| Topic: |
Religions > Atheism |
| User: |
"Elroy Willis" |
| Date: |
27 Apr 2005 11:33:21 PM |
| Object: |
Schrodinger's Cat Stuff |
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
I don't really like the Schrodinger's cat experiment or analogy,
because it seems ridiculous to me to believe that a cat could be both
alive and dead at the same time until someone "opens the box" to take
a peek, so I came up with something along the same line which I think
might be a better analogy...
In order to see or observe where an electron or some other subatomic
particle is at any given moment, we humans have to use some kind of
instrument to detect where they are, and in effect, the observation
itself can cause the particle in question to move or change, thus not
really giving an accurate position of the particle in question. That
is the problem as I see it, but I could be mistaken or misunderstand
the problem...
If, for example, I wanted to see exactly how much my cat's pupils are
dilated in the dark, if I shine a flashlight into his eyes to take a
look, then his eyes will change because of the light shined into
his eyes, and I won't get an accurate measurement.
However, if I use a night-vision light of some sort, which can still
observe or measure my cat's eyes without causing the pupils to
constrict or contract or change due to the light, then I can get an
accurate measurement, and my observation doesn't affect the actual
eyes of my cat.
This isn't possible currently when trying to observe the positions of
subatomic particles, because in order to observe them, we have to
bombard them with other particles or something else which actually
changes their positions, but if it were possible, then we could
actually get accurate measurements, and possibly figure out some
predictable pattern of movement of the particles, from what I
understand.
If we could invent some device which didn't disturb or change the
position or charge or any of the properties of the particles we want
to observe, then perhaps the uncertainty would not be so uncertain at
all, once a pattern is figured out?
--
Elroy Willis
www.elroysemporium.com
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| User: "Ron Baker, Pluralitas!" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 12:26:35 AM |
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"Elroy Willis" <elroywillis@swbell.net> wrote in message
news:ovn071plejmkbb80qt1fglt4apstjj7srq@4ax.com...
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
I don't really like the Schrodinger's cat experiment or analogy,
because it seems ridiculous to me to believe that a cat could be both
alive and dead at the same time until someone "opens the box" to take
a peek, so I came up with something along the same line which I think
might be a better analogy...
Right. That is a case were people wax metaphysical in
trying to explain uncertainty/QM.
In order to see or observe where an electron or some other subatomic
particle is at any given moment, we humans have to use some kind of
instrument to detect where they are, and in effect, the observation
itself can cause the particle in question to move or change, thus not
really giving an accurate position of the particle in question. That
is the problem as I see it, but I could be mistaken or misunderstand
the problem...
Measuring position disturbs momentum.
If you measure position exactly then you can have
no knowledge of momentum.
http://www.aip.org/history/heisenberg/p08a.htm
If, for example, I wanted to see exactly how much my cat's pupils are
dilated in the dark, if I shine a flashlight into his eyes to take a
look, then his eyes will change because of the light shined into
his eyes, and I won't get an accurate measurement.
However, if I use a night-vision light of some sort, which can still
observe or measure my cat's eyes without causing the pupils to
constrict or contract or change due to the light, then I can get an
accurate measurement, and my observation doesn't affect the actual
eyes of my cat.
This isn't possible currently when trying to observe the positions of
subatomic particles, because in order to observe them, we have to
bombard them with other particles or something else which actually
changes their positions,
Momentum.
but if it were possible, then we could
actually get accurate measurements, and possibly figure out some
predictable pattern of movement of the particles, from what I
understand.
If we could invent some device which didn't disturb or change the
position or charge or any of the properties of the particles we want
to observe, then perhaps the uncertainty would not be so uncertain at
all, once a pattern is figured out?
Are you going to invent something smaller and lighter
than a photon?
To measure something you have to probe it with something.
Photons are small and light. They least disturb the thing being
measured. But the smaller they are the more momentum they
have. The less momementum they have the bigger they are.
That is an immutable law of physics.
A photon is the smallest ruler we have but
unfortunately they are effectively made out of rubber.
The physical law that dictates that also applies to everything else in
the universe. The photon and the thing being measured and everything in
the universe, at that microscopic level, is just as rubbery.
There is no inventing a better ruler.
--
rb #2187
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| User: "JTEM" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 12:48:52 AM |
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"Ron Baker, Pluralitas!" <stoshu@bellsouth.net.pa> wrote
"Elroy Willis" <elroywillis@swbell.net> wrote
If we could invent some device which didn't disturb or
change the position or charge or any of the properties
of the particles we want to observe, then perhaps the
uncertainty would not be so uncertain at all, once a
pattern is figured out?
Are you going to invent something smaller and lighter
than a photon?
You don't have to. A far simpler (though vastly beyond
any means I know of) way of doing it is to take numerous,
standardized measurements.
If you could figure out a way of, say, taking 100
measurements on the same particle, you could plot
them and get a good sense as to how your measurements
were changing things, and then work backwards from
there.
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| User: "Ron Baker, Pluralitas!" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 02:34:40 AM |
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"JTEM" <gymraven@hotmail.com> wrote in message
news:Kqudnd_RAPym6u3fRVn-1w@comcast.com...
"Ron Baker, Pluralitas!" <stoshu@bellsouth.net.pa> wrote
"Elroy Willis" <elroywillis@swbell.net> wrote
If we could invent some device which didn't disturb or
change the position or charge or any of the properties
of the particles we want to observe, then perhaps the
uncertainty would not be so uncertain at all, once a
pattern is figured out?
Are you going to invent something smaller and lighter
than a photon?
You don't have to. A far simpler (though vastly beyond
any means I know of) way of doing it is to take numerous,
standardized measurements.
If you could figure out a way of, say, taking 100
measurements on the same particle, you could plot
them and get a good sense as to how your measurements
were changing things, and then work backwards from
there.
Won't work. Can't be done. At the quantum level
everything is subject to the same uncertainty. You can't
produce a photon of a known position AND momentum.
Whatever photons you might have, when you use them to measure
the position of another particle you don't get its momentum
and you change its momentum. You can't control or repeat
the conditions of the particles.
This is not some odd little annoyance that hasn't received
proper attention. It is a major aspect of modern physics.
This has been thoroughly examined by thousands of PhDs for
almost 100 years now. They all know that they would
win a Nobel prize if they could eliminate uncertainty
at the microscopic level. No experiment has ever contradicted
uncertainty.
--
rb #2187
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| User: "Kenny Leong" |
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| Title: Re: Schrodinger's Cat Stuff |
29 Apr 2005 07:56:15 AM |
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Elroy Willis <elroywillis@swbell.net> wrote in message news:<ovn071plejmkbb80qt1fglt4apstjj7srq@4ax.com>...
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
Kenny
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
29 Apr 2005 08:55:10 AM |
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(Kenny Leong) wrote in alt.atheism
Elroy Willis <elroywillis@swbell.net> wrote in message
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal
gas or whatever it's supposed to be to kill the cat, I think if the
cat was dead, you'd start to smell it before long, and I don't think
smelling an odor causes the source of the odor to change in some
way, but I could be wrong...
--
Elroy Willis
www.elroysemporium.com
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| User: "Josef Balluch" |
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| Title: Re: Schrodinger's Cat Stuff |
29 Apr 2005 09:37:25 PM |
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In a message sent 'round the world, Elroy Willis poured fuel on the fire
with the following:
kenny_tm_leong@yahoo.com (Kenny Leong) wrote in alt.atheism
....
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
No, QM considers the cat to be in a superposition of states. The cat is
both alive and dead while it is unobserved.
http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci341263,00.html
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal
gas or whatever it's supposed to be to kill the cat, I think if the
cat was dead, you'd start to smell it before long, and I don't think
smelling an odor causes the source of the odor to change in some
way, but I could be wrong...
Sniffing the air is an observation, just as looking in the box would be.
Making an observation collapses the wave function, if one accepts a
"collapse" hypothesis.
Regards,
Josef
Nature free at once and rid of her haughty lords is seen to do all
things spontaneously of herself without the meddling of the gods.
-- Lucretius
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| User: "Barry OGrady" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 07:44:33 AM |
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On Fri, 29 Apr 2005 22:37:25 -0400, Josef Balluch <josef.balluch@sympatico.can> wrote:
In a message sent 'round the world, Elroy Willis poured fuel on the fire
with the following:
kenny_tm_leong@yahoo.com (Kenny Leong) wrote in alt.atheism
...
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
No, QM considers the cat to be in a superposition of states. The cat is
both alive and dead while it is unobserved.
That sort of nonsense is what gives QM a bad name.
http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci341263,00.html
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal
gas or whatever it's supposed to be to kill the cat, I think if the
cat was dead, you'd start to smell it before long, and I don't think
smelling an odor causes the source of the odor to change in some
way, but I could be wrong...
Sniffing the air is an observation, just as looking in the box would be.
Making an observation collapses the wave function, if one accepts a
"collapse" hypothesis.
That's another statement that bring ridicule upon QM.
Regards,
Josef
Barry
=====
Home page
http://members.iinet.net.au/~barry.og
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 09:20:08 AM |
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Barry OGrady <atheist.xxx@gmail.com> wrote in alt.atheism
Josef Balluch <josef.balluch@sympatico.can> wrote:
In a message sent 'round the world, Elroy Willis said:
kenny_tm_leong@yahoo.com (Kenny Leong) wrote in alt.atheism
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
No, QM considers the cat to be in a superposition of states. The cat is
both alive and dead while it is unobserved.
That sort of nonsense is what gives QM a bad name.
Indeed. The idea is preposterous!
http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci341263,00.html
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal
gas or whatever it's supposed to be to kill the cat, I think if the
cat was dead, you'd start to smell it before long, and I don't think
smelling an odor causes the source of the odor to change in some
way, but I could be wrong...
Sniffing the air is an observation, just as looking in the box would be.
Making an observation collapses the wave function, if one accepts a
"collapse" hypothesis.
That's another statement that bring ridicule upon QM.
The whole "wave function collapse" idea is unbelievable to me, since
it can lead to the idea that a falling tree doesn't make any sound if
there are no animals around to notice the sound, as if the presence
of some observer actually causes the sound to be made in the first
place, instead of them just observing it or hearing it, or in the case
of a rotting cat in a box, smelling the odor of the dead cat.
--
Elroy Willis
www.elroysemporium.com
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| User: "Mark K. Bilbo" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 10:08:40 PM |
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In our last episode <vvru71dggajbvib47eugdj07tmsfeva7uh@4ax.com>, Elroy
Willis pirouetted gracefully and with great fanfare proclaimed:
Barry OGrady <atheist.xxx@gmail.com> wrote in alt.atheism
Josef Balluch <josef.balluch@sympatico.can> wrote:
In a message sent 'round the world, Elroy Willis said:
kenny_tm_leong@yahoo.com (Kenny Leong) wrote in alt.atheism
The half-live and half-dead cat analogy doesn't seem right. I just
try to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
No, QM considers the cat to be in a superposition of states. The cat is
both alive and dead while it is unobserved.
That sort of nonsense is what gives QM a bad name.
Indeed. The idea is preposterous!
Thing is, just about every one of those "weird" quantum effects has been
done in the lab. They really do happen.
Such as in quantum computing. Superpositioning of states is one of the
foundations. As I'm sure you already know, in a regular computer, a bit
can have two states: one or zero. In a quantum computer, a "qubit" can
have *both states: one *and zero (though I believe, technically, a qubit
has four states). And it's real enough that IBM built a rudimentary
quantum computer with 5 qubits about, oh, five years ago. I'm sure they're
further along now.
Interesting thing about quantum computers is you must *not observe their
states or they decohere and won't be quantum computers anymore. It took
some finesse to get the results of the computation out of the computer.
http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci341263,00.html
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal gas or
whatever it's supposed to be to kill the cat, I think if the cat was
dead, you'd start to smell it before long, and I don't think smelling
an odor causes the source of the odor to change in some way, but I
could be wrong...
Sniffing the air is an observation, just as looking in the box would
be. Making an observation collapses the wave function, if one accepts a
"collapse" hypothesis.
That's another statement that bring ridicule upon QM.
The whole "wave function collapse" idea is unbelievable to me, since it
can lead to the idea that a falling tree doesn't make any sound if there
are no animals around to notice the sound, as if the presence of some
observer actually causes the sound to be made in the first place, instead
of them just observing it or hearing it, or in the case of a rotting cat
in a box, smelling the odor of the dead cat.
No it wouldn't mean that. The issue is whether quantum effects can matter
at the macro level. A tree falling isn't a quantum effect, it's not the
same thing.
I understand that in recent years, most lean toward "decoherence" as an
explanation for why we don't see "Schrodinger's cat" kinds of events.
Superposed states are believed to be unstable and easily perturbed. Just
about *any disturbance in the environment collapses the wave function. Not
just an "observation." So the cat may for a time be in an indeterminate
state but it's for a very, very, very brief time. So brief as to be
essentially irrelevant at the macro level.
--
Mark K. Bilbo - a.a. #1423
EAC Department of Linguistic Subversion
Group website at: http://www.alt-atheism.org
-----------------------------------------------------------
"Religion is regarded by the common people as true,
by the wise as false, and by the rulers as useful."
-- Seneca the Younger
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
10 May 2005 11:39:30 AM |
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Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Elroy Willis wrote:
The whole "wave function collapse" idea is unbelievable to me, since it
can lead to the idea that a falling tree doesn't make any sound if there
are no animals around to notice the sound, as if the presence of some
observer actually causes the sound to be made in the first place, instead
of them just observing it or hearing it, or in the case of a rotting cat
in a box, smelling the odor of the dead cat.
No it wouldn't mean that. The issue is whether quantum effects can matter
at the macro level. A tree falling isn't a quantum effect, it's not the
same thing.
I understand that in recent years, most lean toward "decoherence" as an
explanation for why we don't see "Schrodinger's cat" kinds of events.
Superposed states are believed to be unstable and easily perturbed. Just
about *any disturbance in the environment collapses the wave function. Not
just an "observation." So the cat may for a time be in an indeterminate
state but it's for a very, very, very brief time. So brief as to be
essentially irrelevant at the macro level.
I guess that's where I was having trouble visualizing the whole
experiment. If the cat was both dead and alive or in some
indeterminate state for something like a day or more, then it'd be a
problem, but if it's only for a few microseconds, then it's no biggie.
--
Elroy Willis
www.elroysemporium.com
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| User: "wcb" |
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| Title: Re: Schrodinger's Cat Stuff |
10 May 2005 05:10:59 PM |
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Elroy Willis wrote:
Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Elroy Willis wrote:
The whole "wave function collapse" idea is unbelievable to me, since it
can lead to the idea that a falling tree doesn't make any sound if there
are no animals around to notice the sound, as if the presence of some
observer actually causes the sound to be made in the first place,
instead of them just observing it or hearing it, or in the case of a
rotting cat in a box, smelling the odor of the dead cat.
No it wouldn't mean that. The issue is whether quantum effects can matter
at the macro level. A tree falling isn't a quantum effect, it's not the
same thing.
I understand that in recent years, most lean toward "decoherence" as an
explanation for why we don't see "Schrodinger's cat" kinds of events.
Superposed states are believed to be unstable and easily perturbed. Just
about *any disturbance in the environment collapses the wave function.
Not just an "observation." So the cat may for a time be in an
indeterminate state but it's for a very, very, very brief time. So brief
as to be essentially irrelevant at the macro level.
I guess that's where I was having trouble visualizing the whole
experiment. If the cat was both dead and alive or in some
indeterminate state for something like a day or more, then it'd be a
problem, but if it's only for a few microseconds, then it's no biggie.
No, its still a problem. What Schroeding was criticizing is the idea that a
collection of particles, a cat in this case, has a wave function, that is a
quantum charateristic of particles, not large conglomerations of particles.
A cat having a wave function leads to the odd conclusion of a cat neither
idea nor alive.
Since everybody gets this wrong, its not a good reductio ad absurdum as
designed.
It does not matter if its a microsecond or a year, the same principle
applies.
There was another reductio offered at that time, imagine a small
city. It is destroyed by an atomic bomb.
There is an automatic camera that periodically took pictures
every few seconds of the city.
It is beyond the city and is recovered whole and sound.
When does the wave function of the city collapse?
When the film is developed?
When it is viewed?
If the janitor sees a picture, and its just a blob he does
not recognize or understand, does that collapse the wave
function? Or does it have to be somebody who knows what the
film is about to collapse the wave function?
Because of these and other obscure reductio ad absurdums,
many physicists have rejected a lot of quantum weirdness type
phenomenon.
Not wave functions as per se, but what it all means.
From hereon out we get into some heavy duty physics and
there are a LOT of experiments that need to be known and
understood to continue. Double slit experiments over
long periods of time with individual particles for example.
But what is seen and what it all means should not be confused.
--
When I shake my killfile, I can hear them buzzing!
Cheerful Charlie
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| User: "Mark K. Bilbo" |
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| Title: Re: Schrodinger's Cat Stuff |
10 May 2005 07:14:41 PM |
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In our last episode <1182btemgnla460@corp.supernews.com>, wcb pirouetted
gracefully and with great fanfare proclaimed:
Elroy Willis wrote:
Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Elroy Willis wrote:
The whole "wave function collapse" idea is unbelievable to me, since
it can lead to the idea that a falling tree doesn't make any sound if
there are no animals around to notice the sound, as if the presence of
some observer actually causes the sound to be made in the first place,
instead of them just observing it or hearing it, or in the case of a
rotting cat in a box, smelling the odor of the dead cat.
No it wouldn't mean that. The issue is whether quantum effects can
matter at the macro level. A tree falling isn't a quantum effect, it's
not the same thing.
I understand that in recent years, most lean toward "decoherence" as an
explanation for why we don't see "Schrodinger's cat" kinds of events.
Superposed states are believed to be unstable and easily perturbed.
Just about *any disturbance in the environment collapses the wave
function. Not just an "observation." So the cat may for a time be in an
indeterminate state but it's for a very, very, very brief time. So
brief as to be essentially irrelevant at the macro level.
I guess that's where I was having trouble visualizing the whole
experiment. If the cat was both dead and alive or in some indeterminate
state for something like a day or more, then it'd be a problem, but if
it's only for a few microseconds, then it's no biggie.
No, its still a problem. What Schroeding was criticizing is the idea that
a collection of particles, a cat in this case, has a wave function, that
is a quantum charateristic of particles, not large conglomerations of
particles.
A cat having a wave function leads to the odd conclusion of a cat neither
idea nor alive.
Since everybody gets this wrong, its not a good reductio ad absurdum as
designed.
It does not matter if its a microsecond or a year, the same principle
applies.
There was another reductio offered at that time, imagine a small city. It
is destroyed by an atomic bomb. There is an automatic camera that
periodically took pictures every few seconds of the city.
It is beyond the city and is recovered whole and sound.
When does the wave function of the city collapse? When the film is
developed?
When it is viewed?
If the janitor sees a picture, and its just a blob he does not recognize
or understand, does that collapse the wave function? Or does it have to be
somebody who knows what the film is about to collapse the wave function?
From what I understand about decoherence, the "observer effect" has been
essentially discarded. It seems to be thought that interaction with the
environment collapses the wave function without the need for an "observer"
to be involved (it would seem to me that "observation" would be subsumed
as it is a type of interaction with the environment).
So unless a system is "closed" and completely isolated, the wave function
collapses almost instantaneously whether an "observer" is around or not...
--
Mark K. Bilbo - a.a. #1423
EAC Department of Linguistic Subversion
Group website at: http://www.alt-atheism.org
-----------------------------------------------------------
"Religion is regarded by the common people as true,
by the wise as false, and by the rulers as useful."
-- Seneca the Younger
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| User: "Gregory Gadow" |
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| Title: Re: Schrodinger's Cat Stuff |
11 May 2005 10:36:42 AM |
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"Mark K. Bilbo" wrote:
From what I understand about decoherence, the "observer effect" has been
essentially discarded. It seems to be thought that interaction with the
environment collapses the wave function without the need for an "observer"
to be involved (it would seem to me that "observation" would be subsumed
as it is a type of interaction with the environment).
So unless a system is "closed" and completely isolated, the wave function
collapses almost instantaneously whether an "observer" is around or not...
Actually, experiments have shown that the observer effect is fundamentally
correct. The trick is not to fall in to anthropomorphism, where humans are the
only observers. The moon isn't going to disappear into a smear of probable
locations just because no one is looking at it; everything affected by the
moon's gravity acts as a perpetual observer, keeping it's collective wave
function collapsed. At subatomic scales, however, it is easier to find occasions
where nothing is "looking;" at quantum scales, it is more common than not.
I'm reading right now "The Fabric of the Cosmos" by Brian Greene, author of "The
Elegant Universe" and the narrator of the Nova series by the same name. It's a
bit dumbed down but still very readable and interesting. With your thoughts
turning to things improbable, it might be just the thing you are looking for :-P
--
Gregory Gadow
techbear@serv.net
http://www.serv.net/~techbear
"I contend that we are both atheists. I just believe
in one fewer god than you do. When you understand
why you dismiss all the other possible gods, you
will understand why I dismiss yours."
-Stephen F. Roberts
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
15 May 2005 06:01:40 PM |
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Gregory Gadow <techbear@serv.net> wrote in alt.atheism
"Mark K. Bilbo" wrote:
From what I understand about decoherence, the "observer effect" has been
essentially discarded. It seems to be thought that interaction with the
environment collapses the wave function without the need for an "observer"
to be involved (it would seem to me that "observation" would be subsumed
as it is a type of interaction with the environment).
So unless a system is "closed" and completely isolated, the wave function
collapses almost instantaneously whether an "observer" is around or not...
Actually, experiments have shown that the observer effect is fundamentally
correct. The trick is not to fall in to anthropomorphism, where humans are the
only observers.
This is what always bugged me about the tree falling in the forest
scenario. What if a bird observed it, instead of a human? What if
some mushroom on the forest floor was crushed by the falling tree?
As long as something, no matter how small, even a subatomic particle,
was affected by the falling tree, then I see no difference.
The moon isn't going to disappear into a smear of probable
locations just because no one is looking at it; everything affected by
the moon's gravity acts as a perpetual observer, keeping it's collective wave
function collapsed. At subatomic scales, however, it is easier to find occasions
where nothing is "looking;" at quantum scales, it is more common than not.
Even at a subatomic scale, a falling tree is going to interact with
something around it, right?
I'm reading right now "The Fabric of the Cosmos" by Brian Greene, author
of "The Elegant Universe" and the narrator of the Nova series by the same
name. It's a bit dumbed down but still very readable and interesting. With
your thoughts turning to things improbable, it might be just the thing you are
looking for :-P
I watched a show on the science channel narrated by Jane Curtain the
other day, for the second or maybe third time, and the way the quantum
world was depicted seemed to be intentionally mysterious, just to
confuse people, imo.
--
Elroy Willis
www.elroysemporium.com
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| User: "wcb" |
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| Title: Re: Schrodinger's Cat Stuff |
10 May 2005 11:12:31 PM |
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Mark K. Bilbo wrote:
In our last episode <1182btemgnla460@corp.supernews.com>, wcb pirouetted
gracefully and with great fanfare proclaimed:
Elroy Willis wrote:
Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Elroy Willis wrote:
The whole "wave function collapse" idea is unbelievable to me, since
it can lead to the idea that a falling tree doesn't make any sound if
there are no animals around to notice the sound, as if the presence of
some observer actually causes the sound to be made in the first place,
instead of them just observing it or hearing it, or in the case of a
rotting cat in a box, smelling the odor of the dead cat.
No it wouldn't mean that. The issue is whether quantum effects can
matter at the macro level. A tree falling isn't a quantum effect, it's
not the same thing.
I understand that in recent years, most lean toward "decoherence" as an
explanation for why we don't see "Schrodinger's cat" kinds of events.
Superposed states are believed to be unstable and easily perturbed.
Just about *any disturbance in the environment collapses the wave
function. Not just an "observation." So the cat may for a time be in an
indeterminate state but it's for a very, very, very brief time. So
brief as to be essentially irrelevant at the macro level.
I guess that's where I was having trouble visualizing the whole
experiment. If the cat was both dead and alive or in some indeterminate
state for something like a day or more, then it'd be a problem, but if
it's only for a few microseconds, then it's no biggie.
No, its still a problem. What Schroeding was criticizing is the idea
that a collection of particles, a cat in this case, has a wave function,
that is a quantum charateristic of particles, not large conglomerations
of particles.
A cat having a wave function leads to the odd conclusion of a cat neither
idea nor alive.
Since everybody gets this wrong, its not a good reductio ad absurdum as
designed.
It does not matter if its a microsecond or a year, the same principle
applies.
There was another reductio offered at that time, imagine a small city. It
is destroyed by an atomic bomb. There is an automatic camera that
periodically took pictures every few seconds of the city.
It is beyond the city and is recovered whole and sound.
When does the wave function of the city collapse? When the film is
developed?
When it is viewed?
If the janitor sees a picture, and its just a blob he does not recognize
or understand, does that collapse the wave function? Or does it have to
be somebody who knows what the film is about to collapse the wave
function?
From what I understand about decoherence, the "observer effect" has been
essentially discarded. It seems to be thought that interaction with the
environment collapses the wave function without the need for an "observer"
to be involved (it would seem to me that "observation" would be subsumed
as it is a type of interaction with the environment).
Yes. There are many who do not hold with the observer effect
this way. And some who still do. The problem is, the observer effect
is neither provable,nor adds anything to physics.
Many think interaction is a better theory. The question is,what
sort of interactions do collapse wave functions? And not everybody
believes in wave functions as defined.
So unless a system is "closed" and completely isolated, the wave function
collapses almost instantaneously whether an "observer" is around or not...
--
When I shake my killfile, I can hear them buzzing!
Cheerful Charlie
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| User: "Mark K. Bilbo" |
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| Title: Re: Schrodinger's Cat Stuff |
10 May 2005 02:25:14 PM |
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In our last episode <lho181hvs7miamq5lh43n538md38117r0l@4ax.com>, Elroy
Willis pirouetted gracefully and with great fanfare proclaimed:
Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Elroy Willis wrote:
The whole "wave function collapse" idea is unbelievable to me, since it
can lead to the idea that a falling tree doesn't make any sound if
there are no animals around to notice the sound, as if the presence of
some observer actually causes the sound to be made in the first place,
instead of them just observing it or hearing it, or in the case of a
rotting cat in a box, smelling the odor of the dead cat.
No it wouldn't mean that. The issue is whether quantum effects can
matter at the macro level. A tree falling isn't a quantum effect, it's
not the same thing.
I understand that in recent years, most lean toward "decoherence" as an
explanation for why we don't see "Schrodinger's cat" kinds of events.
Superposed states are believed to be unstable and easily perturbed. Just
about *any disturbance in the environment collapses the wave function.
Not just an "observation." So the cat may for a time be in an
indeterminate state but it's for a very, very, very brief time. So brief
as to be essentially irrelevant at the macro level.
I guess that's where I was having trouble visualizing the whole
experiment. If the cat was both dead and alive or in some indeterminate
state for something like a day or more, then it'd be a problem, but if
it's only for a few microseconds, then it's no biggie.
It's one of the more confusing things about the quantum is how the world
of "common sense" manages to emerge from such *weirdness. The weirdness is
really there, it's been confirmed in spades. But at least it politely
stays down in the quantum world. <g>
Or maybe you could say the macro world *is the "effect" of quantum
weirdness?
To the extent I understand decoherence so far, it's that the environment
in which the Schrodinger's cat "experiment" could be done just doesn't
exist. I know when IBM built their little quantum computer, they had to go
to great lengths to keep the system from being perturbed.
--
Mark K. Bilbo - a.a. #1423
EAC Department of Linguistic Subversion
Group website at: http://www.alt-atheism.org
-----------------------------------------------------------
"Religion is regarded by the common people as true,
by the wise as false, and by the rulers as useful."
-- Seneca the Younger
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| User: "wcb" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 02:37:40 PM |
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Barry OGrady wrote:
On Fri, 29 Apr 2005 22:37:25 -0400, Josef Balluch
<josef.balluch@sympatico.can> wrote:
In a message sent 'round the world, Elroy Willis poured fuel on the fire
with the following:
kenny_tm_leong@yahoo.com (Kenny Leong) wrote in alt.atheism
...
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
No, QM considers the cat to be in a superposition of states. The cat is
both alive and dead while it is unobserved.
That sort of nonsense is what gives QM a bad name.
Schroedinger developed his cat thought experiment to criticize
this sort of nonsense.
--
When I shake my killfile, I can hear them buzzing!
Cheerful Charlie
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| User: "Mark K. Bilbo" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 04:18:39 PM |
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In our last episode <q9fu71dnipcesmfp1aihf0gusrh3raupqv@4ax.com>, Barry
OGrady pirouetted gracefully and with great fanfare proclaimed:
On Fri, 29 Apr 2005 22:37:25 -0400, Josef Balluch
<josef.balluch@sympatico.can> wrote:
In a message sent 'round the world, Elroy Willis poured fuel on the fire
with the following:
kenny_tm_leong@yahoo.com (Kenny Leong) wrote in alt.atheism
...
The half-live and half-dead cat analogy doesn't seem right. I just
try to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
No, QM considers the cat to be in a superposition of states. The cat is
both alive and dead while it is unobserved.
That sort of nonsense is what gives QM a bad name.
http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci341263,00.html
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal gas or
whatever it's supposed to be to kill the cat, I think if the cat was
dead, you'd start to smell it before long, and I don't think smelling
an odor causes the source of the odor to change in some way, but I
could be wrong...
Sniffing the air is an observation, just as looking in the box would be.
Making an observation collapses the wave function, if one accepts a
"collapse" hypothesis.
That's another statement that bring ridicule upon QM.
That must be why it's regarded as one of the most successful theories in
the history of science...
--
Mark K. Bilbo - a.a. #1423
EAC Department of Linguistic Subversion
Group website at: http://www.alt-atheism.org
-----------------------------------------------------------
"Religion is regarded by the common people as true,
by the wise as false, and by the rulers as useful."
-- Seneca the Younger
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 05:59:29 PM |
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Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Barry OGrady pirouetted gracefully and with great fanfare proclaimed:
Josef Balluch <josef.balluch@sympatico.can> wrote:
Elroy Willis poured fuel on the fire with the following:
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal gas or
whatever it's supposed to be to kill the cat, I think if the cat was
dead, you'd start to smell it before long, and I don't think smelling
an odor causes the source of the odor to change in some way, but I
could be wrong...
Sniffing the air is an observation, just as looking in the box would be.
Making an observation collapses the wave function, if one accepts a
"collapse" hypothesis.
That's another statement that bring ridicule upon QM.
That must be why it's regarded as one of the most successful theories in
the history of science...
<scoff scoff>
--
Elroy Willis
www.elroysemporium.com
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| User: "Mark K. Bilbo" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 07:47:44 PM |
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In our last episode <2nqv711r75oqdg5qdgvcr92r7i099kfqhu@4ax.com>, Elroy
Willis pirouetted gracefully and with great fanfare proclaimed:
Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Barry OGrady pirouetted gracefully and with great fanfare proclaimed:
Josef Balluch <josef.balluch@sympatico.can> wrote:
Elroy Willis poured fuel on the fire with the following:
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal gas or
whatever it's supposed to be to kill the cat, I think if the cat was
dead, you'd start to smell it before long, and I don't think smelling
an odor causes the source of the odor to change in some way, but I
could be wrong...
Sniffing the air is an observation, just as looking in the box would
be. Making an observation collapses the wave function, if one accepts
a "collapse" hypothesis.
That's another statement that bring ridicule upon QM.
That must be why it's regarded as one of the most successful theories in
the history of science...
<scoff scoff>
Eh?
--
Mark K. Bilbo - a.a. #1423
EAC Department of Linguistic Subversion
Group website at: http://www.alt-atheism.org
-----------------------------------------------------------
"Religion is regarded by the common people as true,
by the wise as false, and by the rulers as useful."
-- Seneca the Younger
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
10 May 2005 11:40:50 AM |
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Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Elroy Willis pirouetted gracefully and with great fanfare proclaimed:
Mark K. Bilbo <alt-atheism@org.webmaster> wrote in alt.atheism
Barry OGrady pirouetted gracefully and with great fanfare proclaimed:
Josef Balluch <josef.balluch@sympatico.can> wrote:
Elroy Willis poured fuel on the fire with the following:
I thought it was about the uncertainty of the state of the cat, but
even without some cosmic particle triggering a dose of lethal gas or
whatever it's supposed to be to kill the cat, I think if the cat was
dead, you'd start to smell it before long, and I don't think smelling
an odor causes the source of the odor to change in some way, but I
could be wrong...
Sniffing the air is an observation, just as looking in the box would
be. Making an observation collapses the wave function, if one accepts
a "collapse" hypothesis.
That's another statement that bring ridicule upon QM.
That must be why it's regarded as one of the most successful theories in
the history of science...
<scoff scoff>
Eh?
I was pretending to be Einstein. :)
--
Elroy Willis
www.elroysemporium.com
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| User: "Barry OGrady" |
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| Title: Re: Schrodinger's Cat Stuff |
09 May 2005 07:44:33 AM |
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On 29 Apr 2005 05:56:15 -0700, (Kenny Leong) wrote:
Elroy Willis <elroywillis@swbell.net> wrote in message news:<ovn071plejmkbb80qt1fglt4apstjj7srq@4ax.com>...
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
The half-live and half-dead cat analogy doesn't seem right. I just try
to picture the quantum system as taught... a vector who's basic
components are probabilities (or really amplitudes of probabilities).
So I think it's really about probabilities of a cat is alive or
dead....and not about a cat being semi-alive or semi-dead... right?
The cat is either dead or alive. Not knowing does not mean it is both.
Kenny
Barry
=====
Home page
http://members.iinet.net.au/~barry.og
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| User: "Gregory Gadow" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 08:49:56 AM |
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Elroy Willis wrote:
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
I don't really like the Schrodinger's cat experiment or analogy,
because it seems ridiculous to me to believe that a cat could be both
alive and dead at the same time until someone "opens the box" to take
a peek,
A common misinterpretation. The cat is *neither* dead nor alive; the
"polarity" of its "liveness" is indeterminate. That indetermination is
removed and the polarity of its liveness becomes fixed once the liveness
is measured.
- snip -
I don't think the Uncertainty Principle *can* be explained easily.
Particles do not, as such, exist; there is only a locus of probabilities
of where the phenomena we think of as particles might be found.
A "particle" in "motion" traces out a probability curve, a line of where
particle phenomina is most likely to be found; that gives you the
"particle's" vector. But the "particle" can be found *anywhere* along that
probability curve, and the more precicely you have defined the vector, the
less you know about where the "particle" is at any given moment. Collapse
that probability curve to a single point, and you have no idea of where
that "particle" was or where it is most likely to pop up next: you have
it's location but not it's vector.
Cat's do share some of these characteristics. If a cat is on the prowl,
you have no idea where it will pop up next, but you can trace a
probability curve of likely places (it has been scientifically proven that
cats are more likely to pop up under your feet when you are handling the
holiday china and crystal than when you are putting away the everyday
stuff, for example.) If you know the location of a cat precicely, it is
most likely asleep and therefore has no vector. Even so, the comparison
between subatomic "particles" and cats is imperfect.
--
Gregory Gadow
techbear@serv.net
http://www.serv.net/~techbear
"I contend that we are both atheists. I just believe
in one fewer god than you do. When you understand
why you dismiss all the other possible gods, you
will understand why I dismiss yours."
-Stephen F. Roberts
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| User: "Mark Stahl" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 01:15:46 PM |
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"Gregory Gadow" <techbear@serv.net> wrote in message
news:4270EA04.CAD7D855@serv.net...
Elroy Willis wrote:
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
I don't really like the Schrodinger's cat experiment or analogy,
because it seems ridiculous to me to believe that a cat could be both
alive and dead at the same time until someone "opens the box" to take
a peek,
A common misinterpretation. The cat is *neither* dead nor alive; the
"polarity" of its "liveness" is indeterminate. That indetermination is
removed and the polarity of its liveness becomes fixed once the liveness
is measured.
- snip -
I don't think the Uncertainty Principle *can* be explained easily.
Particles do not, as such, exist; there is only a locus of probabilities
of where the phenomena we think of as particles might be found.
A "particle" in "motion" traces out a probability curve, a line of where
particle phenomina is most likely to be found; that gives you the
"particle's" vector. But the "particle" can be found *anywhere* along that
probability curve, and the more precicely you have defined the vector, the
less you know about where the "particle" is at any given moment. Collapse
that probability curve to a single point, and you have no idea of where
that "particle" was or where it is most likely to pop up next: you have
it's location but not it's vector.
Cat's do share some of these characteristics. If a cat is on the prowl,
you have no idea where it will pop up next, but you can trace a
probability curve of likely places (it has been scientifically proven that
cats are more likely to pop up under your feet when you are handling the
holiday china and crystal than when you are putting away the everyday
stuff, for example.) If you know the location of a cat precicely, it is
most likely asleep and therefore has no vector. Even so, the comparison
between subatomic "particles" and cats is imperfect.
Just to be clear (I'm sure you know this, but for others who are reading):
the comparison is not *really* between cats and subatomic particles. The
thought experiment has a real quantum event as its trigger-- the decay of a
radioactive isotope, IIRC, that sets off a detector that kills the cat.
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 07:55:40 PM |
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Mark Stahl <stahl@nospam.aecom.yu.edu> wrote in alt.atheism
Gregory Gadow <techbear@serv.net> wrote in message
Cat's do share some of these characteristics. If a cat is on the prowl,
you have no idea where it will pop up next, but you can trace a
probability curve of likely places (it has been scientifically proven that
cats are more likely to pop up under your feet when you are handling the
holiday china and crystal than when you are putting away the everyday
stuff, for example.) If you know the location of a cat precicely, it is
most likely asleep and therefore has no vector. Even so, the comparison
between subatomic "particles" and cats is imperfect.
Just to be clear (I'm sure you know this, but for others who are reading):
the comparison is not *really* between cats and subatomic particles. The
thought experiment has a real quantum event as its trigger-- the decay of a
radioactive isotope, IIRC, that sets off a detector that kills the cat.
It could just as well be a neutrino or some other cosmic particle sent
or caused by an exploding star in some galaxy far far away, right?
The same type particle that might zap a sperm cell and cause a
mutation in a new baby if that particular sperm cell managed to
impregnate a female egg, right?
--
Elroy Willis
www.elroysemporium.com
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 09:30:55 AM |
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Gregory Gadow <techbear@serv.net> wrote in alt.atheism
A "particle" in "motion" traces out a probability curve, a line of where
particle phenomina is most likely to be found; that gives you the
"particle's" vector. But the "particle" can be found *anywhere* along that
probability curve, and the more precicely you have defined the vector, the
less you know about where the "particle" is at any given moment. Collapse
that probability curve to a single point, and you have no idea of where
that "particle" was or where it is most likely to pop up next: you have
it's location but not it's vector.
How then, can quantum computing be reliable?
--
Elroy Willis
www.elroysemporium.com
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| User: "Gregory Gadow" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 10:16:55 AM |
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Elroy Willis wrote:
Gregory Gadow <techbear@serv.net> wrote in alt.atheism
A "particle" in "motion" traces out a probability curve, a line of where
particle phenomina is most likely to be found; that gives you the
"particle's" vector. But the "particle" can be found *anywhere* along that
probability curve, and the more precicely you have defined the vector, the
less you know about where the "particle" is at any given moment. Collapse
that probability curve to a single point, and you have no idea of where
that "particle" was or where it is most likely to pop up next: you have
it's location but not it's vector.
How then, can quantum computing be reliable?
My understanding is that it uses probability functions similar to those used to
describe "particles," then collapse the functions to get a strong probability of
correctness.
Where a digital computer might, after a few tens of thousands of computations,
come up with a precise answer of 5.575, a quantum computer might, after a few
scores of computations, come up wth an answer that 96% likely to be 5.6, more or
less. With the quantum calculations taking so fewer operations, you can repeat
the calculation several times and average out the answer to approach 5.575.
The real strength, though, is that the probability functions can be set up with
a predefined "resolution." If you want a result with 100 decimal places, you can
have the probability function collapse to an answer with 100 decimal places.
Average together 10 such results, and you very quickly have an answer with a
high probability of being the 100 decimal place result you need, and *much*
faster than you would have it doing conventional computations. A public/private
key encryption algorythim that would take an average of 10,000 years to decrypt
using brute force with conventional computers should be doable in about 2 hours
using quantum computing methods.
Scientific American has covered the topic of quantum computings several times in
the last few years. If you are interested in the subject, check them out; I
believe they have an archive.
--
Gregory Gadow
techbear@serv.net
http://www.serv.net/~techbear
"I contend that we are both atheists. I just believe
in one fewer god than you do. When you understand
why you dismiss all the other possible gods, you
will understand why I dismiss yours."
-Stephen F. Roberts
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| User: "Elroy Willis" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 11:03:11 AM |
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Gregory Gadow <techbear@serv.net> wrote in alt.atheism
Elroy Willis wrote:
Gregory Gadow <techbear@serv.net> wrote in alt.atheism
A "particle" in "motion" traces out a probability curve, a line of where
particle phenomina is most likely to be found; that gives you the
"particle's" vector. But the "particle" can be found *anywhere* along that
probability curve, and the more precicely you have defined the vector, the
less you know about where the "particle" is at any given moment. Collapse
that probability curve to a single point, and you have no idea of where
that "particle" was or where it is most likely to pop up next: you have
it's location but not it's vector.
How then, can quantum computing be reliable?
My understanding is that it uses probability functions similar to those used to
describe "particles," then collapse the functions to get a strong probability of
correctness.
Where a digital computer might, after a few tens of thousands of computations,
come up with a precise answer of 5.575, a quantum computer might, after a few
scores of computations, come up wth an answer that 96% likely to be 5.6, more or
less. With the quantum calculations taking so fewer operations, you can repeat
the calculation several times and average out the answer to approach 5.575.
The real strength, though, is that the probability functions can be set up with
a predefined "resolution." If you want a result with 100 decimal places, you can
have the probability function collapse to an answer with 100 decimal places.
Average together 10 such results, and you very quickly have an answer with a
high probability of being the 100 decimal place result you need, and *much*
faster than you would have it doing conventional computations. A public/private
key encryption algorythim that would take an average of 10,000 years to decrypt
using brute force with conventional computers should be doable in about 2 hours
using quantum computing methods.
I'm sure that must be attractive to the military, eh?
Scientific American has covered the topic of quantum computings several times in
the last few years. If you are interested in the subject, check them out; I
believe they have an archive.
The November 2004 issue has an interesting-looking article:
"What is the difference between a computer and a black hole? This
question sounds like the start of a Microsoft joke, but it is one of
the most profound problems in physics today. Most people think of
computers as specialized gizmos: streamlined boxes sitting on a desk
or fingernail-size chips embedded in high-tech coffeepots. But to a
physicist, all physical systems are computers. Rocks, atom bombs and
galaxies may not run Linux, but they, too, register and process
information."
Hmm...
--
Elroy Willis
www.elroysemporium.com
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| User: "Kevin Anthoney" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 03:40:30 PM |
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Gregory Gadow wrote:
Elroy Willis wrote:
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
I don't really like the Schrodinger's cat experiment or analogy,
because it seems ridiculous to me to believe that a cat could be both
alive and dead at the same time until someone "opens the box" to take
a peek,
A common misinterpretation. The cat is *neither* dead nor alive; the
"polarity" of its "liveness" is indeterminate. That indetermination is
removed and the polarity of its liveness becomes fixed once the liveness
is measured.
Sure about that? The wave function inside the box is that of a dead cat
superimposed on one of a live cat. Saying the cat is both dead and alive is
a perfectly valid way of looking at things.
Don't forget that the purpose of the thought experiment is to point out what
Schrödinger thought was ridiculous about the Copenhagen Interpretation. It
was never meant to be a serious illustration of Quantum Mechanics, so it's
not worth picking over the details.
--
Kevin Anthoney
kanthoney[a]dsl.pipex.com
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| User: "Josef Balluch" |
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| Title: Re: Schrodinger's Cat Stuff |
28 Apr 2005 07:25:32 PM |
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In a message sent 'round the world, Elroy Willis poured fuel on the fire
with the following:
I'd like some feedback on an example I'm trying to explain to a friend
of mine who's having a hard time understanding quantum mechanics
and the uncertainty principle.
I don't really like the Schrodinger's cat experiment or analogy,
because it seems ridiculous to me to believe that a cat could be both
alive and dead at the same time until someone "opens the box" to take
a peek, ...
Yes, some quantum physicists also feel that way. This is an example of
a "collapse" hypothesis, with the Copenhagen Interpretation being the
most popular such hypothesis. There are other interpretations of QM
besides this.
BTW, Schrodinger's cat is not an illustration of quantum uncertainty. It
illustrates the superposition of quantum states. The "uncertainty" is
one of knowing which quantum state the system will be found in. The
uncertainty problem you describe below is Heisenberg's baby. It is an
uncertainty or limitation in the accuracy of measurements.
... so I came up with something along the same line which I think
might be a better analogy...
In order to see or observe where an electron or some other subatomic
particle is at any given moment, we humans have to use some kind of
instrument to detect where they are, and in effect, the observation
itself can cause the particle in question to move or change, thus not
really giving an accurate position of the particle in question. That
is the problem as I see it, but I could be mistaken or misunderstand
the problem...
That basically is the problem. Or was ..... See below.
If, for example, I wanted to see exactly how much my cat's pupils are
dilated in the dark, if I shine a flashlight into his eyes to take a
look, then his eyes will change because of the light shined into
his eyes, and I won't get an accurate measurement.
You can use a digital camera with flash. The measurement will not
disturb the cat's pupils, but the cat will be upset! Or half upset, if
it was Schrodinger's cat. ;^)
....
This isn't possible currently when trying to observe the positions of
subatomic particles, because in order to observe them, we have to
bombard them with other particles or something else which actually
changes their positions, but if it were possible, then we could
actually get accurate measurements, and possibly figure out some
predictable pattern of movement of the particles, from what I
understand.
If we could invent some device which didn't disturb or change the
position or charge or any of the properties of the particles we want
to observe, then perhaps the uncertainty would not be so uncertain at
all, once a pattern is figured out?
Until recently it was not thought possible to avoid disturbance while
making a quantum measurement. But a way has been found, and was reported
in the November 96 Scientific American. This particular method is only
successful 50% of the time, meaning that some measurements will be
disturbed, but not all. Unfortunately, SciAm no longer provides free on
line access to their archives. The local library might be able to help
you here.
Regards,
Josef
The Heisenberg Uncertainty Principle:
If you know where you are then you ain't going anywhere.
If you know how fast you are going then you are lost.
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