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Warp wrote:
> It's just a pattern which happens
> to look exactly like an interference pattern, but without being one.
Right! The math works out to be the same, in some limited cases.
Did you watch the youtube video I linked to? Or are you trying to apply
common sense to a field which even nobel prize winners in that field agree
it doesn't make common sense?
> And if I follow your earlier logic, the pattern looks like an interference
> pattern *because* it's not an interference pattern.
No, you misread that. I said you know it's not an interference pattern
because it happens with only one photon at a time.
Look, don't argue with me. Argue with Feynman if you want.
--
Darren New, San Diego CA, USA (PST)
Human nature dictates that toothpaste tubes spend
much longer being almost empty than almost full.
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Warp wrote:
> Your logic seems to be that since photons do *more* than waves do, in
> other words, photons seems to be a superset of pure waves, then they are
> not waves at all.
No, that isn't my logic. Did you watch the video I linked to, where Feynman
talks about a few of the things that show why photons aren't waves? Do you
realize that Einstein got his nobel prize for showing that photons can't be
waves?
The point is that they aren't waves when you look at more than one at a
time, because they don't even cause interference patterns like you would
expect. (Otherwise, lasers wouldn't work.) They aren't waves when you use
electrons, even though you get "interference" patterns as long as you *only*
shoot one at a time. One photon traveling through vacuum (or otherwise not
interacting) follows the same math as a wave. Two photons don't. Two
electrons don't. A photon interacting with an electron 100 feet down the
road doesn't act like a wave *here*.
I'll agree it isn't intuitive that the motion of particles obeys some
unobvious rules. That doesn't make them waves.
> (I'm not saying that's what's happening. I'm saying that the way you write
> makes it sound like that.)
It's not "too hard to swallow". It's simply counter to experimental
evidence. The interference has nothing to do with how many slits the photon
passes through. Indeed, that's the *point* of the two-slit experiment. You
*only* get "interference" patterns if you *don't look*. If the
"interference" patterns were caused by the photon passing through both
slits, then they would persist if you did something to the photon *after* it
passed through both slits. But it doesn't.
Indeed, if it was caused by the photon passing through two slits at once,
you'd expect to get the interference pattern if you closed the slits only
after you'd measured where the photon landed. But you don't. If you can
explain that in terms of waves, there's a nobel prize waiting for you.
Is it really that hard to believe that there are multiple ways to come up
with the same numbers that waves give you?
--
Darren New, San Diego CA, USA (PST)
Human nature dictates that toothpaste tubes spend
much longer being almost empty than almost full.
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Darren New <dne### [at] sanrrcom> wrote:
> Or are you trying to apply
> common sense to a field which even nobel prize winners in that field agree
> it doesn't make common sense?
That is contradictory with:
> I said you know it's not an interference pattern
> because it happens with only one photon at a time.
--
- Warp
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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Or are you trying to apply
>> common sense to a field which even nobel prize winners in that field agree
>> it doesn't make common sense?
>
> That is contradictory with:
>
>> I said you know it's not an interference pattern
>> because it happens with only one photon at a time.
I don't see that as contradictory, unless you mean that if it doesn't make
common sense, you can't talk about it with common words at all. I'm down
with that. The math doesn't work out the same either. :-)
But seriously, for there to be an interference pattern, something has to
interfere with something else, right? As soon as you interfere with the
photon, the pattern goes away. Indeed, the pattern is *only* there exactly
to the extent that there is *no* interference.
--
Darren New, San Diego CA, USA (PST)
Human nature dictates that toothpaste tubes spend
much longer being almost empty than almost full.
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Darren New <dne### [at] sanrrcom> wrote:
> But seriously, for there to be an interference pattern, something has to
> interfere with something else, right?
If the photon is a wavefront which traverses from the emitter to the
detector, passing throug the slits splits it into two wavefronts, which
interfere with each other. When the wavefront collides with the detector,
it collapses back into a particle.
I'm not saying that is what happens. I'm just saying it's exactly as
plausible as eg. a particle being in many places at the same time or
affecting another particle instantly.
> As soon as you interfere with the
> photon, the pattern goes away. Indeed, the pattern is *only* there exactly
> to the extent that there is *no* interference.
So why does the interference pattern appear? Is nature trying to confuse
us to make it look exactly like it was a wave, without it being so?
--
- Warp
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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> But seriously, for there to be an interference pattern, something has to
>> interfere with something else, right?
>
> If the photon is a wavefront which traverses from the emitter to the
> detector, passing throug the slits splits it into two wavefronts, which
> interfere with each other. When the wavefront collides with the detector,
> it collapses back into a particle.
But it doesn't work that way. If you look to see which slit the particle
passed through, you find out that it only went through one. You never, ever
see it go through both slits. You basically never see a wave or measure a
wave. You always measure a particle, even as the whatever goes through the
slits, even *after* the whatever goes through the slits.
> I'm not saying that is what happens. I'm just saying it's exactly as
> plausible as eg. a particle being in many places at the same time or
> affecting another particle instantly.
Plausible? Yes. Confirmed by experimental evidence? No. Contradicted by
experimental evidence? Yes.
I'm just stating what the guys who study this say. You're trying to tell me
it sounds absurd. Sure, maybe it does. Maybe the world *might* work a
different way than it does. Maybe if the only experiment you did was the
two-slit experiment, you'd think photons are sometimes waves. But they're not.
> So why does the interference pattern appear?
You know when you do something with macro-sized objects, you get
one-dimensional probabilities, right? If you say "flip a coin, twice",
you'll have the probability of getting two heads being the probability of
getting one head *times* the probability of getting one head, right? (I'll
leave it as an exercise for you to decide *why* that is the case, beyond
"common sense.") The probability of getting heads either time is the
probability of getting heads the first time *plus* the probability of
getting heads the second time *minus* the probability of getting both (just
so you don't count the same event twice).
It's the same way with quantum particles, except the probabilities are
complex numbers, hence "amplitudes". The probability of it hitting the
screen at a given position is the amplitude of it going from the emitter to
the left slit to that point on the screen *plus* the probability of it going
from the emitter to the right slit to that point on the screen. But those
probabilities change based on the distance the particle travels, and when
you do all the adding and multiplying, the imaginary components wind up
canceling out some of the "real" components in a way that looks like waves.
Because the probability of a quantum particle going in any given direction
is a function of its amplitude. "Amplitude" is a technical term meaning
"two-dimensional probability." You get the probability of finding a particle
at a particular place by adding together all the amplitudes of it getting
there, then taking the absolute value (i.e., the length of the result).
In other words, the probability of something going from A to B is the sum of
all the amplitudes of the ways it can get from A to B, then you take the
resulting size. Just like if you want to get a heads on the first flip or a
heads on the second flip, you add the probabilities.
The probability of two things happening is the multiplication of the two
*probabilities*, because you know the things happened.
If you measure the likelihood of the particle going from the emitter to the
screen without checking which slit it went through, the probability is the
absolute value of the sum of all the ways it could get there.
If you check which slit it went through, it's the probability that it got
there by going through the first slit plus the probability that it got there
by going thru the second slit. (Since it never goes through both, you don't
have to subtract out that possibility like you do with flipping coins.) The
probability of it going from the emitter to either one of the slits, or from
the slit to any point on the screen, you still measure by adding up complex
amplitudes for each possible path, and not just using probabilities.
Note that when you don't check which slit, you add up a bunch of complex
numbers, then take the absolute value. When you check which slit, you add up
a bunch of *real* numbers (one for each possible measurement), each of which
is the result of adding up a bunch of complex numbers.
That's why doing things in the *future* can affect what you measure *now*,
which isn't how waves work.
> Is nature trying to confuse
> us to make it look exactly like it was a wave, without it being so?
Not every addition of complex numbers is a wave. Just so, not every
collection of converging lines is caused by perspective. Having converging
lines in nature that don't converge to the horizon isn't any more
"confusion" than complex numbers not caused by waves. In much the same way,
I can show you that *those* lines are *not* perspective, because if you
shift your point of view, they don't converge at the horizon. But if you
only look at exactly one experiment, namely the two slits with no other
measurements made, it *look* like perspective/waves, but as soon as you do
another experiment, it stops looking like that.
--
Darren New, San Diego CA, USA (PST)
Human nature dictates that toothpaste tubes spend
much longer being almost empty than almost full.
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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> > Darren New <dne### [at] sanrrcom> wrote:
> >> But seriously, for there to be an interference pattern, something has to
> >> interfere with something else, right?
> >
> > If the photon is a wavefront which traverses from the emitter to the
> > detector, passing throug the slits splits it into two wavefronts, which
> > interfere with each other. When the wavefront collides with the detector,
> > it collapses back into a particle.
> But it doesn't work that way. If you look to see which slit the particle
> passed through, you find out that it only went through one. You never, ever
> see it go through both slits.
But if you observe it going only through one of the slits, the interference
pattern doesn't appear, IIRC.
Wouldn't that be kind of evidence that when the interference pattern appears,
it did to through both slits? When someone forces it to go through only one of
the slits (by observing it) the interference pattern disappears.
> You basically never see a wave or measure a
> wave. You always measure a particle, even as the whatever goes through the
> slits, even *after* the whatever goes through the slits.
But does the interference pattern remain if the particle is measured?
If it does, then *that* would be indicative that the pattern is not
appearing because the photon behaved like a wave.
> > I'm not saying that is what happens. I'm just saying it's exactly as
> > plausible as eg. a particle being in many places at the same time or
> > affecting another particle instantly.
> Plausible? Yes. Confirmed by experimental evidence? No. Contradicted by
> experimental evidence? Yes.
Contradicted how? "We forced the photon to pass through only one of the
slits and what do you know, the interference pattern disappeared." That
would be confirming evidence, not contradicting one.
> I'm just stating what the guys who study this say. You're trying to tell me
> it sounds absurd.
I'm not saying it sounds absurd. I'm saying that the argument of "it's
only one photon, it cannot interfere with itself" all by itself doesn't
convince *me*. I need more.
Explaining the reason why the interference pattern appears even though
the photon does not behave like a wave would help.
> The probability of it hitting the
> screen at a given position is the amplitude of it going from the emitter to
> the left slit to that point on the screen *plus* the probability of it going
> from the emitter to the right slit to that point on the screen.
I don't think you can talk about amplitudes after claiming so firmly that
photons are not waves.
--
- Warp
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Warp wrote:
> But if you observe it going only through one of the slits, the interference
> pattern doesn't appear, IIRC.
Correct.
> Wouldn't that be kind of evidence that when the interference pattern appears,
> it did to through both slits?
Not really, no.
> When someone forces it to go through only one of
> the slits (by observing it) the interference pattern disappears.
That would only be true if the observation occurs before the particle goes
through the slits. If it *really* goes through both slits, wouldn't it have
to do so *before* it gets to the detectors on the screen side of the slits?
The whole "quantum eraser" thing is designed to prove you can measure which
slit it went through after it has already hit the screen, and you still
erase the interference pattern. If the interference pattern was based on
the particle turning into a wave and going through both slits, that wouldn't
work.
>> You basically never see a wave or measure a
>> wave. You always measure a particle, even as the whatever goes through the
>> slits, even *after* the whatever goes through the slits.
>
> But does the interference pattern remain if the particle is measured?
No. The "interference" is caused not by the particle, but by the slits.
> If it does, then *that* would be indicative that the pattern is not
> appearing because the photon behaved like a wave.
Correct. But the pattern goes away even if you measure the path of some
*other* particle *after* the particle that went thru the slits has already
been measured. Hence, it's not a property of the particle/wave by itself.
> Contradicted how? "We forced the photon to pass through only one of the
> slits and what do you know, the interference pattern disappeared." That
> would be confirming evidence, not contradicting one.
Contradicted by the fact that the pattern also disappears if you measure
which slit some other particle went through *after* the original particle
has already been measured. In other words, it also disappears if you decide
whether or not to look which slit it went through *after* it has already
been detected.
You have your choice of the particle looking at your experimental setup and
telling itself backwards in time whether to go thru one slit or both, or
just accepting that the particle never goes through both slits.
What you're doing is saying that the medical screening procedure *causes*
cancer, because every time you do the blood test and it comes up positive,
the person has a higher chance of being sick.
> Explaining the reason why the interference pattern appears even though
> the photon does not behave like a wave would help.
http://vega.org.uk/video/subseries/8
http://www.amazon.com/QED-Strange-Theory-Light-Matter/dp/0691024170
I'm trying to. You get an interference pattern because the probability for a
particle to go somewhere is based on 2D numbers that when you multiply them
wind up "interfering" with each other. But there's no wave there.
Watch this, which is Feynman answering exactly your question:
http://www.youtube.com/watch?v=_7OEzyEfzgg
> I don't think you can talk about amplitudes after claiming so firmly that
> photons are not waves.
As I said, "amplitude" is a technical term that means a two-dimensional
probability. It's not talking about the distance from the trough to the
crest of a wave. You can replace it with any word you want, but you won't
understand what quantum mechanics are talking about if you don't know what
the word means.
--
Darren New, San Diego CA, USA (PST)
Human nature dictates that toothpaste tubes spend
much longer being almost empty than almost full.
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Warp wrote:
> when the state of the particle is "observed" (whatever that might mean)
Merely that you have done something to it which changes its unknown
state, usually causing it to make contact with another particle(s), such
as a detector. In effect, if the particle is on its own, and hasn't hit
anything, it can be in a lot of places at once. In the case of light,
"hitting" requires that the thing it hits have optical properties that
have a high chance of making such a change, which things like air don't.
But, don't ask me why in that case, other than it maybe involves optical
properties and perhaps how often it "will" hit the other particles in
the air itself. lol
--
void main () {
if version = "Vista" {
call slow_by_half();
call DRM_everything();
}
call functional_code();
}
else
call crash_windows();
}
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Jim Henderson wrote:
> You could probably see a fair bit from Stonehenge....
With Salisbury 11 miles to the south, and Amesbury 4 miles to the east?
Unrelated but... I gather they don't let you go near Stonehenge any more.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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