What is Schrödinger's Cat? | Neil deGrasse Tyson Explains... 

Should we do another episode on Quantum weirdness?

Tyson is a rare teacher. You can laugh in tears and learn about complex physics at the same time.

What I've discovered is that I exist in a state where I both understand, and do not understand the concept of Schrödinger's Cat, simultaneously.

Chuck Nice has got to be one of the sharpest dudes on the planet. He just moves things along so seamlessly and with so much humor and insight. He's just wonderful!!!

If I had teachers like that growing up I would have definitely paid way more attention, keep it up guys!

Schrödinger's cat is not a quantum system itself but a normal cat that is affected by a quantum system. The original thought experiment places a toxin in the box that is released by the radioactive decay of a particle which is governed by the laws of quantum mechanics. In this setting you cannot know if the particle has decayed enough to release the toxin until you measure the particle (opening the box). This entangles the cat with the particle.

Not enough has been said here about how good the chemistry is between Chuck and Neil - these two are so good together.

Nice to have a straight to the point explanation. The particles are so small that the light we use to observe them changes their existence.

I laughed so hard at Chuck's photon comment 😂 "Photons want to be part of this skin" 😂 I laughed so hard my nose bled.

My brain was not built to handle learning quantum physics, but Neil makes me wish it was, and Chuck could keep me laughing all the while. Great episode.

Other comments have added information and context NDT left out of the description of the experiment. Most people forget, however, that the thought experiment was actually Schrödinger's critique of quantum theory and not an explanation of it.

I love listening to you and learning. You strike me as a very intelligent and not conceited man. I grew up with my stepfather always responding to me "you writing a book" after I asked a question and most of the time never answering the question. Thank you for whom you are.

The man breaks down complicated subjects into pure simplicity. Wow wow.

Man...i am so thankful for StarTalk. Whenever I'm feeling down, I know that I always can rely on Chuck to lift my spirits right back up. Dr. Tyson is _always_ fascinating and illuminating. But both Chuck's jokes, and his genuine delight at learning things, never fails to bring a smile to my face. Thank you both for everything you do!!

another episode on anything would be great. its just the perfect mix of you two with all the intellect and humor. absolutely great.

I never understood Schrodinger's Cat when it was brought up before. But when you explain that you have a cat in a box, but the cat is not a cat; the cat is a quantum particle, the idea of Schrodinger's cat makes much more sense.

The ability to convey information while simultaneously entertaining in order to keep the students' attention is the mark of a real teacher. It's unfortunate that it is so rare.

Chuck, that scene literally always made me think of the cat. You're not alone.

It's intriguing what he says at 1:40 about the scientific illiterate who thinks consciousness affects what is observed, as if he wasn't the one who made us think that way when he starred in the Cosmos documentary

I’ve watched and read myriad pieces and videos trying to teach me Schrödinger’s Cat, and this is the very first time I’ve understood! Well done, guys!

I want to take a moment to appreciate how easily and how deeply Neil laughs. That willingness to be so joyful is a significant part of why I enjoy watching him.

This was one of my favorites for myriad reasons but Chuck struggling to remember Brad Pitt’s name was classic, but his impersonation of Brad saying, what’s in the box was spot on. Thank you both for providing this amazing and fun way of learning.

This is by far the easiest and more insightful explanation about the principle of uncertainty, and without the use of any animations at all! Also we could say that chuck and Neil are like quantum entanglement souls maaaan 😂

Everyone always asks what is Schrödinger's Cat, but no one ever asks HOW is Schrödinger's Cat.

“I’m a tangent man myself…” Hilarious and educational! Thank you both for making thing accessible and entertaining. All love.

I love these two, I wish they had this kind of education in school. We never had any of this! Great show guys truly love it

Schrödinger's cat seems to have become a meme in pop culture, quite detached from its original meaning and purpose. It is very rare that I hear a profound and meaningful explanation of the Schrödinger's cat thought experiment, which is frustrating as it seems meaningful and useful, rather than just a corny depiction of quantum properties. As far as I understand, the purpose of the thought experiment is to challenge the Copenhagen interpretation of quantum mechanics, that is the idea that a quantum state is inherently uncertain until it has been observed, very much different from our everyday experience, and the Cat experiment emphasizes this. I think the approach of speaking of the cat as not a real cat but a "quantum cat" distorts the thought experiment. The point, I think, is that it is a very familiar object, that is a real cat, that gets entangled with a quantum event, and hence forces the cat into a superposition state. Although not being a researcher of physics, it seems to me that the cat experiment actually does manage to scale up quantum level phenomena to the macro scale. And it is a very interesting challenge to the Copenhagen interpretation, and discussing responses to the thought experiment should be more or less necessary for the thought experiment to make sense.

That was the funniest and least confusing explainer of quantum physics concepts. Good job, guys!

"Photons wanna be a part of this, baby." I grew up loving Neil, but honestly-how could you not love Chuck? Perfect informational science/comedy duo right here!

Chuck's reference to the movie SE7EN actually made the explanation much clearer. Well done!

"What is Schrödinger's Cat?" The cat that belongs to Schrödinger.....easy...

Neil is the best. My 7 yr old and I watch all these videos together. He loves to learn and he breaks it down so good for ppl

I was amazed that my 9 yold came to me telling that he wonders how a straight line is actually not straight if seen through a microscope, or that a table edge is not plane. I showed him your talk right away about the measurements and he loved it. Love watching you, thank you so much!

Neil and Chuck you guys are my favorite teachers....everyday I understand more and more about our existence and experiences

I absolutely love, love, both of these guys!! So informative, and always funny!!!❤

I believe we were taught this concept using the double-slit test where observation causes decoherence of the quantum state for binary encoding. The quantum tech course at my school used optics and wave-phasing to manipulate the state before the observer causes decoherence. Im hoping I get a chance to build a FDTD numerical approximation for Schrodingers wave equations to get simulation of the embedded states. Super cool stuff with wave theory perspective that electircal engineers get, but also cool to get more of a quantum persepctive

Im in disbelief right now! I saw a video yesterday that mentioned the term "Schrodinger's cat". I thought to myself I've never heard that before, i should look it up. And of course i never did 🙄 lol. Yet here you are today to teach me all about it! You hit the nail on the head today guys! Thanks 🤙

Chuck is actually super more intelligent than he gets credit for or put out himself. He is the essential piece to making science digestible to the general public

I would love more on quantum show. Im sad, im 63 and i can't become a quantum physics major.. but still am fascinated. I was just born too late. But i still enjoy learning.

I can't tell you how much I enjoy every time NDT speaks. I really want to learn more about quantum mechanics.. Of course, I will never be able to understand it as well as he, but these interviews, commentaries, lectures are helping me get through a very dark period and I am not sure why. But please keep doing these. Thank you.

Fun fact: Even though it was never shown, there was a special effects prop head of Gwyneth Paltrow in the box. That special effects prop was the same prop made for and used onscreen in the film Contagion.

This is why Cats are obsessed with boxes. They've been trying to figure this super position stuff out since they first heard about it.

I think the reason why a cat was chosen versus a coin is because once in the Box, the coin's movement is theoretically static, however, a cat's movement is theoretically variable, at least for some time until the cat expires. So there is a an assumption of a contribution of additional randomness once the unobserved cat is in the Box versus the coin which is assumed to be predetermined once in. You could also say you don't need a box to run the experiment. If a tree falls in the forest and nobody is there to hear it, does it make a sound? The observation theory and simulation Theory answers that question for me. Conservation and efficiency of resources dictate not only does the tree not make a sound, it hasn't fallen until the moment I observe it. That begs the question, if we are in a simulation, are we in it together or is everybody else simply a simulated projection? And if that is the case, why would the individual Observer of those projections be special? Would it be more likely that each projection, including our selves, are artificial intelligence Co-existing in the same simulation? Okay, I'm going into an existential wormhole so I better stop for now 😂

I love this show, I truly appreciate you all, including the behind the scenes folks.

These guys are hilarious! Anyway, I liked that Neil talked about the difference between a classical bit of information (like a computer bit being on or off) and a quantum bit of information (a qubit) when introducing Schrodinger’s Cat. 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. Neil mentioned that, but let me give an example so you can appreciate what it means physically. 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 giving |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 flipping a coin to find heads or tails. 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" due out in June 2024 with Oxford UP.

I'm an avid consumer of all Neil deGrasse Tyson videos, but in this one I loved not only the way he teaches us but also the fact that there is a Lego space shuttle in the back! He is a genius, but also have the nerd little kid inside that some of us still have.

Such a huge fan, Dr. Tyson!! Physicists like yourself has brought my love for math and science back, in turm changing my career path to pursue my Masters in Science. Thank you for all the knowledge!!

I remember when the first Bowmar calculator came out in the early to mid 1970s. It had only the 4 basic functions and cost $180, the monthly rent for my 3-bedroom apartment (split 3 ways). I was taking physics at the time, and I was jealous of those who could afford a calculator because I had to use a lousy slide rule. Today, I have a basic calculator sitting in front of me that cost less than $5, and it does square roots.

How do you measure the particle states, then? If not with light, can you observe or trace their changes via measuring the electro magnetic fields around them or something ?

You two make a fantastic duo. Thank you for making these videos together

As a Mechanical Engineer with 25 years experience I can attest you're totally correct in saying that a black surface absorbs photons and electromagnetic waves without irradiating back out. Excellent heat transfer topic.... Following up on the Stefan-Boltzmann LAW. KEEP THIS CONTENT FLOWING...

I love the level of humor involved in these talks! Thank you for reducing the seriousness involved with the facts and truths revealed! I wish there were teachers like you guys in school growing up. Please keep the format the same!

If all our physical components can be back tracked to atoms and beyond, then where is the transition point between the micro and macro? The Precise Point where it changes... I need a response in order to have any chance of inventing my Super Position Tracker Thingamajig.

Chuck definitely got his 15 minutes of fame in this video!! He nailed it! ;) Word was that Schrödinger took his sick cat to the Vet. After examination, the Vet to him, "I've got some good news and some bad news..."

I love how the chemistry you guys have makes the subject of Quantum mechanics so much more palatable and fun!!!

I had a classmate in my physics class get upset over the cat. She was convinced a real cat was involved.

Man you’ve hit the jackpot on this guy Niel, I don’t know if he’s been your good friend for decades or not but he provides such a good comedic effect and works so well with you

I would absolutely love to sit and discuss things with these two gentlemen. Listening to them makes me want to learn.

Neil was just born to teach. I wish my science teachers would have taught like he does my life would have takin a different path if they did

I think the funniest part of the show is just how tickled Neil is at ALL of Chuck's jokes.

I got my master degrees in quantum physics in 1976 and you guys got it right about Schrodinger's wave equations. Thank God for the equations. I remember those calculators. I had to buy a HP35 to past my final in 4th year electrical circuits class. I still have my HP35. Love you guys in making things simpler.

I got Schrödingers credit card, you don´t have no money when you don´t watch your bank account

Sometimes Chuck hits his stride and is more than just silly. This episode was excellent because Chuck was on fire and Tyson was his usual self. Very helpful, very informative! Thanks for this!

This was a delightful quantum psychic lesson

PS - If you have not explained why atoms spin in opposite directions, even when separated by a wall, please do. Great videos. Thanks!

These guys are a perfect pairing. I think I understand Schroidenger’s cat a bit better. I love the idea of any number of possibilities at the same time. “Fun part of quantum.”

I've been listening to this show ( and looking up! ) for 10 years now. Neil - you are singularly responsible for expediting my curiosity and love of the cosmos. I consider you my generation's Carl Sagan. Chuck - you are the perfect wingman for Neil, and bring so much to the show, kudos brother. Thank you to all involved in StarTalk

"Go have another bowl and get back to me" Neil deGrasse Tyson. A quote that gave me inner peace

The detail about the measurement effect provides significant clarification. Layperson information about things like the double slit experiment mislead by not being nuanced enough to clarify a passive observation outcome versus a measurement-based outcome where the measurement occurs by introducing new energy to the system. I'm guessing that with the double slit experiment, if a passive observation, The particles will remain as a wave as you look at the screen because you're not interacting with the particles other than passively seeing their reflection off of the screen. I have always been confused by demonstrations of this because they use the terminology that makes it appear that the act of just seeing it changes it. But the detail of passive viewing versus introducing energy to view is a very significant detail Is it possible to do these experiments where the "cat" is something giving off energy so that you don't have to introduce energy to get a measurement?

Delayed choice quantum eraser suggests that it's linking light to being above the linear flow of time, and our consciousness effects the choice it makes. To me at least. Would love to hear how Neil explains this one

You guys always have a way of making me think of things from a totally different angle than I have before! Thanks guys!

Without question, this is my favorite of you two! Making science look easy AND a new movie to add to my playlist. Seriously though, thank you for sharing.

casually spoiling one of the best endings of a movie ever 😂

I really love watching Chuck grow in this. Kind of curious to how he would do now with an aptitude test vs when he first started.

Out of all the StarTalk I have watched, Chuck’s energy with Neil easily tops all of the people that I’ve seen on StarTalk with Neil.

I am a sign language interpreter, and I LOVE learning about STEM topics from you, NDT! You help me understand the topics at a much more comprehensible level, which translates into improving my ability to interpret between complex scientific topics in English and American Sign Language (ASL).

Flaws in Schroedinger's experiment. 1. I can shake the box and feel for movement or listen for noise. 2. I can smell the box.( an airtight box ensures the death of the cat ). Even if I'm only allowed to look at the box to make my determination, putting the box on a small balance point would detect movement the second it fell.

Such a good team 👏 👍🏾 I love it when they just let chuck be himself and "learning"

Truly, Neil Tyson is like a diamond of modern physics.

I love these talks. I find all kinds of science fascinating. How things work, what makes them tick, all of it. I live how you break it up into a simpler way to think about it. The problem is I often listen to them on my personal laptop while I'm working on my work laptop and I focus too much on the video and now what i'm doing at work and I have to keep starting over with what i am doing. LOL

Great episode. You guys are perfect together. Thank you.

The brief moment mentioning earth having reflective surfaces is so awesome. I wonder what happens at a solar panel farm. do we need to have more surface area collecting energy? Or reflecting it?

Chuck's imitation of Brad pit asking what's in the box was deaf on! Well done Sir!

Yessss this is such a trippy concept, I'm so happy you did an explainer video on it! Love this! I can listen to Neil explain stuff like this forever 🤣🤩 Thank you🙏🏼🙏🏼

Chuck Nice is completely in the way! I would like to learn! Don't need comedy or tangents!!!!

I read somewhere that Schrodinger's daughter said her father didn't like cats, and she thought that maybe that was why it wasn't a dog in the box🙂. Great clip, and gives better insight and explanation than when I studied it in university so many years ago.

Somebody wrote that in the wikipedia but it is not what "the cat" is about- the Psychological principal was to illustrate the state of mind that "some cat is in a box, we don't know whether it's alive or dead, we'll find out when we open it" because it encompasses the state where someone like a CEO is in charge of a company but can only delegate responsibilities hoping for the best they end up getting high blood pressure and if you just acknowledge that you have no control over what's going on in the box the CEO can relax...

Chuck is the only podcast host that genuinely has me laughing out loud along with him

I suspect there are many who don't know that before calculators came along, the power tool was the slide rule. Analog calculator.

Chuck is HILARIOUS!! I thoroughly enjoy every episode he is in.

Schrödinger was never really sure whether his cat was alive when he shut it in the box, but Schrödinger's dog on the other hand, he always knew because, he could hear it barking each time he shut it in the box it had a sixth sense for "paws"itivity and refused to be in a state of uncertainty!

Chuck trying to explain “what’s in the box” to NDT is my favorite thing so far this week

I wish I had seen this explainer earlier. Now finally I understand a lot more about quantum science. Thank you Neil.

Quantum entanglement is one of my favourite parts of Quantum Theory, mainly because of it's application in science fiction. Using quantum entanglement for faster-than-light communication with no discernable limit to range in distance is a really fascinating and practical application of the concept. Among other media, this has been featured in the video game series Mass Effect, which I absolutely adore. So much so that I have the trilogy on two consoles (PS3 and PS4).

These guys are the "Bomb", I so relate and appreciate their humor in these discussions. It's fun and somewhat easy to learn, as they say it's never too late to learn something new!! So enjoy this, keep up the great work!! Thanks so much!! Love you guys!!

Man Tyson is brilliant. Amazing how he can explain incredibly complex topics in a manner that is so easy to understand. Guy is a national treasure.

One of the best videos on this topic, and entertaining as well.

Why did you spoil Seven? Should put alert in the beginning

🤣🤣🤣 I volunteer to go lay out in the sun in a white bathing suit too 🤣 You guys are great

Many years ago I read an article penned by one of Schrodinger's peers, (I forget his name) that basically said that the cat problem was first created as a joke by Schrodinger to mess with his grad students. Kind of like the Sound of One Hand Clapping, or a Tree Falling in a Forest makes no Sound. Then it just took on a life of it's own and became what ii is today.