>> No. The "interference" is caused not by the particle, but by the slits.
>
>  How does the photon know there was another slit nearby, and behave
> differently if that was so?

If you could answer exactly how a photon "knows" where it can and can't go 
then you'd probably become quite famous.

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> No. The "interference" is caused not by the particle, but by the slits.
> 
>   How does the photon know there was another slit nearby, and behave
> differently if that was so?

Nobody knows.

-- 
Darren New, San Diego CA, USA (PST)
   Human nature dictates that toothpaste tubes spend
   much longer being almost empty than almost full.

Post a reply to this message

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.

-- 
Darren New, San Diego CA, USA (PST)
   Human nature dictates that toothpaste tubes spend
   much longer being almost empty than almost full.

Post a reply to this message

Warp wrote:
>   It was not sarcasm, it was puzzlement.

I will keep that in mind, then. :-)

Generally speaking, as a native speaker of English, when you express 
something like that as a statement rather than a question, it comes across 
with an invisible "Yeah, right, pull the other one" kind of statement. At 
least to me.  Just so ya know.

-- 
Darren New, San Diego CA, USA (PST)
   Human nature dictates that toothpaste tubes spend
   much longer being almost empty than almost full.

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> > Darren New <dne### [at] sanrrcom> wrote:
> >> No. The "interference" is caused not by the particle, but by the slits.
> > 
> >   How does the photon know there was another slit nearby, and behave
> > differently if that was so?

> Nobody knows.

  But it seems that everybody knows that it does not happen by the photon
going through both slits?

  (After all, it would make sense: If there's no other slit to go through,
then it can't go through two slits, and thus its behavior is different than
if there was another slit and it went through both.)

  Or is this again that kind of almost-supernatural phenomena like the
photon somehow knowing that one year from now it will be measured which
slit it went through and thus it will already know to not to produce the
interference pattern?

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Warp wrote:
>>> Darren New <dne### [at] sanrrcom> wrote:
>>>> No. The "interference" is caused not by the particle, but by the slits.
>>>   How does the photon know there was another slit nearby, and behave
>>> differently if that was so?
> 
>> Nobody knows.
> 
>   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. Nobody has ever measured the 
actual wave-like nature of photons, other than that the probability you 
measure one of those particles at a particular place shares much of the same 
math as waves. (The probability that *two* photons do something does *not* 
share the same math as waves.)

The photon, in some very rare cases, might go through both slits, but not at 
the same time as a wave. Instead, it might actually go in a circle and go 
through both. But it's vanishingly improbable, and maybe even impossible if 
the probabilities actually add up to zero.

Essentially, every single time you find a photon, you find an entire photon. 
There's never a case where you get a half a photon. Hence the "quantum" 
nature of it all. You don't get half a photon just like you never ever find 
an electron with half a charge, and just like you don't find a coin that 
comes up half heads half tails. The only "interference" you get is patterns 
when you measure where lots of photons go.

>   (After all, it would make sense: If there's no other slit to go through,
> then it can't go through two slits, and thus its behavior is different than
> if there was another slit and it went through both.)

But it only goes through one slit if you measure which slit it went thru. 
This is true even *if* you make the measurement *after* the slits. You never 
see the photon going through both slits, like you would if it were actually 
a wave.

>   Or is this again that kind of almost-supernatural phenomena like the
> photon somehow knowing that one year from now it will be measured which
> slit it went through and thus it will already know to not to produce the
> interference pattern?

Again, it's not a question of one photon making an interference pattern. 
It's a bunch of photons making an interference pattern. Any one photon shows 
up all at once and makes a single discrete mark wherever it hits. It's just 
more likely to hit in one area than another.

It's sort of like saying that at a sufficiently small scale, there aren't 
waves in water either. If there's a "high" wave, you're more likely to see a 
molecule of H2O high above the average surface level than if there's a 
trough. You can calculate the probability of H2O molecules being in a 
particular place, but you're never going to see an H2O molecule interfering 
with itself. (At least, not in the "classic" size of water waves.) You can 
ask "how does the beach get more wet near the waterline than higher up if 
water isn't waves?" It's because you're more likely to find an H2O molecule 
close to the waterline than higher up the beach. But that doesn't mean H2O 
is made out of waves.

But in short, yes, it's the same weirdness, which is how people know it's 
not waves per se. Being a wave would imply it's actually the photon itself 
that's controlling where it goes. But we already know you can control where 
the photon goes retroactively, which would obviously make no sense if it was 
deciding based on being a wave. If it's interfering *because* it is going 
through both slits, you wouldn't be able to change whether it went thru both 
slits or not after it already hit the detector. There's something deeply 
unintuitive going on that nobody understands.

BTW, it's also pretty easy to prove it's not something in the photon that we 
can't measure controlling how it works. That's what Bell's Inequality is about.

-- 
Darren New, San Diego CA, USA (PST)
   Human nature dictates that toothpaste tubes spend
   much longer being almost empty than almost full.

Post a reply to this message

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?

> Essentially, every single time you find a photon, you find an entire photon. 
> There's never a case where you get a half a photon.

  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.

> >   (After all, it would make sense: If there's no other slit to go through,
> > then it can't go through two slits, and thus its behavior is different than
> > if there was another slit and it went through both.)

> But it only goes through one slit if you measure which slit it went thru. 
> This is true even *if* you make the measurement *after* the slits. You never 
> see the photon going through both slits, like you would if it were actually 
> a wave.

  You also never see the cat in both live and dead states at the same time.

> >   Or is this again that kind of almost-supernatural phenomena like the
> > photon somehow knowing that one year from now it will be measured which
> > slit it went through and thus it will already know to not to produce the
> > interference pattern?

> Again, it's not a question of one photon making an interference pattern. 
> It's a bunch of photons making an interference pattern. Any one photon shows 
> up all at once and makes a single discrete mark wherever it hits. It's just 
> more likely to hit in one area than another.

  Of course I implied that you perform the test many times and see the overall
pattern that the photons create.

-- 
                                                          - Warp

Post a reply to this message

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.

>   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?

Particle *probabilities* are in superpositions. That doesn't make them waves.

But again, this is a question of "why does it work that way", and not "how 
does it work", and AFAIK nobody knows the underlying reason why the 
probabilities work out the way they do.

>> But it only goes through one slit if you measure which slit it went thru. 
>> This is true even *if* you make the measurement *after* the slits. You never 
>> see the photon going through both slits, like you would if it were actually 
>> a wave.
> 
>   You also never see the cat in both live and dead states at the same time.

That's actually evidence for it being particles and *not* waves. :-)

>> Again, it's not a question of one photon making an interference pattern. 
>> It's a bunch of photons making an interference pattern. Any one photon shows 
>> up all at once and makes a single discrete mark wherever it hits. It's just 
>> more likely to hit in one area than another.
> 
>   Of course I implied that you perform the test many times and see the overall
> pattern that the photons create.

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. You 
don't see half the photon's energy hit here and half hit there with a blank 
spot in the middle.

-- 
Darren New, San Diego CA, USA (PST)
   Human nature dictates that toothpaste tubes spend
   much longer being almost empty than almost full.

Post a reply to this message

Darren New <dne### [at] sanrrcom> 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.

  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).

> >   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?

  If it behaves like a wave, what can we deduce from that?

> >> But it only goes through one slit if you measure which slit it went thru. 
> >> This is true even *if* you make the measurement *after* the slits. You never 
> >> see the photon going through both slits, like you would if it were actually 
> >> a wave.
> > 
> >   You also never see the cat in both live and dead states at the same time.

> That's actually evidence for it being particles and *not* waves. :-)

  It's an argument that measurement doesn't necessarily tell what was the
state before the measurement was performed.

> 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.

  It sounds like you are arguing that particles cannot be in superimposed
states 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. In
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?)

  (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.)

> 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.

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
> Patrick Elliott <sel### [at] npgcablecom> wrote:
>> 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.
> 
>   I think the Copenhagen interpretation goes beyond that. If the decay of
> the radioactive substance causes the flask to be broken, killing the cat,
> it has already been "observed" (by whatever detector caused the flask to
> be broken) and thus there are no superimposed states, but according to
> the Copenhagen interpretation there are, until some external observer opens
> the box.
> 
>   That's the kind of "observation" I don't understand.
> 
But, the Copenhagen interpretation is intended as an example, where by 
the "mechanism" isn't part of the system that causes the observation. 
The presumption being that what ever opens the box to look is what 
*causes* the result. It was never intended to be used to imply that the 
state in such a box could/does exist in the real world. In short, you 
are exaggerating the meaning of the example. There may be others doing 
so too, but most understand that the *entire box*, and the cat inside, 
is the particle, and that the observer is basically what ever "looks" 
into the box to see what happened, which could be an X-Ray machine, for 
all that it matters, or a guy with a crowbar, or just some single 
particle, shot at the box, which "quantum tunnels" through the inside, 
and other the other, carrying some information on the state inside. The 
*observer* is never a conscious observer, it is always, "What ever 
happens to interact with the particle, causing it to change."

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. Turn 
on a flashlight, photons cause the state change. There is no way to 
*observe* an object that doesn't involve us hitting the particle with 
another particle, and measuring what the change in *that* particle is, 
thereby deriving what happened to the other one. All Copenhagen really 
says is, "If nothing is interacting with the particle, the particle's 
state isn't known, but the moment something does (which they confusingly 
termed "observer"), the state becomes fixed." Its sort of like the way 
normal people use "theory" to mean guess, but scientists mean, "already 
supported by evidence". "Observer" doesn't mean what the average person 
would mean by it. Imho, it was a really poor choice, but we are, at this 
point, stuck with it. lol

-- 
void main () {

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

<A HREF='http://www.daz3d.com/index.php?refid=16130551'>Get 3D Models, 
3D Content, and 3D Software at DAZ3D!</A>

Post a reply to this message