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Giltwist
Skeptic Friend
USA
69 Posts |
 Posted - 06/10/2005 : 05:18:28 [Permalink]
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quote:
Since the position and motion of all particles can only successfully be described by a probability, there is no determinism in physics.
So what you're saying is that its another instance of the macro scale vs the micro scale? On the macro scale it SEEMS like there's determinism, but on a quantum level there isn't
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After an hour, the cat has a 50% chance of being alive or dead. Which one is it? Assuming the box is soundproof, etc. we have no way to tell. Thus, the cat is assumed to be both alive and dead until the box is opened and the results of the experiment are directly observed.
So it's a koan?
If a tree falls in the woods and nobody's around to hear it...
G. |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 06/10/2005 : 05:52:49 [Permalink]
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quote:
If a tree falls in the woods and nobody's around to hear it...
No... Shroedinger was being critical of the idea that subatomic particles don't appear to follow the same set of rules as larger objects.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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Giltwist
Skeptic Friend
USA
69 Posts |
Posted - 06/10/2005 : 05:58:37 [Permalink]
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quote:
Shroedinger was being critical of the idea that subatomic particles don't appear to follow the same set of rules as larger objects.
I'd love to know where the demarcation line between micro and macro is and why it's there. Damn it! Now I have one more question to answer ;) |
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Boron10
Religion Moderator
USA
1266 Posts |
Posted - 06/10/2005 : 06:34:26 [Permalink]
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quote:
Originally posted by Giltwist
So what you're saying is that its another instance of the macro scale vs the micro scale? On the macro scale it SEEMS like there's determinism, but on a quantum level there isn't
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I'd love to know where the demarcation line between micro and macro is and why it's there.
There is actually almost no difference between the micro wavefunction and the macro wavefunction; however, they both have the same scale of uncertanty. That is, the position uncertainty for the planet is about the same order of magnitude as the position uncertainty for a given atom. Since the scales are so different, you treat macroscopic objects as if there is no uncertainty.
To make an analogy, it's like saying there's a $1000 uncertainty in a high school student's bank account vice a $1000 uncertainty in Bill Gate's bank account. There is still uncertainty, it just doesn't really matter for Bill Gates.
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So it's a koan?
Hmm... Quantum Zen. That has an interesting ring to it. |
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woolytoad
Skeptic Friend
313 Posts |
Posted - 06/10/2005 : 07:50:30 [Permalink]
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Well, w.r.t the cat in particular, yes is it mostly just a math thing. But superposition of states do occur. Take Young's double slit experiment. You will still get the diffraction pattern if you used a light source so dim that only a single photon was shot towards the slits at one time. Which shows that a single photon goes through both slits! Young's experiment carried out with detectors inside the slits, will result in no interference pattern. The act of making a measurement will change the quantum state of the system we want to measure!
Actually Baron10, the wavelengths of macroscopic objects is much much much smaller than that of particles. Recall De Broglie's Wavelength.
wavelength = plank's constant/momentum
also
energy = momentum*c = plank's const*c/wavelength
So a subatomic particle with kinetic energy of 1keV
wavelength = 1240eV.nm (look it up) /1000eV = 1.24nm
Wavelength of a baseball of mass .2kg and speed 10m/s:
momentum = .2*10 = 2kgm/s
wavelength = h/2kgm/s = 3x10^-34m
The baseball has a wavelength that is 25 orders of magnitude smaller.
Demarcation of theories is easy. When a particular theory starts producing bad results, chuck it and try a new one. For example trying to apply the aerodynamics that explains air plane flight to an insect. |
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Boron10
Religion Moderator
USA
1266 Posts |
Posted - 06/10/2005 : 08:12:39 [Permalink]
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quote:
Originally posted by woolytoad
Actually Baron10, the wavelengths of macroscopic objects is much much much smaller than that of particles. Recall De Broglie's Wavelength.
Good point, I had forgotten (it's been a few years since I've played with that.
For any who want to look, the University of Colorado (Boulder) has a good simplified web-based lecture on the double-slit experiment. |
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 06/10/2005 : 08:55:39 [Permalink]
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I'd like to add, that making people look like idiots is an unfortunate by-product of skepticism in general. That we are viewed as narrow minded a-holes is only a natural reaction to this problem, and one that will not go away.
Also Ive noticed that those skeptics who seem to enjoy tearing apart others beliefs are usually only because they have had to listen to the same wrong info repeated endlessly year after year, when the correct information is clearly available. This pisses us off. |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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Giltwist
Skeptic Friend
USA
69 Posts |
Posted - 06/10/2005 : 10:18:34 [Permalink]
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quote:
Hmm... Quantum Zen. That has an interesting ring to it.
I concur ^_^
quote:
To make an analogy, it's like saying there's a $1000 uncertainty in a high school student's bank account vice a $1000 uncertainty in Bill Gate's bank account. There is still uncertainty, it just doesn't really matter for Bill Gates.
Ah, that's neat.
W.R.T. the double slit experiment, that IS a mind-boggler isn't it. I've heard as one possible explanation an interaction with a neighboring brane.
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repeated endlessly year after year, when the correct information is clearly available.
I can understand that. In the words of C.S. Lewis, humans have a certain horror at the concept of The Same Old Thing. Unfortunately, some of the clearly available information is mystified by technical terminology. Also, people tend to encounter things in a different order from each other. So, essentially there will always be someone asking a question, even if it does already have an answer.
Thanks all,
G. |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 06/10/2005 : 16:14:47 [Permalink]
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quote:
Originally posted by Dave W.
It's a math thing, H. The "superposition of states" with a live and dead cat at the same time doesn't actually occur, it only exists when examining the equations that describe the state of the cat. Obviously, there are a lot of map/terrain problems involved in classic QM thought experiments.
Well, I've heard both. I understand that in "math world" the cat is both alive and not alive. I also understand that to a mathematician, it isn't even a consideration to think of the cat as alive or not since for all intents and purposes, it doesn't matter to him.
But I've also heard many people say that this "math world" scenario is an accurate reflection of our reality. That the observer is necessary to create reality--to "lock it down" into one state from a sea of probability. (I'm not sure why all observers seem to catch objects in the same "state" so often, then.) Obviously, this has more profound metaphysical implications, to which Einstein famously objected "I like to think the moon is still there even when I'm not looking at it."
But there is still that disconnect between the behavior of things on the macro level and things on the quantum level. Most physicists seem not really to worry about it. The "observer" theory works as a model whether it's really true or not. I don't know. I've just never been comfortable with that notion.
I did read about a new theory this guy was working on to explain this in last months issue of Discover. His idea is that gravity, which most quantum physicists discount as too weak to affect their equations, plays a roll. Essentially, his idea is that low mass objects can exist in multiple locations (exerting multiple distortions in space-time) because they need so little energy. Gravity's affect is negligible. But larger objects--about the size of a dust speck on up--need too much energy to distort space-time, and so collapse into the lowest energy state possible (a single position), which is why we don't perceive objects in multiple locations simultaneously.
Or at least that's my best layman's interpretation. I'll try to dig that article up if anyone's interested. Discover has a website but you need a subscription to view their articles.
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
| Edited by - H. Humbert on 06/10/2005 16:24:40 |
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woolytoad
Skeptic Friend
313 Posts |
Posted - 06/10/2005 : 18:08:32 [Permalink]
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quote:
Originally posted by H. Humbert
The "observer" theory works as a model whether it's really true or not. I don't know. I've just never been comfortable with that notion.
Do you think anyone is comfortable with it? As my first quantum lecturer told the class, "If you think you understand it, you probably don't." But this has all the elements required to satisfy a skeptic. So you've got to at least accept it.
What's the original topic again? |
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Giltwist
Skeptic Friend
USA
69 Posts |
Posted - 06/10/2005 : 18:27:08 [Permalink]
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quote:
Obviously, this has more profound metaphysical implications, to which Einstein famously objected "I like to think the moon is still there even when I'm not looking at it."
Actually, isn't that one of the more philosophy attempts to define what God is? The eternal observer? The entity who continuously observes everything so that the moon doesn't disappear when we aren't looking at it?
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Gravity's affect is negligible.
Speaking of gravity, I'd like to point out that the effect of gravity would make any physical object in the universe "observed" simply because everything exerts gravity on everything else. Even if you didn't look into the box, the cumulative effect of gravity would be subtly different if the cat's heart stopped beating and it slumped over. |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 06/10/2005 : 18:44:33 [Permalink]
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quote:
Originally posted by woolytoad
But this has all the elements required to satisfy a skeptic. So you've got to at least accept it.
I need to accept it so far as it applies to quantum equations, which I've never actually done. I don't need to accept that it applies to macro reality any more than I would accept the idea that a peculiar race of demons exists everywhere someone isn't looking at any particular moment. It might agree with my perception of reality, but that says nothing about whether it's actually true. For now, I believe it's true of "math world" only. As I mentioned, there are enough competing theories to the "observer" theory that one doesn't necessarily need to accept it.
quote:
Originally posted by Giltwist
Actually, isn't that one of the more philosophy attempts to define what God is? The eternal observer? The entity who continuously observes everything so that the moon doesn't disappear when we aren't looking at it?
Yes, that's been one of philosophical/religious implications drawn from the theory, but I don't believe that idea was the basis for devising it. Personally, as I really don't accept the intial premise, I certainly am not going to accept the existence of an added deity on top of that.
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
| Edited by - H. Humbert on 06/10/2005 19:26:38 |
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Giltwist
Skeptic Friend
USA
69 Posts |
Posted - 06/10/2005 : 19:01:29 [Permalink]
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| Yeah, I don't really buy the need for observation either. What happens when I'm asleep and nobody is observing me? Poof! Kinda the problem with some of Des Cartes' stuff as I recall. Sure, you can't doubt you are doubting, but what happens when you stop doubting? |
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woolytoad
Skeptic Friend
313 Posts |
Posted - 06/10/2005 : 19:37:59 [Permalink]
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You need to think laterally about the definition of "observer". All they are really talking about is having an interaction take place. When you are sleeping and there's no one around, you are still interacting with the bed, air, everything. You can achieve a sufficient level of isolation to keep some quantum properties unaffected though.
While I agree that we do not know exactly what is happening, "observation" does have an effect. Again with Young's double slit. If you fire single photons or electrons at a double slit, you still get the interference pattern. Put a detector inside the slits (to count individual photons/electrons say) and the pattern disappears. The particles are clearly not in just one place until we try to measure each one. |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 06/10/2005 : 20:01:52 [Permalink]
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quote:
Originally posted by woolytoad
While I agree that we do not know exactly what is happening, "observation" does have an effect. Again with Young's double slit. If you fire single photons or electrons at a double slit, you still get the interference pattern. Put a detector inside the slits (to count individual photons/electrons say) and the pattern disappears. The particles are clearly not in just one place until we try to measure each one.
Yes, but don't the detectors interfere with the photons in some way? It isn't just "observing" which changes the experiment, it's actually introducing a detector that interacts with the particles.
And again, what happens if you run the experiment with tennis balls? Clearly, whatever is going on, it isn't analagous to what happens on the macro scale, observed or not.
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You can achieve a sufficient level of isolation to keep some quantum properties unaffected though.
Not sure what you mean here. Can you explain?
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
| Edited by - H. Humbert on 06/10/2005 20:05:01 |
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