I always thought Schrödinger's cat was both dead and alive.. until now!

[@Mahesh_Shenoy]

Head to squarespace.com/floatheadphysics to save 10% off your first purchase of a website or domain using code FLOATHEADPHYSICS

[@Professordowney]

keep doing it buddy. we love you and your way of being in our feet. we love you no matter what. no matter the subscribers

[@JohnKNMurphy-nz]

Mahesh, please stop and think about blindly repeating the tired old "expect two bars" trope. To be a committed physicist, I believe it is highly misleading to repeat it, it doesn't do justice to Feynman, and adds unnecessary "mysticism" to the analysis. When fringes are visible, the overlapping single-slit interference patterns form the outer envelope of the double-slit bar pattern, this is also a condition derived from quantum theory. The key to the apparent mystery of the fringes is that all of the dots across a single slit pattern become concentrated into the bright lines of the fringes to leave dark areas within the pattern. At distances where fringes are visible, closing one hole barely shifts the overall pattern. Also, according to quantum theory, observing the particle as it transits must scramble the fringe pattern and widen the overall single-slit envelope width. If the screen is close enough to see two distinct bars or lumps, the double slit interference fringes are not visible because you can tell which slit a particle went through. Only when the single-slit patterns merge can you see the fringes. Finally, if the screen is at a distance where two-slit fringes are visible, the single-slit pattern/envelope will also clearly have its own single-slit pattern of fringes overlaid and not be a generic 'lump'. Closing one slit removes the inner fringes, and the interference pattern becomes a single-slit interference pattern with the precise form of a |sinc|^2 function - also as predicted by quantum theory.

[@quantumgyaan]

If molecules of water binding with a state of quantum superposition then how can water even exist after a light source on them....? Doesn't it be that water molecules get detached after any kind of light source

[@HoSza1]

Electrons, they all interact with gravity like they interact with your imaginary light source that you used to try to detect which slit went they through, yet they don't lose the pattern in this case?

[@notmyrealpseudonym6702]

If, at the point of opening the box, both Schroedinger and the cat died ... and there was an afterlife that applied to pets and humans ... then they both would appear alive to each other though dead to all other observers.

[@MannyBrum]

One thing will always be true though, a USB-A connector will always be both upside-down and rightside-up until you look at it. That's why it doesn't go into the port even though you already tried it both ways.

[@fredrik3685]

🎯

[@devonmarcus101]

Dude. This killed me.🤣

[@JokerDoom]

The USB-A is actually a wonderful layman’s explanation of quantum superposition.

[@azmonrougier]

Thought it was just me lol

[@Yipper64]

Actually im pretty sure the reason this frustration happens is because you either start with it the right way, but dont feel it go in immediately, you dont wanna break the port so you dont force it, and try flipping, only for it to be the wrong way, or it starts the wrong way, naturally you flip it over, but you feel resistance again and, again, dont want to break the port so you dont put too much force even though it would just go in. I think the first one is more common.

[@jaredralls9221]

My last job I was in quantum superposition; I was neither working nor fired at the same time

[@NotSoMuchFrankly]

So, you were a quantum physicist.

[@ManOfMonism]

You were working AND fired at the same time

[@jonnelson9760]

I had the same experience. My last job was also in quantum superposition. I too was neither working nor fired. Unfortunately that was until my boss observed me; then I was fired.

[@1949cr]

And there were four of you because of interference?

[@jaredralls9221]

@@1949cr I project well, what can I say….

[@5001Fergies]

oh my god, finding out that covalent bonds are just a result of electrons being in superposition just absolutely blew my mind

[@JvL-e5w]

If covalent bonds are electrons in superposition, why don’t molecules just fall apart if they interact (eg by drinking)?

[@yashen12345]

@@JvL-e5w because superpositions dont fall apart just because of interaction

[@yashpalan6315]

​@@JvL-e5wumm can you explain a bit more what you mean by "when they interact "? The covalent bonds are formed BECAUSE they interact. Which is why I am unable to completely understand your question.

[@nsacockroach4099]

​​​@@JvL-e5w Because in order to localize an electron to such a degree requires strongly interacting with it. However when touching a material you are interacting with an untold number of electrons and atomic nuclei, meaning the individual interaction are not strong enough to collapse the electrons wavefunctions to a smaller space. This also relates to the uncertainty principle. When you localize a particle to a smaller space you increase it's momentum uncertainty, which in turn will give it more energy uncertainty. So you need energy to localize a particle. The type of interaction that you do when touching a material just isn't one that localizes electrons in the material. The energy of that touch is just to spread out.

[@quantumgyaan]

​@@yashpalan6315If molecules of water binding with a state of quantum superposition then how can water even exist after a light source on them....? Doesn't it be that water molecules get detached after any kind of light source

[@gilbes1139]

Schrödinger's cat is meant to demonstrate the absurdity of some interpretations of quantum mechanics, it is not meant to be a demonstrative analog. The double slit experiment is a lot of things, and it is usually misinterpreted. It just shows that all measurement requires interaction and interaction affects outcomes.

[@spartax8986]

This. The amount of times I've had to explain that consciousness isn't what's meant by "observation" is absolutely absurd lol

[@jay9368]

​@@spartax8986So are the conclusions portrayed within this video incorrect?

[@spartax8986]

@@jay9368 In all honesty I stopped watching after I commented. I wasn't remarking on this video just the general idea sureounding observation within quantim physics.

[@huttarl]

So that raises the question, what constitutes "interaction"? For example, is an electron passing through a slit in the original double slit experiment considered to be an "interaction"? Why or why not?

[@jamestaylor3805]

Not measurements in this case... it's just comparison between state A and state B and if they affect Outcome A and B.

[@philipgmetcalf]

The meowing from the box was probably a give-away.

[@Anotherhumanbean12345]

this comment deserves an award

[@rajeshc8587]

@@Anotherhumanbean12345 YEAH

[@rajeshc8587]

WHATIF THE CAT WAS SLEEPING.

[@philipgmetcalf]

@@rajeshc8587 Cats snore

[@user-gr5tx6rd4h]

Does the cat know whether it is alive???

[@TechnooRam]

To be or not to be- Shakespeare. To be and not to be- Schrodinger

[@UKG.science]

😂

[@platypi_otbs]

Brilliant 😂

[@Mahesh_Shenoy]

@@TechnooRam love it! 😻 Also love this.. -curiosity- Schrödinger killed the cat!

[@matthewsheeran]

Technically its an and/or: and before measurement, or afterwards to be precise!

[@Viertelhund]

To be m c times c, that is the energy.

[@mahadevparmekar2565]

Small correction regarding the covalent bond. Its not the quantum superposition that keeps the two nuclei (of the bonded atoms) together. Its the 'energy barrier'. When two elements with valence electrons come together (that is unpaired electrons in outermost shell), the valence electrons have the choice to stay with one nucleus or both nucleus (achieve superposition). But a stable covalent bond is only formed if the total enery of the electrons in superposition is less than the two electrons that are with individual nuclei. This energy is lost in the form electromagnetic radiation (typical infrared or visible frequency for most chemical reactions). That's what 'binds' the covalent bond together. In order to separate them, you need to supply that extra energy from outside. This difference of energy is the 'energy barrier' that makes a covalent bond stable. (Not quantum superposition per se). If this energy is supplied (like electrolysis of water) the base nuclei will get separated and you get the ingredient elements in pure form again. (Hydrogen and oxygen in case if water). So its not the superposition that keeps the covalent bond together. It is responsible for forming the bond, but if no net energy is lost, the elements will separate again. It's the loss of energy during the process that makes a covalent bond stable. (Keeps the nuclei together).

[@atlasxatlas]

thank u

[@romaincorthesy6896]

A very clear explanation ty

[@leonhardtkristensen4093]

I am glad that you put that explanation in. I agree with you. I believe that all the positions of electrons in the atoms are bound with similar energy minimal positions that correspond with what Bohr called the energy level for rings. I believe every thing are energy waves and what we call particles are these energy waves at a local position like standing waves. There are a number of possible positions and each position has an energy level and every thing attempts to get to the lowest possible level. I have found explanations using this principle that explain both electricity and magnetism as pushing forces. We just need a good explanation for what energy really is - not how we perceive it and measure it but what it is. That I think will be the basic fundament for every thing.

[@foodsafari-rj3uq]

​​@@leonhardtkristensen4093 clearly you read or heard some pop scientist talk about particles as excitations of quantum fields and are pretending otherwise.

[@andreyassa7638]

@@leonhardtkristensen4093 Nobody will ever be able to explain what energy really is. That's an inherent aspect of the world. Edwin Powell Hubble once said: 'Equipped with his five senses, man explores the universe around him and calls the adventure Science.' We can't explore the world itself. We can only explore our way of experiencing something, we call world, or universe.

[@galen1957]

The cat has been in that box since 1935. It's dead!

[@dragonking2126]

Fr tho 💀

[@nickeldragon9666]

...or is it?

[@bat2906]

Lol

[@ATHEIST_NEPAL]

😅😅😅yeah i guess

[@KaustubhSingh-m5s]

@nickeldragon9666 *Vsauce music intensifies*

[@LogicalNiko]

One of the more interesting things is that we do not really know how complex a system can be before quantum superposition collapses. We’re actually discovering new areas all the time that can only be described by the superposition state. One of the more complex systems we discovered a few years ago is that photosynthesis depends heavily on superposition. If we attempt to model photosynthesis purely in classical particle physics we find that the photon distribution of energy would overwhelm the cells and pretty much result in bonds being broken and the chlorophyll being destroyed. Instead the photon’s energy is actually behaving similarly to the double slit behavior and being optimally distributed across many different channels at the exact same time, leading to less stress on any particular chlorophyll. Thus without this mechanism plants would not exist and we would not have an oxygen rich atmosphere.

[@whocares.20]

LMAO. Word salad. No physical proof. That did make me laugh.

[@watema3381]

Source(s)?

[@mihailmilev9909]

@@whocares.20 insane

[@mihailmilev9909]

@@whocares.20 you not understanding is not the won you think it is

[@mihailmilev9909]

@@whocares.20 unless you can explain otherwise and why the classical particle model doesn't overwhelm the bonds of the chlorophyll?

[@rune_ined]

My 9th grade chemistry teacher actually had a really good analogy for measuring the speed and spin of an electron. She compared it to a spinning fan blade. When it was on, you could determine its speed based on the button or dial, but couldn't get its position since it was constantly moving. When it was off, you could determine its exact position, but could never get the speed since it wasn't moving at all. Good analogy. Of course not exact, but it definitely helped me understand electron spin well.

[@anupammaity7807]

This explanation is used in Heisenberg theory

[@CookieMage27]

No way you were learning electron spin, in ninth grade, no way…. Sigh… my school was boring

[@meredithgreenslade1965]

We had a cat and named it Schroedinger. Best cat I ever had. He went missing. I didn't know whether he was dead or alive. He was very laid back sort of guy, so very friendly. I missed him so much. True story.

[@CarterRobert-xt4kf]

I want you to know the cyber bullying and harassment that's been going on the slide condescending remarks that are being directed towards me are also going to be directed towards the authorities not only that screenshot there might not be any major laws that are being broken but I'm making this accountability be liable I'm trying to be open-minded and not being harassed by you or your little Conrad's motherfukers in cyber bullying me stealing my cat and then try to make fun of me we're trying to point out the fact that you are being malicious being very very condescending critically above the everybody else is there being keyboard warriors or whatever and trying to be Sly about s***everything on the internet is recorded whether you're doing it out of just trying to make any humor about my losses won't you look in the mirror and see how you're being corrosive towards your own people they had done nothing but help you and you're going to harass me your comments towards me if you are and it will be brought up to the proper channels not only that I will find out who you are whether it's now 14 years down the road I just don't understand how you think being this way towards me is doing any good p I'm the one who lost everything and you want to continue to poke and prod what should be done towards me weather Savannah or Billy Kurt or any of the other people that I will give their names to the authority of possible others trying to cyberbullying me for what reason I have done nothing to nobody and you'll find out

[@wolfyakuza]

wow now i really want a cat to name schrodinger

[@AudaciousBean]

He fulfilled his destiny of mystery.

[@charg1nmalaz0r51]

If a cat goes missing its eitehr they got run over or they were ill. They tend to hide away before they die.

[@GonzoTehGreat]

The cat in this thought experiment wasn't called "Schrodinger", because it was his cat! If HE actually had a cat IRL then that's the name you're looking for...

[@vanillabean7832]

This is the best explanation for quantum superposition and Schrödinger’s cat that I have found, and you explain it in a very engaging way. Thank you

[@nikpil93]

Your ability to explain things, ask the questions we all have, and then answer them is impressive and makes your content stand out. Keep up the great work!

[@duprie37]

Schrödinger's cat both dead & alive inside the box is the biggest clickbait ever in quantum physics. Schrödinger intended it to highlight the absurdity of quantum mechanics, that something is missing, then a thousand popular physics authors took it at face value because simultaneously dead/alive cats in superposition sounds super-cool & sells more books lol. Also: nobody ever seems to care that the cat in question constitutes a sentient observer.

[@minimal3734]

The Copenhagen introduction of the requirement of a conscious observer is where the mess begins.

[@synchronium24]

@@minimal3734 Are you a Many World's proponent?

[@FAK_CHEKR]

You are the first person other than myself that I have ever known to mention that the cat is an observer.

[@mikekolokowsky]

@@FAK_CHEKRBut in quantum physics, the electrons that the cat represents are not observers. So we don’t count the cat.

[@FAK_CHEKR]

@@mikekolokowsky are you saying the cat is not conscious? Or the cat is not the one doing the experiment? I don’t understand.

[@airmanfair]

Every time I see one of your videos I think "oh that's basic stuff, I don't need to watch that", then I think "oh wait that guy always makes great videos" and lo and behold you've taught me something again.

[@GonzoTehGreat]

Quantum Physics is fundamental, but it's not simple or easy to understand, which is why revisiting familiar topics to think more deeply about them is rarely a waste of time.

[@White-tq3si]

I love the fact that I started out this video clueless about a single thing regarding quantum mechanics except that I know the Schrodinger's cat and now I'm invested in the topic.

[@BigWhoopZH]

While I'm sleeping my cat is definitely in a superposition of everywhere on the bed. And sometimes when I wake up just for a brief moment I can see his 9 moonlight shadows on the wall.

[@stevekessell9255]

Probably already mentioned, but it is not true that any interaction collapses the superposition. For example, if an electron/positron 'particle' (i.e. still in the superposition of both) passes near a magnet, the particle interacts with the magnetic field and will bend both up and down. The interaction results in a superposition of paths, where an "electron" would bend up and a "positron" would bend down. But they are still a superposition despite the interaction (a superposition of the particle AND its interactions). If a detector is placed above the magnet, the detector will interfere with whatever turns up (will require some form of entropy change to make the measurement) and it is THEN that the superposition is destroyed. I like the idea that if the decision here is a positron, then the fact the detector 'detects' NO electron, this also collapses the superposition, and a now definite positron continues along on its merry journey, undisturbed, but a fully fledged positron. This experiment has been done many times. When I was taught quantum superposition long ago, the understanding was that it took a "non reversible" interaction (i.e. where the entropy changes due to the interaction) to collapse the superposition. I still believe this to be true. Happy to hear other opinions. Cheers.

[@nikitakipriyanov7260]

Magnets interact with electrons and positrons exactly the same way the light does, via electromagnetic force (the light being an electromagnetic wave). No wonder that in the presesence of magnet the quantum superposition breaks - exactly as it breaks with the two slits and lamp experiment.

[@stevekessell9255]

Except a magnetic field *doesn't* break the superposition, exactly as the two slits experiment *doesn't* break the superposition -- if it did you would not get a diffraction pattern with the 2 slits, nor the results observed when charged particles pass by magnets, or bent by prisms and all the other many experiments that result in the "spooky action". This is well tested and understood, though the actual moment/cause of collapse is still up for grabs - the entropy theory, though strong, may still be wrong, but we CAN say that it is not at the moment it is affected by a magnetic field. If that was the case every particle pair would dissociate immediately as space is filled with magnetic fields. This is not observed. I hope that makes sense. Cheers.

[@silentobserver3433]

@@stevekessell9255 Your entropy theory is actually just Many Worlds Interpretation in disguise: entropy only makes sense as a macroscopic concept, it doesn't really make sense to measure entropy of some small set of particles because *all* their interactions are reversible. So the collapse only happens when particle's superposition seeps into the macroscopic environment (what we would normally call entanglement), i.e. quantum decoherence. It doesn't make a huge step then to see that everything is supposed to be entangled with everything at all times and that's why we don't see quantum superpositions, because our brains are also entangled with the environment and so only perceive a single term of the global superposition at a time. The "collapse" of a wavefunction is then simply the moment when the quantum particle gets entangled with the environment and so with the observer too.

[@FromThe3021]

First of all, thank you for elaborating. Secondly, I don’t expect you to have the answer but I would like to know what your thoughts are in response to my questions, your perspective as to what, if any conclusion you come to. Third and finally, my questions. _Is a superposition simply an unknown? Can Schrödinger’s cat really be neither dead or alive? If it was a little less Luka Magnotta and more of a Adolf type thought experiment where instead of a cat, a human was in the box keeping record of his living moments, does this effect superposition?_

[@silentobserver3433]

@@FromThe3021 1) No, superposition is a precise mathematical object with well known properties. We just don't encounter them in our daily lives, so we don't have "layman" words to describe them, but they are definitely not "unknowns", simply a different state of being. 2) Schrödinger’s cat is just a metaphor for a quantum particle being in a superposition of two different states. If you try this with an actual cat it obviously won't work because a cat is too big, superposition will get destroyed instantly. Even interacting with air molecules is enough to destroy it, so as long as your cat needs to breathe that won't work. 3) Same for humans, humans aren't any special just because we're sentient. Consciousness has no effect on quantum mechanics, an "observer" is simply any macroscopic interaction.

[@ETBrooD]

The act of observing (rather measuring) does not change reality, that's just a very common misunderstanding. Interferrence changes the pattern. When measurement = interferrence, then the pattern must end up being different, because it was interferred with. This is very important to understand because measurement cannot take place without interferrence. On an electron level it's not possible to measure without interferring. By the way this is one of the best videos on the matter I've ever seen. You've done a great job!

[@GrammeStudio]

there's this imagery of wave pattern emerging when a character doesn't look at it. when it does, double bands are formed. but anyone who has performed the double slit experiment in high school knows that's not what happens. at no point during humans looking at the pattern, does it ever display as double band, even when one atom is released at a time. the only time it ever displays double band is when a non conscious detector is introduced. it is NOT consciousness affecting the change in pattern it's such a popular misconception that conscious observation plays a part, that oddly enough even physicists Sean Correll posted that meme.

[@breno2024]

Reality is a conceptual construct. All notions of reality require a conceptual construct, therefore there is no reality outside of consciousness therefore the act of observing creates reality.

[@Slipperyslidin]

But The act of measurement makes it real. Which means your mind is projecting itself to make it 'real' when it is not.

[@GonzoTehGreat]

​@@GrammeStudioMost of your comment is a good explanation of why "experimental observation" doesn't imply "interaction with consciousness". However, Sean Carroll never claimed that consciousness determines QM outcomes. He understands QM better than most.

[@RedRouge-j4j]

Some of us remember the time when voltmeters needed measurable current to work. So when precision was needed this had to be taken into account. Simple case of the measurement affecting result. You try telling young people today....................

[@joedirty6543]

This is one of the best videos I’ve ever seen on this topic. Amazing work! Not only teaches superposition well, but also teach HOW to think about complex topics in general.

[@trevoryoung2447]

The analogy that makes the double slit experiment make sense in my head involves a boat in the ocean. (Disclaimer: I'm not a physicist, just a science enthusiast watching from the side lines, and this is an analogy, so most likely wrong in innumerable ways...) Imagine that you're in a boat out in the ocean. The rudder is broken, so you can't steer, but the engine still works at a slow speed. You're generally pointed towards land, and you start the engine moving forward. Where exactly are you going to land on the beach? Well, the waves of the ocean are pushing the boat around as it moves toward land, adding some variability as to the exact landing spot. Now let's add some giant cliffs between you and the beach, with a small ravine in the cliffs that you could pass through to reach the beach (one slit). Now, assuming that you manage to make it through the ravine without crashing on the cliffs (an electron has to make it through a slit in order to be counted in the experiment), then the cliffs and ravine will shape the waves that you're riding in a way that will make it fairly predictable that you'll hit the beach somewhere in front of the ravine. Now let's change it to where there are two ravines (two slits). Once again working under the assumption that your boat manages to make it through one of the two ravines without crashing on the cliffs, we're now in a situation where, even though you only went through one ravine, the water and waves that you're riding goes through both, and this will cause a wave interference pattern in the water that will influence where your boat will land (something similar to the pattern seen in the double slit experiment). So what about the observability part? My (possibly flawed) understanding is that at such a small scale, you can't observe something without affecting it simply because our tools of observation are too big and can't really get smaller. I mean, how do we observe things? By bouncing photons or electrons (or some other particle) off it and seeing what comes back. Well, an electron colliding with another electron or a photon is almost like two cars crashing into each other. Of course that's going to affect the system. So going back over to the boat and two ravines analogy, you could compare putting a light in the double slit experiment to having the waves in the ocean die down and the water becoming glassy smooth. Under those circumstances, if you make it through a ravine, then it's easy to predict that you'll end up on the beach directly in front of the ravine that you passed through. So in this analogy, the boat is clearly the electron, and the cliffs and ravines are the slits, and the beach is the setup that registers where electrons land. But what about the water and waves. What's the equivalent in the double slit experiment? My current understanding is that the electron is both the boat and the water, and that the waves could be analogous to the quantum superposition. But this is also getting to the point where both the analogy brakes down and our understanding of what happens at the quantum level is incomplete. Perhaps there is no water. Perhaps the water is something that we haven't identified yet. Or possibly something completely different. I ultimately don't know. In any case, that's my two cents from the sidelines all the way back in the nosebleeds. That's the best I've got for trying to make it make sense in some relatable way.

[@Vector12345t]

I like your analogy. As for the water equivalent I may have a possible answer. Some time ago I stumbled upon a video made by Anton Petrov about a theory on the Higgs's Boson and how it works. From what I understood the Higgs's Boson is a particle that interact inside a special kind of "field" that contains the whole universe. He also compared that field with water,even if it was in a different context. Maybe the electron's path is dictated by this field that acts similarly to a fluid and interacts with it in a similar way of the water and the boat in your example.

[@trevoryoung2447]

@INFamousJudge576 Interesting. Admittedly my understanding of the Higgs Boson is quite limited. I'll have to do some further research on it. If you happen to have a link to the video that you're referring to, I'd be interested in seeing it.

[@silentobserver3433]

What you're describing is almost exactly de Broglie-Bohm interpretation of Quantum Mechanics, and the "water" is called a "pilot wave", and yes, it does perfectly describe QM with all the math and whatnot. The only issue is that this "water" has to be able to react to things happening at a distance at speeds faster than light for the theory to work, so...

[@trevoryoung2447]

​@silentobserver3433 That's actually pretty cool that my analogy happens to line up with one of the theories of QM. I'll have to add Broglie-Bohm to my list of things to read up on. But, yeah, I can imagine the need to react faster that the speed of light could be somewhat problematic...

[@johnmangos1512]

You’re analogy reminds me of the aether existence idea.

[@TerryBollinger]

18:16 “[Schrödinger and Einstein’s] argument was, ‘Does it make sense for that cat to be in quantum superposition? No! Therefore, quantum superposition is not real.’ But today, we know it is real, with … double-slit experiments [and] spin, we have a lot of experiments that show … quantum superposition is indeed real.” You mentioned Feynman. Think carefully about what you just said. What, precisely, do double-slit and spin superposition experiments prove? Be as careful as possible to describe what the experiments prove or do not prove, then look for a pattern. Here’s the tricky part: Do either of these examples or others prove that the _internal_ states of complicated objects can be superposed? After all, if you wish to prove Schrödinger and Einstein unequivocally incorrect, that is what you need to prove. A closer examination shows this is not the case. Lab experiments have shown that remarkably large, complicated molecules can form interference patterns after encountering double slits, with the current record using molecules similar in mass to about four DNA base pairs. But what does this well-proven example effect say about the _internal_ state of the object? Well… nothing. If one of these molecules spontaneously “died” (changed state) in the middle of a two-slit experiment, the best prediction available is that the molecule could continue to exhibit two-slit superposition interference during the process. It would land either “alive” or “dead” but still show the interference pattern in both cases. (I am unaware of any interference experiments explicitly looking for interference in small entities that change state.) Okay, fine. But if double-slit experiments don’t say anything about the superposition of alive and dead states, what _do_ they superpose to create such odd behaviors? Do you see the answer? Think about it a bit before reading more. … The critical clue on what is superposed is always what is measured: the two _paths_ that a complicated molecule could have taken to reach the screen. In a lightless environment, the entire universe - not just you - remains clueless about which path was used. As Feynman noted in the 1963 audio recording used to write Lectures Volume III, Section 3-4 (Identical particles), paragraph 1, “If there is a physical situation in which it is impossible to tell which way [a quantum event] happened, it _always_ interferes; it _never_ fails.” There is a reason why Feynman’s method for calculating the most likely outcome of a quantum system is often called the “integral of all possible histories.” That is the most accurate description of what his method does: Add together all of the possible historical paths that an object isolated from the rest of the universe _could_ have taken. We like to think of _history_ as rigid and certain, but experimentation shows something much odder. Quantum mechanics occurs always (and only) when some bit of _history_ remains unknown. One of my favorite elevator-question descriptions of quantum mechanics is that it is “the physics of systems for which history has not yet been set in stone.” Also, I must mention this quibble: In common with most such figures, your visual description of what happens when one slit is closed is not quite right. When one slit is closed, the electrons _do not_ travel like particles for the rest of the trip, at least if they travel in a dark vacuum. When in the dark, they spread like simple waves that _must_ cover almost identical areas on the screen for interference to appear when both slits are open. This need for spreading is also why the interference effect disappears when you place the slit just behind the pattern. If you want a deeper look at just how deep and odd the full implications of double-slit experiments can be, including figures you may find useful, KZbinr Dibyajyoti Das and I did a paper a while back that takes a closer look at Feynman’s double-slit paradox.

[@iosifszilagyi3118]

Believe and don't doubt. This "superposition" explanation is a metaphysical shit. "superposition" is a shorthand for a formula structure, not for the physical reality. Why nobody asks what is happening with the electron which is a current pulse crossing the slits on a physical wall, actually some dielectric or metal resonator structure?

[@JonBrase]

The big problem with Schrödinger's cat is that "alive" and "dead" are not states, they are regions of a large state space, each including many superposition states, and, at the temperatures required for the cat to be in the "alive" region: 1) For every set of macroscopically observable properties the cat can have, there are many individual states that have that set of properties, and so there are many ways for the cat to be in a superposition of two or more states that look identical macroscopically. 2) The cat doesn't remain in any given state (superposition or not) for very long. Thus, to actually observe the cat in a superposition between macroscopically distinguishable states, you have to have it cold enough that any given macroscopic state doesn't have a lot of microscopic variants, and that the cat actually stays in a given state for a length of time sufficient to make the observation. And if you cool a cat down that much, it ceases to be alive.

[@liaxnoelle]

​@@JonBrasesomeone can correct me if I'm wrong, but i think the quantum mechanics exploration doesn't really include the cat at all- the cats state is only a downstream consequence of whether the initial atom is in superposition or collapsed. The thought experiment relies on the atom, as well as a detector which triggers the poison, being in superposition. If the atom decays, the detector releases poison, if it doesn't decay, it doesnt release poison. The question schrodinger (sarcastically) had was whether the 'superposition' implied in the copenhagen interpretation could mean that the atom being in superposition of decayed/not also put the detector in superposition of detected/not, and therefore also all downstream macro consequences also in superposition - i.e., the poison, and then the cat. Rather than saying anything about the quantum state of the cat itself, its kind of asking, "could we create macro events on a human level which depend on a quantum switch that remains in superposition? If so, would we consider those macro events to also be in 'quantum' super position, since their non-quantum deterministic states initially rely on a quantum superposition?"

[@TerryBollinger]

@@liaxnoelle, yes, the cat expands the original atomic superposition state. That’s permissible under the math model used, provided only that no one “observes” either the atom or the cat. Folks debate whether this is possible because no one agrees on what “observation” means in terms of physics.

[@JonBrase]

@@liaxnoelleMy point is that the argument breaks down because the atom being in a superposition can (and generally does) put the detector into superpositions of states that are macroscopically indistinguishable. By the time we get all the way to the cat, the cat both has lots of options for macroscopically indistinguishable states that it can be in superpositions of, and is flitting around rapidly through different states and superpositions of states while nothing appears to greatly change macroscopically. So the argument breaks down because Schrödinger misunderstood the thermodynamics of the situation: if the cat is warm enough to have any possibility of being alive, there are plenty of ways for the superposition of the atom to put the cat into a superposition of states that all look alive or all look dead, and a vanishingly small number of ways for it to put the cat into a superposition that would look "weird" to us.

[@llozhic1]

Well done, sir. Great job explaining this difficult subject in an understandable way, without falling into the trap of using common, but inaccurate, words and phrases. This is very important to understanding science, do this is an important video. I hope a lot of people view it!

[@cadbane9072]

omg bro, I love the way you explain these complicated stuff! It's so much easier to understand. Keep it up, you got a new sub.

[@malachiteofmethuselah9713]

You, still, do NOT understand Schrodinger's cat. The original intention of the thought experiment was meant to demostrate the concept that; No measurement may be made without interacting with the box. You cannot know the state without touching the box, therefore there is no way to know the state of the cat without becoming a part of the data. Superposition is a new interpretation/highjacking of the original cat in a box.

[@minimal3734]

He missed the point.

[@patrickriggenbach3127]

Hey, I‘m asking myself what about the observations or interactions the cat is making (i know it‘s dark but maybe the radioactivity glows…) are they of the same implication as the observation by a human when he opens the box?

[@minimal3734]

@@patrickriggenbach3127 You can't make sense of the Copenhagen interpretation because it is silly. A system does not care if it is observed or not.

[@patrickriggenbach3127]

@@minimal3734 For me quantum physics seems to describe the world of potentials compared to classical physics that focuses on the actual reality?

[@minimal3734]

@@patrickriggenbach3127 'Actual reality' is a difficult term. QM describes the statistical landscape of our world. This only appears as 'potential' from the limited perspective of the experiencing individual. So one could say that the apparent randomness is an artefact of the sampling of the distribution. At the fundamental level, there is no randomness.

[@justinbailey6515]

If you think you understand quantum mechanics, you don't understand quantum mechanics.

[@ayoCC]

It's only important for people who are actually using it to build things, but its fascinating to people for a reason.

[@levimatthew8911]

The best form of the quote is: Anyone who isn't confused by quantum mechanics doesn't really understand it.

[@Drteomas]

@@ayoCC That's a crazy thing to say..

[@armandoramirez714]

Or is it both awesome and crazy to say … 🤔

[@MindovermatterQED]

​@@levimatthew8911 yes, but being confused by it does not mean that one understands quantum mechanics. So if you are confused by Quantum mechanics, you do and don't understand it. Quod erat demonstrandum 🙂

[@ErikTheHighlander]

Man I am so glad I found your channel by accident! The way you explain things and how it clicks in my brain is just perfect!

[@soyanshumohapatra]

Same bro

[@gm5569]

That was absolutely the cleanest ad break transition I've ever seen 100%

[@Gabriel-mf7wh]

13:48 the Schrödinger equation of quantum mechanis is not called the wave equation because it looks like a wave equation. It IS a wave equation. The difference is that it has a non-trivial dispersion relation, so waves can travel at different velocities

[@richardspectacular5327]

It's not a wave equation. It's a diffusion equation.

[@SamiAhmad36]

Such an amazing way of delivering discussions in physics. You held me captive the whole time! It felt like I woke up when the video ended and it was all a dream all along- a beautiful one!

[@hihungryimcam]

The transition into the Squarespace ad was hilarious and genius lol. Great video in general! I've been interested in particle physics and astrophysics for the past few years (very amateurly since I'm 22), and I've also misunderstood this concept. Thank you for a clearer explanation!

[@kzar42]

You have one of the very best channels about physics on KZbin. Thanks for what you do!

[@HardRockMiner]

His neighbor's are just really tired of the avoidance.. They just want to know where their cat is?!

[@Jamius01]

And is he or she alive or dead... >

[@suspicioussand]

​@@Jamius01 so uhhh... the cat isn't exactly dead, but it isn't exactly alive either

[@CarterRobert-xt4kf]

U got it I hope one day that you can get it

[@johngorn268]

I believe the fundamental mistake is in viewing the electron as a dot (particle), when the result of the experiment clearly shows it is not. The dot represents only the portion of the electron that we are able to detect at our scale. As an example, as a three dimensional being, if you look out at the ocean, you will see a mass of water waves, with crests and troughs. If you are a two dimensional being looking out at the same ocean, you will not see the water waves. Or, rather, you will see only the portion of a wave that happens to cross your horizontal line of sight. Each wave will appear as a dot as the crest crosses your line of sight. You would make a fatal mistake in assuming these ocean-objects are dot particles, because there is a great deal of additional structure you are not equipped to see. In fact, if you run experiments, you will find that these ocean-objects appear to produce an interference pattern which will seem to make no sense to your two dimensional world view, but make perfect sense if the fuller reality of the objects is seen in three dimensions. So in summary, there is more structure to the electron than than the dot we are able to directly detect, and the reality of the interference pattern is undeniable evidence of that fact. We need to dismiss the preconceived idea that these subatomic "particles" are actually simplistic solid objects that move like a baseball, when clearly they are not, and rather they are something more akin to strands of spacetime fabric that ripple like waves. The "particle" is the sliver of this object that we can detect with current methods.

[@dennis4419]

Interesting way to think about it. But how would you explain the ability we have to describe physics phenomena in 3 dimensions? Is it just an emergent behaviour of these multidimensional processes we don't understand? Or are even these 3 dimensional processes not 3 dimensional in reality and we just perceive them as such?

[@johngorn268]

@@dennis4419 I'm probably not the best person to answer that question, but I'll try. All scientific models are approximations of reality. The best models have wide applicability and reliability for a broad range of practical observation and use. Newtonian physics has been supplanted by Einsteinian physics. The latter is more broadly applicable, but that doesn't make Newtonian physics wrong. It's just more limited regarding the scope of applicability. Likewise, quantum physics models things that Einsteinian physics cannot, and vice versa. Both work within their scope of applicability. From a practical standpoint, we are three dimensional beings. Technically, we operate in four dimensions since we are time travelers (in one direction and essentially a fixed speed), but even that's a bit hard for us to grasp and visualize. At the sub-atomic scale, our constituent bits may be stuff that involves many more dimensions, but it's pretty much impossible to visualize how that "looks", and is literally beyond our senses or even our current instruments to detect. We need complex math to model it, which will be beyond most people's understanding, and without a lot of everyday practicality. So, physical models that solve problems at our scale and (perceived) dimensionality, and make precise and reliable predictions about real things that we can see or detect, work well for almost everything that matters to us, yet they are not complete. If and when a complete theory is developed that accurately describes everything we can sense or detect at all scales, without exceptions, technically such a theory would replace our current models which are more limited in scope, but may not be practical for normal people to use. We'd probably continue to use our existing models, just as Einsteinian physics replaced Newtonian physics, but regular people continue to use Newtonian physics because it's a lot easier and it works for everything at the normal human scale and scope: we don't normally encounter black holes and speeds where time dilation is an issue, so only physicists need to use the more complex models. I'm not sure if I answered your question, or wandered off the trail a bit. :)

[@dennis4419]

@@johngorn268 thats a great answer, thanks hahah. I guess I was just wondering if 2D beings would also consider their world "complete" and logical, it's just very hard to comprehend that we as humans live in a world that seems so logical but really isn't if you look closely.

[@johngorn268]

@@dennis4419 I think that's a fair question. I would guess the answer would be yes, 2D beings would consider their world "complete", but only up until they developed the scientific method and began to build evidence that there was more "behind the scenes", such that they would begin to question prior assumptions and kick around crazy ideas like the existence of an unseen third dimension. Regarding your final sentence, my view is that we evolved as a species based on the need to do the things necessary to survive in a hostile environment. This would be the end result of millions of years of pressure to learn to recognize and defend against predators, successfully pursue prey, find suitable shelter, learn how to communicate and work cooperatively, and so forth. Our present-day instinctive understanding of how the world works is based on this scope developed by our evolution, of things that we could see and touch. The scale of things that mattered to the developing species ranged from the size of, say, dirt, to mountains, and within a range of miles, and a timescale of a human lifespan or two. There was never a need to understand the scales as vast as the universe or as tiny as a quark, or time scales of billions of years, so we didn't develop those instincts, and if confronted with it, would consider it "illogical" even though it is not. Even as the species developed as far as Newton, its methods served to explain these things at our instinctive scale. It wasn't until about 100 years ago that we began to probe significantly beyond the scales that are instinctive to us. As such, it shouldn't be that surprising that these things seem to be "illogical" in contrast to the more humble instinctive scales that emerged from our long evolutionary history. In my view, the bigger, deeper context is in fact perfectly logical, we just lack a complete understanding of it, and it will seem illogical until we obtain that fuller understanding. It's a slow process because we always try to explain something new in terms of our current understanding, which is a form of confirmation bias. Also, it's difficult to adapt our brains to accept what the evidence shows, and that comes with time. I mean, when I was a kid, the notion of millions of years and millions of stars seemed kind of incomprehensible, but now we talk in terms of billions of years and a trillion trillion stars. We have adapted our thinking to allow us to wrap our brains around realities derived from mounting scientific evidence that cannot be reasonably denied. I would say that trend will continue, and if/when a complete theory is developed that gives explanatory and predictive power to the entire spectrum of scales and dimensions, we'll find ways to get our heads wrapped around it. At least, I would hope so.

[@dennis4419]

@@johngorn268 thanks for answering, you have great takes on these topics.🙏🏻

[@girlinagale]

My friend recently lost her cat, she may have died in a hedge of old age, or be straying out there like a sanyasin. But what's for sure is that cat is in quantum superposition.

[@kristopherguilbault5428]

I have a quantum super cat 🐈😺

[@NarutoUzumaki-om1jw]

My cat wears glasses and it can do quantum mechanics super duper position.

[@tikaanipippin]

smooth transition from quantum space to squarespace

[@ruanholtzhausen4000]

Video on why energy levels need 2 electrons (and why they need to be different spins) with why orbitals are shaped the way they are ,and there are that many energy levels in a orbital, PLEASE😊

[@foodsafari-rj3uq]

Bruh, it's not like he was correct in this video. Spin is even more notorious and complicated to explain. Quantization of orbits as well.

[@avibhagan]

😮, NO the experiment was meant to highlight the mathematical absurdity and to prevent people from applying the mathematical ratchet to reality. The cat had a 50% chance of being alive and a 50% chance of being dead. It doesn't mean that the cat is simultaneously alive and dead at the same time. It's meant to be a warning against assuming that QM solutions are real. For example, when an electron's position is defined as a wave function, it doesn't mean that the electron is evenly distributed within the boundaries of the function. That is what the cat in the box experiment is supposed to explain.

[@minimal3734]

The video completely missed its point.

[@Dick_Gozinya]

The only point of Schrodinger's cat is as a joke. It's just a physics joke, like Werner von Heisenberg getting a speeding ticket, or spherical chickens in a vacuum. That's why the punchline properly goes "...until you open the box and collapse the wave function!"

[@DiscoFang]

Thank you.

[@jeezuhskriste5759]

We aren’t assuming quantum mechanics are real. After almost a century of research, it isn’t really an assumption any more. Schrödinger’s cat doesn’t work because the cat is way too big, not because the underlying principles are necessarily false.

[@avibhagan]

@@jeezuhskriste5759 , no son. Quantum Mechanics is a model. A nice statistical mechanics model. It's a nice model to house separate theories and fill in the blanks. It's become a huge problem in physics because the majority of physicists can't distinguish between the actual theories in the model and the made up tricks of the model which were designed to copy our observations (where no working theory exists). QM is both simultaneously always right and always wrong. If you understand this statement then you understand QM.

[@tomhenninger4153]

Great video! So well explained, as well as it can be understood. Thank you!

[@prayagpr3449]

The Ads are getting too subtle now. Usually I can see a Mid-Video Ad coming ages ago, but in this channel!!!! I am caught off-guard. Good job I guess 😅😂

[@sleethmitchell]

i wonder if ads are effective... i still haven't constructed a web page.

[@prayagpr3449]

@@sleethmitchell yeah same, Ads are almost never effective especially if it interrupts you in the middle of something.

[@lforlight]

SponsorBlock marks these sponsorships regardless of subtlety, to be skipped automatically. If you don't want to waste your time on watching ads, get the extension.

[@mikekolokowsky]

So it’s an ad but not an ad simultaneously?

[@prayagpr3449]

@@mikekolokowsky I think Quantum superposition is getting in your head 😂. It's definitely an Ad, But sure...

[@marie-curiereborn8654]

I've got a question : when there isn't any observer, the electron still interacts with the matter constituting of the two slides device (since he "knows" where he can go, he also "knows" where he can't). Why in this case the electron doesn't loose his superposition state ?

[@minimal3734]

You won't be able to make any sense of QM, unless you familiarize yourself with the many worlds interpretation.

[@OliveVerte-d9m]

The interference pattern will disappear if you can extract the "which-way" information of the electron. For example, you could imagine a double slit device so thin that the electron momentum transfer to the device is great enough to tell you which hole it went through, and in this case you won't see any interference. If any measurement on the slit device itself is not sufficient to extract this "which-way" information, then you will have interferences.

[@silbury2325]

The way I wrap my head around the base of this is to understand how we, as humans, measure or observe things. When we observe a ball with our eyes, photons (light) are being emitted from some source, hitting the ball, and being radiated back out, having interacted with the properties of the surface of the ball. Some of those photons enter our eyes and we interpret the shape and color of that object. So to abstract the "how" of "observation", we need a "thing" to interact with the THING we are trying to observe, before being detected by a sensor of some kind and interpreted into data of some kind. When you start talking about fundamental particles on the scale of electrons and photons, those "things" are really small. That works fine when you're observing something orders of magnitude larger like a ball, but what happens when you try to observe electrons with... electrons? Imagine trying to observe a ball's behavior by hitting it with an identical ball. The measuring ball hits the observation ball and bounces it in another direction. This doesn't answer all the nuances of the quantum, but it's one of the root cause-and-effect cycles that ground our inability to adequately explain what's happening with conventional language. We literally do not know because we don't really have anything smaller than an electron THAT WE CAN EFFECTIVELY USE that we can use to observe an electron without changing the outcome.

[@undefuz]

You are on the right track. The next thing you need to conceptualize is "decoherence" and how "wave function of the universe" split on two independent substates. I hope it will give you satisfied answers.

[@ghffrsfygdhfjkjiysdz]

The reason why this does not work is that the light is still hitting the ball regardless of whether we're looking at it.

[@TheArt3mis]

@@ghffrsfygdhfjkjiysdz The experiment is conducted in complete darkness. It’s only when we introduce something new into the environment-like a small light-that we observe different results. Even the photons from the light are enough to drastically affect the experiment and alter the outcome. Those electrons might be doing something entirely different in the dark. The problem is, any observation we make influences the result, so we’re left in the dark-literally and figuratively. We can only observe the final outcome, not the process itself. It doesn’t mean understanding it is impossible, just that we’re not there yet.

[@MarthaStill-y1v]

I can hardly express how much I love your videos. I have been studying physics informally without the hardcore math usually required for basic understanding. You break it down so well that it is mind-boggling! Also, I love the fact that this video debunks so many ridiculous videos that have tried to say that the act of observation changed the outcome, when it is actually it interfered in a physical way! 💖🌠💖🙂🌞

[@JarmezGD]

I clicked on this code thinking “a 20 minute video will teach me about this seemingly incomprehensible topic? Yeah right” but actually I feel I have a decent understanding of this now! Thanks, great video :)

[@haadislays3138]

when u think you have a decent understanding of quantum mechanics. YOU don't.

[@JarmezGD]

Well I have a better understanding of it than I did before the video

[@prayagpr3449]

Thank you for making Physics even more interesting. Love your job sir ❤❤

[@prayagpr3449]

Thank you so much for the Heart❤❤❤

[@garrick3727]

I'm a statistician not a physicist, but i always thought the cat in the box was to show that the idea of quantum mechanics is absurd because it relies on probability math and the true state cannot be measured. I run into this all the time with expected loss and probability of default. I have to explain to crusty business guys that every loan is both a default and a non-default, with different probabilities of each (summing to 1). The loan is in two different states at the same time. If you sum up all the default amounts across all the loans, it provides an accurate estimate of the overall final state even though we don't know the state of individual loans. Business people rightly find this hard to grasp. They often find examples of single loans where they dispute their state, not understanding that this only works in aggregate. Its like have 1 million cats in boxes, each with a 50% chance of being dead. We can say that it's likely half the cats are dead, but we can't say which ones. Einstein thought that was of limited use.

[@davidtuer5825]

Surely with your loans, what you are explaining is that your stats show that, over a large number such, loans have a statistical loss percentage. It's nothing to do with an individual loan being both non default and a default at the same time. You're just blinding your clients with science.

[@leelee1286]

thank you for this explanation! As a curious person, who is not a math guy, I appreciate this real life example!

[@davidfrigolatubert7621]

The thing is, it is indeed absurd with the cat because the cat is not a quantum object. However, with quantum particles you definitely see experimental behaviours that can NOT be explained with the probabilistic interpretation: it's not that half the particles are in one state and half in the other but you don't know which, they are actually in a superposition state. (If you want an example, I think an early result that shows this is the Stern-Gerlach experiment)

[@HiArashi13]

That's exactly why Schrodinger suggested it. He strongly opposed Copenhagen interpretation, and subjectivity. And the absurdity of the experiment was exactly what he had in mind. Multiverse explanation kinda fixed it (for supporters of subjectivity), but AFAIK Schrodinger was never convinced.

[@HiArashi13]

@@davidfrigolatubert7621 In the experiment, cat is not quantim object, but the radioactive atom, that triggers the poison capsule is. That was the idea of experiment, because Heisenberg stated that only a sentient observer affects the state of the quantum system in superposition. And even more. Subjectivity also dictates that if there's a "presumed" sentient observer inside that closed system, who cannot relay information of the system to second sentient observer, that closed system is in superposition from the perspective of the second observer, but not from the perspective of first. So second (less known) Schrodinger's experiment was kinda continuation of the first. Behind closed doors, one scientist opens the lid and checks the state of the cat. Then after 5 minutes he leaves the room, and another scientist asks him how does it feel to be in superposition.

[@RonDaSantis]

You are so good at this! You explained this better than I’ve ever heard. And I’ve seen many videos on the subject.

[@ExistenceUniversity]

It baffles me that people thought a reductio ad absurdum was a whole theory!! Like Schrodinger was like: "If the earth is flat, and finite, we'd fall off if we went too far." And everyone was like: "Dang, I guess the earth flat and people having been falling off it for decades and nobody knew until now!"

[@shanggosteen9804]

I don't think reductio ad absurdum should ever used for proofs in reality. Do physics even have proofs??

[@MN-dh8vy]

@@shanggosteen9804 no, physics doesn't have proofs indeed. all nature laws are defined from experience and not from a priori knowledge.

[@modfather1964]

yes the earth is flat and non rotating, read the first page of a pilot manual. Hundreds of proofs , you observe but don't believe your senses. On internet archive there are over 200 declassified NASA and military documents stating , flat non rotating earth. the truth is out there, you just need to know where to look. x

[@ExistenceUniversity]

@@MN-dh8vy What is proof if not a call to experience?

[@BudewFan_]

@@MN-dh8vyphysics has proof????? We can have an equation, plug numbers into it, get an answer, and then use the same amount of force wind speed etc to throw something and see if the equation lines up What are you even on bro???

[@originalhgc]

FloatHead in a nutshell: I didn't really understand until I read Feynman's lectures!

[@Rollmops94]

He still does not understand.

[@sarthaksingh5405]

Elaborate pls​@@Rollmops94

[@nikolayzapryanoff1032]

@@Rollmops94 Explain, please. What do you think he failed to understand?

[@DrDeuteron]

@@nikolayzapryanoff1032he’s got nothing. Idk why physics deniers love to post on serious videos.

[@quantumgyaan]

If molecules of water binding with a state of quantum superposition then how can water even exist after a light source on them....? Doesn't it be that water molecules get detached after any kind of light source

[@tm_gura]

My head hurts 🤕

[@nidhinhs9778]

Wow, this is by far the clearest explanation of the double-slit experiment I've come across!

[@IDK._X]

Mahesh sir explained so well, physics is ❤

[@da54177]

Fantastic video! But one thing I'm still unsure about is what counts as an interaction? Clearly gravitational force does not, or else we could never observe a quantum effect. EM interaction does sometimes, but light doesn't break every covalent bond it reflects off of so not always. Same with electromagnetic force, as this would mean we can't have a superposition near any charged particle. This has always been the sticking point for me!

[@PJ-oe6eu]

Making a comment in case someone explains this

[@SachinChauhanDev]

@Mahesh_Shenoy Good question. Could you please answer this?

[@arandomtaco8608]

also making a comment in case someone answers

[@ErnestoStaccolanana]

interested here too

[@OneLine122]

It's not really interactions per say. You can have multiple interactions and it won't change the superposition. I guess it's an interaction that would allow you to pinpoint an exact location. So in the case of the double slit it's the light that pinpoints the particles, so they loose that state. It's basically as if you were funneling a wave through a tunnel, or two tunnels. Since now the possibilities are very restrained, you can observe a position and it's what is meant by "interaction". "Observation" is a better term, but still misleading. It's why when you close a slit, you take out possibilities and you loose the interference pattern. So it's not really the observation, but you need to do something like that to observe the exact position at a certain time. It's the same with the cat, but now it's a specific time, not a location. But the thought experiment is a bit misleading, because there are no superposition to start with but if you open the box and the cat is dead, it represents superposition and if he is alive, it represents a single slit opened, or a state where you can determine position, since you know it was always alive. But if the cat is dead you cannot tell when it died. In that experiment, it's the lack of interaction that makes the cat not superposed. So it's not even about interactions or observations. That's what Shrodinger probably wanted to show.

[@3zdayz]

Hyugen optics did an experiment using light amd a simgle slit and got a bar pattern. The experimental apparatus for electron beams is based on charges and matter the electrons passing next to the electrons in the matter of the slit are going to interact with those too and you're going to get a spread in bars too. I've never actually seen the apparatus for electron interference. I've seen light interferometers all over. And again I've even seen single slid interference with the diffusion of the photon bu the edge of the slit into split bars.

[@sammedia3d]

FINALLY! This is the best explaination i was always looking for. I was always confused as well but not anymore! Thanks a lot! Got you my sub for sure

[@boogieboss]

In video games, the world is calculated by a processor. The visible world is made up of polygons, which only become visible when they’re rendered on the screen. As you zoom deeper into this world, you begin to see the building blocks of the game world polygons, textures, and eventually the underlying mathematics that governs the game. In quantum physics, there’s a similar concept. On the smallest scale of our reality, like with particles in the double slit experiment, things remain undefined until we measure or observe them. It’s almost as if reality is “calculated” when we look at it, much like the world in a video game only truly appears when it’s rendered on the screen. These parallels raise the question, is our reality possibly also “calculated” or generated, similar to a video game? And just like in a game, the laws and logic in our reality might eventually reach a point where they no longer function properly or where the “simulation” shows breaks or glitches.

[@Rere.xierra]

Quantum superposition : condition that we never know cause it was the the condition when things r not seen

[@lc3853]

People raised on immersive video games have a tough time accepting reality.

[@zvijer2960]

And when I turn of the game console, I can see the microwave background from the big bang on my tv.

[@wmstuckey]

Great introduction to Schrodinger's Cat. Allow me to add something to it using quantum information theory. What people fail to mention when talking about quantum superposition using Schrodinger's Cat is the difference between a classical bit of information (like a computer bit being on or off) and a quantum bit of information (a qubit). Both bits produce one of two outcomes when queried (measured), but a classical bit has only one measurement possible while a qubit can be measured in many different ways (infinitely many, actually), each with two possible outcomes. Consider electron spin for example (as mentioned in this video). When you pass an electron through an inhomogeneous magnetic field, the electron is either deflected towards the North magnetic pole ("up") or towards the South magnetic pole ("down"). You can orient the N-S magnetic field in any direction you like and the electrons will still give one of those two outcomes, so electron spin is a qubit with two outcomes of spin "up" and spin "down" relative the the N-S magnetic field. Now suppose you pass electrons through a N-S magnetic field oriented vertically and then send those that were deflected "up" (literally up in this case) to a N-S magnetic field oriented horizontally. What do you expect to find? Well since the electrons have vertical spin up and spin is a vector (picture an arrow pointing upward here), then you probably expect the electron to pass straight through the horizontal magnetic field, i.e., they won't be deflected left or right at all ("up" or "down" relative to the horizontal N-S field). That's because the electron's spin vector (arrow) points up which means it doesn't point side-to-side (left of right) at all, so your horizontal spin measurement of a vertical spin up electron should seemingly yield a result of zero horizontal spin. But what you find instead is that 50% of the vertical spin up electrons are deflected left ("up" towards North pole) and 50% are deflected right ("down" towards South pole). True, 50% left plus 50% right *averages* to zero, but that's not what you expect from the measurement of a vector quantity in ordinary classical mechanics. [Aside: Quantum mechanics gives the classically expected results on average over the discrete or quantum measurement outcomes.] This is quantum superposition, a vertical spin up electron is a quantum superposition of 50% horizontal spin left and 50% horizontal spin right and we write that as |V+> = |H+> + |H-> (divided by root 2 for normalization, but I don't need that to make my point). The point here is the horizontal spin measurement of the quantum state |V+> produces each of its two "up"-"down" (left-right) results in 50-50 fashion. This is exactly what you hear people say about Schrodinger's Cat, i.e., you open the box and find the cat is dead with 50% probability or find the cat is alive with 50% probability. With that information alone, Schrodinger's Cat could be a classical bit or a qubit. If Schrodinger's Cat is a qubit, then there must be a measurement of the cat-box system like the vertical spin measurement of the state |V+> that produces |V+>, i.e., |H+> + |H->, with 100% certainty. We know the measurement "open the box" producing "Live Cat"-"Dead Cat" results in 50-50 fashion is analogous to the horizontal spin measurement of |V+>, so what is the measurement of the cat-box system corresponding to |Live Cat> + |Dead Cat> with 100% certainty in analogy with the vertical spin measurement of the state |V+> that produces |V+> with 100% certainty? And what does its outcome mean physically? If you can't articulate that measurement and outcome of the cat-box system, and every possible measurement between that measurement and the "open the box" measurement, then the cat-box system is just a classical bit ... like opening a box to find a ball or no ball. No quantum superposition there 🙂 To read more about the quantum information approach to entanglement for the "general reader," see "Einstein's Entanglement: Bell Inequalities, Relativity, and the Qubit" (Oxford UP, 2024).

[@tonydamiani8029]

Math is the Truth we use to build the construct of Physics. When the two don’t add up (no pun intended), it’s the physics which is inaccurate. Math is older than the universe, yet abstract.

[@BHFJohnny]

I keep hearing about the double slit experiment, but I've never done it myself. I don't have an electron gun and I don't even know what the dimensions of the slit should be.

[@christianlibertarian5488]

I did it accidentally one day. Sunlight is sort of like an electron gun. By coincidence, two holes in a blind lined up, and broadcast an interference pattern.

[@IGNEIRecords]

you can do it with light

[@joshw3654]

​​​@@christianlibertarian5488this wouldn't be the same effect observed in the double slit experiment though because in the experiment you are dealing with individual quanta. Sunlight is many many photons so it loses its quantum nature. What you're seeing is the wave nature of light but not the quantum effects of individual photons. you can see something similar using a laser pointer

[@nikhilsharma32907]

broke an old crt box like Television and inside it u can find an electron gun

[@Martin_Edmondson]

You can do it with a laser, a few microscope slides blackened with soot, and a needle to score a line in one and 2 lines in another. The distance between the slits can be about 0.5 millimetres or so. Its not that important what it is, just that the point light source (created by the first slit) will go through both double-slits at the same time. The distances between them will determine the interference spread and the ease at which it can be observed. Its not the most practical experiment to do at home, but it is not impossible. The laser is important as it has a single wavelength and has a narrow beam of light which is a point source.

[@checkmates_only]

First video in a long time that i have watched from start till the end.❤🎉🎉

[@alejrandom6592]

18:50 I think you kind of skimmed over the fact that, the modern consensus is that the cat is actually just dead OR alive, since cat is macroscopic.

[@dustinhaas8538]

Right, but this is just a thought experiment or analogy, trying to visualize superposition. We don’t actually care about a cat.

[@stevenbcowan]

Option 8: There are no electrons.

[@TheOGJeff]

Exactly. What even are "electrons"

[@BlueGrenadeTom]

Acorns from the 1980s.

[@shiva4774]

A bunch of electrons not believing in their own existance 😂

[@jack.d7873]

Finally someone understands QFT. Thank you.

[@Sapphairis]

This is a golden comment section

[@cleverkids9897]

One of my students brought my attention to this video. I read some of the comments to the video. Most of them value your explanations and enthusiasm, but I hope you also read comments challenging your explanations. I believe there is a loophole in your reasoning to disregard the case in which the electron goes through the two slits simultaneously. Following your explanation, if one electron goes through the two slits and the screen is located very close behind the slits one should observe two spots rather than the single spot that is actually observed. This is NOT correct. One will never observe two spots on the screen if a single electron is sent. The electron, as long as we know, is indivisible. Each spot observed on the screen is due to a single electron, independently of the path they follow or whether there is interference or not. When the screen is far behind and the two slits are open, you have the formation of interference pattern upon the arrival of many electrons at the spots corresponding to the maxima. However, if you send just one electron you won’t see several spots on the screen, you will see only one spot. Therefore, your reasoning for ruling out that the electron goes through both slits at the same time is not correct. The other point is that if the screen is close behind the slits, quantum superposition is suppressed, and one just will observe two fringes produced by say half of the electrons going through slit 1 and the other half going through slit 2. Since one gets an interference patter only when the two slits are open AND there is quantum superposition (two have the two slits open is a necessary but NOT sufficient condition for the formation of the interference pattern, one will also need the existence of quantum superposition and to send many electrons - after all it is an interference pattern of a probability wave, so one can’t make conclusions from a single event, one need many events [many electrons in this case]). Since your explanation for ruling out option 4) is based on a wrong interpretation, the only valid possible answer to the question is actually that the electron goes through slit 1 and 2 (as long as there is quantum superposition). On the other hand, this is exactly what the math of the wave function tells us, you will have interference in the probability wave only if the wave function is in a quantum superposition in which the electron goes through both slits. Finally, I’d like to suggest not to constantly referring to Feynman, especially on interpretations that are of your own and not made by him. I understand that mentioning Feynman may create more motivation and give you more clicks, but viewers can get the wrong idea that all what you are saying is Feynman’s explanation. I guess the misinterpretation to rule out the option 4) is your own and not Feynman’s. Other than that, I think the intention of the video is a good one. So, I wish you all the best in continuing creating content about science!

[@afrosymphony8207]

this was verrry difficult to read let alone understand

[@khachoang1719]

Thank you. I was so bugged by that point.

[@skjelm6363]

I love your passion and how you share it!

[@portillamail]

Does he tickles you?

[@subhamdekhawat5608]

Your video is very help full for me

[@hussainahmed5837]

Oh man you are just a 💎 You explain all the complex theory easily from the bottom to the top. I really love it💙💙 Love From bangladesh 🇧🇩

[@twiddlinbits]

I don't know much about physics, but the objection to the double slit case 4 seems wrong to me. I see an electron as the process of wave propagation, which may result in a single "particle-like" interaction. The wave not only goes through both slits, it goes lots of other places as well, and it results in a single particle-like interaction, which may, with a certain probability, be at some point on the detection screen. An electron doesn't have a certain probability of being at a given point. It has a certain probability of having a particle-like interaction at a given point. And the observer business is certainly nonsense. An observation is always an interaction, and interactions have effects. If an electron causes a flash at one of the slits, that must be because it has resulted in a particle-like interaction at that point. And I guess, in addition to causing the flash, that interaction also happens to cause a new electron wave which propagates from that point. And a wave initiating from one of the slits will not pass through the other slit such as to interfere with itself on the way to the detection screen.

[@alexbenzie6585]

"I don't know know much about physics" but...I'll just give my uninformed opinion really confidently anyway. I love the internet 🤣🤣🤣

[@mahinshahrier7022]

@@alexbenzie6585 well, they still clearly know more than the person making the video… let’s not even get into that

[@twiddlinbits]

The confidence level isn't as important as the idea. The fact is a potentially fatal flaw in my line of reasoning has occurred to me, but rather than delve deeper down the rabbit hole of uneducated speculation, I figured I'd let someone who actually knows about these things call it out. Thankfully we have people to mock us for having ideas, even when we explicitly don't take them too seriously. What a valuable contribution to the internet.

[@alexbenzie6585]

@@mahinshahrier7022 not really though 🤣

[@casual_sky2]

I'm with Schrödinger and Einstein on this one. I feel a truly deep unsettling feeling about how society is interpreting Quantum Mechanics

[@mineduck3050]

Yes, it is broken. We have mathamagic instead of physics. They build nonsense upon nonsense. We shouldnt have let math people describe and define physics. Should be crunching numbers and weighing things for scientists, physists, and natural phiosophers. Im pretty much down to say its lying now. Radiative gravity? Dark matter placeholders that become real?? Its a crisis of flaws.

[@minimal3734]

How about MWI?

[@drdca8263]

How “society is interpreting it”?

[@scottsycamore8209]

This guy (@FloatHeadPhysics) did a great job in how he explained this to me (this Mechanical Engineer). I feel like he is saying to NOT interpret! It is it's own new thing.

[@casual_sky2]

@@drdca8263 Yes, physicists have widely accepted the Copenhagen interpretation as reality. Especially after Bell's inequality experiment. I don't like it, I feel like we shouldn't just give up and say it's spooky, we should be unsatisfied with these conclusions and observations.

[@ZachsMind]

I'm gonna put this here now at 2:24 and we'll find out how off kilter I am by the end of this video but here's where I am on Schroedinger's Thought Experiment. There is a difference, or should I say distinction, between two states of being. There is Subjective Perception, and Objective Reality. When we're sitting here together in our mutual mindscape and I'm typing these words and you're reading them later, we're both looking at this box with a cat and the poison inside. We assume it's either alive or dead. We can opt even to place a bet. Let's say I assume the cat's alive and you say the cat's dead. Neither one of us know. It's a fifty/fifty guess, but cuz I put money down I'm hoping it's alive. You put money down so you're hoping it's dead. Each of us have a different Subjective Perception of Reality in this instance. Then we agree to open the box and peer inside. Now, I just went to a random virtual coin toss web app and said heads I win tails you win. It was heads. So the cat's alive. So now we can say this is Objective Reality. We're both looking inside this box and we both see that the cat is alive. You can keep your money by the way. I don't believe in gambling. It's just a thought experiment. The point I'm trying to make here. Objectively, the cat was always alive. It's not that it was half dead half alive or both dead and alive or whatever. It was always alive until we opened the box to confirm its status. From our subjective perception of reality, it's a miracle. Yay! \o/ The cat lives. Objectively speaking, it's just something that happened. Or in this case something that didn't happen. The cat's alive. It was alive before. It will remain alive until whatever happens objectively happens to the cat. Our subjective perception has no ramifications on the result. This is where I feel the argument comes in for many people. They're under the impression that Subjective Perception does play a part, but it doesn't. NOW. I ALSO happen to FEEL there is validity to The Many Worlds Theory of Quantum Mechanics, where somewhere beyond our Subjective Perception of Reality there are potentially infinite alternate realities. Not just for this cat's box. Not just for you and me standing here in front of the box. Not just for the room we're in together. Not just for this building or this street or this town or the land we stand under or this planet or our solar system or this galaxy, but this entire universe. We only exist inside one of the potentially infinite alternate realities. We will never be able to open that proverbial box to confirm whether or not there really are Many Worlds out there. So. Do they exist or do they not? Objectively, the Many Worlds Theory of Quantum Mechanics may or may not be true. We have no sufficient evidence to prove it one way or the other, but from our Subjective Perception of Reality... you see what I mean? I could look at this universe from my perspective, and based on what little I know about everything, I can say there are Many other Worlds out there beyond space time. You may agree with me, or you may opt to say it's an absurd concept and there's no evidence to support it. And you'd be right. It is absurd. We can't prove The Many Worlds Theory. Does that mean it's not real? No. Does that mean I'm right and there are Many Worlds out there? No. So. Which is it? Subjective Perception versus Objective Reality. One of those possibilities IS true. We just can't open the proverbial box to confirm the existence of entire universes outside our own. Freaky, eh?

[@henrikaugustsson4041]

That’s basically my understanding of it as well, and I think the video did a mess of trying to explain anything. Just big, fancy words, no real understanding. You explained it much better, imo.

[@DennyDupuis]

Agreed

[@________no-u]

in short "we don't know yet"

[@rickfinn4834]

Thank You! I love to learn about physics but my background is in Biology/Psychology. I've seen over 30 videos on this, many advanced level and very many an hour or longer. I never really got it until I stumbled upon this video. You completely nailed it for me and I instantly liked and subscribed. I also went back to review some others that I watched and now I understanding those as well. I can't wait until I have more time so I can watch more of your work. Brilliant job!

[@EstrellaViajeViajero]

I find a big problem with science communication is that scientists forget the common meanings of words. Colloquially - observation means passive. Unlike Superman's X-ray vision - we are not shining light out of our eyes to look at things. Scientifically - quantum observation is active. And people naturally understand this if you use appropriate analogies. For example - if I could only measure where you are by throwing a basketball at you with a cannon - it's not surprising that when the basketball finally hits a wall (a detector) you might be in a different place or have a different velocity than before the basketball hit you.

[@VikingTeddy]

This is one of my small pet peeves, few science communicators think to explain what an observation is. I understand that when we put a light at the slit, the photons from it will bump in to the incoming electron, giving it a nudge, making it visible and coherent. In physics lingo that's an observation, right? But I rarely see anyone pointing it out.

[@yashpalan6315]

​@@VikingTeddy in physics, especially in theory, the word "observation" is one which no one completely understands. We all kinda know what it means but have no clue what is actually happening during and observation instance (in the sense that we understand how let's say classical balls work). Again one analogy could be that of charge. We all inherently know what a charge is, but if someone asks you to explain what a charge is how will you do that? You just can't, since it is just a fact, one which our current theory cannot explain. Same goes for the word "observation".

[@sensorer]

That still doesn't solve it for one simple reason: if you treat the detector as a quantum system, it shouldn't ever collapse the system it measures. It gets entangled with it, yes, but the superposition should persist. This is what's called as the measurement problem. The collapse appears to have happened at some point(the word appears is crucial here because there are properties of quantum measurement that suggest that there is no such thing as a collapse), but there is no rigorous description of this process and what caused it.

[@yashpalan6315]

@@sensorer yes, but why do you say the superposition should still exist? In principle any interaction with an external system in general leads to decoherence and this decoherence leads to a loss of the superposed states, which is similar to the collapse hypothesis.

[@sensorer]

@@yashpalan6315 Decoherence isn't some kind of magic. It has a mathematical description. And the reality of this description is that superpositions do not disappear

[@straightdrive6192]

Profound. regretting not knowing this when I was learning chemistry.

[@minimal3734]

Far from profound.

[@youngphilosophy6178]

Theoretical physics PhD here. I think this video is more about semantics than anything. When we say the electron is in a superposition, it is wrong to say we don’t have words to describe it. Of course we do. Quantum mechanics can be thought of as a special type of probability/statistical system. Where outcomes are coupled to the basis (direction you decide to measure in) and the Hilbert space. Therefore, quantum mechanics says the ingredients to build superposition is as follows: give me a Hilbert space, and give me a direction to measure in. Superposition is neat and all but it’s a basis dependent phenomenon. What is truly wonderful about quantum mechanics is that the basis you choose to measure in affects what you measure. It is true that the particle is an AND state. But it depends what you mean by and. You cannot say the particle is in two states simultaneously. Instead, the and should refer to the possibilities. Reality hasn’t made its mind so it cannot BE both. It is neither, it is the collection of what it could be.

[@MrJahnic]

Initially I assumed that the applied measurements might be some type of interfering interaction causing the observed difference in behaviour of the classical Doppel slit experiment. However, this was before getting introduced to the delayed-choice quantum eraser experiments. My initial gut assumption might still be correct but it seems that these types of experiments make it less likely. Or am I overlooking some important aspect?

[@atanudas1054]

Hey, Can you help me with one of my doubt? what happens when the experiment is done under light but not observed ? does the particles still acts normally?

[@youngphilosophy6178]

@@atanudas1054 The interference occurs with all elementary particles. It has even been shown with large molecules. The correct choice of word isn’t observe. The correct choice is measurement.

[@youngphilosophy6178]

@@MrJahnic Measurement collapses the wavefunction.

[@furkanunsal-ht5wi]

​@@youngphilosophy6178the question wasnt about the particle used, the question was would the interference pattern still emerge if the measurement device is activated but the device is in complete isolation too. The measurements arent observed by anyone and they doesnt interact with anything else. Would the measutment device still collapse the superposition?

[@ysc.watchdog4743]

You did a fantastic job my hat is off to you, keep doing what you are doing because you can make a difference in many people's understandings and education, you're fantastic

[@lasshaley]

I never understood superposition or wave function collapse before the graphic at 3:12. I actually got a small chill watching it cuz I felt my perception of reality changed right when you showed the collapse. Thanks for this brilliant video.

[@rushikeshkirtikar6147]

Wife: What do you want to have for dinner tonight? Me (after thinking): Rice Isn't this thought superposition? My mind decided only after the question was asked. Before asking there was no answer that existed already in my head. The answer is formed after the mind's 'interaction' with the question. Seems a good analogy to me!

[@steakholder2119]

good one. because it looks like is giving off some information component when it is asked before it enters the slit

[@prayagpr3449]

@@rushikeshkirtikar6147 great analogy, in that case we can say that all of our thoughts and information's are in quantum superposition and when something specific is asked we choose the information relevant to it.BUT the problem is it isn't probabilistic, unless you are guessing. Ah that's it, so all of that is true when we are guessing....

[@MarkAhlquist]

Except, no one would ever choose "rice" Jk

[@sarathi35able]

That's SUCH A GOOD ONE man

[@sarathi35able]

Pretty much sums it up

[@quantum4everyone]

Thanks for the nice video. There are a few things you don’t quite have right. First, an electron traveling through a narrow slit will diffract, and spread out, not appear as sharp lines , as you show. This is much clearer with light, and single slit diffraction (which has its own interference effects as well). The interference from the two slits is in addition to the diffraction effects. Second, there never has been any experiment with a light between the slits as you describe. A much better way to determine the slit it went through is to use light and polarizers that are V for one slit and H for the other. Then shine D polarized light through and you can tell which slot it went through. Note, that while this is a measurement, it preserves the superposition, making an entangled superposition. Interference goes away. Now, add a D polarizer before the screen, and interference comes back. I think of this as a much better way to explain the results, and to bring entanglement into the picture, which Feynman did not choose to incorporate. You can find videos of this on youtube and an older Scientific American article about it. Finally, philosophers have helped us discover the right language, they prefer us to say the slit that the quanta goes through is indeterminate. It still does not explain the how this works in any simple picture though, and I do agree with Feynman that this is indeed the quantum mystery.

[@vitoramaral9730]

Entanglement was the Key point of the schrodinger cat proposal . That you cannot assign an individual state for a cat + radioactive source.

[@quantum4everyone]

@@vitoramaral9730 Agreed. But Schroedinger cat is not a very good way to describe entanglement in spite of its popularity on modern culture. The experiment I described above with two-slits and polarizers is much more plausible. One has to be careful not to conflate a superposition, where the state is indeterminate, with the special form of superposition called entanglement, which requires two degrees of freedom to be indeterminate in a way that their properties will be correlated when measured.

[@vitoramaral9730]

@@quantum4everyoneSure. This was what Schrodinger could find back in 1935: a ridiculous case with a diabolic device to show how quantum effects are strange.

[@quantum4everyone]

@@vitoramaral9730 Actually he used it to show what he disliked about the way quantum was formulated. It has since been perverted as a way to show the bizarre behaviors of quantum. But Schroedinger’s original take remains true.We do not expect macroscopic objects lIke cats to be in a superposition ,only smaller quanta will be in superposition.

[@DevinDTV]

This is a great example of what happens when you try to explain a phenomenon using an incorrect theory. The fact that we can't use logic to explain what is happening with the experiment shows we have something wrong at a fundamental level.

[@mikebull7775]

I am so far from a scientific or mathematic person yet I'm drawn to your Channel just from how excited you are and the way you deliver the content!

[@gregorygant4242]

It can be both dead and alive MATHEMATICALLY speaking but in reality when you make the observation it can only be one or the other.

[@joeboxter3635]

Nature is not waiting for you mrasure before it evolves into the next state. You have set up an experiment, and the outcome will occur. You just don't know the outcome until you look. You have put a detector, and at some point, the detector will detect a decaying particle and kill the cat. When is the only thing we don't know. The cat is not in a superposition. Our calculation of the expected value of the state is. But that is not the state.

[@tejeskave00]

Right, i always found the cat metaphore stupid. What if my college looks into the box without telling me the answer? Then for him the cat is either dead or alive, but for me its still in a super position? What if we make a video of the cat in the box, until we dont watch the video its on super position? Cant the cat be its own observer? So many questions...

[@RabblesTheBinx]

​@@tejeskave00 it was _intended_ to be stupid. The whole point of the thought experiment was to express discontent with the idea of quantum superposition.

[@AlexeiXRomanov]

The thought experiment raises more questions than it answers, and that's intentional-it’s designed to push the boundaries of our understanding and make us question how we interpret quantum phenomena. Your questions are exactly the kind of critical thinking Schrödinger intended to provoke! @tejeskave00

[@jbunstoppable5074]

​@imJACOB99 That is fair because in quantum states all possibilities exist, but once you see it you only can see what is seen

[@kilianklaiber6367]

Schrödinger wanted to disprove the Kopenhagen interpretation of QM. A statement cannot be true and false at the same time, therefore the cat cannot be alive and dead at the same time. Basic logic tells you that this is impossible.

[@kilianklaiber6367]

The probability wave is not the electron and it is not the "state" of the electron. The probability distribution for the cat being dead or alive does not represent the cat. I think you have to discard this notion.

[@kilianklaiber6367]

OH, the "quantum superposition" does indeed apply to the cat in the box. That's the whole point of this thought experiment. Schrödinger transferred the quantums superposition of the decaying radioactive atom to the cat by placing it into the box with the atom!!

[@minimal3734]

The video misses its point.

[@TimJBenham]

Why cat? you could just as well say that basic logic tells you an object cannot be in two places at once so there is no interference pattern. Yet there it is.

[@kilianklaiber6367]

@@TimJBenham It could be any macroscopic object alive. Schroedinger obviously liked cats.

[@baertheblader9402]

I feel you still didn’t answer the question about the cat itself. Is it dead or alive? Was the poison released or not? I believe you said that a cat cannot be in a superposition. And also the atom would have needed to interact with something in order to release the poison, right? And the cat itself is an observer, is it not? So why would opening the box have any effect on whether or not the cat is dead or alive? Also couldn’t you hear the cat meowing or would that be the same as opening the box? So you said it’s not an either or situation but something else, but it was unclear if you agree that the entire thought experiment is invalid or if opening the box actually has some effect on the cat.

[@redseventyfiveprime5018]

The cat is in (|alive>+|dead>)/√2 state that has no classical analogs (and you can't observe it directly). Also, you'll need insanely sophisticated machinery to create and detect such a state. The machinery will also allow to rotate 1|dead>+0|alive> state into 0|dead>+1|alive> state. That is to resurrect the cat, if we'll observe it dead.

[@drdca8263]

@@redseventyfiveprime5018Who says it is in |dead>+|alive> and not |dead>-|alive> ? Or any other pair of coefficients? (:P)

[@redseventyfiveprime5018]

@@drdca8263 You should consult "On the Hardness of Detecting Macroscopic Superpositions" by Scott Aaronson to gather further information. I don't feel sufficiently qualified to answer your question.

[@redseventyfiveprime5018]

​@@drdca8263 You should consult "On the Hardness of Detecting Macroscopic Superpositions" by Scott Aaronson to get further information. I'm not sufficiently qualified to answer that question.

[@OliveVerte-d9m]

The correct answer is to say that the cat is, in a sense, dead OR alive. The cat being a macroscopic object, it will rapidly decohere into a mixture of two classical states, i.e. dead or alive. The superposition disappears and you cannot do an interference between the dead and alive state. However, you still cannot tell if the cat is dead or alive before you open the box.

[@aschwally]

Great description and explanation! Best I've ever heard, super faithful to limits of logic and speech.

[@studywithanimation-xk7fy]

❤❤ your explaination is just 🔥🔥

[@Angi_Mathochist]

Try this: Each electron is going through both slits at the same time as a probability wave, but the probabilities aren't going through both slits equally. Always one slit or the other is more probable. That's why if you put the screen right behind the slits, you detect just one spot behind one slit. And yeah, the cat experiment was supposed to explain what would happen if you could do these things on the level of macroscopic things. Which you can't. The complaint was, "that can't be real, it's like saying this cat is neither dead nor alive, that's ridiculous!" But in reality, what happens on the scale of electrons is not the same as what happens on the scale of cats, and we should never have expected it to be. Electrons aren't cats. Cats are either alive or dead. Electrons have quantum superpositions.

[@thomasmaughan4798]

The idea is to use the cat as the indicator of whether or not a radioactive photon was emitted. The uncertainty at subatomic levels has implications for visible stuff.

[@hannesaltenfelder4302]

The more I "understand" about quantum mechanics, the more fishy that whole science becomes... You once said, "interviewing" Einstein: "But hey Einstein, that sounds like you are making this up, just to keep your theory right." That's exactly how I feel about subatomic everythings. If you can't observe it directly, it seems to be always just theory. This is like: Who ate the cake? And a boy with cake crumbs around his mouth says: it was a big black hole. It lives in the fridge and vanishes every time you close the door.

[@Martin_Edmondson]

The word 'theory' here is used as a framework to describe observations and measurements. Like if you drop an apple it falls, we have the theory of gravity to explain it. It does not mean that the theory is true or not but if the theory is inconsistent with observations the theory is incorrect. That does not mean to say the theory does not have merit and is not true for every situation. Your fridge analogy is indeed a theory, but it is one that can easily be disproven. The effects of 'subatomic everythings' can be observed directly, as in the double slit experiment, the electron scattering experiment, the Michelson-Morley experiment etc etc. Einsteins theories are often counterintuitive but they (with caveats) accurately explain the observations we make. It may sound 'fishy' but that it likely due to you misunderstanding the science and reasoning behind the theories. It 'is' in many ways counterintuitive and does not make a lot of sense when you compare it to classical physics. It requires a new way of thinking about the universe. There are still a great many things that we don't understand, and science is always a work in progress, but that does not mean that it is wrong. Quantum mechanics is real, as real as classical mechanics. Despite our imperfect ability to fully understand it.

[@awebmate]

The theory was good enough for us to create lasers, electron microscopes, diodes, transistors, MRI devices and just about every component in your computer and phome.

[@ChiyokoMcNair]

Amazing. I cannot tell you how much I was enlightened by your inspiration and your fluent explanation. Looking forward to watching many more of your videos now.

[@SystemUpdate310]

For me the only interpretation of the collapse of the wave function that makes sense is, that we are living in a simulations which runs on a computer with limited resources. Then it makes perfect sense that there are shortcuts in the simulation to save resources: by calculating wave functions instead of individual particles saves an immense amount of processing power, but when you measure (interact with the system) on the level of particles you are "forcing" the system to use the more calculation demanding algorithm, but you get a different result. It's like peeking behind the curtains, like when you clip through some geometry in a video game and you see that surfaces that you were not supposed to see, and the texture are not rendered at all to safe processing power...

[@misterprakash]

Interactions are bound to create complexity. On the other hand, who's to say the wave functions are accurate though? Experiments have limitations and so does our theory and understanding.

[@vstankovski]

Would you see this aligned with the 2nd law of thermodynamics?

[@anonymes2884]

The problem is your "shortcut" idea is indistinguishable from "That's just how reality works". (which in general is why, to me, the simulation hypothesis is metaphysical speculation dressed up in sciencey looking clothes - it might even be right, it just seems unfalsifiable)

[@SystemUpdate310]

​@@anonymes2884 Well, if the simulation theory is correct, then what we can perceive is not what we traditionally call "reality" or at least not ultimate, root reality, so it's not a form of "That's just how reality works", but rather "what we experience is not root reality". We have a pretty good intuition about levels of simulations, especially if you have tried VR or similar technologies. As of the matter of unfalsifiability: there are lots of popular but unfalsifiable theories, the many worlds interpretation being one. But I would argue that the simulation hypothesis explains our perception way more adequately than the many worlds hypothesis.

[@tuluppampam]

​@@SystemUpdate310the thing is that the many world hypothesis isn't considered a true hypothesis, because we literally have no way to prove it. To consider a hypothesis true it must be: 1) verifiable 2) falsifiable 3) useful to explain a gap in knowledge 1 allows us to assume a useful theory to be true without proving it, 2 just means that a theory should be allowed to be discarded when false, and 3 is to ensure that we do not end up with pointless theories, although it is far less important than the other two. The many worlds theory and the simulation theories both fail 1 and 2, so they cannot be scientific. It is important to note, however, that scientific knowledge stems from an unverifiable and unfalsifiable metaphysical core of theories, from which we build our own understanding. This 'core' holds stuff such as "1+1=2", and "if something exists it exists", and "laws of nature are constant through time (not in the spacetime sense)", et cetera...

[@charlesco7413]

9:04 I'm not a physicist but you are only focusing on the slits but not the sensor. Perhaps the sensor cause the interference pattern?

[@subhapradosh1384]

11:37 sounds like an excuse to me 🤷

[@tuminhthien8074]

Isnt it like people try to explain what spacetime is or what 4 dimensional is? Cause the one explain to u still dont know exactly what they talking about or is it true. Cause it all the theory .

[@rolandmuncher5438]

Dude if you are not an academic teacher something has gone wrong in the universe. This was one of the clearest and most well thought out explanations of anything I've ever watched.

[@theunseenstevemcqueen]

It wasnt a thought experiment. Schrodinger meant it as a troll on the absurdity (the non-tethered-to-reality-ness) of believing in quantum superposition. A cat cannot be both alive and dead.

[@wbrehaut]

Suppose a cat has spent 5 of its 9 lives: Is it alive or dead?

[@theunseenstevemcqueen]

@@wbrehaut fishing for compliments I see

[@NarutoUzumaki-om1jw]

@@wbrehaut The cat still got 4 more lives. The cat is alive. LOL

[@minimal3734]

You're still misunderstanding. Researching the 'measurement problem' can get you started. Without discussing and comparing the various QM interpretations you won't come to an understanding of the problem.

[@foodsafari-rj3uq]

You can understand it very well without diving into interpretations if you study quantum foundations. But the way he's gone about it is messy and childish.

[@minimal3734]

​@@foodsafari-rj3uq Of course, you can limit yourself to just looking at the maths. This was suggested by David Mermin, who was a proponent of the Copenhagen view (‘Sh*t up and calculate’). This video, however, is about the absurdity of Copenhagen. And to overcome this absurdity you have to look at the alternatives.

[@foodsafari-rj3uq]

@@minimal3734 you have to look at that math for everything. The video is not about the absurdity of Coppenhagen at all. Neither is the cat experiment for that matter.

[@minimal3734]

@@foodsafari-rj3uq The title of the video is ‘Schrödinger's Cat’, a thought experiment designed to demonstrate the absurdity of Copenhagen.

[@normanstewart7130]

@@foodsafari-rj3uq The cat thought experiment was devised to demonstrate the incompatibility of the Copenhagen interpretation with everyday experience.

[@LowellBoggs]

Yo floathead! Outstanding presentation. Thank you Mahesh for this wonderful, thought provoking explanation,

[@User213-z5f]

You are really genius in explaining difficult concepts!!! Love from India❤❤

[@frenchyroastify]

If you wait long enough, you can be pretty sure the cat is dead.

[@Martin_Edmondson]

Yes, you are getting it! Immediately when the cat goes in the box you can be pretty sure the cat is alive. There is a probability distribution describing the likelihood of decay (and subsequent death of the cat) to describe the two states that the cat will be in. Until making a measurement, we don't know for certain wether the cat is alive or dead but we do know the probability distribution (or wave function in quantum mechanics) of the two states. Until the wave function collapses and the state is determined the wave function (or probability distribution) is the reality. When you say 'pretty sure' the cat is dead, you are correct. It is not absolutely true until the metaphysical box is opened and the state determined. Exactly!

[@Achrononmaster]

But Mahesh... @12:40 you *_can_* use prior knowledge to say what superposition is, if your prior knowledge includes Einstein's other paper with Nathan Rosen, the ER one. Just think about it for a minute.

[@Achrononmaster]

@14:10 Feynman did not know this, but all superposition arises from entanglement, hence *_could_* arise from ER bridges (this will be testable some day). It is not always easy to do the analysis this way, far easier to use the tools of Schrödinger or Dirac theory or QFT, but this is one way of giving a realist account for the path integral (or your other favourite formalism for computing QM). Moreover, it is local realism, but will *_appear_* nonlocal if you ignore the topology and presume everywhere local Minkowski topology (but that'd be your mistake). Or you could say this differently: if you cannot see the ER bridges then they'll look like hidden variables... nonlocal HVs. There is no inconsistency with gravity or classical physics with the consequent closed timelike curves, since the minimal ER bridges are just those which cannot Hawking evaporate (conservation laws) but those are the ER bridges that collapse if probed classically (Geroch's topology censorship theorem). However, 'qubits' can traverse the minimal ER bridges, and that is all we need to derive the nondistributive orthomodular lattice of measurement propositions, or equally interference, or equally nondeterministic Hamiltonian time evolution, or equally to explain effectiveness of the superposition principle (a future Cauchy horizon will provide _non-redundant_ information). More here (with a touch of comedy): t4gu.gitlab.io/t4gu/

[@tomriddle8933]

If I had a dollar Everytime I heard someone talk about nondistributive orthomodular lattices...

[@Luc9Nine]

This was the most simple and didactic explanation i have seen so far, and I have seen and read a lot haha. thank you sir!

[@DanielHalperin-i2b]

The more science reveals, the more God is revealed.

[@ArabDweller]

Ah yes, this has been a thing for thousands of years. Back then people didn't know what the Sun was and therefore called it God. Now you're no different from them, stating shit like this on a science video, on an Internet built by humans, after thousands of years of us evolving. Yet, you're still here, making the same exact remarks those people did. Congratulations.

[@TheCudder4life]

@@ArabDweller So in your view, unless God is found God isn't the answer, yet we have theories that we don't know for a fact but still rely on them. Quantum Superposition is a state that cannot be properly explained by human but yet we accept it regardless. Some people think they're going to find out everything about everything. I think maybe one day, when humanity is truly stumped people like you might actually accept the reality.

[@ArabDweller]

@TheCudder4life No need to find out everything about something to call it real. Just like we don't know about "Dark Matter" but we understand it's there. You can measure somethings effect. There is no measuring God's effect as an entity anywhere, let alone the clear given descriptions of Gods from different cultures and centuries. Btw, you might be confusing Theory with Hypothesis. So again, in conclusion, we can't claim the existence of God without evidence of him of any kind. Anyone who believes in God should do so based on evidence, otherwise they should attest to be delusional.

[@TheCudder4life]

@@ArabDweller Dark Matter is indeed a hypothesis about why we believe the universe expands because it seems like something is doing this and we are supposed to be OK and accept it as we continue to do further research. However, say that God did X or Y and your kind will say it's an outrage. Since you cannot definitely prove there is not a God, why can't God also be used for things that just don't make sense or the things that we say we "may never know"? Because you believe we'll eventually find the answer one day? And if we don't we STILL cannot say it's God because of your stubborn refusal to acknowledge there may just be someone or something bigger than your own existence. People like you in a nutshell; "I don't know what it is for sure, but it's definitely not God".