Skip to comments.Chinese Physicists Teleport Photons Over 100 Kilometers
Posted on 05/12/2012 7:52:50 PM PDT by Innovative
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I think your reading too much into this. We can manipulate objects at a distance with magnetism. We can manipulate charged particls in an electric field. We can predict orbits in a gravitational field. Now scientists are manipulating particle states at a distance. All this stuff is "action at a distance." For all the clever calculations and speculations scientists make, they still can't tell us the underlying mechanics of how forces act at a distance. It's spooky, erie, otherworldly for the time being.
What too many authors bent on teleological interpretations or metaphysics don't understand (and, I'm afraid, too many adherents of the Copenhagen School did not appreciate) is that the experimental design is itself the most important part of the observation, as you imply. In graduate school our prof in the second Quantum Mechanics course passed out a mimeographed essay (this was 1979) entitled: Congratulations! You've Created an Apparatus That Might Kill a Cat: It's Really Not That Interesting. It was a terse rant against the Tao of Physics and other alleged profundities then plaguing the scene. I have been hoping it would surface again on the Internet, but have not yet seen it. A pity.
It is, but it's not all quite the same kind of "action at a distance." The correlation of wave functions in quantum mechanics happens without intermediaries, and at superluminal velocities. It is "instantaneous" in fact, although that phrase actually has no Lorentz invariant meaning.
For all the clever calculations and speculations scientists make, they still can't tell us the underlying mechanics of how forces act at a distance.
This statement is false.
We understand quite well how forces act at a distance, and quantum teleportation does not involve those mechanisms. Fundamental interactions are mediated through particles called gauge bosons. The gauge particle of the electromagnetic field is the photon. In order for an electric field to exert a force, the charged particles involved exchange photons. There are gauge particles for each of the fundamental interactions: gluons (strong nuclear force) W and Z bosons (weak nuclear force) and gravitons, in addition to photons. There is some controversy about whether gravitons are actually gauge particles; we do not have a quantum theory of gravity.
All of those gauge bosons provide attractions or repulsions at the speed of light.
The correlation of coherent quantum particles has physical consequences, but is not one of those interactions. It is not a "force" and does not occur at light-speed. This is the essence of Einstein's objection to it.
There are gauge particles for each of the fundamental interactions: gluons (strong nuclear force) W and Z bosons (weak nuclear force) and gravitons, in addition to photons. There is some controversy about whether gravitons are actually gauge particles; we do not have a quantum theory of gravity.
That is entirely correct and beautifully slides over the current central mystery; do gravitons exist or is gravity really geometry?
Gravity behaves like a force in that it propagates at lightspeed (unlike the spooky QM stuff) but nothing like a graviton has been detected. Not for want of trying, but it's a hard problem.
Gravitons are an attractive notion because then all the things that look like forces work the same way and there is some hope of wrapping it all up in one equation that is the literal word of God in the original language.
The trouble with all this tidiness is that it breaks down when we start to think about mass and inertia. And when we collect enough mass to have interesting amounts of gravity it appears that thinking about space-time bending instead of an exchange of gravitons might be a more useful model.
What mass/inertia is exactly is of much interest as there are hints in the math that superluminal velocities are possible (actually required) for objects with an imaginary (square root of -1) rest mass, whatever that means.
No we don't. Claiming that bosons are force mediators still doesn't explain the mechanics of attraction or repulsion. There is still action at a distance between bosons and mediated particles. What pulls them? Every time I ask, I get the answer we don't know. The graviton is still speculation. They haven't confirmed it yet. When it comes to gravity, it's one hell of a long pull between fermions. If they do find a HIggs boson, they still won't be able to explain what the fabric is that provides the resistance to acceleration.
No. There is not. You are mistaken.
What pulls them? Every time I ask, I get the answer we don't know.
Nothing pulls them. They are the pull. I don't know who you're asking, but you are not asking physicists if you're getting this answer.
The graviton is still speculation. They haven't confirmed it yet. When it comes to gravity, it's one hell of a long pull between fermions.
First, it's more than speculation. It is a well-informed draft concept based on the behavior of the other interactions which we do understand and the large-scale effects of gravity which are quite well known. Second, agreed, it has not been detected, but that is not the same thing as speculation. The current theory -- that gravity imposes curvature on space-time -- is adequate for all but the very shortest range interactions; it has tremendous explanatory and predictive power. It is only unsatisfactory because it is not a quantum theory of gravity, but, it may even be fully correct. It may turn out that gravity is not a field in the quantum mechanical sense (I, and a great many other people will be very surprised if so.)
Third: gravity is not limited to fermions, and fourth, gravity has no more "longness" associated with its pull than the electromagnetic field, which is also infinite in its effects; and photons account for infinitely long-distance attraction and repulsion quite well. In fine and in sum, your objections are ill-informed and incorrect.
If they do find a Higgs boson, they still won't be able to explain what the fabric is that provides the resistance to acceleration.
There is no such thing as acceleration at the quantum mechanical level (mathematically acceleration does not correspond to a bounded Hermitean operator on the Hilbert space of state vectors. Colloquially, The Uncertainty Principle rules out measuring the quantities required to make acceleration sensible for a particle), so no one expects the Higgs to explain a concept which has no quantum mechanical meaning.
If you are interested in the gross properties of matter, like acceleration -- which is not quantum mechanical -- those properties are described quite well by the Equivalence Principle and the relation of gravitational mass to inertial mass; they are the same, and Einstein explained why. Having explained why, we know that acceleration is a measure of the curvature of space-time.
The Principle of Stationary Action is at the bottom of all of these things, whether quantum mechanical or classical, and whether you believe in gravitons or curved space-time (or both.) Saying that we don't "understand them" because we don't understand why there is is a Principle of Least Action is a metaphysical question, not a physical one.
Why are there laws? That's not for physicists to answer and we don't try. The Pope -- among many -- has a theory. Check with him.
Saying that physics does not "explain" Stationary Action because you don't see how a variational law can operate over the entire universe is either a problem with science, or a problem with you.
The problem with you, I am trying to help you with. Here is one analogy which may make a connection for you: Feynman Diagrams for Vector Bosons. But in any event, you are not being well served by people who say we don't understand.
The scientific problem is an ontological one, and a problem with all science: science does not "explain" anything in the deepest sense. It merely offers better and better, and deeper and deeper, descriptions. But this, again, is not because we do not "understand the physics."
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