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Off Topic => General Discussion => Topic started by: LionKing on June 12, 2015, 04:19:03 AM
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http://www.pbs.org/wgbh/nova/next/physics/physicists-finally-see-light-as-a-particle-and-a-wave-at-the-same-time/
what do you think?
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I think the title of the article is misleading, as we cannot see light as a wave and a particle at the same time. In fact the idea of 'see' has no real concept in quantum mechanics. We can observe, but not really see. The act of observing plays a central theme in quantum mechanics, it causes the wave function to collapse. We can measure the effect of making an observation.
However, the experiment demonstrates the steps made forward in physics and from the perspective of what has been reported, it is very interesting.
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I think the title of the article is misleading, as we cannot see light as a wave and a particle at the same time. In fact the idea of 'see' has no real concept in quantum mechanics. We can observe, but not really see. The act of observing plays a central theme in quantum mechanics, it causes the wave function to collapse. We can measure the effect of making an observation.
However, the experiment demonstrates the steps made forward in physics and from the perspective of what has been reported, it is very interesting.
thnx
can you expand on why observing causes the wave function to collapse? I have read things about consciousness and stuff related to this topic
also can you comment on the double-slit experiment and quantum physics explanations? thnx
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thnx
can you expand on why observing causes the wave function to collapse? I have read things about consciousness and stuff related to this topic
Many of the great quantum physicists exclaimed that those who claim they understand quantum mechanics don't really understand it at all. In quantum mechanics, a particle is described by the wavefunction. It has no physical meaning in the purist sense of quantum mechanics. As an undergraduate one is led to believe that it describes the particle as a wave in the same way the wave equation describes a wave on a string. This does not truly describe the wavefunction in quantum mechanics. Wave functions are continuous mathematical functions, and if you were to play them you would get what appears to be a particle trajectory or wave. This is the wrong interpretation, and the wave function needs to be used on conjuction with its conjugate to determine a probability density. A particle can exist in many states, but some states are more likely than others. It is only when we observe a particle do we actually see a particle in a particular state. The wave function just helps us with the expectation of that state, namely which one is most likely.
also can you comment on the double-slit experiment and quantum physics explanations? thnx
This is a bit cheesy, but it explains the idea of observation on the wave function.
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thnx
can you expand on why observing causes the wave function to collapse? I have read things about consciousness and stuff related to this topic
Many of the great quantum physicists exclaimed that those who claim they understand quantum mechanics don't really understand it at all. In quantum mechanics, a particle is described by the wavefunction. It has no physical meaning in the purist sense of quantum mechanics. As an undergraduate one is led to believe that it describes the particle as a wave in the same way the wave equation describes a wave on a string. This does not truly describe the wavefunction in quantum mechanics. Wave functions are continuous mathematical functions, and if you were to play them you would get what appears to be a particle trajectory or wave. This is the wrong interpretation, and the wave function needs to be used on conjuction with its conjugate to determine a probability density. A particle can exist in many states, but some states are more likely than others. It is only when we observe a particle do we actually see a particle in a particular state. The wave function just helps us with the expectation of that state, namely which one is most likely.
also can you comment on the double-slit experiment and quantum physics explanations? thnx
This is a bit cheesy, but it explains the idea of observation on the wave function.
Thanks dear Luke,
I read more and I watch more videos such as this
and it is coming down to consciousness..matter being somehow conscious (now I wonder if at any level thsi goes with the theory of evolution?)
what do you think of the video because the role of the detector is explained and is weird enough. I am not sure if you agree with what the physicist here. he seems to be saying that the probability is determined by the detector, not the particle itself.
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also on Entanglement!!!
hmmm
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and it is coming down to consciousness..matter being somehow conscious (now I wonder if at any level thsi goes with the theory of evolution?)
That's a heck of a conclusion to jump to! Quantum Mechanics is weird enough without anthropomorphising it.
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thnx
can you expand on why observing causes the wave function to collapse? I have read things about consciousness and stuff related to this topic
Many of the great quantum physicists exclaimed that those who claim they understand quantum mechanics don't really understand it at all. In quantum mechanics, a particle is described by the wavefunction. It has no physical meaning in the purist sense of quantum mechanics. As an undergraduate one is led to believe that it describes the particle as a wave in the same way the wave equation describes a wave on a string. This does not truly describe the wavefunction in quantum mechanics. Wave functions are continuous mathematical functions, and if you were to play them you would get what appears to be a particle trajectory or wave. This is the wrong interpretation, and the wave function needs to be used on conjuction with its conjugate to determine a probability density. A particle can exist in many states, but some states are more likely than others. It is only when we observe a particle do we actually see a particle in a particular state. The wave function just helps us with the expectation of that state, namely which one is most likely.
also can you comment on the double-slit experiment and quantum physics explanations? thnx
This is a bit cheesy, but it explains the idea of observation on the wave function.
this is a new explanation rather than the 'collapse' theory
I am confused
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I think LionKing may be making the common mistake of misunderstanding the physics definition of observing. In physics, particularly QM, observing simply means that something detected (or interacted with) the system. It could be as simple as a piece of film. No intelligent, or conscious, entity is involved.
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https://en.wikipedia.org/wiki/Observer_effect_(physics)
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https://en.wikipedia.org/wiki/Observer_effect_(physics)
http://www.sciencedaily.com/releases/1998/02/980227055013.htm
Apart from "observing," or detecting, the electrons, the detector had no effect on the current
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The article you have linked to describes the Observer Effect, LionKing.
I'm not sure what the purpose of the quote is?
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https://en.wikipedia.org/wiki/Observer_effect_(physics)
http://www.sciencedaily.com/releases/1998/02/980227055013.htm
Apart from "observing," or detecting, the electrons, the detector had no effect on the current
Like Andromeda, I'm not sure what you're getting at here, especially with the quoted passage. The article confirms what I, and Andromeda, are saying: in physics, an "observer" is not an intelligence or consciousness. Perhaps you could elucidate?
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https://en.wikipedia.org/wiki/Observer_effect_(physics)
http://www.sciencedaily.com/releases/1998/02/980227055013.htm
Apart from "observing," or detecting, the electrons, the detector had no effect on the current
Like Andromeda, I'm not sure what you're getting at here, especially with the quoted passage. The article confirms what I, and Andromeda, are saying: in physics, an "observer" is not an intelligence or consciousness. Perhaps you could elucidate?
well, the QM says that it is an extension of our consciousness. We put it to observe, so it is not separate from our consciousness
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QM doesn't say anything about consciousness - the Observer can be a machine.
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Which is exactly what the article says: a machine 'observes' the electrons, resulting in the QM determination. Absolutely no consciousness involved.
This mistake is very common with non-physicists, especially ones given to theological or "new age" interpretations. Bottom line is that the system, or event, needs to be detected by something: a machine, a piece of film, a lump of rock in space, a hydrogen ion in an interstellar gas cloud - or any eye. The QM determination happens when it is detected (e.g. in your eye), not when your consciousness receives the input from your eye.
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Which is exactly what the article says: a machine 'observes' the electrons, resulting in the QM determination. Absolutely no consciousness involved.
This mistake is very common with non-physicists, especially ones given to theological or "new age" interpretations. Bottom line is that the system, or event, needs to be detected by something: a machine, a piece of film, a lump of rock in space, a hydrogen ion in an interstellar gas cloud - or any eye. The QM determination happens when it is detected (e.g. in your eye), not when your consciousness receives the input from your eye.
first thanks for taking time to comment on this.
what is being argued by the pro-consciousness group is that the machine is an extension to our consciousness. we are observing behind it, so it is observing, maybe arguably, consciously, but
what I want to know is the other point of view: HOW does the machine interfere? this is the basic question that I want a scientific answer for. had it been that explainable, the article wouldn't have referred to this as strange in a sense. thnx
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what I want to know is the other point of view: HOW does the machine interfere? this is the basic question that I want a scientific answer for. had it been that explainable, the article wouldn't have referred to this as strange in a sense. thnx
I don't think anybody really knows. Hence "quantum weirdness".
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With respect to the "pro-consciousness group", I think it's sophistry. In particular, if you follow that argument to the ultimate point (reductio ad absurdum), the universe did not exist before there was consciousness.
There is no apparent link between the object "measuring" or "sensing" the event and a final, conscious, observer; as far as we can tell, all that is required is that something "senses" the event.
As to why "sensing" the event causes the QM determination, as Andromeda says we don't really know. QM is weird, and not just in this way; at this level our everyday experiences are not only not applicable but interfere with understanding what is going in. I can say, as mentioned above, that it is not possible to observe a system without interacting with it in some way; i.e. the act of observing necessarily affects the system being observed. (Note I say system and not event; you can observe the effects of an event without directly affecting the event itself, but the system - everything connected to the event - must be affected in some way.)
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Yup.
A macro scale example of observation/measurement interacting with a system would be the act of measuring the temperature of a cup of hot water with a mercury thermometer. By the very nature of it, the thermometer must take some heat energy from the water (which then expands the mercury and provides a reading). There is no way to use a thermometer to "observe" the temperature of water without changing the temperature of the water.
Hope that makes sense, I'm on my phone!
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Yup.
A macro scale example of observation/measurement interacting with a system would be the act of measuring the temperature of a cup of hot water with a mercury thermometer. By the very nature of it, the thermometer must take some heat energy from the water (which then expands the mercury and provides a reading). There is no way to use a thermometer to "observe" the temperature of water without changing the temperature of the water.
Hope that makes sense, I'm on my phone!
albeit we understand that the thermometer takes the heat and it is in direct contact with the particles. can we say this about the observer here??
also see this if you want, especially to the end..
but I have to re-watch it as I don't claim I understood fully.. OMG my brain will burst..
take care
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Well - what does "direct contact" mean? On a quantum level, interactions are different. That's why it's so difficult to understand - it is at odds with our everyday understanding of how things work.
I might watch the video later.
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I will add to this with Heisenberg. Many scientists were really uncomfortable with the uncertainty principle (UP) because they believed it meant that we cannot measure a system accurately. They understood that the uncertainties in QM meant that physics could not be measured with certainty. A great misconception with undergraduates is to take the same world view, and take the naive understanding that the UP means that quantum systems have error which cannot be resolved.
What many people do not understand it the dx (position) and dp (momentum) are non-commuting operators in quantum theory, so as we observe one with more certainty, the less we know about the second. John Gribbin explains this in a beautiful way that makes sense (even in the weird of QM).
dx describes the wave part of the quantum wave function and dp the particle part of the quantum wave function. If we set up an experiment to make dx small we can determine more about the wave but little about the particle. If we set up an experiment to make dp small we can determine more about particle part but less about the wave part. In other words, depending on the conditions of how we observe, we can see something behave as a wave or something as a particle, but never both at the same time.
Point being is that the nature of observing in itself has meaning at the quantum level, and by the very nature of quantum mechanics, the notion of of observing is embedded in quantum interactions with the film, eye, CCD as they themselves are quantum in nature.
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They get pulled over. Heisenberg is driving and the cop asks him "Do you know how fast you were going?"
"No, but I know exactly where I am" Heisenberg replies.
The cop says "You were doing 55 in a 35." Heisenberg throws up his hands and shouts "Great! Now I'm lost!"
The cop thinks this is suspicious and orders him to pop open the trunk. He checks it out and says "Do you know you have a dead cat back here?"
"We do now, asshole!" shouts Schrodinger.
The cop moves to arrest them. Ohm resists.
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They get pulled over. Heisenberg is driving and the cop asks him "Do you know how fast you were going?"
"No, but I know exactly where I am" Heisenberg replies.
The cop says "You were doing 55 in a 35." Heisenberg throws up his hands and shouts "Great! Now I'm lost!"
The cop thinks this is suspicious and orders him to pop open the trunk. He checks it out and says "Do you know you have a dead cat back here?"
"We do now, asshole!" shouts Schrodinger.
The cop moves to arrest them. Ohm resists.
Heard it many times before, but still makes me laugh. I'm a sucker for physics jokes.
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Ernest Rutherford splits.
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Ernest Rutherford splits.
You're spoling me. Stop it ;)
Bar tender says 'Sorry, we don't serve tachyons in here.'
A tachyon walks into a bar.
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Ernest Rutherford splits.
You're spoling me. Stop it ;)
Bar tender says 'Sorry, we don't serve tachyons in here.'
A tachyon walks into a bar.
I prefer poetry here to jokes :D
"And I'd choose you
in a hundred lifetimes,
in a hundred worlds,
in any version of reality,
I'd find you and
I'd choose you"
-THE CHAOS OF STARS
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Which is exactly what the article says: a machine 'observes' the electrons, resulting in the QM determination. Absolutely no consciousness involved.
I like to replace the word 'observes' with 'hit by a hammer' or just 'hits', it gives a more accurate impression.
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'Activates' would work too, I think.
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Quantum Entanglement & Spooky Action at a Distance
not sure I understood. is he saying that they neither communicate faster than light nor do they have information inside them?
EDIT: and this teleportation trial that succeeded between Tenerife and La Palma islands..I want a clarification: does the third particle that afected the first one get teleported meaning it was vanished from la palma ? or did it stay there and changed the spin of the first particle on la palma, which changed the spin of the second on tenerife gettign the same spin of the third particle without that third particle being moved ??
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well, the QM says that it is an extension of our consciousness. We put it to observe, so it is not separate from our consciousness
Please note: I am NOT a quantum physicist, or even much of a mathematician. I'm just repeating things second-hand.
As far as I've seen people explain the whole "consciousness and quantum physics stuff", they've basically said "all this wavefunction and observer stuff is just a mathematical model. Don't read more than that into it".
By way of analogy (and please understand that this is JUST a rough analogy with many flaws, but hopefully it gets the point across), when considering the effects of the moon's gravity on something on Earth, we can treat the moon as if it were a single point, and that gives an accurate mathematical model. That doesn't mean the moon IS a single point, just that the math works if we treat it as one.
Does that make any sense?
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well, the QM says that it is an extension of our consciousness. We put it to observe, so it is not separate from our consciousness
Please note: I am NOT a quantum physicist, or even much of a mathematician. I'm just repeating things second-hand.
As far as I've seen people explain the whole "consciousness and quantum physics stuff", they've basically said "all this wavefunction and observer stuff is just a mathematical model. Don't read more than that into it".
By way of analogy (and please understand that this is JUST a rough analogy with many flaws, but hopefully it gets the point across), when considering the effects of the moon's gravity on something on Earth, we can treat the moon as if it were a single point, and that gives an accurate mathematical model. That doesn't mean the moon IS a single point, just that the math works if we treat it as one.
Does that make any sense?
excuse my English but I am not sure what do you mean that the moon is not a single point here
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It's the concept of "center of mass", sometimes incorrectly called "center of gravity". It was originated, to my knowledge, by Isaac Newton. He showed that for the purposes of computing the effect of a rigid object's gravity on something, you could treat that object as though all its mass were concentrated at a single point. Then you use Newton's Laws of Motion on that infinitesimal object. E.g., if all the earth's mass were concentrated at its center, the Moon would still orbit it exactly as it does now, and the earth-moon system would still orbit the sun as it does now.
But this is just a mathematical trick that saves a lot of calculation while getting the same correct result. It doesn't mean that the earth's mass really is concentrated at one point.
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But this is just a mathematical trick that saves a lot of calculation while getting the same correct result. It doesn't mean that the earth's mass really is concentrated at one point.
Thank you for the excellent explanation ka9q! I was struggling with how to explain that.
I guess I'm probably at the point of knowledge where I know just enough to get myself in trouble. :P
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You're welcome. It's a general principle in physics that we have to be careful with our mathematical models lest we read too much into them. Concepts like center of mass, quantum wave functions and the like are useful because they make it easier to predict the outcome of an experiment in the real world, but that's not always the same thing as providing insight into what's "really" going on.
When Newton devised the center of mass concept, he showed that if you divide up a large, massive object like a planet into a whole bunch of little objects stuck together, each with a mass and its own position, and then compute and add up all the gravitational forces on some distant object from these teeny little objects, you get the same answer as a far simpler calculation: pretending that all of those little masses are piled on top of each other at a single, tiny point in space corresponding to the real object's center of mass. It means that a black hole and an ordinary star with the same mass will have exactly the same gravitational effect on some planet orbiting it, but it does not mean that the star and a black hole are the same type of object!
In fact, you also have to be careful with more ordinary uses of the center of mass. Newton's result is strictly true only for a spherically symmetric object. Real planets are usually not symmetric, with fast-rotating objects like Jupiter (or even the Earth) very decidedly so. If you ignore the planet's true shape and just model it as a point mass, you'll get almost the correct orbital path for a satellite but not quite right. You'll see "perturbations" from classical 2-body motion. To get the right answer you have to take the planet's true, detailed gravity field into account because it changes depending on where you are, not just how far you are.
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Not just Jupiter either. The moon's mascons (i.e. mass concentatioons) make long term orbits very tricky. I wonder what that will mean for c Apollo style moon missions with a CSM style orbiter, extended over longer periods.
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Yes, that's right, plus you have significant perturbations from the earth even at low lunar altitudes (remember the earth is ~88x heavier than the moon).
I've since heard that there are a few special values of inclination that are unusually long-lived, but I don't know the details.
The perturbations of a lumpy gravity field aren't just a nuisance, sometimes they actually have a practical use. Every rotating planet or moon has an equatorial radius larger than its polar radius; the actual shape is a "prolate spheroid" rather than a perfect sphere.
Jupiter spins so fast that its oblateness is actually visible to the eye in a telescope.
The difference in polar and equatorial radii for the earth is 21.3 km, which is considerably higher than Mt Everest. This equatorial bulge nudges an orbiting satellite slightly to the west or east depending on the angle at which it crosses the equator, causing the orbital plane to precess around the earth's axis. If you get the right combination of altitude and inclination, this precession will exactly match the earth's motion around the sun so the satellite will always pass over the same local time on the earth below. This is very useful for earth reconnaissance satellites such as weather, spy, earth resources, etc. Nearly all of the satellites launched from Vandenberg AFB in California go into these "sun synchronous" orbits.