Quizzes & Puzzles77 mins ago
What Scientific Idea Is Ready For Retirement?
Question posed at Edge magazine website.Among them some fairly controversial recommendations, I think, either because to discard them seems counter-intuitive, or because others are somewhat cherished, like Moores Law.
Have a browse at your leisure, see what you think :)
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Have a browse at your leisure, see what you think :)
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jim360 //Quantum Mechanics is a mathematical description of reality, and I think several people have taken the mathematics too literally. My own interpretation runs along the lines of "Quantum Mechanics is probability in nature". Things are not in two places at once, but they could be in either place and you don't know which.//
You misunderstand QM. It isn't just a matter of not knowing and this is confirmed by experimental evidence. With clever setups, things have even been observed to be in two places at once.
You misunderstand QM. It isn't just a matter of not knowing and this is confirmed by experimental evidence. With clever setups, things have even been observed to be in two places at once.
I disagree, beso -- nothing has been "observed" in the formal sense to be in two places at once, that I'm aware of. If you could find an experiment that contradicts that claim that I'd be interested to hear of it. More often, things merely "appear" to be in two places at once. But that's not actually an observation, but rather a backwards deduction. For example, in the double slit experiment, the electrons passing through the slits form a diffraction pattern consistent with the idea that the electron passed through both slits. On the other hand, if you set up the equipment such that you were watching the slits, then you would see the electron passing through one slit, or the other, but never both simultaneously.
When a quantum particle is in "two places at once", that is a statement that can only be made before you observe it, and means in practice that you don't know where it is. Instead there is some probability of it being either at point A, or at point B, and until you observe it then you write its wavefunction as |A>+|B>, a superposition of the two options. Usually, this is interpreted as a particle being in neither position, or being nowhere. Once the particle is observed (at A, say) then its wavefunction becomes just |A> (or, equally, just |B>. But if you were trying to find where it was, it never stays as |A>+|B>, and is therefore never seen in two places at once.
Again, if you can find an experiment in which an electron actually was formally seen at two separate locations simultaneously, I'd be very interested to hear it. But so far as I am aware, in every case where something is in two places at once, it's a statement to describe what is going on before you observe it, rather than when you observe it. There is a significant difference.
When a quantum particle is in "two places at once", that is a statement that can only be made before you observe it, and means in practice that you don't know where it is. Instead there is some probability of it being either at point A, or at point B, and until you observe it then you write its wavefunction as |A>+|B>, a superposition of the two options. Usually, this is interpreted as a particle being in neither position, or being nowhere. Once the particle is observed (at A, say) then its wavefunction becomes just |A> (or, equally, just |B>. But if you were trying to find where it was, it never stays as |A>+|B>, and is therefore never seen in two places at once.
Again, if you can find an experiment in which an electron actually was formally seen at two separate locations simultaneously, I'd be very interested to hear it. But so far as I am aware, in every case where something is in two places at once, it's a statement to describe what is going on before you observe it, rather than when you observe it. There is a significant difference.
Incidentally, the galaxies idea is different. The particles you are seeing are separate photons from the same galaxy, forming multiple images because there are multiple paths the photons can take. It is, then, the image that is being duplicated several times, rather than the object, and is just a more complicated version of, say, any time when you are in a lift with back-to-back mirrors or something similar and see an almost infinite set of your own reflection. Of course, you aren't actually in loads of places at once, but there are several images of you caused by several billions of photons able to take different paths to your eye, all of them together forming a complete image.
Again, nothing ever is in two places at once as long as we are watching it. But while there is no observation being made, our ignorance of its location can be captured by a mathematical statement that implies that, before a measurement, the particle could equally well be in any of two places (or three or four or indeed anywhere). The statement "two places at once" is in a sense misleading and unhelpful, tied down to a false view of the world where something must have a fixed location.
Again, nothing ever is in two places at once as long as we are watching it. But while there is no observation being made, our ignorance of its location can be captured by a mathematical statement that implies that, before a measurement, the particle could equally well be in any of two places (or three or four or indeed anywhere). The statement "two places at once" is in a sense misleading and unhelpful, tied down to a false view of the world where something must have a fixed location.
jim
QM is an affront to common sense and those who do not understand it are often led to classical interpretations that do not accurately describe the true nature of reality.
The experiment is well known tot hose who understand QM. It secured a Nobel Prize for its designers.
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"Wineland achieved it in the lab. When he hit the atom with half of the light needed to move it, it was simultaneously immobile and in motion, until eventually it was in two locations, 80 nanometers (billionths of a meter) apart, at the same time."
QM is an affront to common sense and those who do not understand it are often led to classical interpretations that do not accurately describe the true nature of reality.
The experiment is well known tot hose who understand QM. It secured a Nobel Prize for its designers.
http://
"Wineland achieved it in the lab. When he hit the atom with half of the light needed to move it, it was simultaneously immobile and in motion, until eventually it was in two locations, 80 nanometers (billionths of a meter) apart, at the same time."
jim //For example, in the double slit experiment, the electrons passing through the slits form a diffraction pattern consistent with the idea that the electron passed through both slits. On the other hand, if you set up the equipment such that you were watching the slits, then you would see the electron passing through one slit, or the other, but never both simultaneously. //
The best known experiment is done with photons.
Once again a failure to understand QM leads to misinterpretation. Even if the experimental setup is configured such that only a single photo is passed, its wave function interferes with itself if two paths are available and it will be diffracted.
If the second path is blocked the photon passes straight through.
The best known experiment is done with photons.
Once again a failure to understand QM leads to misinterpretation. Even if the experimental setup is configured such that only a single photo is passed, its wave function interferes with itself if two paths are available and it will be diffracted.
If the second path is blocked the photon passes straight through.
jomifl
/things have even been observed to be in two places at once. /
couldn't that be an artifact of the observational method?
This is what many scientists from Einstein on would have suggested.
However a series of experiments like the one I referred to show it is beyond question. It is not a matter of limited observation or the result of an unknown classical relationship.
Reality is indeed random.
/things have even been observed to be in two places at once. /
couldn't that be an artifact of the observational method?
This is what many scientists from Einstein on would have suggested.
However a series of experiments like the one I referred to show it is beyond question. It is not a matter of limited observation or the result of an unknown classical relationship.
Reality is indeed random.
I'll have a look at the original papers if I can. But I fancy that I understand QM rather better than Reuters does. It -- and you -- are confusing the concept of superposition, when a particle exists in a number of states simultaenously, but is not being observed, with what happens after it was observed. If you went and watched that particle, you would see it stationary, or in motion, but not both. Before that observation, it could have been both, but it could not have been both while being seen.
That is the nature of Quantum Mechanics -- observation, or Quantum Measurement, selects one of the options possible, but before observation the particle must be regarded as being in a superposition of those options.
Nothing is ever "seen" in two places at once.
That is the nature of Quantum Mechanics -- observation, or Quantum Measurement, selects one of the options possible, but before observation the particle must be regarded as being in a superposition of those options.
Nothing is ever "seen" in two places at once.
And again, on the double slit experiment, you can only say that the photon is interfering with itself if you don't watch it until after it passes through the entire experiment. Thus you can deduce that it, or something, passed through both slits at once, but you certainly weren't watching it pass through both slits simultaneously. If you tried to watch it pass through both slits at once then you would see it go through just the single slit, and the diffraction pattern becomes that of a one-slit experiment.
ZEN KOAN.
'Two monks were arguing about the temple flag waving in the wind. One said,"The flag moves." The other said, "The wind moves." They argued back and forth but could not agree. Hui-neng, the Sixth Patriarch, said, " Gentlemen! It is not the flag that moves, it is your mind that moves."
The monks were struck with awe.'
'Two monks were arguing about the temple flag waving in the wind. One said,"The flag moves." The other said, "The wind moves." They argued back and forth but could not agree. Hui-neng, the Sixth Patriarch, said, " Gentlemen! It is not the flag that moves, it is your mind that moves."
The monks were struck with awe.'
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