I highly recommend Richard Feynman's QED (quantum electrodynamics) lectures. You can find them by googling something like feynman qed lecture auckland.
The quality of the videos is marginal, but the content is spectacular. I am not exaggerating or being metaphorical when I say my jaw dropped (open) while watching these.
I have bought the book many times, as I have given previous copies away to friends when the subject comes up. I wish science at school was first presented this way. It clarifies so much, so quickly, and without anything really complex behind it. Feynman's real-world examples (mirrors, water refraction, etc.) are so clear, it's really a joy to read.
The book is first among a long list of physics books I sound advice to the neophyte. I first came about the book in the library when I was twelve and it triggered my lifelong interest in nature and technology. Good reminder to read it again.
From what I read in the reviews, some physics background is needed to understand this book. Could you perhaps recommend some reads/lectures/moocs that would prepare a physics newbie to be able to read this and comprehend most, if not all, of it?
It really is one of the best books I've ever read.
The explanation of why the angle of incidence is equal to the angle of refraction, or how and why oil makes such pretty colors when mixed in water was mind blowing.
Thanks for the video reference. Part way through corpuscles of light (1/4). Feynman is engaging. From the bit i've seen, yeah, i second the recommendation.
The pilot wave interpretation of quantum mechanics is not a consensus, or even mainstream view. It is not helpful to blankly suggest that these videos illustrate the answer.
"Bohmian mechanics is an interpretation of quantum mechanics (other popular examples are the Copenhagen and the Many-World interpretation). They try to explain the origin of the weird behaviour of measurements in QM. The problem is that these interpetations don't actually make predictions, so you can't do an experiment that tells "Bohmian is right and Copenhagen is wrong". That's why physicists don't research a lot in this area, it is more at the boundary between physics and philosophy. Copenhagen is easy to understand, so in most cases that's being taught (despite its issues)."
The rest of the story as to why Bohmian mechanics is not currently favored as the mainstream interpretation of quantum mechanics can be traced back to orthodox philosophical intransigence. Those that fail to comprehend, or factor in, the ontological advantages that come from the determinism and mathematical clarity of Bohmian mechanics often attempt to downplay the formalism by pointing out that it “doesn’t make any predictions that differ from those of ordinary quantum mechanics.” Technically, that’s not much of an objection because we could equally argue that empirically “the standard theory doesn’t go beyond Bohm’s theory.”
As soon as I read "those that fail to comprehend, or factor in, the ontological advantages" I roll my eyes and stop reading. It matches my quote: "it is more at the boundary between physics and philosophy." So, again, for physicists, it still doesn't matter.
Whenever I read the texts of philosophers and see the "ontology" mentioned as argument, I just conclude "one more guy who wants to find the proof that his god exists." Or remain being paid for something close to the religious thinking which is not called so.
I enjoyed watching the videos with the drops jumping above the waves, it is nice and visual, but the things the physicists have to work with in QM still aren't drops but the measurements and the formulas. If you like to imagine the waves visually, you're free to do it, but it's still not physics.
Feynman: "I think it's much more interesting to live not knowing than to have answers which might be wrong. I have approximate answers and possible beliefs and different degrees of uncertainty about different things, but I am not absolutely sure of anything and there are many things I don't know anything about, such as whether it means anything to ask why we're here. I don't have to know an answer. I don't feel frightened not knowing things, by being lost in a mysterious universe without any purpose, which is the way it really is as far as I can tell."
Of course it matters. Your ontological beliefs define the questions you feel you're allowed to ask and the kinds of experiments you will design.
Copenhagen is just as much "at the boundary between physics and philosophy" as any other interpretation is.
The foundation of QT has been stuck for almost a century now. There's been a lot of detail filled in, but no truly fundamental movement towards answering the hard questions - what does quantum collapse really mean in physical terms, and how do you get from QT to relativity and back again?
What's so terrible about supporting alternative views that may shed some light on those questions?
Physics is ontology. There is nothing else involved. If you're going to pretend the true nature of reality is either irrelevant to physics or is somehow mystically unknowable, you may as well stop doing science altogether.
I'm very sure that as soon as you make any useful prediction from your favorite interpretation you'll get a Nobel prize (and then it would be a real discovery in physics and not a philosophic talk) but nobody produced anything from these interpretations up to now, except maybe getting paid for doing a non-physics work. To me it sounds only like a philosophy question when you write "what does quantum collapse really mean in physical terms" and that "really" exposes it. To compare, there's no "real meaning" in the existence of atoms, electrons and them making molecules, but we still know it makes calculations of chemical reactions obvious. What does it "really" mean? It doesn't matter, they exist, and behave as they behave. What does it "really mean" that the electrons exist can be pushed through the conductors? It doesn't matter if you formulate the question like that, but without them existing, I wouldn't be typing this on the computer, I wouldn't even be sitting on my chair etc. Even more profound, without the electromagnetic force existing there would be no stars and no galaxies. We know that because physics. You can talk about the "meaning of it" but you won't make any discovery unless you actually do some physics.
It's looks like we are talking about differences of use of physics in practice versus advancing of physics as science. No doubt, if I will need to calculate something, being paid for that, I will use proven formulas. Totally agree with you at that point.
However, current major theories are in stuck, they cannot explain what we see, because now we have more data. So it is better to look for something else, which will explain everything we know already and more.
The theories aren't stuck, the existing ones cover everything we can measure, and that is amazing. Once the experiments make any new discovery which wouldn't match with the current theories the changes will be needed. So if you want the faster progress, support the experimental physics and the advancement in astronomy, don't repeat the talk of philosophers who do the equivalent to "how fairies really dance on the pin."
But don't forget: Einstein didn't disprove Newton, Newton's formulas are just a good approximation under the circumstances that were easier for us to observe. So most of what we now know will also remain as a "set of simpler models", as it is based on the valid experiments.
Yep, field is covered by formulas with pretty high accuracy. AFAIK, the only practical field when correction is needed is GPS satellites, but correction is extremely low. However, our vision is moot. Video above just opened my eyes.
I had good teacher of physics. He always told to us that we must fully understand what happens at physical level, and only then start to calculate. „Shut up and calculate“ is not an answer for me.
I also don't feel frightened not knowing things, but now we know more than before. It's hard to imagine that particle must go through all slits and then God must play dice when you saw above video at least once.
General Relativity is based on assumption that speed of light is constant regardless of direction, and tests, done with 1E-17 accuracy, are proving that. But tests done with 1E-21 accuracy shows that speed of light is not constant, so whole theory was built on wrong assumption, but it still accurate to 1E-17, which is huge accuracy, much more than we need in practice.
I don't know what you talk about, if you give some links, maybe it would help. You are free to believe whatever you will, and these "god playing dice" arguments I don't even want to discuss, I'm curious just about the seriousness of this light "tests" you claim, given that the speed of light in vacuum is by definition now fixed -- it is the basis "meter" for the other things to measure. Thanks.
The paper of the guy who can't even publish it on arxiv because he's banned there (it seems that's why it's on vixra instead)? And not because of what he writes but because it is below the necessary scientific literacy level. Arxiv's standards aren't particularly high. Is there any physicist in the world taking his papers seriously?
"I'm serious --- the writing appears to be that of a very intelligent schizophrenic who was trained in physics. It alternates between true statements and nonsense like rap rhymes. A key symptom is the various forms of "holistic fields" or what not that connect to DNA and brains --- this is part of the schizophrenics search for the origin of his internally-created hallucinations and delusions and feeling of "understanding the Universe"."
Regarding the paper you quote: it is... weird... and had he really found anything that would disprove the Michelson-Morley results (what he tries to claim between the lines) he'd already be famous and with his Nobel prize or just wait to get it.
You know "Extraordinary claims require extraordinary evidence"? It appears he doesn't even know (or doesn't want to know) what the necessary evidence for his claims would be.
Is your name by any chance Stoyan Sargoytchev (or B.M. Quine)? If not, where have you even heard/read about that paper?
Edit: (the answer to the response) thanks for answering with "I used first link with keywords similar to what I expected to find. I read linked articles and they are crap, so let dismiss this paper. Sorry." Regarding your question: "Can you accept, after confirming of gravitational waves, that there is field, called „gravitational field“, which affects speed of light, at least temporary?" the answer is: no, it seems you don't understand the basics of physics -- that is, the issues that were known before Einstein and the way he solved them, making the testable predictions. As the Michelson–Morley experiment was performed around 130 years ago, and confirmed many times since, it's really a lot that you miss, so I'm not going to continue the discussion.
I tried to Google article I want to show, but I'm not able to find it, so I used first link with keywords similar to what I expected to find. I read linked articles and they are crap, so let dismiss this paper. Sorry.
Article, I looking for, is about experiment conducted using Sagnac interferometer for more than year to detect deviations of predicted Sagnac effect, from Earth rotation, during year, from actual measurement. They tried to account everything they know and still had small anisotropic variations across year. I'm not able to find that article, so I will try to use LIGO observation of gravitational wave as argument.
Can you accept, after confirming of gravitational waves, that there is field, called „gravitational field“, which affects speed of light, at least temporary?
PS.
It's looks like we cannot continue discussion because of larger delays between posts, so just thanks you for your replies — they were helpful. I will try to prepare better for next time.
Thank you too for answering my questions. And to answer your last: You can imagine that what is measured with LIGO is the change of the space itself as the wave hits the detector. The speed of light remains constant. But please let's not discuss it more in this thread, I also prefer continuing somewhere else on some other occasion.
I found papers: they are calibration results of LIGO detectors. I read them years ago, so I forget anything except that they found systematic temporal variations across day and year, and they are using long 2km arms. Their latest paper: https://arxiv.org/pdf/1608.05134v1.pdf . Systematic error is still there.
Speed of light will remain constant, no doubt, so observer need to be far away to feel difference, otherwise it will be affected by wave, with his instruments and clock. It's why 2-4km arms are able to pickup temporal signal, while smaller setups are able to pickup thermal noise only.
PS.
Not sure that I will survive for so long, because of war with Russia — next week will be hard for me. :-)
It's a LIGO paper that you link now but it doesn't support any of your old claims, sorry. I still have an impression that you don't understand the physics, especially as you claimed before the "variable speed of light," it looks that you throw around something you remembered but never understood. So I'm more interested what's that "war with Russia"? Why next week? Is there a new conscription wave in Ukraine going on? I thought this was the latest state, only professionals:
English language is foreign for me and physics is my hobby, so you can safely assume that I'm noob in physics and use plain English and simple explanations. I need much more time to read in English that in my native language, especially in areas I'm not familiar with. I cannot just look at page and understand it, like in my native language.
Yep, it was not LIGO. LIGO uses Michelson inteferometer, while I'm looking for Sagnac interferometer results. As far as I remember, I started with that article: https://arxiv.org/pdf/gr-qc/0401005v3.pdf , then started searching of articles about rotation sensing mentioned in the article. It looks like that it: http://porto.polito.it/2460498/1/G_GranSasso_18.pdf (or a newer paper).
I looked at FIG. 10: The rotation rate of the Earth measured with the G ring laser as a function of time. Averaging over 2 hours was applied to a corrected dataset, where all known geophysical signals have been removed
But their measurements were done with up to 1E-11 accuracy, which is just not enough, because (IMHO) signal will be 10-100x weaker than gravitational wave, so, IMHO, 1E-21 accuracy is required. So my comment, which started that discussion, is just wrong. :-(
About war: war is still here. We are switched to professional army (hence no new conscription) and situation is stable enough (1-7 killed, 3-15 injured every day). Crimea is still captured. Next week will be hard because I will have meeting with my killers. But, after 2 month of preparation, I forgot about one small but important detail, so I am basically unprepared now. Unfortunately, I cannot stop my play because I want to free Crimea next year, and lot of people are already involved, and contact with Russians is important in this case, so I will try to improvise, like before, when I was unprepared. I will delete that text tomorrow.
I cannot edit previous message, so let discuss a bit further. I'm sick, has high body temperature and unable sleep anyway.
To develop intuition, first you must understand that we are not moving through space, we are propagating through space, because we are waves. Actually, nothing is moved, hence no drag between material objects and space.
I will use video above as example. If you measure speed of sound in water between waves around droplets, you will found that speed of sound is constant, regardless of speed of droplet, because water is not moving at all. Water is contracting and expanding in place. We can perceive «lower» speed of sound in water in case of really big waves, because distance to travel will increase slightly. This is how gravitational waves are caught. Otherwise we are out of luck: we are counting waves to measure distance and time, and that count is not changing when space contracts and expands.
So the only two solutions I see to prove that space is real thing, like water, using waves only, is to:
1) cool vacuum below 0K — cooled vacuum will have slightly different speed of light (someone in USA is already working on that, shortly after discussion about „frozen vacuum“ at HN ;-). It's possible to cool or heat water using acoustic, but we are propagating through space, so cooled vacuum will be left in place while we will propagate away. Hard task. Can be done in interstellar space if ship will be able to stand at same place, or if large enough setup will be used quickly.
2) measure tiny asymmetry of front vs back of pilot wave using Sagnac effect to show that there are small deviations between predicted values and actual values, which are varying over year, as direction of movement and our position in Solar system changes (Solar system already had that asymmetry as measured by Voyagers). I saw (or I think that I saw) paper with exactly that information: experiment with large Sagnac interferometer conducted for over year with high precision which was focused on these deviations, but I still cannot find it. :-(
It's an interesting theory though. What makes it less mainstream than other interpretations? (And is any interpretation of quantum mechanics a consensus?)
John Bell himself, the original author of one of the impossibility theorems, recognized its irrelevance, but he was systematically misquoted, misunderstood, or ignored as he tried to call attention to it. Ironically, he was then portrayed as being against Bohmian mechanics, despite the fact that he was its prime supporter during his lifetime.He said:
“But in 1952 I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the ‘observer,’ could be eliminated…
But why then had Bohm not told me of this ‘pilot wave’?... Why did von Neumann not consider it? More extraordinarily, why did people go on producing “impossibility” proofs, after 1952, and as recently as 1978?... Why is the pilot wave picture ignored in textbooks? Should it not be taught, not as the only way, but as an antidote to the prevailing complacency? To show us that vagueness, subjectivity, and indeterminism, are not forced on us by experimental facts, but by deliberate theoretical choice?”
John S. Bell, "On the impossible pilot wave". Foundations of Physics 12 (1982)
Can't say i can explain it, but the words you're looking for are "local realism".
I really like the pretty pictures from walking droplets, and it makes the thing seem very intuitive. But they're a little disingenuous. It's easy to imagine, or just see a drop of water bouncing in the air on a wave of water. But all this stuff happens in 3d. There's (as far as i know) no separation like air and water. It's more like a sound wave expanding out in all directions.
How do you surf on a sound wave? Not saying it can't be done, it's just that the pretty picture has to be a lot more complicated for the particle to have something to bounce off of. Maybe there are some weird hard thin shells that hover around particles. Who knows? For sure i can say 'not me'.
Yep, you are right — 3D version will be very different. Why not to conduct such experiment in space, where 3D version can be constructed with ease?
Moreover, electromagnetic waves are very different from sound waves, so physic process involving them will be very different. Can you imagine an experiment, which will be closer to reality?, e.g. spinning eccentric charged particles in space.
We have, at this point, strong evidence [1,2] against the straight-forward version of pilot wave theory. Thus pilot wave theory is forced to add more and more epicycles. This, IMO, is part of the reason why it's not becoming more mainstream today.
Can you explain how these are evidence against pilot wave theory? It's entirely compatible with Bell's inequality and indeed makes all the same predictions as other, more popular interpretations of QM, so it's not clear why these papers would be evidence against it.
When any theory has to add more and more complexity to explain the data it tends to be an indication that there is something wrong with the theory and that another theory may be more supported.
> (And is any interpretation of quantum mechanics a consensus?)
There is, broadly speaking, a consensus view. Whether this is because the consensus best matches reality or whether it's dogmatic is probably up for debate, but I don't personally know any professional scientists who believe pilot wave theory (Bell's theorem largely disproved it).
Just by looking at video, it's clear that interference pattern appears because of interference of particle wave with itself. It's also clear that speed of sound in water is constant regardless of speed of particle, particle cannot reach speed above speed of sound in water, speed of particle affects particle itself, and so on.
If the number of energy states of a system are reduced to very few of course the quantum mechanical effects will be more noticible since the "blurred" system that fakes continuity is no longer there to mislead.
Perhaps, this is the case when an observer affects the observation. It appears to the instrument, created according to a model, that electrons are "like grands of sand" when they should be "fields".
But how could these "fields" in principle be observed with an instrument made out of atoms?
This is with electrons and solid state physics where the quantum effects show up at a few mK versus atomic BEC's which must be cooled to the 10's-100's of nK.
The quality of the videos is marginal, but the content is spectacular. I am not exaggerating or being metaphorical when I say my jaw dropped (open) while watching these.
I intend on reading the book soon: http://www.goodreads.com/book/show/5552.QED “QED: The Strange Theory of Light and Matter”