Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thebrain13 on 03/05/2011 01:53:00
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Many particle accelerators have bubble chambers. Bubble chambers can measure the charge to mass ratios of particles by looking at the amount of curvature of their paths in a magnetic field. The reason for this is because charged particles will curve left or right in respect to their motion depending on their charge and the magnetic field they are around.
Consider the second picture down in the link, with the black curvy lines.
http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Bubble_chamber (http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Bubble_chamber)
Many created particle qualities are determined using experiments like this. My question is, why do the curves in the bubble chamber look completely smooth when magnetism is being propagated by individual quantized particles(photons)? If magnetism is carried in "chunks" shouldn't the particle make "chunky" turns?
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Electric and magnetic fields are not quantized, though the electric charges which generate them are. Besides, the distances in the bubble chamber are macroscopic, so even if the fields were quantized, that would be on a much smaller scale than what you can see in the photos.
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EM fields are quantized as are the Hamiltonians they are based upon. On the macroscopic level - you are quite right
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I don't understand how this is a macroscopic phenomenon, that picture was of the path of individual particles. If individual particles get bent smoothly than what doesn't? What is more microscopic than one particle?
If the exchange of virtual photons doesn't knock the path of individual charged particles off in little "bunches" but smoothly like in the picture, then what evidence exists that virtual photons are necessary at all, and that the charged particles don't just react with the magnetic fields directly?
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But in order to observe you need some way of bringing it into the macroscopic sphere - ie creation of tiny bubbles or droplets. We can only observe these particles through the "destruction they leave in their wake" - and that is on quite a large scale; ie the picture is of the large scale result of the small particle's path. if we could observe particles directly and accurately we would have no need for bubble chambers - and certain uncertainty principles might have to be reconsidered.
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Unfortunately, the scale of the picture is not shown, but it's probably several centimeters across. So if there were quantum increments to the curve, there would be billions of them adding up to the curve that your see.
I reiterate; electromagnetic waves may be quantized, but electric and magnetic fields are not. The electric field around an ion is proportional to the inverse square of the distance, and distance is not quantized. The magnetic field around a moving charge is proportional to the relative velocity of the charge, and velocity is not quantized. So a charge moving in a field follows a continuous curve, not a series of angles.
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Imatfaal, regardless of how we classify the experiment, whether we want to call it macroscopic or microscopic. These individual particles are still getting bent smoothly by the magnetic field. The bubble chamber isn't stopping the photons from curving "lumpily" only the particles properties and the field is causing it. If the photons caused little bursts of direction change the bubble chamber would track that.
If an experiment that is capable of tracking one individual particle is not valid, then what is? And if no experiment exists that can track that (for whatever reason), then why create the extra "virtual photons create all forces" step if we can't measure it in a way that distinguishes it from using field only theories? (which would show total smoothness)
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Okay phractality, I agree with what you say. I don't think any evidence exists that shows that electric and magnetic fields bend things in little pieces, but they do it smoothly like gravity.
The only thing that urks me now, is if objects bend smoothly in electric and magnetic fields why unnecessarily complicate the situation with force carrying virtual photons?
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It is only unnecessary if you are observing a macroscopic system. No one uses quantum electrodynamics in scenarios where classical electrodynamics provides the correct answer. When you are dealing with the finer points of inter-particle interactions however, Maxwell's equations aren't much use, and QED gives correct predictions.
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Quantum Mechanics = Religion for Atheists. It's jam-packed with assertions that can neither be proved or disproved, just like religion. God could of created everything, nobody can disprove that. Little virtual photons can pop into existence with supershort lifespans so we can't measure them and create electric forces, nobody can disprove that either.
But where is the evidence for that? If this bubble chamber can't prove or disprove it, what can?
Quantum mechanics advocates always use the, "you are too ignorant to even follow this logic, there are special quantum mechanics geniuses that know everything and you don't even know" spiel whenever they can't disprove a well put together argument. Just like religion uses the, "you cant even understand the logic of the lord" spiel when they can't come up with answers.
Einstein, who encountered the same attacks when he was trying to disprove q.m. used to say, "if you can't explain it to your grandmother, you are the one who doesn't understand it".
I think his statement should include 24 year olds, who major in physics with above 3.8 gpa's and are former poker pros. If you make a well thought out logical argument I will follow it.
But nobody can disprove ideas you can't test, I merely choose not to support them.
Show me one spot where somebody answered the question, instead of implying the answer is "somewhere in qed". What evidence supports virtual photons, when magnetic and electric forces act smoothly? If you say the bubble chamber or the heisenberg uncertainty principle muddies the evidence, well that's still not evidence. The experiment which involves the motion of singular particles is as microscopic as it can possibly be.
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I reiterate; electromagnetic waves may be quantized, but electric and magnetic fields are not. The electric field around an ion is proportional to the inverse square of the distance, and distance is not quantized. The magnetic field around a moving charge is proportional to the relative velocity of the charge, and velocity is not quantized. So a charge moving in a field follows a continuous curve, not a series of angles.
Phract - whilst we can use coulomb's law etc in a highly predictive classical theory of electromagnetc fields - the origin of quantum field theory is premised on the force between charged particles being mediated by the exchange of a virtual photon, and this is surely quantized. It was the development of this theory that lead to Feynman, Schwinger and Tomonaga's Nobel prize. This allows us to explain phenomena that have no classical explanation.
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Brain - if you are majoring in physics I am stunned that you have not engaged with quantum mechanics to the extent that you would know the answers to the questions you pose. Do you have classical explanations for the photoelectric effect, blackbody radiation curve, the line spectrum problem etc.
We create virtual particles to solve problems that classical physics cannot - read up on the lamb shift which was one of the first. http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/lamb.html
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"Do you have classical explanations for the photoelectric effect, blackbody radiation curve, the line spectrum problem etc."
If by "classical explanation" you mean from the late 1800's then no. If by classical you mean, using logic without quantized concepts, then yes. It's a piece of cake(if you use my own rules)I can even relate those three effects to each other and then compare it to an effect witnessed in galaxies with dark matter. But I'm not going to write anything unless you agree to actually read it and criticize my solutions. If I just posted it, nobody would respond.
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Brain - classical in these terms means without QM/QFT. I will read it - but I cannot guarantee that my physics is strong enough to see your errors. Best post in a new thread in New Theories as it is definitely not mainstream.
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The strength of a "more fundamental" theory is that it can quantitatively model physical phenomena that less fundamental theories can't. It should also be able to explain how the less fundamental theory emerges from its more fundamental rules.
Quantum theory is accepted because it does both of these things. While you can quantize the electromagnetic field and then explain macroscopic phenomena from that quantization, that would be a nightmare scenario for calculations.
If you have a theory that can do everything quantum mechanics can, including making quantitative predictions, it would be interesting to see (in New Theories, of course, since it isn't mainstream). If it can't make quantitative predictions, it isn't going to be well-received, since such predictions are a cornerstone of science.
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allright, Ill post it in new theories, but not for a couple days. I've got a ton of chemistry to catch up on before my next test.