slits but a particle by the time it
gets to the detector?
> (I believe this has something to do with wave-particle duality: In the
> double-slit experiment the wave nature of the electron shows up: The wave
> goes through both slits and starts interfering with itself.)
That's the older explanation from when physicists thought like you're
thinking, yes. The math works like a wave function, so people thought it
was a wave. It's not.
>>> So you are saying that, even though the only possible explanation for
>>> interference patterns is that the electron passed through both slits,
>>> there's still no evidence of that?
>
>> Yes. What makes you think that the only *possible* explanation is that
>> the electron passed through both slits?
>
> What is the other explanation?
I don't know, and as far as I understand, nobody else does either. But
all of the evidence so far suggests your interpretation is incorrect.
For example, if you do the same thing with photons, wait for them to go
thru the slits, and after they've already passed through, you either
turn on or off the detector that says which slit they went through, you
always see them only go through one slit when the detector is on, and
always generate interference probabilities when the detector is off. How
do you explain that?
> The interference can be explained with the electron passing through both
> slits at the same time.
Yes. But that's also at odds with many other experiments. If the
electron goes through both slits, why is it that you never see it go
through both slits when you put a detector behind each slit? It's one
possible explanation with reams of experimental evidence against it.
The sun rising can be explained by angels pushing it along, as well, but
that too is at odds with many other experiments. "I can't think of a
better explanation" isn't the same as "the one I thought of must be
true", *particularly* when evidence from other measurements is
consistently at odds with one's explanation. (True regardless who "I" is
in there.)
--
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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