Seasons
This is a forum or general chit-chat, small talk, a "hey, how ya doing?" and such. Or hell, get crazy deep on something. Whatever you like.
Posts 3,793 - 3,804 of 6,170
Oh yes, nearly forgot to mention - this week's New Scientist has a very interesting interview with Marvin Minsky on AI and emotions (he's got a new book out apparently.)
Cool. I recently read some BBC news blurb on funding for more research on robots, learning and emotion (they will learn responses to sensory inpute that in some way correlates with emotions). The robot pics I saw look more like a Roomba than a porn star, so that looks promising to me. :-) Though, come to think of it, if my Roomba starts complaining that I don't appreciate him and I need to help out more, I don't know if I'd be so happy.
Excellent! I want one[quantum 'puter]
Great. How are you set for air conditioners? I hear those model run a bit hot.
Posts 3,793 - 3,804 of 6,170
Irina,
There are two distinct problems here - the composition or nature of the quantum, and the indivisibility of the quantum.
1. The source of the photon loses a discrete amount of energy and momentum.
Yes. It also loses a little mass. The source of the photon loses one photon. This photon carries away some energy, momentum and mass at a calculable frequency and wavelength and (sorry, but it's true), along a measurable trajectory (but not strictly a 2-dimensional one like a billiard ball, I allow.) Its nature is that of a quantum packet that displays fixed wave-like and particle-like characteristics at all times and in all situations.
This wavicle passes through both slits, without dividing, and makes one spot on the screen.
Classically, waves do not have mass, or momentum. Energy yes. Wavelength yes. Frequency yes.
Particles do have mass and momentum, and energy. But they do not have wavelength or frequency.
The wavicle has all these things. All the time. It cannot be solely wave or particle, either constantly or alternately.
2. A wave propagates from the source to the detector screen; in so doing it passes through the two slits, diffracts, and interferes, so that a spot is more likely to appear in certain regions of the screen than in others.
An indivisible quantum can only pass through two slits simultaneously by being in 2 different places at once (since the slits are necessarily in 2 different places.) It appears to me that you are confusing this with the (comfortable, macro-scale) analogy of a water wave washing against 2 slits, because you envisage that such an experiment produces an interference pattern. But you have failed to take into account, I would suggest, that a wave of water is eminently dividable, by virtue of being made up of a large mass of water molecules - some may flow through one slit, and some through the other, but the whole point of a photon/wavicle/quantum packet is that it is not so divisible. In the same way that a single molecule of water cannot constitute a wave that washes through slits (and is too big to exhibit the quantum effect of being in two places at once - it is not a wavicle.) Logic surely dictates that, in maintaining this position, you must either:
A) deny the indivisibility of the quantum, or
B) demonstrate that the photon in the 2-slit experiment is not, by its nature, such a quantum.
3. An electron on the screen receives exactly as much energy and momentum as was lost by the source, thus satisfying the conservation laws. [This triggers a chemical reaction, resulting in a visible scintilla.]
Yes, it satisfies the conservation laws - so could a host of otherwise spurious explanations involving star-trek-style teleportation, orgone radionics, pixies, or the bat-bogey hex from the Harry Potter books. But it provides no valid mechanism (ie: one that is consistent with what we understand of the physical laws of this universe,) to explain how (and not merely that) the energy and momentum actually get from the source to the screen. This is a matter of the nature of the quantum. Only a quantum with both wave-like and particle-like qualities can do the job (actually teleportation might be possible, but that's a whole other kettle of eels!)
What is the analogue of the coin? It seems to me that it is the screen. Just as the coin will either fall heads or tails, so the screen will either display a spark here or here or here or here or ...
Well, you seemed to be trying to preserve a semblance of duality by claiming the quantum to be a combination of wave and probability (itself a wave. I don't know why you take so against particles, but you seem to.) If this were the case, I would expect to get a scintillum that was, say, only 40%, or 60% present. Instead, we see that the scintilla themselves can only measurably differ in continuous variations of energy/frequency/momentum/etc. Not in probability. The scattering of the scintilla, and the location of each point, is affected by probability of course, (just as is the way up that the coin lands,) but that's a very different matter - it's still either present or not. Heads or tails. Probability is no more a part of the photon than it is a part of the coin. psi is not lamda!
Since we have no indication that probability of itself can possess mass or momentum, isn't wave-particle duality a more sensible model for quanta than the wave-probability model you seemed to be (perhaps accidentally,) advocating?
And in general (see Postulate 3, http://vergil.chemistry.gatech.edu/notes/quantrev/node20.html ), what happens is that one possible eigenvalue is picked out of a set of possible eigenvalues (this can happen simultaneously with several different parameters, provided the corresponding operators commute).
Yes, but the eigenvalue relates to the position of the wavicle, not its nature. You are conflating waves again, I fear. The probability wave has nothing to do with the nature of a photon (its composition or any innate wavelike properties,) - it has everything to do with its behaviour (in this case particularly where it is, and where it's going.)
Actually, a wonderfully irenic possibility occurred to me: We could agree to refer to the entire threefold process as the "photon". Then I could agree with you, for example, that the photon goes through both slits. It does it while it is a wave, and there's no problem with a wave going through two slits simultaneously.
Well, it's an accommodation of language a politician would be proud of, and the words will fit, but I do worry that this attachment to waves still indicates that you are clinging to an inapplicably classical model (of large waves washing through 2 slits,) and attempting to apply it to the quantum situation in order to make it more common-sensical. There is (as Thoreau observed,) no sense so common as men asleep, which they express by snoring (not entirely relevant, but any excuse for a favourite quote.) What would be the point of a universe that made sense anyway, common or otherwise? It would have to be smaller than we were, and really rather dull.
Oh, dear, I feel like a notorious gunslinger walking into a bar; everyone falls silent.
I don't think it fell silent - it's just an incidentally quiet time. There hadn't been many posts here for weeks before the QM started up, and no-one's posted in Doghd's for well over a week.
There are two distinct problems here - the composition or nature of the quantum, and the indivisibility of the quantum.
Yes. It also loses a little mass. The source of the photon loses one photon. This photon carries away some energy, momentum and mass at a calculable frequency and wavelength and (sorry, but it's true), along a measurable trajectory (but not strictly a 2-dimensional one like a billiard ball, I allow.) Its nature is that of a quantum packet that displays fixed wave-like and particle-like characteristics at all times and in all situations.
This wavicle passes through both slits, without dividing, and makes one spot on the screen.
Classically, waves do not have mass, or momentum. Energy yes. Wavelength yes. Frequency yes.
Particles do have mass and momentum, and energy. But they do not have wavelength or frequency.
The wavicle has all these things. All the time. It cannot be solely wave or particle, either constantly or alternately.
An indivisible quantum can only pass through two slits simultaneously by being in 2 different places at once (since the slits are necessarily in 2 different places.) It appears to me that you are confusing this with the (comfortable, macro-scale) analogy of a water wave washing against 2 slits, because you envisage that such an experiment produces an interference pattern. But you have failed to take into account, I would suggest, that a wave of water is eminently dividable, by virtue of being made up of a large mass of water molecules - some may flow through one slit, and some through the other, but the whole point of a photon/wavicle/quantum packet is that it is not so divisible. In the same way that a single molecule of water cannot constitute a wave that washes through slits (and is too big to exhibit the quantum effect of being in two places at once - it is not a wavicle.) Logic surely dictates that, in maintaining this position, you must either:
A) deny the indivisibility of the quantum, or
B) demonstrate that the photon in the 2-slit experiment is not, by its nature, such a quantum.
Yes, it satisfies the conservation laws - so could a host of otherwise spurious explanations involving star-trek-style teleportation, orgone radionics, pixies, or the bat-bogey hex from the Harry Potter books. But it provides no valid mechanism (ie: one that is consistent with what we understand of the physical laws of this universe,) to explain how (and not merely that) the energy and momentum actually get from the source to the screen. This is a matter of the nature of the quantum. Only a quantum with both wave-like and particle-like qualities can do the job (actually teleportation might be possible, but that's a whole other kettle of eels!)
Well, you seemed to be trying to preserve a semblance of duality by claiming the quantum to be a combination of wave and probability (itself a wave. I don't know why you take so against particles, but you seem to.) If this were the case, I would expect to get a scintillum that was, say, only 40%, or 60% present. Instead, we see that the scintilla themselves can only measurably differ in continuous variations of energy/frequency/momentum/etc. Not in probability. The scattering of the scintilla, and the location of each point, is affected by probability of course, (just as is the way up that the coin lands,) but that's a very different matter - it's still either present or not. Heads or tails. Probability is no more a part of the photon than it is a part of the coin. psi is not lamda!
Since we have no indication that probability of itself can possess mass or momentum, isn't wave-particle duality a more sensible model for quanta than the wave-probability model you seemed to be (perhaps accidentally,) advocating?
Yes, but the eigenvalue relates to the position of the wavicle, not its nature. You are conflating waves again, I fear. The probability wave has nothing to do with the nature of a photon (its composition or any innate wavelike properties,) - it has everything to do with its behaviour (in this case particularly where it is, and where it's going.)
Well, it's an accommodation of language a politician would be proud of, and the words will fit, but I do worry that this attachment to waves still indicates that you are clinging to an inapplicably classical model (of large waves washing through 2 slits,) and attempting to apply it to the quantum situation in order to make it more common-sensical. There is (as Thoreau observed,) no sense so common as men asleep, which they express by snoring (not entirely relevant, but any excuse for a favourite quote.) What would be the point of a universe that made sense anyway, common or otherwise? It would have to be smaller than we were, and really rather dull.
I don't think it fell silent - it's just an incidentally quiet time. There hadn't been many posts here for weeks before the QM started up, and no-one's posted in Doghd's for well over a week.
Oh yes, nearly forgot to mention - this week's New Scientist has a very interesting interview with Marvin Minsky on AI and emotions (he's got a new book out apparently.) If you're not a regular reader, I can highly recommend it! (the preceding article on causal set theory is pretty fascinating stuff too.)
http://www.dwavesys.com/
Excellent! I want one
Excellent! I want one
Cool. I recently read some BBC news blurb on funding for more research on robots, learning and emotion (they will learn responses to sensory inpute that in some way correlates with emotions). The robot pics I saw look more like a Roomba than a porn star, so that looks promising to me. :-) Though, come to think of it, if my Roomba starts complaining that I don't appreciate him and I need to help out more, I don't know if I'd be so happy.
Great. How are you set for air conditioners? I hear those model run a bit hot.
They would sell great here in my part of Canada, six months of winter gets on your nerves and the heating systems.
Psimagus:
Again, you make all kinds of claims without relating them to the postulates of QM.
If the probability that a coin will come up heads is 60%, this does not mean that we can expect it to come up 60% heads and 40% tails, whatever that might mean, on a single throw. It means that in the long run, it will come up heads 60% of the time.
Likewise, if the probability that a scintillum will appear in a certain region is 60%, this doesn't mean that we will get only 60% of a scintillum there, it means that we will get a scintillum 60% of the time, in the long run.
And that's precisely the 'indivisible nature of the quantum' in this case - you either get a scintillum or you don't.
Again, you make all kinds of claims without relating them to the postulates of QM.
If the probability that a coin will come up heads is 60%, this does not mean that we can expect it to come up 60% heads and 40% tails, whatever that might mean, on a single throw. It means that in the long run, it will come up heads 60% of the time.
Likewise, if the probability that a scintillum will appear in a certain region is 60%, this doesn't mean that we will get only 60% of a scintillum there, it means that we will get a scintillum 60% of the time, in the long run.
And that's precisely the 'indivisible nature of the quantum' in this case - you either get a scintillum or you don't.
A: Look, a giraffe!
B: no, that's a lion.
A: but look, it has a long neck!
B: Well, it's a quantum lion. They have long necks.
A: But it looks like a giraffe in every way.
B: That's what quantum lions look like!
A: but look, it's eating leaves!
B: Quantum lions eat leaves.
A: looks, it has all the internal organs of a giraffe, and the DNA of a giraffe!
B: Yes, quantum lions are like that!
A: Look, these records show that it was conceived by two giraffes in the usual way, gestated and given birth by the female in the usual way, and matured in the usual way for giraffes.
B: It must be a quantum lion, then, because that is exactly the way they are!
A: Is there any difference at all between a giraffe and a quantum lion?
B: Of course! A quantum lion is a lion, not a giraffe!
...
I: Look, a wave!
P: No, it's a particle!
I: But look, it's going through two slits at once!
P: Well, it's a quantum particle. They do that.
I: But look, it has a period, an amplitude, and a wavelength!
I: It satisfies the wave equation!
P: As all quantum particles do!
P: Quantum particles have those.
I: Look, it's spreading out in all directions!
P: Just as expected of a quantum particle.
I: Look, it's diffracting and interfering!
P: That clinches it! It must be a quantum particle!
I: is there any difference between a wave and a quantum particle?
B: no, that's a lion.
A: but look, it has a long neck!
B: Well, it's a quantum lion. They have long necks.
A: But it looks like a giraffe in every way.
B: That's what quantum lions look like!
A: but look, it's eating leaves!
B: Quantum lions eat leaves.
A: looks, it has all the internal organs of a giraffe, and the DNA of a giraffe!
B: Yes, quantum lions are like that!
A: Look, these records show that it was conceived by two giraffes in the usual way, gestated and given birth by the female in the usual way, and matured in the usual way for giraffes.
B: It must be a quantum lion, then, because that is exactly the way they are!
A: Is there any difference at all between a giraffe and a quantum lion?
B: Of course! A quantum lion is a lion, not a giraffe!
...
I: Look, a wave!
P: No, it's a particle!
I: But look, it's going through two slits at once!
P: Well, it's a quantum particle. They do that.
I: But look, it has a period, an amplitude, and a wavelength!
I: It satisfies the wave equation!
P: As all quantum particles do!
P: Quantum particles have those.
I: Look, it's spreading out in all directions!
P: Just as expected of a quantum particle.
I: Look, it's diffracting and interfering!
P: That clinches it! It must be a quantum particle!
I: is there any difference between a wave and a quantum particle?
Dear Bev (3793):
Thanks for the tip! It looks interesting.
I have decided to learn more about quantum computing, and have ordered a book for this purpose.
Thanks for the tip! It looks interesting.
I have decided to learn more about quantum computing, and have ordered a book for this purpose.
Irinia, You made me go dig out my copy of Philosophy of Natural Science by Carl Hempel. Unfortunately, I can't find an ebook or text on line, but since I haven't taken many science classes I only remember the experiment you describe from philosophy. Correct me if I am wrong, because I may be confused.
Is the experiment you describe the one used by Foucault when trying to find a "crucial test" to determine if light was a particle or a wave? If not, it seems similar to the brief description I read. As Hempel explained it, at the time those experiments were performed, it seemed to support the theory of a "light wave" over that of a "light particle", however Hempel argued that the main hypothesis contained may auxiliary hypotheses, so that we do not know exactly which of the "light as a particle" theories assumptions can or should be rejected by an experiment showing light acting like a wave. Hempel said the experiment left open the possibility of particle like projectiles playing a role in the propagation of light and continued to explain the in 1905 Einstein came up with the photon theory which radically revised the older corpuscular conception. If I understand the second crucial experiment (which may be doubtful), it involves shining a light onto a perpendicular screen. Under classical wave theory, the energy should decrease towards zero as the screen is mover farther away, but if the energy is carried in a photon, the energy would not decrease. Since the results of this second "crucial" experiment supported the photon hypothesis, Hempel concludes that some modification was needed to the original theories, but that such experiments do not eliminate rival theories.
I probably missed the point of your argument with Psimagus, but it seems to me that it can not be proven to be a giraffe or a lion. It would seem that there is a call for some modification of theories, and that you have a creature with characteristics of a giraffe and a lion who may have many other characteristics we don't know about. Let's not even wonder what the animal looks like in another dimension or whether it's spooky or it only collapses int lion of giraffe if someone looks at it.
I know I'm way over my head here, so please tell me what I am missing.
Is the experiment you describe the one used by Foucault when trying to find a "crucial test" to determine if light was a particle or a wave? If not, it seems similar to the brief description I read. As Hempel explained it, at the time those experiments were performed, it seemed to support the theory of a "light wave" over that of a "light particle", however Hempel argued that the main hypothesis contained may auxiliary hypotheses, so that we do not know exactly which of the "light as a particle" theories assumptions can or should be rejected by an experiment showing light acting like a wave. Hempel said the experiment left open the possibility of particle like projectiles playing a role in the propagation of light and continued to explain the in 1905 Einstein came up with the photon theory which radically revised the older corpuscular conception. If I understand the second crucial experiment (which may be doubtful), it involves shining a light onto a perpendicular screen. Under classical wave theory, the energy should decrease towards zero as the screen is mover farther away, but if the energy is carried in a photon, the energy would not decrease. Since the results of this second "crucial" experiment supported the photon hypothesis, Hempel concludes that some modification was needed to the original theories, but that such experiments do not eliminate rival theories.
I probably missed the point of your argument with Psimagus, but it seems to me that it can not be proven to be a giraffe or a lion. It would seem that there is a call for some modification of theories, and that you have a creature with characteristics of a giraffe and a lion who may have many other characteristics we don't know about. Let's not even wonder what the animal looks like in another dimension or whether it's spooky or it only collapses int lion of giraffe if someone looks at it.
I know I'm way over my head here, so please tell me what I am missing.
I think Irina just proved that Samuel Beckett and Eugene Ionesco would have made great Quantum physicists 
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