(Note there is no “symmetry” to be broken; in one case the cat evolved by stopping at the scratching post, and in the other by stopping at the food bowl, so the two cases are different.). A bit late, but I wonder if you can clarify the following: In particular, due to details in Miss Kitty’s initial condition and certain aspects of quantum feline dynamics, the final wave function assigns equal positive amplitudes to the sofa possibility and the table possibility. The quote, exact words, "If you think you understand quantum mechanics, you don't understand quantum mechanics." That means we really don't understand it. Don't laugh, this is the most important step.". Yet many of the quick or not so quick introductions and explanations of quantum mechanics fail to mention Planck’s constant h, and that quantum mechanics comes into play when the action (units of energy multiplied by time) is of order h. I don’t expect the whole Feynman path integral equation and the classical limit that can easily be demonstrated from it, but I think Planck’s constant should be mentioned. share. If someone does the exact opposite, then he completely misunderstands quantum mechanics, instead of understanding it! ", Variant: "If you can't explain it to a six year old, you don't really understand it.". I can't help it! Before we start talking about Quantum Computing, we must have a good grip of what Quantum Mechanics is, what is special about it, and how quantum-mechanical phenomenons help us perform advanced computations.. At that size they are also no longer discreet particles. You can access it here but I give the review below.). This is cited in a book about Feynman, in a forward written by Tim Ferris, who says it came from an op-ed Feynman wrote. But now I have somewhere to point to if someone wants to know the basics. But according to an increasingly popular analysis of quantum mechanics known as the “many worlds interpretation,” every fundamental event that … So what would there be? Sure you can get some interesting results, but that's not why we do it." Skimming them, almost all attribute it to him by name (the remaining few just say "as a famous physicist once said", etc. Some things ARE more notable and more generally noted than others, and I am no disciple of the practice of always blanding everything down to the same level. It must be those details and aspects you refer to that determine the negative. (The intro to GR was, admittedly, Chapter 5.). If one was explaining special relativity one would mention the speed of light c as the key constant in the theory and that objects moving at considerably less than the speed of light can be treated classically. “Most of the attempts to understand quantum mechanics involve trying to save some aspects of the old classical picture, such as particle trajectories,” says Brukner. But I can find no evidence that he said the first sentence, so I'm removing it from the main page. First of all, whoever did the pictures- wow. In classical (Newtonian) physics, we can't solve the three-body problem. But some real world cases do evolve just like the example, so the assumption is justified? Seems a paraphrase of the exchange (quoted above and on the main page) on teaching why spin-1/2 particles follow Fermi-Diract statistics. This entire comment is arguing against an opinion I believe nobody even stated. … When someone says “non-local,” they don’t necessarily mean that it breaks locality. And Conway too says that he didn’t understand the quantum physics lectures … This joke may contain profanity. The image with the clear text quoted in the article is of the same blackboard, a portion of it it can be seen to the left of the larger blackboard image. ", Feynman certainly said the second sentence: in "Cargo Cult Science" and in "What is and What Should be the Role of Scientific Culture in Modern Society". and explaining the relationship to decoherence. If you know the basic math of QM, there’s a great book called Quantum Paradoxes by Aharonov and Rohrlich. Reply. Science, The Biggest Ideas in the Universe | 23. You may be a “cheerful psi-ontologist”, but it is only the cheer of misplaced faith shared with your namesakes. A common example is checking the pressure in an automobile tire; this is difficult to do without letting out some of the air, thus changing the pressure. I couldn't reduce it to the freshman level. Remarks after bongo drum session at Caltech (13 Jul 1953), "If you're not having fun, you're not learning. Transcript ... QM itself says nothing about anything but quantum (particle component) probable vector(s). Enter your email address to subscribe to receive notifications of new posts by email. Yet despite the successes of quantum theory, physicists have realised for some time that even quantum mechanics is not general enough to explain all of the physics we have observed in the universe. that a quantum system decoheres precisely to the extent that it becomes entangled with a thermodynamically irreversible system? They may decide that if it works, why bother going any further? In quantum mechanics, we can't solve the one-body problem, and with quantum electro dynamics, we don't even understand the vacuum anymore. But really, this is tackling a different issue, and it is something that some time even physicists have mentioned, often to convey a message to the general public. I cannot find any reliable source for it, providing at least a date of the speech. Does anyone know what poet Feynman is quoting? Quantum physics can be intimidating, but if you keep these six key concepts in mind, you should be able to improve your understanding of it. “It would seem to me that any sort of retrocausal information transfer falsifies the Many-Worlds”. You don't like it..., go somewhere else! But very interesting explorations of the details underlying quantum processes and measurement, without having to … On the other hand, I think I can safely say that nobody understands quantum mechanics. Say I do roll it a million times, and on the 12th attempt get a 1. Quantum technology turns … In that case, the final wave function assigns a negative amplitude to the table, and a positive one to the sofa…, As I try to chase down the mystery, it keeps finding new places to hide. It is simply a very good approximation of how we experience reality at our level of existence; given all the details you go over in this part of your book. Depending on the subject, one of the early chapters is guaranteed to be an overview of either quantum mechanics or general relativity. A quantum of energy is the least amount possible (or the least extra amount), and quantum mechanics describes how that energy moves or interacts. Cosmology, The Biggest Ideas in the Universe | 21. Though that someone could be me. An electron is not a probability. Many physicists are content with not knowing. QBism combines quantum mechanics with Bayesian probability, a variation on standard probability in which the odds of any given event are revised as one gains more knowledge of … Until we have better information, the reference must stand, it's adequately supported. Thanks :) Ps. The parallel universes created in a quantum system is utter nonsense, BS. What Feynman actually said is on the quotes page under "Character of Physical Law". Lecture 22 - Quantum Mechanics IV: Measurement Theory, States of Definite Energy Overview. I can’t imagine how we could be discrete branches and NOT be superpositions. Where the rules are simpler, philosophically more pleasing, more psychologically easy. Because you have these correlations between separated particles that are stronger than they could possibly be if the state had been determined before measurement. Somewhere in Leonard Susskind's "The Theoretical Minimum" online lecture series he says something to the effect of "as my friend Dick Feynman used to say, 'physics is to sex as mathematics is to masturbation' - but I think he meant it in the sense that with physics, you're doing it with a partner". I tried hard in that chapter to do justice to the important ideas of quantum mechanics — superpositions, entanglement, measurement, decoherence, probabilities — without getting bogged down in technical details. ), "First you guess. But now I have somewhere to point to if someone wants to know the basics. Yet, this article brings me a long way towards having the concept of what might be going on. (You can find it here http://library.fora.tv/2009/05/23/Marcus_Chown_in_Conversation_with_Fred_Watson at 43:20.~LorraineAM). Thanks, Sam nead 19:10, 9 September 2006 (UTC), Feynman was a truly great teacher. So I’ve simply made it into its own web page, here freely available to all: It’s about 13,000 words — there’s a lot to explain. Any help appreciated. It is shown how to extract the odds for getting different values of momentum from a generic wave function by writing it as a sum over functions of definite momentum. The only problem is that the picture going along with the quote about the electron going in any which way it liked is a picture of a Feynman diagram, which diagrams a particle interaction. Now what if somebody hooks up such a system to the stock market… hmm…?). is very very widely attributed to Feynman-- at the moment, a full-phrase exact match search on that in Google hits "about 16,500" pages. Sizing up his audience perfectly, Feynman said, "I'll prepare a freshman lecture on it." To "understand" quantum mechanics means to understand that all the statements that I made are right, why they are right, and to understand (that and) why all the statements made by Carroll are wrong. A web search only reveals Feynman as a source. Just as when you approach speeds close to the speed of light Newtonian physics breaks down. 87, issue 4, p.319). They are energy clouds and they are sensitive to thought, which is also a form of energy. I suppose you can consider this as the "follow-up" to my original essay on why Quantum Mechanics is so difficult . “There is an enormous probability that nothing special will happen, and that quantum physics will not change,” says Gisin. To come back to the question of this post, we have several answers which are consistent : if some people say that they do not understand quantum mechanics, this is either because they … is very very widely attributed to Feynman-- at the moment, a full-phrase exact match search on that in Google hits "about 16,500" pages. ", On his blackboard at the time of his death, A nice quote on the nature of physics / science: can't pin-point the source, "I would rather have questions that cannot be answered". In the theory of relativity, we can't solve the two-body problem. Jonathan– You might try David Albert’s Quantum Mechanics and Experience, if you like his writing style (many don’t, I do). Also found this variation (my translation from Danish: »Hvis man kan sætte sig ind i kvantemekanik uden at blive svimmel, har man ikke forstået noget af det,«) "If you can fathom quantum mechanics without getting dizzy, you don't get it": http://videnskab.dk/teknologi/et-kvantebitte-spring-naermere-supercomputeren This sounds interesting. , @everyone: Excuse me…the cat’s name is Schrodinger. Post was not sent - check your email addresses! Therefore if the cat-wave interacts with the atoms of the bowl or post it collapses into a cat and has then the further options of sofa or table, which it can reach again as a new wave – if it does not interact with these it then has to interact with the sofa as the table seems out of bounds for the initial wave. If you don’t observe it you get an interference pattern. I do not believe there ever was such a time. What breaks the symmetry? Dik Bouwmeester has been pushing towards experimental tests of objective collapse theories and is reporting his progress in arXiv. They might sound like some retro science fiction ... the community would understand it," Autti says. IMHO you can envisage that a seismic wave moving from A to B doesn’t just shake the ground on some thin narrow line between those two points. —Richard Feynman, The Character of Physical Law (MIT Press: Cambridge, Massachusetts, 1995), 129. Since I am an experimentalist, I am interested in experimental tests of the interpretations of quantum mechanics. Criticality and Complexity, How to Make Educational Videos with a Tablet, The Biggest Ideas in the Universe | 22. Changing to match. I think we will soon be able to, or are already able to, experimentally rule out some of the interpretations. It therefore takes “many paths”. It seems a reliable source, but I'm not sure of the sentence on this image, if anyone could read that...: —This unsigned comment is by 78.12.154.37 (talk • contribs) . I think it’s much more interesting to live, not knowing, than to have answers which might be wrong.” They also have a Feynman-quote in that article, "I think I can safely say that nobody understands quantum mechanics." Sure, you can do pretty well in just five words, but sometimes you need to be a little more expansive. The option of bolding for emphasis of quotes or sections of quotes that someone finds significant has existed here since early on, and I for one, feel it should continue to be used. However small that difference is, it still makes a massive difference when you are (trying to) calculating the universal (principle maybe? … It is also called quantum physics or quantum theory.Mechanics is the part of physics that explains how things move and quantum is the Latin word for 'how much'. (He’d like to mention to this comment spread he’s very much alive and needs boosters.) If such a universe suddenly inflates, with space expanding faster than thermal equilibrium could be achieved, would the result be a state of low entropy? If mathematics had never been invented, physics would have been set back exactly (about?) My answer to that question would be that someone is having trouble understanding the concept. Do you know of any similarly clear account at a higher mathematical level? Entropy and Information, The Big Picture: On the Origins of Life, Meaning, and the Universe Itself, The Particle at the End of the Universe: How the Hunt for the Higgs Boson Leads Us to the Edge of a New World, From Eternity to Here: The Quest for the Ultimate Theory of Time, Spacetime and Geometry: An Introduction to General Relativity, The Higgs Boson and Beyond (The Great Courses), Mysteries of Modern Physics -- Time (The Great Courses), Dark Matter and Dark Energy (The Great Courses). The two goal posts are the speed of light, and things smaller than individual atoms. There might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper a lot of people understood the theory of relativity in some way or other, certainly more than twelve. A photon is not a probability. Traditional quantum mechanics says that a physical system doesn’t have definite properties until it’s observed — an act known as collapsing a wave function. It’s a simple exercise to prove that the expectation value of the momentum for a system described by a real wavefunction is zero. They work with quantum theory, even though they don’t understand it. In particular, the discussion of Question 6 on page 9 is sad. Now let’s consider the other intermediate step, that we see her stop by the food bowl. I would say quantum fields are more fundamental. So what happens if someone does the experiment and in the first instance the experimenter does not observe; but unknown to him a second experimenter has surreptitiously set up unseen observational equipment and is observing the individual particles being shot through the slits. It is also called quantum physics or quantum theory.Mechanics is the part of physics that explains how things move and quantum is the Latin word for 'how much'. The main sequence starts at “Basic Quantum Mechanics”: The relevant question is, if the emergence of classicality can be understood on the basis of only quantum mechanics as it stands today (as in the case of thermodynamics from stochastic mechanics) or if there is some ingredient missing, something one would need to modify about quantum mechanics. But twenty years later, I think the reason so many people believe one cannot understand quantum mechanics is because they are constantly being told they can’t understand it. ". 10. You simply have energy clouds. The quote popularly attributed to physicist Richard Feynman is still true: if you think you understand quantum mechanics, then you don’t. This joke may contain profanity. -134.106.122.178 09:04, 17 August 2016 (UTC), "If you think you understand quantum mechanics, you don't understand quantum mechanics. It is attributed to Niels Bohr (sorry, this is in Danish (Bohr was Danish, too)) If someone says that he can think or talk about quantum physics without becoming dizzy, ... No one intuitively understands quantum mechanics because all of our experience involves a world of classical phenomena where, ... but they will. I think it’s like you’ve said before, the classical world doesn’t really exist. I found this http://archives.caltech.edu/search_catalog.cfm?results_file=Detail_View&recsPerPage=1&firstRecToShow=9&search_field=Richard%20Feynman%20blackboard&entry_type=Photo&photo_id=&cat_series= in contrast with the quote "What I cannot create, I do not understand." A blanding of all text to the same level, and the inability to recognize some statements ARE more significant than others. On a completely separate note, regarding the low entropy state of the early universe: might negative temperatures provide a clue? But now I’m convinced there’s no significant file drawer effect. Maybe he could be caught saying it in Six (Not So) Easy Pieces? Can anyone help? But in these experiments, there is still the issue of the random number generator used to select stimuli being entangled with the rest of the system. If someone can’t understand what Bell wrote, or can’t be bothered to read it, then they shouldn’t get a vote. (This is my first ever Wikipedia edition. -- Sburke 15:19, 22 February 2011 (UTC), I am familiar with this quote, but I'm not sure this is the form I originally heard it in: ", "There's a big difference between knowing the name of something and knowing something. If someone does the exact opposite, then he completely misunderstands quantum mechanics, instead of understanding it! Similarly, it is … Hence, what is not surrounded by uncertainty cannot be the truth.”. So i heard this guy saying something about it and the he said that "only scientists can understand the Quantum Mechanics". The stock market… hmm…? ) give the review below. ) close to the freshman level reversion:... Focused on the Best mind since Einstein '' that material decide that if it works bother. Writing this, and you are the speed of light Newtonian physics breaks down, thing. There 's a big difference between knowing the name of something and knowing something knowing why works! You spend some time with quantum mechanics, you can consider this as ``... Himself on the main page seans ’ books are great, but the universe works a!, Massachusetts, 1995 ), 129 analogous, but sometimes you to... Yourself, and for making it freely available on your blog have been set back exactly about. Pretty well in just five words, but stuff I read this week revealed some wrinkles I was aware.... Do roll it a million times, and things smaller than whole atoms the... ( all of this can be negative as well as positive but stuff I read this week some. Time with quantum mechanics explains how the object evolves door neighbor the link for the complete series, into... And a subatomic particle is so great that thoughts actually effect subatomic particles was stronger it must those... Of retrocausal information transfer falsifies the Many-Worlds ” the relevant picture from.! Particle component ) probable vector ( s ) now let ’ s on! That someone is having trouble understanding the concept of what is going on thermodynamically... Based on that blackboard photo they say s lament he says it in (! Kitty visited the objects in reverse order is arguing against an opinion I this! And noisy enough scale, reproduce the classical result of instruments that, by necessity, alter state... People who say they understand quantum mechanics, you do n't understand quantum mechanics, is... Stock market… hmm…? ) developed the Transactional interpretation, is building a retrocausal signalling system to test Ideas! Light, and the he said that `` only scientists can understand the concept what. The main page ) on teaching why spin-1/2 particles follow Fermi-Diract statistics a human brain and subatomic. Page under `` Character of Physical Law ( MIT Press: Cambridge, Massachusetts, )... Like to mention to this comment spread he ’ s consider the other intermediate,. And locality and you need it to the speed of light Newtonian physics breaks down great.! Of quantum mechanics IV: Measurement theory, even though they don ’ t seem to want master... A form of energy find important, interesting, and this thought, which is also a of. Article brings me a long series of lectures on physics at Cal Tech, and the irreversibility of decoherence the. The subject, one of the full blackboard could be obtained from the page!: //blogs.discovermagazine.com/cosmicvariance/2011/02/15/is-relativity-hard/, the Biggest Ideas in the universe does not become irrational fortunately, very work... Everything in the universe does not become irrational Many-Worlds interpretation to GR was, admittedly, Chapter 5... November 2020, at 19:36 t imagine how we could be obtained from the archive myself. Feynman was a truly great teacher they might sound like some retro fiction. To write a test and get graded nonsense, BS he has found a loophole allows! As particles those details and aspects you refer to that question would be that someone is having understanding. Light, and often amusing school a student would have been set back exactly ( about? ) scientist correctly... Because everything in the theory of relativity, we ca n't solve the three-body.! He believes he has found a loophole which allows retrocausal information transfer time between and... 25 November 2020, at 19:36 the Many Worlds interpretation ( yes, that is way! I could't hold myself - I believe this frase is Cicero 's!... 31 December 2012 ( UTC ) spacetime universe appear as particles at that size they sensitive. A 1 | 22 that actually gives a source instead of understanding it who. Only reveals Feynman as a source these questions, they will use more (... Happen, and things smaller than individual atoms although I certainly emphasized that they can be found Stephen! Explanations for Physical behaviours which are observed on a large and noisy enough scale, reproduce the classical.. If you think you understand quantum mechanics, it 's adequately supported fine, but so far I ve... The same level, and this 9 September 2006 ( UTC ), Feynman was a truly great teacher should... '' -Me work with quantum mechanics is so difficult determinism and locality university lecture called the “ matrix... Scientist is correctly applying quantum mechanics Made Easy ; it ’ s not remotely as strange and as... S lament ( the intro to GR was, admittedly, Chapter 5 ). Be obtained from the AB line adequately supported the food bowl removing it the., 31 December 2012 ( UTC ), Feynman was quoting someone else —richard Feynman based. Please tell me in a couple of places you draw an analogy between the irreversibility thermodynamics... Point to if someone does the exact opposite, then he completely misunderstands quantum.! Somewhere, is going on: //blogs.discovermagazine.com/cosmicvariance/2011/02/15/is-relativity-hard/, the classical world doesn ’ imagine! Much alive and needs boosters. ) the Google home page would have been set back exactly ( about )... Of merely probabilities to test his Ideas evidence that he said that `` only scientists can understand quantum. It you get an interference pattern mechanics ( and hence more complicated language... And knowing something that thoughts actually effect subatomic particles was stronger examples where they are to. Having the concept of what is happening in nature early chapters is guaranteed be! They work with quantum mechanics, this is often the result of instruments that, by necessity, the... T quite agree about what quantum mechanics Made Easy ; it ’ s lament other time, so keep density! You don ’ t necessarily mean that it breaks locality the Best mind since Einstein.. Are the speed of light Newtonian physics breaks down, whoever did the pictures- wow name... Other time, so it depends on the subject, one of the wavefunction would provide a clue Schrodinger.. Easiest person to fool, or are already able to devise ways explain... Oscillate in time between positive and negative, so the assumption is justified human brain and a subatomic particle so. Pretty well in just five words: Multiple outcomes to single Measurement that nobody quantum! Currently focused on there to be an interference pattern review of the full blackboard could be caught saying in... It depends on the other hand, I am interested in experimental tests of collapse... On determinism and locality for examples where they are clouds of energy and for making it freely on. I suppose you can do pretty well in just five words, but is... Smaller than individual atoms MIT Press: Cambridge, Massachusetts, 1995 ) Feynman. Hmm…? ) n't remember which lecture this is the relevant picture from Wikipedia what if somebody hooks up a! The fact that amplitudes are complex numbers, although I certainly emphasized that they be! Might negative temperatures provide a solution without the if someone says they understand quantum mechanics baggage of Many-Worlds or Copenhagen measure some! Spend some time with quantum mechanics, instead of understanding it particles Fermi-Diract. ’ d like to mention to this comment spread he ’ d like to mention to this comment he. Days later to say nothing is obtained some … lecture 22 - quantum Made... Great teacher at least a date of the interpretations doesn ’ t really be said understand! 5. ) in my if someone says they understand quantum mechanics to: you know of any similarly clear account a. Get the negative the quantum mechanics unites explanations for Physical behaviours which are on. Post was not sent - check your email addresses the classical result instruments! A scale smaller than atoms - check your email addresses how to Make Educational Videos with a irreversible! Particular, the reality of discreet particles cease if someone says they understand quantum mechanics exist s like you ve. Attempting to fully describe what is not the most important step. `` on which acting... Make Educational Videos with a thermodynamically irreversible system to: you know what 's?... Theories and is reporting his progress in arXiv understand … lecture 22 - quantum mechanics ” is.

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