Physicists Propose New Kind of Quantum Tunneling 163
KentuckyFC writes to tell us that scientists from the UK and Germany are proposing a third kind of quantum tunneling. They propose that a quantum particle is capable of changing into a pair of "virtual particles" capable of passing through a potential barrier before changing back. The supposition also provides some interesting methods of possibly testing string theory. So many interesting and useful possibilities, I guess that just means it will be debunked faster than other scientific theories.
let's hear it for optimism (Score:4, Funny)
So many interesting and useful possibilities, I guess that just means it will be debunked faster than other scientific theories.
Your glass the wrong size often there, mate?
A good percentage of us believe FTL travel is possible. You came to the wrong place with that attitude.
Re:let's hear it for optimism (Score:4, Informative)
Does anyone else get an uneasy feeling about the use of the word debunk in the summary?
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Lets face it, if FTL travel isn't possible, the human race is doomed. Therefore, having the attitude that it is impossible is not useful to anyone. I know that as a scientific mind, you're supposed to follow logic and precedence. But if you plan to make a groundbreaking discovery, you pretty much have to chase what's believed to be impossible.
If there's any limitation to the scientific mind, it's that it dismisses the far out there, which is (sometimes) the next step forward.
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Lets face it, if FTL travel isn't possible, the human race is doomed
Why? If FTL is impossible then it is unlikely that there will be a single human civilisation spanning the galaxy, but that doesn't preclude interstellar travel. Even at 10% of the speed of light it would be possible to colonise the entire galaxy in as little as a million years; a small fraction of the time that life has existed on this planet and much less time than some of the previous dominant species have survived.
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I wonder if we'd be able to proliferate quickly enough, however, to prevent ourselves from being wiped out by a catastrophic occurrence in our local neighborhood within our galaxy. Say, a supernova a few hundred light-years away.
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Broadly speaking, if we can cross those distances at a reasonable sublight pace, we've clearly already solved that problem.
Travelling at high speed through interstellar space exposes the spacecraft to deadly levels of radiation. Remember that space is not strictly a vacuum, and motion is relative, so at 0.5c every hydrogen atom you cross paths with is, from your frame of reference, hitting you at half the speed of light. The faster you go, the worse this problem gets, to the point where at near light spee
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"Lets face it, if FTL travel isn't possible, the human race is doomed."
That's not a valid assumption. It is absolutely viable to colonize planets around other stars with slower than light travel. It's just not practical to do round-trips. There probably are many viable rocks within a 20 light-year radius.
We need the kinds of non-reactive propulsion needed to propel spaceships to the speeds needed to reach their destinations before the grand-grandchildren of the crew forgets what they are doing.
Without FTL,
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I'm not completely convinced that 20 light-years is nearly "far enough".
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20 light-years is about by Wolf 562. There are about 5 stars with detected gas giants around them in this radius, about a dozen without them but with no data on smaller rocky planets we can't yet detect.
There must be plenty of rocks we could live on within this distance. I don't say Earth-like planets, because we would need to replace the whole biosphere with something that doesn't want to kill itself by eating reciprocally toxic earthlings, but Ganymede and Europa-like bodies with low gravity, plenty of wa
Re:let's hear it for optimism (Score:5, Insightful)
So, to put it more succinctly, you advocate that we delude ourselves?
No, but I advocate that we advance science with the hope that our hypotheses might be correct, rather than with a firm belief that our hypotheses are incorrect.
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The good folks doing all the science can hope whatever they like, so long as they don't fall victim to confirmation bias. It just seems easier to avoid junk science creeping in, if everyone involved is taking a skeptical view in both their work and their general life
On the other hand, if they're hoping to discover something crazy, that could be a powerful motivator to keep trying at a theory to get it right... just got to be careful not to be so hopeful as to ignore contradictory evidence.
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So many interesting and useful possibilities, I guess that just means it will be debunked faster than other scientific theories.
Your glass the wrong size often there, mate?
Not necessarily... the more exciting an idea is, the more interest it attracts, and so the quicker its ideas are either proven true or false... or, since we're dealing with quantum physics, we'll discover a whole bunch of other stuff which makes absolutely no sense, but is nonetheless true.
Re:let's hear it for optimism (Score:5, Insightful)
Not necessarily... the more exciting an idea is, the more interest it attracts, and so the quicker its ideas are either proven true or false.
Ideas in physics are never proven true. They are shown not to contradict any existing evidence, that is all. I can't think of any more than a few decades old which have survived even this. The best most theories can hope for is being shown to be a reasonable approximation within certain constraints. Eventually it may be possible to find a theory which both makes meaningful predictions and isn't contradicted by experimental results for a much longer time, but this hasn't happened yet and is unlikely to for quite a long time.
Physics is not about finding things that are 'true' it is about finding things that make useful predictions. Newtonian motion is not 'true', but it makes predictions that are sufficiently accurate (as long as you are not travelling at more than a tiny fraction of the speed of light or near a very large gravitational force) that we can use them.
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Ideas in physics are never proven true. They are shown not to contradict any existing evidence, that is all. I can't think of any more than a few decades old which have survived even this.
I may be a bit behind the times, but the Law of Conservation of Energy comes to my mind pretty quickly.
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That doesn't really contradict what he said. The net energy is still always conserved, even if locally it appears to be violated. From a "big picture" point of view, wherein we consider local quantum effects in relation to one another, not just by themselves, conservation is as true now as when we first proposed it.
Conservation of mass/energy goes back how far? The concept of mass equivalence is Einstein's era (more or less), but the concept of conservation in the first place is nineteenth century. Cert
Popper and Kuhn (Score:2)
Ideas in physics are never proven true.
The insight above is basically the philosophy of science of Karl Popper. Theory implies experimental predictions. If experimental predictions are false, then theory is false.
Then Thomas Kuhn pointed out that it's even worse than that. Really, it goes: Theory+Auxiliary Assumptions => prediction. If prediction=false, then (theory=false OR auxiliary assuptions=false).
The OR in that statement can never be completely eliminated. For example, if you assume there is a small invisible planet somewhere insid
Relativity and QM (Score:2)
Ideas in physics are never proven true. They are shown not to contradict any existing evidence, that is all. I can't think of any more than a few decades old which have survived even this.
I can: Relativity (both Special and General) and Quantum Mechanics. These have been around for over 100 years (since 1905). SR and quantum theory are the two most precisely tested scientific theories ever.
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I'm not sure I get what you mean by "truth". As the GP said, physics is about making useful predictions within constraints. Under whatever definition of truth you choose to use (it's hard to tell from your post), it would inherently require contradictions to abound. I certainly don't like any definition that allows us to derive contradictions, since that means we can derive anything, which is certainly pretty useless.
One of the biggest advances in scientific thinking in the 20th century is Popper's analysi
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Glass is fine. Received less than ordered.
Re:Please explain to me the following... (Score:4, Informative)
Um, I am not sure where to start.
You are spouting physics buzzwords with no apparent grasp of what they are or what they mean. Don't try and learn about science from the media - this is the kind of confusion that results.
Dark matter is just matter we can't see. It almost certainly has nothing in particular to do with the Higgs Boson, which is a proposed mechanism by which all matter (dark or otherwise) has mass.
The barrier in question is a potential barrier, and seeing as we live in a three dimensional universe it is a three dimensional barrier; sometimes a potential barrier will be represented in 1 or 2 dimensions for clarity.
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technically dark matter is matter we can't detect. i.e. if there is dark matter it is weakly interacting - which obviously is a real pain if you are trying to work out if it exists.
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"Can't currently detect in a direct way" would be a better description.
I thought we could detect dark matter relatively easily, by its gravitational effects. It's not being able to "see" it, in the sense of detect photons that it has emitted or interacted with that is the problem.
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well we suppose it is there to explain anomalous gravitational effects. The main problem is that there are lots of ideas about what this dark matter could be - WIMPs or black holes etc...
Is real but rare (Score:5, Informative)
.
Quantum Mechanics [feeddistiller.com] feed at Feed Distiller, come there and make your own feeds
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Yes, that would seem to be a similar issue to Hawking or perhaps Cherenkov radiation.
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After looking around a bit, it turns out that the phenomenon I was postulating, but not describing well, is pretty much the same as vacuum fluctuation. (I am aware that it does not look that way, but I had not worded it well.)
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"This won't be debunked, its true. Once you look at the feynman diagrams its......"
And even though everything else may be uncertain, and a thoery which predicts everything down to the smallest bit of truth is lacking, you state with confidence that anything found in feynman diagrams must be true?
Models are just models.
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Maybe, but some [ipernity.com] are better looking than others.
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/note to self: do not read slashdot with girlfriend beside me. ;-)
Valtor
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There is no such thing as "true" in Physics. There is "fits the measurements" and "doesn't fit the measurements".
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You can't say 'it is true' if it hasn't been observed. Just because it falls nicely out of the maths, doesn't mean it corresponds to a physical reality. Hell, string theory has some nice maths to it.
Because it would be incredibly rare even if it did happen, it being forbidden by some currently unknown physics would not have been noticed before now.
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Just because it falls nicely out of the maths, doesn't mean it corresponds to a physical reality.
I don't think you really know that, one way or another.
I remember my theoretical calculus prof threatening to fail me if I didn't give up the idea that when Reimann was referring to dimensions greater than 3, he really did mean, dimensions. For me, it all fell out of the math and had to be reality.
Our search for the subatomic has opened the door for understanding our universe in many dimensions - latest M theory, anyone?
So, I'm just saying - maybe you're on a roll...
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Wrong Diagram! (Score:3, Informative)
This won't be debunked, its true. Once you look at the feynman diagrams its obviously a possible effect.
If you read the paper and not the very bad summary in the article - along with a wrong diagram - then this is not what they are suggesting. They calculate the neutrino digram shown in the article and which you estimated and come up with a probability of O(10^-130) times a function of the neutrino mass, barrier thickness and photon energy. This would be an interesting way to measure neutrino mass if the probability were not so low.
What they are actually wanting to test is whether there are new, fractiona
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exp(-delta E L/hbar c)
where L is the length it needs to tunnel and E is energy barrier the particles tunnelling though.
The second type of light through walls, depends on there being a axion or some other very light weakly interacting particle for the photons to change into, and so the probability could be anything, depending on the properties of the new particle.
Neither the second or third kinds, depend (much) on the length the particle has to tunnel through.
cat (Score:5, Funny)
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Alternatively, perhaps Schrodinger is right now tunneling out of his grave with all these lame jokes ;-)
Re:cat (Score:5, Funny)
He's just spinning in his grave. We're just not sure what direction he's spinning.
Re:cat (Score:4, Funny)
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But we know exactly where his grave is...
...just not its velocity.
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Hard to believe it's been 10 years eh. Greatest movie ever.
Too bad they didn't make any sequels.
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I'm not sure I'd want Catbert as the messiah...
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Great!... Now we need to not only guess if Schrodinger's cat is alive or dead but also if it is still inside the box as well.
- Year 2137. Classroom -
"...And thus was proved that, until we open the box we can only know one of the animal's five fundamental variables: it's life/death state, location, speed, species and political orientation.
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bah, quantums (Score:3, Funny)
I just tunnel over SSH. It works fine...
theory, then experiment (Score:3, Interesting)
From the paper, it looks like this is enough stronger than a hypothesis, to justify the appellation "theory". There's enough information to build detectors that can discriminate the rate of tunneling (if any, of course) between this virtual particle mode, the conversion mode, and "classical" (uncertainty) tunneling.
Time for the experimentalists to take their shot at confirming/denying this one.
One question, though, about the conversion mode: where's a reference for a description of the impetus for the conversion? Is it a sort of uncertainty where the "current" mode of the particle is one of the allowed states of its energy, an oscillation like neutrinos, or does the string (if you go there) pick up energy from an extra-dimensional impact (changing its "tune") then release it in another impact or emission to return to the previous state?
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From the paper, it looks like this is enough stronger than a hypothesis, to justify the appellation "theory".
They are suggesting a new type of charged particle that somehow we have not seen - the diagram in the article summary is the wrong one, you need to read the paper. As such it is extremely hypothetical and, unless the experiment is trivial (and at the sensitivity levels suggested I'm not sure that it is), it would be good to see some evidence that these new charged particles are consistent with the ultra-precise g-2 experimental results testing QED. There are also precision K and B physics experimental data
No, no, no! They cannot do this. (Score:4, Funny)
They already don't quite understand the two types of quantum tunneling they already have, and they want to have a third? Everyone knows that you get your existing shit in order before you go expanding, especially in the current economic climate. Like two types isn't enough already anyway!
Who do they think they are, string theorists??
Serious hypothesis does not equal bunkum (Score:3, Insightful)
I object to using the term debunk when referring to disproving a scientific hypothesis that was put forth in good faith by those willing to have it tested. The word debunk means to expose bunkum - which originally meant empty speech and which came to mean claims made by people who knew they were spewing crap.
The proposed model may turn out to exist only in the brain of a couple of overcaffeinated physicists, but it is not bunkum and cannot be debunked.
So its true then - (Score:3, Funny)
Heh (Score:2)
Only if they use gravity bongs.
Slashdot (Score:2)
I find it interesting that I browse a site that casually has a story like this: "They propose that a quantum particle is capable of changing into a pair of 'virtual particles' capable of passing through a potential barrier before changing back" sandwiched between two stories about video games, as though they both belong in the same broad category (of "nerdy" or something).
A third form of tunneling? (Score:2)
I believe it's actually the fourth. Quantum macroparticle tunneling [trygve.com] was first documented in 1987.
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...but the evidence is clearly stacking up that quantum theory, and with it string theory & m-theory, are pretty much all wrong and utterly flawed.
[citation needed]
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(1) It's supposed to be funny.
(2) I'm not the one making the extraordinary claim that quantum theory is utterly flawed.
(3) There's not enough days left in my life to slog through all the woo-woo sites that I'd get if I googled for claims that QM is wrong.
(4) I'm just fucking lazy, and like to poke fun at people making outrageous claims. This *is* Slashdot, after all.
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Where's the revolution when you need one?
In the spirit of flammable open-source retorts: so, where is it? Post a patch or STFU.
Re:What? (Score:5, Insightful)
Where's the revolution when you need one?
Yeah, why haven't you been doing your math and physics to create this revolution that you see so clearly?
The standard model isn't wrong, any more than newtonian physics is wrong. It works great until you get to the edges, then of course you need relativity, but no one knew that until a few hundred years after Newton when we started getting experiments with strange results. Einstein was the one who explained those results.
Physics models are explanations of what we observe, which is why experiments are crucial. Unless we make more observations, we will have nothing to do but extrapolate current theories, which as you mentioned, break down at extremes, since we don't have as much experimental data at those points.
You want a revolution? Make one!
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This is a problem I see quite often when people try to "counter" a popular scientific theory. They give an example of where the results get blurry and assume some new theory, right around the corner, will topple centuries of research and we will begin anew. Such things are an extreme rarity. For example, if we discovered an entirely new theory of gravitation, hypothetically, that better explains how large bodies move in space, it won't likely change the fact that here on Earth, gravity is fairly constant ev
Wrong is wrong (Score:2)
The standard model isn't wrong, any more than newtonian physics is wrong.
Sorry but we know that both Newtonian physics and the Standard Model are wrong - in the case of the SM we just don't know exactly how it goes wrong yet - other than neutrino masses which are easy to fix. Just because Newtonian physics works for everyday events does not make it correct - it is fundamentally wrong but it is a good and useful approximation to what is really happening.
In the same way the SM is also wrong. It has no explanation of gravity, a huge fine tuning problem and no explanation of Dar
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~phantomFive
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It wasn't until Eddington observed that stars appeared to move during an eclipse that there was an experimental result that contradicted Newton but not Einstein.
Sorry, not an astronomer, but I was under the impression that the inability of Newtonian mechanics to properly account for the precession of Mercury was well known before Einstein's time...
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Let's not forget the black body radiation problem, which Max Planck observed went away if you made this weird assumption that light came in individual little packages whose energy varied with frequency. Of course, light was really waves, not packages, but it did make the calculations come out right. Einstein's contribution to the photoelectric effect was to show that it was also explained by those odd little quanta.
Re:What? (Score:5, Insightful)
There is at present no evidence whatsoever that quantum mechanics, quantum electrodynamics, and so on are wrong. These theories are the best tested theories in human history (certain predictions about energy levels such as those in the hydrogen atom have been verified to 12 or so digits of accuracy.) Quantum mechanics is at this point the best tested and thus most probably correct theory in physics by far. This does not mean that there isn't another underlying theory that will make somewhat different predictions, but the differences would have to be fantastically small.
String theory, on the other hand, has basically no evidence against it, but also virtually no supporting evidence. This is mostly because it hasn't really come up with much in the way of testable claims.
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Re:What? (Score:5, Insightful)
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MoND does a good job of explaining rotation curves of spiral galaxies, but that's about it. It fails on the scales of clusters of galaxies, as even its proponents acknowledge. Nor does it make useful predictions for the growth of large-scale structure.
I have no idea what you mean when you say it explains the same things as the "String Hypothesis."
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There is always MoND, which explains some of the same things as "Dark Matter" and "String Hypothesis", and then there are also some recent findings that suggest that the Universe is not expanding after all... which would throw the String Hypothesis right out the window.
MoND is more like a curve fit through all the existing data than an explanation of its cause. Every time some new piece of data shows up, the curve fit is redone and the mechanics of MoND change to match the new big picture. At any given time, it's self-consistent, but it's never made a prediction that was then proven correct by later evidence.
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I think you sum up quite nicely what a lot of people are failing to understand|: what ever new models / theories we come up with they have to account for everything we currently observe and the new things that current models / theories don't explain correctly.
I think a lot of people think that when we discover a theory of everything or at least the next quantum mechanics we will suddenly unlock the ability to teleport our selves, have faster than light travel and a multitude of other things that are strictl
Completely agree, but... (Score:2)
I totally agree with you that quantum mechanics is very well tested and extremely accurate in every domain we can test.
However, it is known to be wrong. Quantum mechanics (and even quantum field theory) is incompatible with general relativity. As far as I know, no one knows how to reconcile the two. It's the same situation as blackbody radiation prior to quantum theory - we have one model that works on one scale, and another model that works on another scale, but they are known to be incompatible.
The dif
Re:What? (Score:5, Insightful)
I suggest you take up the notion that E=MC^2 is 'wrong' with a survivor of Hiroshima or Nagasaki. If matter/energy equivlance were wrong nothing nuclear would work. Including the Sun, which is essentially a giant, gravitationally bound, thermonuclear explosion.
The notion that light bends is not 'probably' true, it IS true because it was famously measured by Eddington during a solar eclipse. There seems to be some notion amongst the general public that Einstein pulled relativity out of his butt and physicists just accepted it because it was cool. This is not the case at all.
Special relativity was accepted because it explained phenomena that could not be explained by previous theories, and because it has been constantly verified by experiment ever since (time dilation has been measured on aeroplanes using very accurate atomic clocks, and mass dilation is a daily fact of life in any particle accelerator facility you care to name).
General relativity was accepted only because someone went out there, took some measurements, and saw they confirmed Einstein's predictions. Furthermore, we now have everyday technology that depends on GR being, admittedly within certain bounds, correct.
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Right. BTW, one of the earlier difficulties with estimating the age of the planet and time for evolution was that there was no known mechanism for the Sun to continue to shine for more than several thousand years. Something like somebody coming up with an explanation for things that includes a process that started a trillion years ago.
The notion among the general public you state is half right. Einstein did come pretty close to pulling relativity out of his butt. However, physicists didn't accept it
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There is no point arguing with anyone who quotes E=MC^2 as part of relativity. The correct formula, which anyone who studied physics at school, let alone university, would know has a momentum component as well.
You mean the total energy of an object also includes its kinetic energy? Thank you, Captain Obvious! You've certainly toppled damburger's house of cards.
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http://en.wikipedia.org/wiki/Cherenkov_radiation [wikipedia.org]
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However, there is a slight practical problem. While we can measure these things to phenomenal accuracy (10 or 12 digits) the predictions of string theory would only become different from the predictions of quantum theory at somewhere in the range of 25 to 35 digi
Re:What? (Score:5, Insightful)
I never ceased to be tickled by people loudly and ignorantly arguing against the reality of quantum mechanics USING A MACHINE DRIVEN BY FUCKING SEMICONDUCTORS. Its like the flat Earth society getting its message out through satellite television.
Quantum mechanics, like any science, is not a religious doctrine. It doesn't have to be complete and all encompassing to be right; it just has to fit the observations for everything we have tried so far. When it stops fitting the observations, we will give it up (or more likely, refine it in some subtle way) and move on.
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This leads to a fundamental axiom, that truth is more of a philosophical concept than a scientific one. Sometimes that distinction can seem hazy, but I believe it's there.
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QM isn't a 'subatomic' theory - it works at atomic scales, specifically on electrons in atomic orbitals.
You've obviously got the impression that you understand QM, but you clearly don't understand either it or the nature of semiconductors, because you assert the absurd physical proposition that something can be a theory of electrons and holes without being a quantum theory.
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The proposition does not seem that absurd to me considering that I did study such a theory without any quantum mechanics at all, unless quantum mechanics means something other than what I think it means. The whole theory of transistors that
Re:QM explains Transistors? (Score:4, Informative)
The Bohr model of the atom, while incorrect, is a quantum model because it predicts that the electrons of a hydrogen atom can only hold specific quantum energy levels.
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I've never seen a theoretical description of any transistor device that required any form of quantum mechanics for its explanation.
Maybe not transistors as usually used, but LEDs show quantum mechanics quite directly. Here's a simple lab [web.cern.ch] to measure Planck's constant using LEDs.
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While I accept quantum mechanics and its power to describe the sub atomic universe, I still have no idea where this claim about QM being used in the development of the transistor comes from. I learned about transistors using a theory of electrons and "holes" and in fact this viewpoint comes from no lesser source than Shockley himself.
I've never seen a theoretical description of any transistor device that required any form of quantum mechanics for its explanation. Given the fact that transistors are to this day, macroscopic devices, I still fail to see how QM comes into their theoretical explanation. It's a subatomic theory.
Your education was sufficient but incomplete. Note that the Fowler-Nordheim effect was first identified in 1928: http://en.wikipedia.org/wiki/Field_emission [wikipedia.org]
Typical semiconductor QA testing of transistors includes not only hot carrier testing (small channel length in mosfets lead to high electric fields localized close to drain terminals, high electric fields cause energetic carriers that cause interface states or become trapped in oxide) for electron traps and holes, but the principle subtest of hot carrie
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Science was wrong about something in the 18th century != science is equally badly wrong about the nature of atoms now.
Machines that require phlogiston theory to be true simply would not work. Machines that require QM to be true do work, and they enable you to spout your ignorance of the subject to a wide audience.
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