Comments by "Lepi Doptera" (@lepidoptera9337) on "Veritasium" channel.

  1. That's because the headline is not even true. If you are trying to design a CNC router, then bending is to be avoided at almost all cost, otherwise your machine will only do three things: 1) destroy your workpiece, 2) destroy your tools and 3) destroy itself. If you don't understand why, then you still have a lot to learn, "mechanical engineering student". Engineers who are designing bridges and railways and pipelines, however, have learned centuries ago that compliance against thermal stress, etc. is absolutely required to prevent failure. You just don't know what you don't know.
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  2.  @iPlayDotaReligiously  Most machine tools are made for highly rigid tooling processes. If the tool is allowed to move in the direction in which it "bites", then we get a destructive positive mechanical feedback where the machine gets deflected ever farther into the wrong direction. The way to counteract that is with rigidity and mass. "Soft" machining can be done, of course and it's highly useful. That's how optical manufacturing processes work, for instance. Grinding and polishing can produce near atomic precision with machines that are all but precise and are completely floppy at the scale of the final precision. I find that absolutely fascinating in its own right. A stone mason is, if you want, also a "soft manufacturing process". He constantly compares the shape of the stone he has with the shape he wants. The tradeoff is time... soft processes take much longer than a rigid process. So yeah, there are plenty of applications, but one has to chose wisely.
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  3. Visible photons are typically detected with photomultiplier tubes. Less common are bolometers. At higher energy other types of detectors can be used. There are, as far as I know, no reliable direct detection methods below microwave frequencies, one can, however, pull a few tricks from the atomic and nuclear spin spectroscopy repertoire and excite atoms (and their nuclear spins) into semi-stable excited states, which can then absorb a low energy photon (in the range of MHz or potentially even kHz), which transitions them out of the semi-stable state into one that decays rapidly by emitting a visible photon, which can then be detected with a photomultiplier, again. That's a very fun experiment that I did in university once. It's quite amazing how much "gain" a single atom can produce under the right circumstances (on the order of 9 orders of magnitude or more).
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  4. I hope you are not betting, your picks are awful. ;-)
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  5. The detector detects a quantum of energy, not a particle. If there is not enough energy in the field, then the detector can not detect anything. However, emission and absorption processes are all quantized, so one can never emit "less" energy than can be detected.
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  6. There aren't, but you weren't paying attention in school. ;-)
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  7. You didn't listen to the video. This is a problem where even the smartest people are meeting their limits, so much so that it's considered futile to even engage with the problem.
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  8.  @Vichu.  I didn't know about this particular problem in school but I knew about many others... from books I got from the library. One could always learn extracurricular things, most kids simply don't care.
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  9. The problem is that the halt problem is unsolvable.
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  10. For one thing... nobody has ever seen either a particle or a pilot wave. Physics is not religion. It's not in the business of inventing invisible, unknowable entities. All physics has to do is to describe what can be observed, preferably with as little effort as possible. Standard quantum mechanics does just that. At a somewhat deeper level it turns out that the physical vacuum is not made of single-particle states. Quite the contrary. It is not made of particles at all, but of a non-trivial number of quantum fields that interact strongly with each other. As "elegant" as pilot waves may look for the trivial case, trying to describe actual high energy interactions with them would be a horrible mess.
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  11. No. You are welcome. :-)
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  12. It doesn't. You simply don't understand physics. :-)
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  13. Yes, and it's still as false as on day one. ;-)
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  14. Why not? Interference is the result of the absence of interaction. All it says is that electromagnetic waves are extremely linear phenomena.
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  15.  @kennethgee2004  Yes, that things add up in a linear fashion is the absence of interaction. I know that it is counterintuitive, but if you think about that for a little bit, then it will sink in, eventually. Just look at the wave equation. You can see that there are absolutely no mixing products coming out of there. In a self-interacting non-linear field two wave packets with frequencies f1 and f2 will produce mixing products which have the frequencies (f1+f2) and (f1-f2). If electromagnetism were like that, then we would be looking at a totally foggy world with all kinds of weird halo effects wherever two beams pass trough each other. I know what they say about single photons in the double slit experiment, but that's simply total nonsense. Photons only exist in two locations in this experiment: at the light source and at the detector. There are no photons anywhere in the free space between. That's why the double slit is not even a quantum experiment. There is, unfortunately, a long history of Chinse whispers about this experiment that get repeated by pretty much everybody who hasn't spent any time on actually thinking about this.
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  16.  @kennethgee2004  Linear is linear, my friend. Think about it some more. As of now you are very confused about what "interaction" means.
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  17.  @kennethgee2004  The classical wave intensity is simply the average photon density in this case. Photons are energy and energy is the square of the amplitude. Amplitudes add up in a linear fashion, but energy is zero at all times in those minima. There is simply no field at all where you can't find a photon. Your ontological problem stems from the fact that you have been schooled to be a physical realist for classical waves, i.e. you think that classical amplitudes actually exist in nature. QFT proves that they don't. They are just as un-real as the wave function is in quantum mechanics.
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  18.  @kennethgee2004  You mean you are not a physicist. There is no such thing as negative pressure in sound waves. I know, that sucks. :-)
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  19.  @kennethgee2004  There is no such thing as negative pressure. What you are talking about is a linearized sound wave model. Sorry, "physicist", but you are not getting any points for this one.
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  20.  @kennethgee2004  There is nothing less than vacuum, kid. You are making a high school physics mistake here. :-)
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  21.  @kennethgee2004  So you agree that there is no negative pressure and that you made a mistake. Very good. :-)
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  22. That was not a very good book, then.
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  23. Nope. First of all, interference is a linear effect, which literally means that there are no interactions, whatsoever. One part of the wave passes through another without either of them being changed in the slightest. Curiously, humans are having a great deal of intellectual trouble with the absence of interaction. One can see the same problem in relativity, where it is the absence of a global coordinate system that causes all kinds of interesting (and counter-intuitive) effects.
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  24. Nope.
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  25. Magical waves? And why are you using a wrong definition of photon?
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  26. There is no energy to be found at those places. Energy is conserved and a plane wave with constant energy density turns into maxima with higher and minima with lower energy density.
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  27. Veritasium is now physics trolling. There is no such thing as single photon interference.
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  28.  @rysn4566  No, of course not. How are you going to see interference stripes or diffraction patterns if all I give you is a single dot on the screen? You are simply another person who can't tell the difference between one and many. It takes many photons to produce a noticeable diffraction pattern.
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  29. A single photon makes exactly one dot on the screen. How are you seeing an interference pattern in a single dot? Now, do you mean that you don't understand how the ensemble, i.e. an infinite number of independent repetitions of the experiment makes an interference pattern? Why not? Even the classical electromagnetic field is linear, i.e. it does not interact with itself. So why does it bother you that it does not take any interaction between single photon measurements to create a pattern? The pattern is being created by the strong interaction of the field with the geometry of the slits. That is what modulates the photon distribution.
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  30.  @keiyakins  I am also not saying that everything has to be rigid. We have plenty of examples from biology that prove that flexible structures are useful. We make our planes fairly flexible so they can withstand turbulence without catastrophic structural failure. It just happens that most of our technology is built using rigid design. Time will tell if this will change.
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  31.  @johnholmes-rz3vj  Why are you telling us that you don't know anything about machine tools? We don't care about all the things you don't know about. ;-)
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  32.  @johnholmes-rz3vj  Maybe, but you don't know how to use them. ;-)
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  33.  @bunsenn5064  I am a bit more than a geek. I am actually a physicist. ;-)
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  34. @ A photon doesn't have a size. It's just a small amount of energy. Energy is not quantized. What is quantized is angular momentum. And, yes, one can demonstrate angular momentum quantization rather easily with e.g. a Stern-Gerlach experiment. Remove it from atomic physics and there is no stable matter. You would simply not exist and you could not ask stupid questions that were all answered in high school science class. :-)
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  35. Sounds great, until you realize that the double slit experiment is not even a quantum mechanical experiment and that the actual quantum mechanical description of reality is not based on Copenhagen, but quantum field theory. At that point trying to replace Copenhagen with something else to explain a non-experiment begins to look a little silly.
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  36. Yes, actually, "we" do know. A "photon" is an irreversible energy transfer between an electromagnetic field and another physical system. It does not have a shape, a size, a power or a frequency. It has an energy, a momentum and a spin. Those three quantities are necessarily present (and related) because of special relativity. Shape, size, power and frequency are classical properties of electromagnetic waves that are formed by many photons.
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  37. Yes, you don't understand physics. ;-)
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  38. Copenhagen can be easily tested in the lab and has been many times.
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  39. That's cool. Now please calculate the most likely Higgs energy range with it. :-)
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  40. There is nothing to prove. Everett simply didn't understand quantum mechanics and you can find his logical mistake in the second sentence of his thesis.
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  41. What about it? It shows a slightly different interference pattern that's just as easy to calculate.
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  42. Quanta are energy values. They don't have sizes. You don't need to believe every nonsense that is being published on the internet.
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  43. Sounds good, but why are you completely clueless about physics, then? ;-)
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  44. Photons don't have a path. A photon can only be measured once, while objects with paths require at least two independent measurements.
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  45. Then you were screwed because this was the wrong explanation. ;-)
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  46. False and false. ;-)
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  47. No.
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  48. It went into stronger maxima. You were clearly not paying any attention in physics class. ;-)
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  49. @ Photons don't have a path. Photons are small amounts of energy. Energy never had a path, not even in classical physics. It's a system property that gets exchanged between physical systems. That photons are said to have a path is simply the side effect of the unfortunate fact that nobody is paying any attention in science class when the concept of energy is being discussed and then they are not paying any attention, again, when we explain the Copenhagen interpretation. Light is neither a wave nor a particle. Light is the excitation of a quantum field. Wave-particle duality is simply a false dichotomy fallacy. Dirac pointed this out in the 1930s, but, again, nobody was paying any attention in science class, even back then. That still hasn't changed. ;-) If you want to understand what is going in here then you will have to learn to let go of "particles" and "waves" and you have to replace these concepts from classical physics with working concepts in modern physics like "boundary value problem" and "Lie group symmetries".
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  50. A photon is not a wave front. It's a single energy value.
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