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Darren New wrote:
> Warp wrote:
>> That's the kind of "observation" I don't understand.
>
> They're still working on that one. Someone recently proposed it's
> actually gravity waves causing the "collapse", which is why it doesn't
> happen until you get enough particles that gravity becomes significant.
> Or some such.
>
> That's another one of those "nobody is sure why yet" kind of things.
>
Ok. Already gave and answer to why this is odd, but.. Just to let you
clarify - How do you "measure" or "observe" what a particle as even
done, without colliding it with something? What process do you use that
doesn't involve a "state change" resulting directly from a scientific
instrument *causing* the state to change? There isn't one, so the
Copenhagen interpretation can't be arguing that "looking at something",
without actually, you know... "looking at it", does anything. By
definition, anything you can/do do, which looks at a particle, involves
*other particles*, so I am unclear what the heck either one of you are
claiming is different here from any other sort of quantum physics.
Again, we can't measure/observe a particle, without interacting with it,
so claiming that "changing" it by observation differs from changing it
by hitting it with another particle is just... not making any sense at all.
--
void main () {
If Schrödingers_cat is alive or version > 98 {
if version = "Vista" {
call slow_by_half();
call DRM_everything();
}
call functional_code();
}
else
call crash_windows();
}
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Warp wrote:
> Darren New <dne### [at] san rrcom> wrote:
>> Warp wrote:
>>> Darren New <dne### [at] sanrrcom> wrote:
>>>>> But it seems that everybody knows that it does not happen by the photon
>>>>> going through both slits?
>>>> Correct. Or, rather, nobody has ever measured anything that would imply the
>>>> photon goes through both slits as a wave.
>>> The interference pattern in the detector is not a measurement?
>
>> No. It's a bunch of individual measurements of different photons. There's no
>> way to look at *one* photon and decide whether there was one slit or two.
>> Because it's not a wave, it's a particle, so it always makes the same sort
>> of single-spot quantum event in a single place.
>
> That's like saying that you can't measure the probability of a coin
> giving heads because you can only toss one coin at a time.
No. It's like saying a coin doesn't land half-heads-half-tails. You can
certainly measure the *probability* of a photon hitting in a particular
place. That doesn't mean the photon is or ever was a wave.
> I'd say tossing 100 coins one after another is exactly as valid as if you
> had tossed one coin 100 times simultaneously (if that was physically possible).
Yes. And even tho you get about half heads and about half tails, not a
single one of those coins wound up with half the heads showing or half the
tails showing. They were all either 100% heads or 100% tails, when you look
at each one individually.
Similarly, each photon is a particle, and it never goes through both slits,
just like a coin never lands 50% heads and 50% tails.
>>> But I thought that's the whole idea in the Copenhagen interpretation:
>>> Particles are in superpositions until they are measured, in which case
>>> they collapse into a definite state. Thus when you measure a photon, you
>>> will always find a collapsed photon.
>
>> If every time one measures something, one gets "it isn't a wave", then why
>> would one think it's ever a wave?
>
> Because of the interference pattern?
There's one set of measurements that give the same probabilities as if the
photons were propagating as waves. But there's also other ways to explain
the interference pattern (mathematically speaking) that has the same
arithmetic but a different interpretation. This different interpretation is
consistent with *all* the measurements.
It's like looking up at the sky and saying "The sun goes around the earth,
obviously." But yes, maybe the earth goes around the sun, and you'd get the
same appearance as the sun, but if you look at other *planets* you can tell
they're all going around the sun.
> If it behaves like a wave, what can we deduce from that?
If you flip 1000 coins, and it comes up 500 heads and 500 tails, can we
deduce that each flip landed half heads half tails?
> It's an argument that measurement doesn't necessarily tell what was the
> state before the measurement was performed.
But *no* measurement *ever* detects waves. They only detect distributions of
particles that match the mathematics of complex numbers. Waves also match
the mathematics of complex numbers. But not everything that matches the
mathematics of complex numbers is a wave.
>> Yes. But if a photon was a wave, it could interfere with *itself*. It could
>> split up and go through two separate slits. One photon doesn't make an
>> interference pattern, and that's how you know the photon isn't a wave.
>
> That just doesn't convince me. Just because the photon collapses when it
> hits the detector doesn't mean that on the way it didn't pass through both
> slits at the same time and interfered with itself.
Well, you're arguing the question that has confused nobel-prize-winning
physicists. I can only try to explain what I understand them to say. I can't
really convince you per se.
Nobody can figure out what would cause a "collapse", nobody has math that
explains when the collapse happens, nobody has ever observed a particle in a
non-collapsed state.
> It sounds like you are arguing that particles cannot be in superimposed
> states
No, I'm saying they aren't waves. What's superimposed isn't a "wave", but
probabilities. Yes, particles are in superimposed states. That doesn't make
them waves. Since the states particles can be superimposed and tangled up
with the states of other particles, and that tangling does *not* act like a
wave, then it's experimentally determined that superimposed states aren't
waves either. It only looks like a wave if you look at one of them.
> and that there's no collapse phenomenon when they are measured, but
> instead they are always at single places at a time, in particle form.
That's not what I said. You only ever *measure* them in a single place at a
single time in particle form. How would you really know what it's doing if
you never observe it doing it?
There are theoretical reasons to believe it's impossible to observe them
being waves. (Otherwise, they wouldn't be quantum, for example.) Indeed, the
whole "black body radiation" question that started quantum physics falls
down if photons are waves in flight, which is why people stopped thinking
they were waves in the first place: it was impossible to understand
something glowing hot if light is waves.
> other words, that the Copenhagen interpretation is wrong. (Of course, if
> I have understood correctly, nobody has proven that it's right, but you
> are seemingly claiming it's wrong. Has that been proven?)
I think people are still debating, but as far as I know, all the really
smartest people think quantum theory comes in quantums. :-) The whole
problem with the Copenhagen interpretation is that nobody knows why it would
collapse, nobody has any math to explain the collapse, and it doesn't give
you any answer better than you get with "it's never a wave", especially
without being able to explain why it collapses.
Maybe if someone knew what caused the collapse, or under what circumstances
it happened, you could test if Copenhagen was valid or not. But it doesn't
make any predictions the always-a-particle theory makes.
> (Not that I have the slightest idea what I'm talking about. The problem
> I'm having is that, seemingly, people have no idea why the interference
> pattern appears yet are completely sure it's *not* because photons are
> in wave state at any point.)
They know because when you actually put *two* photons together, they *don't*
make an interference pattern. If photons were waves, you wouldn't get
lasers, for example. And they wouldn't interact with electrons in the way
they do, even when you're not "observing" them.
I may have no idea if you start out in your automobile in your driveway
where you got to, but I'm pretty sure you didn't drive to Hawai'i. :-)
>> You
>> don't see half the photon's energy hit here and half hit there with a blank
>> spot in the middle.
>
> You don't see it because if you try to see it, the photon collapses and
> the only thing you see is a particle.
I think it's Occam's Razor here. Why postulate a quantum being a wave if (1)
no observation is capable of ever seeing it as a wave, (2) it behaves in
ways contrary to it being a wave when in flight, and (3) everything you *do*
see can be explained without it ever being a wave?
--
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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Patrick Elliott wrote:
> Ok. Already gave and answer to why this is odd, but.. Just to let you
> clarify - How do you "measure" or "observe" what a particle as even
> done, without colliding it with something?
You don't. But you can make a measurement after it has done something, and
change what it "has done" already.
> definition, anything you can/do do, which looks at a particle, involves
> *other particles*,
Right. But it might involve *other* particles *after* the measurement of
interest has been completed.
> Again, we can't measure/observe a particle, without interacting with it,
Sure you can. Look up Bell's Inequality, or Quantum Erasers.
http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser
> so claiming that "changing" it by observation differs from changing it
> by hitting it with another particle is just... not making any sense at all.
That's what makes the copenhagen interpretation problematic, yes.
--
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:
> I think it's Occam's Razor here. Why postulate a quantum being a wave if (1)
> no observation is capable of ever seeing it as a wave
I suppose that means that all phenomena caused by electromagnetic waves
(which light is) has to be explained by non-wave means, such as for example
electromagnetic radiation having a frequency and amplitude, as well as
exhibiting wave-like behavior such as polarization (how can you polarize
a particle given that polarization is by definition a property of waves
that describes the orientation of their oscillations?) and the effect
electromagnetic waves have on electric conductors (which is what radio and
TV broadcasts, among many other things. are based on).
The effect on eletric conductors is interesting: Electromagnetic waves
cause electrons to move at the same frequency than the frequency of the
incoming radiation, which clearly demonstrates that it does have a
frequency. The amount of movement is proportional to the amplitude of
the incoming radiation, which demonstrates that it does have an amplitude.
The amount of movement is also proportional to the direction of oscillation
of the incoming radiation (something which is also demonstrated by
polarization).
The double-slit experiment also demonstrates wave-like quality.
If it looks like a wave, feels like a wave, smells like a wave, what is it?
Not a wave, it seems. It just fakes being one quite well.
--
- Warp
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Patrick Elliott <sel### [at] npgcablecom> wrote:
> It was never intended to be used to imply that the
> state in such a box could/does exist in the real world.
AFAIK there's a big difference between an analogy and a thought experiment.
An analogy is describing in layman terms something complicated. The analogy
is not to be taken literally, but just as a way to visualize the concept
being explained.
A thought experiment, however, is something which should happen (even if
it's physically unfeasible to put into practice). It's not an analogy, but
an actual phenomenon which should happen if the theory is true and the proper
conditions could be set up.
Schrodinger's cat is a thought experiment, not an analogy.
> And, if you think about it, it can't be otherwise. If you observe a
> particle with a detector, the detector "causes" the state change.
But in the thought experiment the detector already measured the radioactive
particle and caused (or not) the hammer to break the flask. The cat itself
also observes what happens (quite literally). Yet the thought experiment
still maintains that (given that the inside of the box is completely isolated
from the outside), the cat is in two superposed states. Not as an analogy or
figure of speech, but literally.
If the solution were that simple, it wouldn't be a thought experiment
(with multiple possible explanations) at all.
--
- Warp
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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> I think it's Occam's Razor here. Why postulate a quantum being a wave if (1)
>> no observation is capable of ever seeing it as a wave
>
> I suppose that means that all phenomena caused by electromagnetic waves
> (which light is)
I think it's not considered to be an electromagnetic wave any more.
> has to be explained by non-wave means, such as for example
> electromagnetic radiation having a frequency and amplitude,
Yep. Explained.
> as well as
> exhibiting wave-like behavior such as polarization (how can you polarize
> a particle given that polarization is by definition a property of waves
> that describes the orientation of their oscillations?)
Not in QM. I don't know too much about polarization, but it's not purely
based on "wave" stuff.
> and the effect
> electromagnetic waves have on electric conductors (which is what radio and
> TV broadcasts, among many other things. are based on).
Sure. Particles of light hitting the metal of the antenna and knocking
electrons around causes radio reception, for example.
> The effect on eletric conductors is interesting: Electromagnetic waves
> cause electrons to move at the same frequency than the frequency of the
> incoming radiation, which clearly demonstrates that it does have a
> frequency.
The change in quantum-amplitude has a frequency, because you're changing it
in a regular pattern at the transmitter.
> The amount of movement is proportional to the amplitude of
> the incoming radiation,
It's proportional to the number of photons arriving. If by "amplitude" you
mean "strength", then yes. If by "amplitude" you mean what people who talk
about QED mean, then no.
> which demonstrates that it does have an amplitude.
> The amount of movement is also proportional to the direction of oscillation
> of the incoming radiation (something which is also demonstrated by
> polarization).
>
> The double-slit experiment also demonstrates wave-like quality.
>
> If it looks like a wave, feels like a wave, smells like a wave, what is it?
> Not a wave, it seems. It just fakes being one quite well.
As I said, the probability of finding a particle in a particular place is
based on multiplying complex numbers. But since you never actually find a
wave, but only interference patterns (so to speak), it's probably not a
wave. The "wave" properties don't explain *all* the different kinds of
interference, but only the kinds that interfere like waves do. There's also
interference patterns that are the opposite of what you'd get with waves
(lasing vs exclusion principle) that is *also* explained by the theory in
which everything is a particle.
You really should watch the lectures (or read the book) I pointed you to.
They do a very nice job of explaining it. Both the video and the book are
Feynman, who got a nobel prize for figuring out how to explain to other
quantum physicists how to figure out wtf is going on with quantum mechanics,
so it's really quite interesting.
--
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:
> Schrodinger's cat is a thought experiment, not an analogy.
It's not even that hard to set up. :-)
I think the point is that you have to question what an "observation" is. If
the particle gets emitted and runs into the detector when the power is
turned off, is it "observed"? If the power is on but the detector isn't
connected to anything? If it's connected to a speaker you can't hear? If
it's connected to poison but there's no cat in the box? Etc?
In other words, if it takes an "observer" to collapse the wave function, is
the cat enough of an "observer" to count? If so, how does the human get
involved? According to the math, the cat is still superimposed. But that
would imply the cat isn't sufficiently an observer to cause the collapse.
*Or* that the math doesn't match reality. And multi-worlds is an attempt to
say "no, the math really matches reality."
--
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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On 12/02/09 19:06, Darren New wrote:
>> I suppose that means that all phenomena caused by electromagnetic waves
>> (which light is)
>
> I think it's not considered to be an electromagnetic wave any more.
Throughout this thread (which I admit I did not read all of), you've
stated stuff a bit too definitively for my taste, as if all the top
physicists agree on this.
I can only abuse David Mermin's quote: "Shut up and calculate!"
I'm guessing that the actual mathematical formalism that we have for QM
addresses all that is _needed_, in that it always works, and we know of
no phenomenon (except perhaps gravity) that our mathematical formalism
fails at. Given that, having an argument about whether it's a wave or a
particle is philosophy of the pointless kind. The theory will remain
unchanged.
I'm truly baffled as to why y'all are arguing so much about this.
*Knowing* that it's a particle or a wave is not (as far as anyone
knows) going to change physics, or its rules, or even give better
results, or allow you to do better calculations. I'm not even sure if
any of you has bothered to *define* what a particle is or what a wave
is. Without doing so, the argument becomes even more amusing -
especially considering that what an electron/photon is may truly not fit
either one.
Which is likely the view I favor: Notions of particles and waves for
things like photons and electrons are somewhat meaningless Heck, a wave
was "meaningless" for light even before QM was known - what is it waving
in? I'm sure some of your (Darren's) arguments against viewing it as a
wave were as applicable in the 1800's, before QM came around.
Particles/waves, to me, are macroscopic phenomena. Photons and
electrons are described accurately by the mathematical rules in QM.
That's all there is. There's really nothing more to know about it. We
know as much as there is to know about QM as we did classical mechanics.
Ultimately, the latter was also properly described by a mathematical
formalism. We had an illusion that we understood that better merely
because we were used to it in our daily lives. But that's just an illusion.
(OK, I may be exaggerating a tiny bit in the last paragraph, but the
main point is that just because it seems "weird" doesn't mean it's any
weirder than classical mechanics).
>> as well as
>> exhibiting wave-like behavior such as polarization (how can you polarize
>> a particle given that polarization is by definition a property of waves
>> that describes the orientation of their oscillations?)
>
> Not in QM. I don't know too much about polarization, but it's not purely
> based on "wave" stuff.
In general, are you sure polarization cannot be described just by
waves? If you have waves in 3-D materials? FYI, the standard model for
sound waves in solids (i.e. phonons) assumes they have a polarization.
> You really should watch the lectures (or read the book) I pointed you
> to. They do a very nice job of explaining it. Both the video and the
> book are Feynman, who got a nobel prize for figuring out how to explain
> to other quantum physicists how to figure out wtf is going on with
> quantum mechanics, so it's really quite interesting.
I haven't read the book, but my physics professor said that it's THE
book to read (QED) if you want to get an understanding of light/EM
phenomenon.
--
Even if you win the rat race, you are still a rat.
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Neeum Zawan wrote:
> Throughout this thread (which I admit I did not read all of), you've
> stated stuff a bit too definitively for my taste, as if all the top
> physicists agree on this.
I'm just stating my understanding of the general consensus. I freely admit
that maybe they're wrong, but when the guy who got the nobel prize for
explaining to other theoretical pysicists how it works says "It's never ever
a wave", I'm gonna go with his explanation. :-)
> I'm guessing that the actual mathematical formalism that we have for
> QM addresses all that is _needed_, in that it always works, and we know
> of no phenomenon (except perhaps gravity) that our mathematical
> formalism fails at.
The other quantum stuff is similar but not identcail formulas, yes.
> Given that, having an argument about whether it's a
> wave or a particle is philosophy of the pointless kind. The theory will
> remain unchanged.
Yep.
> any of you has bothered to *define* what a particle is or what a wave
> is.
Well, I tried to indirectly describe things a wave would do that a particle
doesn't, but yeah.
> We had an illusion that we understood that better merely
> because we were used to it in our daily lives. But that's just an illusion.
True. It's like asking *why* there are three dimensions, or *why* you
subtract the square of time instead of adding it in GR.
> In general, are you sure polarization cannot be described just by
> waves? If you have waves in 3-D materials? FYI, the standard model for
> sound waves in solids (i.e. phonons) assumes they have a polarization.
I think the effect of polarization of quanta does stuff that polarization
based entirely on the directions of waves can't do, like lasing and fermion
exclusion.
> I haven't read the book, but my physics professor said that it's THE
> book to read (QED) if you want to get an understanding of light/EM
> phenomenon.
Yep. It's awesome, explained by the guy who invented the way to calculate
the stuff *based* on the explanation. The link to the videos is Feynman
presenting the lectures that got edited into the book, which is also
fascinating.
--
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 wrote:
> In other words, if it takes an "observer" to collapse the wave function,
> is the cat enough of an "observer" to count? If so, how does the human
> get involved? According to the math, the cat is still superimposed. But
> that would imply the cat isn't sufficiently an observer to cause the
> collapse. *Or* that the math doesn't match reality. And multi-worlds is
> an attempt to say "no, the math really matches reality."
>
One tends to suspect that, as a thought experiment, it runs into the
same problem as Zeno's Paradox. Which is to say, there is some specific
minimum interaction/time frame/minimal distance, or what ever, in which
something either does *or* doesn't happen, and you can't have it be both
at the same time. In Zeno's case, there is literally a very small, but
provable, distance that you *must* move, if you move at all, and
crossing that line eliminates the paradox (in this case, probably
something like the closest you can get to another particle, without it
nudging the other particle, or something to that effect). They have
already proven, using QM experiments, that they *is* such a limit with
time, and that *before* that point you can nudge a particle back into
what ever state it had prior to measurement, but, anything after that
you are stuck with what ever the prior interaction gave you. The
previous assumption was that such events where instantaneous, and no
such micro-time event was possible.
Thus, the thought experiment is flawed, unless, as I said, you assume
that the entire box, everything in it, and thus what it does, is all
*one* object. A classic case of, "Of course a tree makes a sound if it
falls in an empty forest with no one to see it." The flaw is the
assumption that *someone* has to look into the box. I am not sure how to
put it.. Basically, its like astrology. Imagining that just because a
lot of big stuff is wandering around the universe, the small stuff
**must** be so drastically influenced by it that a cat can actually *be*
in such an indeterminate state. Not so. Either *any* interacting causes
a state change, in which case the cat *must* be in a known state
already, or nothing is, including the poor deluded fool worrying about
whether or not he killed the neighbors cat in the experiment, in which
case we might as well start talking to priest and gurus about
transcendentalism, and give up on physics.
Yeah, there are some goofy theories that sort of allow for it, but most
of them are notable in that they have to do things like throwing out
time, without having any damn math, never mind real theory, about how to
replace it with something that still *acts* like time from our view. Its
one thing to propose a thought experiment, its another to invent an
entire branch of, "this will fill in all the holes, I promise",
'science', which consists of no concrete data, experiments, theories, or
plausible mechanisms, and amounts to nothing *but* a long list of
thought experiments.
People tried that once before. It was called Alchemy, and, within its
own, flawed and incorrect, framework, everything known at the time
"worked" by its rules, including the math involved. It would be nice of
we at least tried to stick with dealing with the universe we can
observe, instead of wandering off into 50,000 of them we can't, trying
to find some weird sort of universe that would **look like** ours, if
stuck inside it. Not even string theory gets that odd, most of the time,
and it, so far, is about as useful at explaining anything as staring at
a something like the "accidental isosuface" thread is *actually* an
accurate method of predicting planet formation.
It might lead some place, maybe. At the moment, even some of the people
that wanted it to lead some place are looking at those studying the math
and thinking, "Ok, so... when are we going to get a theory, never mind
actual useful data, out of this 'science'?" lol
--
void main () {
If Schrödingers_cat is alive or version > 98 {
if version = "Vista" {
call slow_by_half();
call DRM_everything();
}
call functional_code();
}
else
call crash_windows();
}
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