#science #physics #ideas The Biggest Ideas in the Universe | 5. Time

#science #physics #ideas The Biggest Ideas in the Universe | 5. Time 217,819 viewsApr 21, 2020 Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is Idea #5, "Time." We talk about what time is, whether it's "real," and about why it seems to move in just one direction. That gets us a bit into entropy, which is a teaser for a later video in the series. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/watch?v=HI09k... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: https://commons.wikimedia.org/wiki/Fi... #science #physics #ideas #universe #learning #cosmology #philosophy #math #time 638 Comments rongmaw lin Add a comment... Goat boy Goat boy 2 years ago (edited) For some reason, I find you the most eloquent professor while also being the most informative in the whole field of science popularization. I watch all of your videos and read all of your books for years now and you always seem to give the most understandable definitions for science readers while not making a lot of compromises and avoiding bad analogies. Sometimes I wonder if science popularization would benefit more if you gave talks to your colleagues about how to explain things and how to structure talks then just educating the public directly. But please don't stop :) These are great. 26 FGMT FGMT 1 year ago (edited) Thank you for all your time and effort. I left school with no real education, but I find all this stuff fascinating. It always felt academically impenetrable to me, and while I do occasionally get a bit lost, I can actually follow along with most of it. You’re a great communicator and teacher, you can convey complex ideas without being too esoteric, and yet you don’t tend to over simplify difficult concepts. It feels very genuine, honest and accessible. Thanks again! 9 Corey Chambers Corey Chambers 2 years ago (edited) Sean Carroll is among the greatest teachers of all time. 59 wagfinpis wagfinpis 2 years ago I can not get enough of Sean's awesome consideration's. Great sense of humor, I love this guy every time I tune in! Only way to keep the appreciation short is to not even begin to mention it. 8 Konstantin Konstantin 2 years ago Please, don’t stop these videos. This format is awesome! 9 733 733 2 years ago I use to watch you back in the day i think it was the Universe or some series. You have always been able to talk to me as the years go on. I have no background in physics/maths but after a few years of watching your lectures and the many others like you it starts to make sense. Anyhows I guess all I wanted to say was thank you for being here all these years. Cheers 14 Dylan Dylan 2 years ago Thank you for doing these videos Sean! The content is fascinating and your delivery is so well articulated. Love it. James James 2 years ago You sir have an incredible gift as an educator 8 PhysicsOH PhysicsOH 2 years ago Great video! For the Q&A: Do you believe "Time Physics" is different and unique enough to be the next field of physics such as QFT, GR, QC, etc. or do you think it will always be considered a sub-field of these? 1 pizzacrusher pizzacrusher 2 years ago These are so excellent! Thank you very much for doing this!!!! I wish everyone was as generous with their knowledge & expertise. Thanks again! 3 නැවුම් සිතුවිලි නැවුම් සිතුවිලි 2 years ago Thank you for taking the time for this incredible series is videos. It felt like reborn. One question. Is space-time conversion factor (C) only defined in a linear manner? Can we define a maximum angular velocity in the fabric of space-time? 1 NicleT NicleT 2 years ago (edited) Thank you for these video courses. They’re very important! I want also to share that I had myself a big accident when I was a teen that let me saw time slowing down significantly. This is what I felt while it was happening. My mind was “ultra aware” of each details that was unrolling from the accident but also I was struck to realize that at the same time, my perception of time was different. So I’m not saying time was running slower with my physical movements, but more that my perception of it let me feel it slower. It’s also important to say it was not a souvenir aftermath, but really while it was happening. JiminiCrikkit JiminiCrikkit 2 years ago (edited) Thanks for another great episode ... this one reminds me of the old Greek god(S!) of time - Chronos and Kairos - where the former is how we think about time nowadays sequential (chronological), but equally back in the day there was Kairos - the god of timeliness, of situation... Love this idea. 1 Jim Wolfgang Jim Wolfgang 2 years ago Thanks Sean, I've watched and listened to so many of your lectures and podcasts; but I think this format is the best yet imho. 👍 1 Brian Cannard Brian Cannard 1 year ago Great lecture, thanks Sean! It's a mystery that a body in an inertial system preserves its velocity and pace of time relatively to another inertial system in a way that the 2nd law of thermodynamics resembles Newton's first law of motion. Mohammad Reza Mohammad Reza 1 year ago (edited) Wish you talked about time itself, and how it (& mass) are emergent properties of timeless & massless particles bumping around fields, resisting acceleration. 12 Sadra Boreiri Sadra Boreiri 2 years ago Thanks Sean for these series of incredible videos. I have a question regarding the second law of thermodynamics. Why do we probably end up in a higher entropy macrostate? If we look at the phase space, each point has a determined future and the volume of the macrostate is time-invariant. No? and what about the conservation of information that you mentioned before? 1 Ali Karimi Ali Karimi 2 years ago I'm a big fan of the time topic. Thanks Sean for starting this. I'm looking forward to next videos about time 🙌 1 Konsam Tambradhwaja Konsam Tambradhwaja 1 year ago Thank you Sean for this lecture.Very interesting and enjoyable talk. Dean Batha Dean Batha 2 years ago (edited) Hello, Sean. Thank you for these wonderful videos. I have some thoughts regarding the relationship between the second law of thermodynamics and the arrow of time. Suppose all of the gas and dust molecules in the room I'm in are collected in one corner (a very low entropy state), and I observe them as their entropy increases until they fill the room. I can use their progress from a small volume to filling the room as a kind of clock, dividing the elapsed time into units of volume filled. Once that happens (the room is filled), let's say we expand the room, so the gas and dust are no longer at maximum entropy and must expand further. If we continually expand the room, faster than the gas can fill it, the gas will continue expanding, the room will get colder, and the process will stop once the room reaches absolute zero and the gas molecules have no kinetic energy left and can expand no further. Let's say we call this process of expansion, "time." This "time" is not a dimension of the room, nor is it a property of the gas in the room. It's simply a way of describing the behavior of the gas as it fills the room until it can expand no further. Now imagine that the gas and dust are the entire, observable universe (and my room is space), and I'm watching it expand from the Big Bang, to fill all of the available space. Now imagine that space is expanding faster than the stuff within it can catch up. Let's also imagine that space is expanding at an accelerated rate so that it's impossible for the gas to ever catch up and completely fill the space. The description of this ever-expanding space, and the ever-increasing entropy of stuff within it, we call "time." This expansion, of course, requires energy, just as inflating a balloon requires pressure. Let's call this energy, "dark energy." Let's further suppose that the amount of dark energy is proportional to the volume of space, so the larger space gets, the more dark energy it contains, and the faster it expands. Just as inflating a balloon requires pressure from a source outside of the balloon, the energy needed to inflate the universe must come from outside of the space within the universe. The TL;DR of this is that time is not the same as space. It's not simply a 4th dimension, as in general relativity. You can't exchange time with any of the three expanding spacial dimensions; they are not equivalent. Time is a relative measure of how fast the stuff (matter and energy) within the universe is expanding to fill the volume of space, i.e, how fast its entropy is increasing. Time is the increase in universal entropy and its driven by the expansion of the universe, which is powered by dark energy. If the universe were to stop expanding, time would stop as soon as universal entropy is maximized. As for the debate between "presentists," and "eternalists," the eternalists are right. Our perception of the past, present, and future are a consequence of how (human) consciousness perceives time, not a feature of time itself. Time is a process, not a place. I can be at a place in space and remain there forever. But I can't remain at a time forever. Whether I like it or not, time moves on and carries me with it. The "present" time is wherever I find myself "now." In other words, the present is my position in space, along with the positions of every particle in the universe, relative to me. As soon as anything moves with respect to me, time advances, entropy increases, the universe expands, and life goes on. The entire history of the universe, from the Big Bang to its eventual heat death, is determined by the Second Law and the accelerating expansion of space. We perceive time in slices, like frames in a movie, so the present seems qualitatively different from the past and future. But physically, they are all the same. Mape Andrews Mape Andrews 2 years ago Loved the last part of the video about how the study of entropy progressed 👏🏻 wish you could have included Complex Systems and Emergence but I know it would have been of topic too much. But one day it would be nice to hear about this part of your own research. A bit hesitant to ask for requests after you mention in one of your podcasts that requests tend to have an adverse effect on you. Thanks for providing necessary food for thought. Phillip Gregory Phillip Gregory 2 years ago Thank you very much for these lectures you are a great teacher… Could you discuss the quantum eraser if you have time please thank you 1 In Coath We Trust In Coath We Trust 2 years ago Hey Sean, could you please explain how the spontaneous radio-active decay of an unstable nuclei does not actually violate time-reversal symmetry, contrary to what most people are inclined to believe? Thanks! 17 C.J. McELEAVY C.J. McELEAVY 2 years ago Just like to give a huge thanks to Sean for putting together these incredibly illuminating and engaging Y.T talks /presentations. Green screen,apps and real time iPad usage works beautifully. 1 Jason Burns Jason Burns 2 years ago Yesss I’ve been waiting for you to talk about this! I discovered the block universe theory a few years ago and kind of became obsessed with it. I’ve been wondering where you stand on it and now I know. I also know that I’m an “eternalist” which is a really cool word! Why is time such a fascinating subject!? Ry Rez Ry Rez 2 years ago (edited) awesome thank you Sean Carroll! btw i really appreciate that you know so much about philosophy as well. makes these videos even that much more interesting 1 Charles LaCour Charles LaCour 2 years ago For more on the arrow of time and entropy my favorite book by Sean Carroll is From Eternity to Here. I would highly recommend it. normskis69 normskis69 2 years ago You're very kind to do these lectures for everyone. Thank you xxx 2 Edwin van Gent Edwin van Gent 2 years ago (edited) Thanks Sean, your a great communicator, I can listen for hours, to make really difficult stuff easy marks a good teacher, in the movie Lucy at the end she said time is the fundamental unit of measure I kind of agree. DVOSS DVOSS 1 year ago Sean, I really enjoy your work and your lectures. I bought a few of your books and just wanted to say I really appreciate you. Thank you! 1 Narayan Mohanram Narayan Mohanram 2 years ago Thanks for the great videos. You alluded to "is time emergent" at the end of the video. Is time a macroscopic concept much like entropy? Are we Botlzman's brain "experiencing" time? 4 Jeremy Geltman Jeremy Geltman 2 years ago (edited) @Sean Carrol Amazing as always! Two questions: 1) It seems to me that physics doesn’t treat arrow of time agnostically; in reverse time like charges attract and opposite charges repel. 2) How can entropy create the arrow of time if entropy cannot "occur" without time? Gabriel Marcos Gabriel Marcos 2 years ago Great series of videos! Love your books, too, always make me think! Would you do a video on the Ads/CFT correspondence, please? What is it? Why is it important? Ethan Block Ethan Block 2 years ago (edited) Thank you for posting these videos. I have a question for your followup Q&A: If the past and future are as real as the present why is there no force exerted from past or future states (e.g. mass exerting gravity from an object that is no longer at a location or has yet to arrive)? Bruno Prates Bruno Prates 2 years ago (edited) Hi Sean, big fan here! Love you podcast and books. I have a few questions (you can choose any to answer), feel free to reformulate in your own words if you want to make it clearer. Q1 – You defined entropy as a measure (log) of the number of microscopic arrangements that appear indistinguishable from a macroscopic perspective. Isn’t this notion of “appearing indistinguishable” and “macroscopic” pretty ill-defined to be used in calculating a numeric value of a quantity? Suppose a person has a VERY good eyesight, to the point he can distinguish molecules from each other. Even if you changed the position of just a few molecules of milk, this person would be able to tell the difference. Would we measure different values for the entropy? Where is the catch here? (You can go mathematical if needed) --- Q2 – Do you think time is discrete or continuous? Why? Could this be tested someday? --- Q3 – How would you treat past and future equally, if you take into consideration quantum uncertainty? (I can only see MW as a solution here...) Thanks! 1 gkelly34 gkelly34 2 years ago Wish I had a physics teacher like this at school. Fascinating stuff 33 llaauuddrruupp llaauuddrruupp 2 years ago I love these videos, and this was maybe my favorite of them so far. 1 Sully Sullivan Sully Sullivan 2 years ago you're a brilliant man Sean. thanks once again for making these vids. much respect. 6 Mr.Someone Mr.Someone 2 years ago (edited) Thank you for these great lectures. Time loses meaning in a macroscopic sense if a closed system of particles has reached max entropy. So if particles are not decaying/changing and if they have mass (so they are not traveling with the speed of light, e.g. electrons) can we still talk about passage of time for individual particles (their proper time)? Or do we believe that the system/universe would always ultimately end up consisting of massless particles (photons) that travel at the speed of light and everything happens instantaneous to them so time has no meaning for them. Tony Cotto Tony Cotto 1 year ago This is simply the best explanation of time I've ever heard. Igor Shvab Igor Shvab 2 years ago Dear Sean, can you please make a video or elaborate on the difference between wave function and the quantum field? I.e between wave function and potential field 1 Kamran Razvan Kamran Razvan 2 years ago (edited) You have a great course on "Great Courses" about the arrow of time. I "think" I finally grasped, in that course, what entropy is! 5 SebastianM SebastianM 2 years ago OMG!!!!! I didn;t know you had a youtube channel!! I love how you explain things nad i hope you keep posting videos here. You are really brillant! 2 Margarita Hernandez Margarita Hernandez 2 years ago Thanks. Very interesting.I am understanding more of the issues presented in your last book. I am not a physicist but I always was amazed about physics and got great grades in math and physics 👌 long time ago. Johnson Gibbs Johnson Gibbs 2 years ago Thank you for the video Mr. Carroll. I posit that time has wave properties. Can you consider this a fundamental aspect of time? I suggest this because it helps me understand the prevalence of wave mechanics in nature. Lorentz transformations, Planks constant, Schrodingers Equation... everything we know about physics suggests fundamental wave characteristics. This supposition infers that time is a measure of progress. Time has wave properties and time progresses at a relative rate for all things and is directly affected by temperature. I even refer to the effect of Bose Einstein condensate on light as experimental confirmation that progress through time is directly affected by temperature and relative, meaning its' progress is independent. I would love to hear your thoughts. Time has wave properties. Time is a measure of progress. Progress though time is directly related to temperature. The prevalence of wave characteristics in nature is explained by time having wave properties. Planks constant is direct evidence of wave characteristics in nature. Everything points this posit as evident. GodlessPhilosopher GodlessPhilosopher 2 years ago These lectures are incredible and Sean is a genius. Highly recommend his new book defending the many-worlds "interpretation" of QM. 105 Jacob Canote Jacob Canote 2 years ago (edited) We love you Sean! Best of luck! You are a rebel and I know it. Your role just changed. You do a wonderful job of opening up people for different ways to frame things. Theoretical physics and allowing liberties to probe different depths are a priceless tools for discovery and understanding... too drunk. To drunk Andrew C. Mumm Andrew C. Mumm 1 year ago (edited) Sean, without knowing it, you kept me in the game when I was a grad student studying general relativity. I was lucky to come across the early .pdf notes of your general relativity book (you were offering them for free online) and it was such a relief to finally read a book that explained things clearly. I ended up writing my masters thesis on the Kerr metric and your book helped so much in that respect. You're an outstanding educator and I'm really enjoying some of you mindscape podcasts and youtube videos. If you ever come to Hong Kong (in a post-corona world), then please come give a talk to the awesome physics students at my school - we would even love to host you as a resident scholar for a short while if that could interest you. My school is an outstanding place that wants to push the boundaries of what's possible in high-school (we've hosted an AI researcher who spoke about entanglement, another Caltech quantum-professor who is an alumnus of our school, Jerry Coyne from Chicago U. on evolution - you would fit right in!). Take care. 1 Robby Johnson Robby Johnson 1 year ago Been looking for something like this for years. The equations in the last episode went way the hell over my head, and I got quite seriously lost. This one, though, I was able to follow the entire time. Blew my mind multiple times. Thanks for this. Badron88 Badron88 1 year ago These talks right here, and others like it, are the reason I'm planning to study physics. I'm coming up with some great ideas but don't know enough yet to answer them. Mr Carroll, thank you. Laurentiu Stancalie Laurentiu Stancalie 2 years ago Very nice and useful trainings! Thanks for the good usage of your spare time! About "space usage" I have a comment: when you are showing your hands, they look bigger compared to the rest of picture. Probably you are using low res camera and distance to it is too close. Solution could be increase distance to it and zoom in. Laurentiu, Romania party 1999 party 1999 2 years ago Thankyou Sean. Very enjoyable and interesting talk. Glad I took the time to watch it! Pranay Sheshak Pranay Sheshak 1 year ago Watching this at 1.5x speed and thinking "I live life faster than 1 second/second" 86 Pete Brisbourne Pete Brisbourne 2 years ago Fantastic video Sean! Here's a question and forgive me if you perhaps already addressed it in the video but do you think there is any possibility that 'time' could be a particle or wave (thinking of ideas like the Chronon by Chen Ning Yang) Anthony Pazana Anthony Pazana 2 years ago (edited) When my daughter was an old 7 year old, I tried to explain the concept of time to her as I understood it. I drew a circle and divided it into 24pie shapes. I told her that each pie represented 1 hour. I then asked her, "what time is it at the point at the atomic level, where all the pie slices(hours) meet. My answer to her was there is no numerical value, that time as we measure it on earth, is arbitrary, so that we know what "time" the Mario Bros and the Smurfs go on TV. Your moment in Universal time.... \ bestape bestape 2 years ago This one was a lot of fun, thanks! I think time is like the color purple. It's the point at which the ouroboros eats itself. The parietal eye. Can you talk about -(entropy) = k log (1/D) described in Schrodinger's "What is Life?" p. 73? What I associate with exergonic process. Ghan04 Ghan04 2 years ago I've heard before that there are some solutions in general relativity allowing for movement backwards in time. Would this truly reverse the arrow of time and as a result would that also imply some decrease in entropy would be occurring? ManWhoUsesComputer ManWhoUsesComputer 2 years ago Question: If spacetime is emergent from entaglement, could a form of entanglement also explain this "dark" matter? CaptainFrantic CaptainFrantic 2 years ago (edited) @Sean Carroll - I appreciate your point about space and time having different properties but it has always seemed to me that space at least IMPLIES time. In other words, if two objects are seperated by space then it takes TIME to get from one to the other (somewhere, a photon is laughing at me right now). Is this assumption of mine essentially correct? Furthermore, I too subscribe to the block universe AND the Many Worlds Interpretation. Together, these suggest that not only is our universe done and dusted (everything has already happened) but that EVERY possible universe has (in a sense) already happened in their entirety. This is one among several reasons that I don't get much sleep. :D Kaare Gustafsson Kaare Gustafsson 2 years ago I just found your channel and love it. I have a few experiences that go with the time in bad situations. I used to ski race, downhill, and had a crash at over 65mph and landed on my back, slid under the safety fence, and wrapping myself around a tree, breaking my femur and major internal injury's, and no, time did not slow down as i was sliding on my back watching the trees's come at me. If anything, it sped up. Another one, was my own fault, but decided to jump off a bridge (for fun not suicide) that was about 90 feet. It, again, sped up for sure. (broke my tailbone and ankle). These things might be different for each person, but for me, things went faster then I could mentally process as they where happening. boo Jay boo Jay 2 years ago Really needed this. Thanks Sean. Henri Maes Henri Maes 2 years ago (edited) There are some excellent books on time (imo) Julian Barbour's "The End of Time" and Huw Price's "Time's Arrow & Archimedes' Point' . Pier Francesco Peperoni Pier Francesco Peperoni 7 months ago Seeing these concepts finally popularized on YouTube always fills me of joy: I had the intuition about eternalism and the block universe at age 15 without knowing about Einstein's theory of relativity, and since then I started studying physics. I also had an intuition about identity, deriving naturally from the eternalism, which fits perfectly the many world interpretation (though I haven't taken yet a position on interpretations of quantum mechanics): I think that we all are one conscious being, which is the only existing "whole thing" in the universe, or even better, which is the universe itself as one conscious being, and the only one being at all. I'll explain my intuitions and mental experiments in the answer to this comment, since it will take some lines. ManWhoUsesComputer ManWhoUsesComputer 2 years ago (edited) Question (Asked and Answered by Mike): Do both matter and antimatter interact with the same fields; or, are there fields and "anti-fields"? Thank you. Will Jeremijenko Will Jeremijenko 2 years ago Wow! Shaun has incredible communication skills and is very pioneering in his work Kidz Bop 38 is Straight FIRE!! Kidz Bop 38 is Straight FIRE!! 11 months ago Your ability to comprehend complex ideas and explain it to us laypeople is, in my opinion, as good as Feynman's. Well done. 1 Gorazd Žagar Gorazd Žagar 2 years ago For QA: 1) Is it valid to say that time is a part of space-time conceptual model because it is impossible to measure time without space being involved (changes in time are tracked through space)? 2) What is the smallest measurable unit of time we can measure? Meaning, what is the smallest unit measurable where we can see a change in space? Thank you! Dobby Dazzler Dobby Dazzler 2 years ago So, so good. One of the greatest scientists and communicators of our age. Or should that be ‘time’? Thank you Sean for your time, and energy, an amazing mind! 🎋🦋🌿 MadderHat MadderHat 2 years ago Question. 4:30 I thought given that everything in the universe is moving, that cancels out the idea of "choice" in moving through space. Wouldn't the only way not to move through space is not to move through time? 1 Stewart Hayne Stewart Hayne 1 year ago I did a masters degree in physics 25 years ago and then became a lawyer. All forgotten until now. This is so amazing to watch. So well presented. Thank you! BitwiseMobile BitwiseMobile 2 years ago This guy reminds me of my Calculus professor. He makes complex things seem simple and easy to understand. RiotGear RiotGear 2 years ago Thank you! Also, question. Planck time must be the shortest possible amount of time(measured by lightspeed I'd guess), and as GR binds time with gravity, then doesn't knowing the least possible timespace above zero have some say/hint at / in quantum gravity? Quantum time should have correlation with quantum gravity, or no? You can measure speed, can you measure gravity by time changing due gravity? Blabber probably but .. Cyclopropane Cyclopropane 2 years ago (edited) In Forward's Dragon's Egg, a species lives on a neutron star. Gravity is so warped that time travels differently for them. They travel quicker through time than beings in another frame of reference. Granted, everyone in their frame of reference travels at the same time. 1 Andrew Cozens Andrew Cozens 2 years ago Great video about time but regarding your explanation of entropy how does the evolution of life and us as highly ordered systems fit into this? beeble2003 beeble2003 1 year ago "Clock: changes reliably & predictably with respect to other clocks." Here, I like the parallel with something that came up a couple of talks ago, where you said that one solution to a set of conservation of energy equations is that a ball on a slope stays exactly where it is. Similarly, one solution to this system of "clock equations" is that a rock is a clock, because it changed reliably and predictably (i.e., not at all) with respect to other rocks. 2 Contemplate Eternity Contemplate Eternity 2 years ago I'm working with time as a spatial dimension and it's been working to explain some universal phenomenon surprisingly well! I am just starting this channel to help tap into a community of like-minded folks interested in understanding the mechanisms of the universe/multiverse. I would greatly appreciate feedback. <3 Mark G Mark G 2 years ago Could the quantum wave function of the universe, as it moves through the universe, create time or the illusion of time for us? Even a static wave moves and could there be any relation to our experience of time somehow be related to this flowing? duggydo duggydo 2 years ago Sean, I have a question about light travelling vast distances across expanding space. I know light red shifts as it travels through expanding space. Does it eventually red shift completely out of existence and further contribute to the expansion of space? If so, is it possible that this is somehow "feeding" the Arrow of Time by adding energy (Dark Energy) to spacetime? yeti yeti 2 years ago Sean: Great lecture, as usual. The concept of time reminds me of something I read regarding the Mahabharata (Indian epic) story. This epic or the battlefield scenes were recited to a blind king by “time” itself. Interesting! So, the statement that “time travel” or “movement across time” has not been found to be imagined in any ancient culture may not be quite correct. In fact, the Bhagawat Geeta (ancient eastern —Indian— text) seems to have contained some of these time travel ideas. There are plenty of stories about sages moving across space. Schrodinger himself was quite fascinated by these Vedantic texts especially the All in One concept. 8 NoFunNoMoshNoCoreNoTrends NoFunNoMoshNoCoreNoTrends 1 year ago Sean, this is absolutely fantastic content. Holy cow man. icesrd icesrd 2 years ago Dr Carroll... I hope you enjoy making these lectures as much as we do listening to them. Please keep up the good work. Can't wait for the next installment. Be-lal Alkad-imi Be-lal Alkad-imi 2 years ago Such a convenient way to speak and illustrate...very cool !...Thank you Sean, you have a very pleasant voice for explaining things. Phillip Gregory Phillip Gregory 2 years ago Also one of the thing I’ve always wondered since the universe is expanding does that mean the plank distance is expanding as well… Tony Gingrich Tony Gingrich 2 years ago Something I've "seen" since I was old enough to have an intellectual thought about time, is close to how you described "block time" near the beginning of this lecture. Where the person is inside the block and residing at a specific point in time, I imagine another outside of the block, looking at the block as completed physical object, end-to-end (more like a sphere, actually, but I'm saying ends to keep my point simple). I've heard others describe this same scenario, but they seem to be unable to see that as anything other than deterministic. I see it as neither deterministic nor nondeterministic. To give my answer about "multiple times", I see that as a yes. The person outside the block is in sort of "super" time. He can reach into the beginning of the block and, say, change the color of the Sun. The person inside the block, being well ahead of that moment in "his" time, would now suddenly have been seeing the Sun as the new color for all his life--never knowing anything ever changed. That difference in color will inevitably cause his reality to be very different than what it was prior to the change. My point: Both the past and future are dynamic. And the states of those periods are influenced by the the "super" times, which are unsynchronized and therefore unbound. I don't believe in deterministic universe because of the dynamics introduced by the extra dimensions. And likewise, I don't believe in nondeterministic--influential events of the extra dimensions don't necessarily "have" to occur. I instead describe our universe as dynamic. And with that said, I personally prefer to separate the concepts of time and entropy. "Time" is simply and illusion of how we sense entropy; entropy, of course, being the real "time" that is of scientific interest. Time, for me, will abruptly stop at the moment of my death, but entropy will persist. Stefan Ekman Stefan Ekman 2 years ago Life surely exists. Maybe, as a growing life-entity with a mind, my perception just involves "time". And "matter", which gives me "space". Or "space-time". "Reality" is hard to separate from some kind of "experience". So a completely different kind of being probably could have another notion of space-time, like a fly for example. Different "personal", "macro-state" journeys through experiences of space-time? Thank you for these great lectures! Piotrekk99 Piotrekk99 2 years ago What I could never wrap my head around was the curvature of time. For example, I heard that what we perceive as force of gravity on earth is mostly the result of the curvature of time rather than space. If you could find a way to explain this or correct me if I wrong that'd be really great. Veselin Manojlović Veselin Manojlović 2 years ago Great lecture! Regarding reality of the past, present and future, it seems to me that more intuitive view on time, based on observation of the Game Of Life simulation (example of cellular automaton), would be to think of: - present as real, - future as completely determined by the present state, and, in that sense, certain and real, but - past as uncertain, of which we only know from our memories and "fossils", which are all prone to decay. In the Game Of Life, and many other non-linear thresholded processes, the same present state can be result of different pasts. If that is so, then, regarding the free will problem, we can't hope to directly change the future, but only by changing the way of looking at the past, by hunting consistency in it. Another similar approach to this in "pop-culture" is the movement called lastthursdayism, which states that everyhing (including fossils, our memories, etc.) came into being last thursday :) Xavier Gamer Xavier Gamer 2 years ago You are emerging as the early 21st century premier world’s science teacher to the average modern man. 1 IncompleteTheory IncompleteTheory 2 years ago (edited) 52:20 "The universe begain in a low entropy state." Now, Sir Penrose maintains that the CMB clearly shows a very high entropy state. Based on this ground he constructed CCC. So far I can't help but finding this initial argument (which Penrose even calls the "Mamoth in the room") nothing but compelling. What is your reaction to this, Sean? Rodrigo Nader Rodrigo Nader 2 years ago Question: Regarding entropy being the measurement of the disorder: what forms of disorder? Arranging particles by one property could affect the arrangement by another property. So isn’t entropy relative as well? R C R C 2 years ago I enjoy when Professor Carroll covers the bases in philosophy including the original Greek philosophers. I find that it enriches my understanding and familiarity with science. Pandemic Players Pandemic Players 11 months ago Thank you for sharing your genius regarding the science behind space and time. Personally, my spiritual philosophy positions me as an "eternalist," I suppose. I see time, or rather the 'flow of time' to be fully illusory, much like watching a motion picture. To me, Time is primarily a method to measure the motion of physical objects through Space, nothing more. In the absence of a physical universe, there is nothing to measure, and therefore no time. HST, there is a physical universe, albeit illusory, and I also hold that ours is but one within a truly infinite multiverse, or the MWI of QM. I believe the only actual thing that exists at all is Infinite Consciousness, which is an absolute formless and purely subjective existence unlimited by time and space, or rather truly Infinite and Eternal/Timeless in nature. Neither Consciousness nor the spacetime illusion actually 'moves' at all. In other words, both Observer (infinite Consciousness) and multiverse (finite projections of Consciousness) are completely static existences. Within this seemingly infinite multiverse projection exist all possible 'moments' available to be experienced by Consciousness, be that in either individuated or collective form. As an individuated and localized projection of Infinite Consciousness, the Self (me) pieces my life story together much like a film editor cuts a movie. Because Consciousness is truly 'static,' as well as the projected multiverse, all possible Moments of experience are like a holographic 'frame' that is chosen (Free Will) by the Self one after another out of all possible 'next Moments' available to add to our story. Our brains experience this super-rapid experiencing of holographic frames which surround our localized Consciousness as the "flow of time" very much like when we watch a film in a theater. It is even possible to experience this projection during brief periods between deep sleep and wakefulness when first getting up and turning on the lights. Anyone who's experienced that 'flickering' in their peripheral vision is actually noticing the very similar process in film projection that is the 'blacking out' between frames on a projected strip of film caused by the rapid opening and closing of the 'gate' mechanism of the projector. Without that gate, the illusion of motion on a film would not be perceived by our brains, and all we'd see is a continuous blur of images much like the blur of a waterfall photographed at slow speeds by a still camera. Nothing actually moves, ever, in all of Existence! We already see this in current computer technology and VR. Spinning hard drives are now old tech, replaced by chewing gum-stick-sized SSD's with no moving parts. I am a VR flight simmer, and the illusion created by all motionless parts of my PC in concert with the motionless tech of the headset provide a rather sophisticated illusion of both motion and fully immersive experience of being within an actual airplane's cockpit and flying above anywhere on this planet! Yes, it's a tech that's in its infancy still, but it's no stretch of the imagination to predict how much more real and indistinguishable it will be from waking life within the coming decades. It does an incredibly decent job of fooling my Consciousness even at its current state, so much so that I have little doubt we are not that far off from having the ability to completely convince ourselves of the 'reality' of these purely illusory experiences. Surely any civilization in the multiverse even just one or two centuries more technically advanced that humanity will have already achieved this ability, and with the exponential advances in computing technology, it's no great stretch to reasonably posit that we may well be experiencing just such a simulated 'life' at this very moment. Personally, I hold that infinite Consciousness is the ultimate Projector, and therefore easily capable of creating the Ultimate Illusion of a spacetime experience. This is why I believe the entirety of the infinite Multiverse to be a block of all possible Moments, out of which both individuated and collective Consciousness creates both individual and collective 'stories' through the rapid focusing and refocusing from within one holographic and fully static Moment into the next. Why? Because Consciousness is the only actual thing that exists, and it is absolutely pure Subjectivity. Only the balance of Existence also requires an objective world to serve as an illusory 'opposite' to the Self to give Itself meaning, thus the Eternal projection of the duality illusion. The Perfect Is projects Itself into the imperfect "is not," and that is the perpetual fuel of Creation and Experience, turtles all the way down. Namaste'. Richard Schuerger Richard Schuerger 2 years ago (edited) Love this series - Ty for doing this. If we were to exist at an event horizon while time flows past us, we would be able to "see" one direction (the past) but not the other (future). Essentially time is flowing past us at the speed of causality and our perception of present time emerges from that nathanisbored nathanisbored 2 years ago If I'm in a building, there's lots of air particles flying around. I would describe the room as a complex system with high entropy. But a giant standing next to the building would look at it and say it's a very simple system with low entropy: just a small collection of particles that can't get very far. It would take a lot of math to describe what's going on in the building from my perspective, but it would take very little math to describe what's going on in the box from the giant's perspective. It's a bit like studying the behavior of atoms in a system vs studying the behavior of molecules in the same system. It's mathematically more elegant to describe what the molecules are doing than what the atoms are doing. Another way to say that is: chemistry emerges from thermodynamics and in the process, the mathematical theory jumps down in complexity. You could say this jump is also less fundamental and therefore is just an approximation, but then you could use the same argument to say that everything is just an approximation of something at a lower level. Question: Is there a sense in which entropy measures the zoom level required for a system to be mathematically elegant? A bit like how a Reynold's Number tell you what equation to use, entropy tells you whether you should be talking in terms of thermodynamics or in terms of chemistry, for example. 1 Christine LaBeach Christine LaBeach 1 year ago Here's my definition of time: Time is the rate at which everything in the universe changes and the universe is always changing until the heat death of the universe. Jason Petersen Jason Petersen 2 years ago I've heard our spatial movement through time described as the way us three-dimensional beings perceive the fourth dimension, and that each successive dimension is basically the set of all sets of the previous dimension. Would you agree? And would that mean that a theoretical, say, 5th-dimensional being would experience their 6th dimension as time? Nartana Premachandra Nartana Premachandra 2 years ago Sean I just heard Roger Penrose talk about the randomness of the cosmic microwave background and how no one has offered an answer for its high entropy back then. Any ideas? Thank you for these lectures! Dean Dean 2 years ago I think enough people have a hard enough time grasping reality without science.😷🇺🇸💗 1 bruinflight bruinflight 2 years ago (edited) Sean Carroll is my favorite science guy (along with Dr Lincoln at Fermi Lab) and I just heard him utter what is now my favorite Sean Carroll quote (19:11), "That's crazy talk!" Love ya Sean!!! Thanks for all of your great, great internet chats, buddy! Be well! John P John P 2 years ago I'm surprised that Sean didn't talk about how/why time behaves differently wrt gravity and speeds. Also, is there a different concept of time in the context of quantum mechanics? DX Helios DX Helios 2 years ago @Sean what is the difference between entropy and time? Times defines entropy, entropy allows us to define time. 1 Kepler Gelotte Kepler Gelotte 2 years ago The arrow of time moves forward at the same rate in an absolute vacuum so entropy doesn't apply and cannot be the driving force of time. I think time drives entropy not vice versa. Paul1239193 Paul1239193 2 years ago Dr. Sean :-) The question I would ask for you is do you think that the increase in entropy is merely correlated to time, or that one causes the other, or they cause each other, or that they are both caused by a third thing, or indeed that they have somewhat independent causes? The theory of time that you're looking for is here (link below). The paper is about 1/5 wrong, but it is about 4/5 right. (The horror, the horror!) We are working on a publishable version. https://philpapers.org/rec/MERANT-3 #science #physics #ideas The Biggest Ideas in the Universe | Q&A 5 - Time 67,543 viewsApr 26, 2020 1.4K DISLIKE SHARE DOWNLOAD CLIP SAVE Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is the Q&A video following Idea #5, Time, the video for which can be found here: https://www.youtube.com/watch?v=KYfFC... My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/watch?v=HI09k... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: https://commons.wikimedia.org/wiki/Fi... #science #physics #ideas #universe #learning #cosmology #philosophy #math #time 212 Comments rongmaw lin Add a comment... Michael Biebl Michael Biebl 2 years ago Might I just say, you, Sir, are our generations Feynman. Different character, but approaching the same hair style (like it) and keeping us normies amazed with physics. Thank you! 6 Tiaan Tiaan 2 years ago Im from africa & i wish we had things like this growing up. I basically just watch physics topics on youtube & i wouldve loved to actually study it but physics just wasnt in our imagination. I did really well in science at school & it was my favourite subject but when it came time to go to college we were basically told go into engineering or law. I received a schoalrship for engineering degree, but looking back its actually very strange because i achieved top 3 for science in the school. If youre a young person watching these videos youre lucky & should go chase your dreams because its all there for you, just go for it & do it. 17 Christoph Hipp Christoph Hipp 2 years ago The Q&A session is even more fun to watch than "lecture" session. 🙂 19 Nic holas Nic holas 2 years ago Excellent! Sean Carroll makes things so much easier to understand for the average person 13 nathanisbored nathanisbored 2 years ago I like time travel stories in which event A causes event B, which then causes event C, and then C re-enforces B to happen and creates a loop. In this sense, A is no longer needed to sustain the loop, and may as well have never happened, but explains where the loop came from. This loop could then be considered a "whatever happens, happens" situation, where no matter what you do, you will always re-enforce the loop. 3 Matko Smat Matko Smat 2 years ago Hey, Sean, thanks for a nice lecture! About 15 minutes in, I start losing some frames of your head, while the blackboard is smooth, not sure if it's my problem or yours, or YT's decreased quality policy. I watch other videos without a glitch. Stay safe and keep them coming! 2 Steven Lang Steven Lang 2 years ago Great fun, thanks for doing these videos. I have a question about free will with respect to time reversibility. Maybe there's no point to thinking about them together, but the thought popped into my head, so... It seems like the notion of free will isn't reversible. Say you went to a shooting range and fired ten shots. Running that backwards wouldn't mean you were "willing" bullets back into the gun, which is a weird enough thought. But maybe it would mean you had the will and ability to somehow "catch" speeding bullets into the barrel of a gun every single time, which is it course impossible even if you had the will to do it. In reality, with your brain also working backwards, no such thought could occur in the first place, so the concept of free will is simply not reversible. Is there even a point to thinking about this scenario? Thanks again and looking forward to more videos! 2 nick name nick name 2 years ago Thank you for your time and effort for making those videos. It's really helping. I'm a bit confused about light travelling and our mind making tricks on us as you said in the video. In this case; we had a black hole picture in the past months. This picture is NOW for us. However, that light had been travelling billions of years. Is this picture states NOW for that black hole too? Or is it past for the black hole when it is NOW for us? P.S.: Also, would love if someone can share some detailed source about this topic. Shpongle Shpongle 2 years ago These videos are truly so fun to watch!! Thanks man! 2 Narayan Mohanram Narayan Mohanram 2 years ago Thanks for telling us about the books (of which I was unaware). I will get it. I am sure it is good bed-time reading 1 Olver's Ears Olver's Ears 1 year ago Thank you Sean. I'm a bit late with this, not sure it was covered or asked. Can time be quantized or is it purely smooth and contigouis? peksi peksi 2 years ago (edited) Can the Universe remember itself? I've listened to Leonard Susskind's fractal time interpretation, and that seems to be robbing us from any insights into the past. Also, how far can a gravitational wave propagate? Does it have some sort of a Hubble radius before it dissipates? 2 Dean Batha Dean Batha 2 years ago Hi, Sean. I just started reading Something Deeply Hidden (Kindle edition). I just downloaded From Eternity to Here, and it will be next on my reading list. Thanks. 2 CyrilleParis CyrilleParis 1 year ago I thought the weak interaction violates the CP symetry...? Thanks for your wonderful videos! Spin Paint Spin Paint 1 year ago Does time travel affect the hallowed conservation of {mass, charge, etc}? Moving matter through time via time travel would seem to require conservation to be across the entire block of time, but that counts things more than once, which seems fishy. 1 Farzher Farzher 2 years ago your ability to explain is very impressive! Joe Milano Joe Milano 2 years ago Can you talk about the Fine-structure constant, what it is, why it's important, etc.? Devon Wlodyga Devon Wlodyga 2 years ago I know you probably won't do a Q&A of a Q&A, but I wonder how we would reconcile free will, to whatever extent it exists, with the block universe concept of time. Stelios P Stelios P 2 years ago another great video. thanks Dr. Caroll. Loved the Lost reference. 1 duggydo duggydo 2 years ago The audio is is good, but the video is choppy. Great info also. Love these videos! mightyNosewings mightyNosewings 1 year ago I imagine you've read it yourself, but one of my favorite philosophy reads is "Bananas Enough for Time Travel?" The argument in that paper is that consistency-preserving backwards time travel requires the presence of consistency-preserving coincidences; e.g., just as you are about to pull the trigger on Baby Hitler, you slip on a banana peel. This is eventually spun into an argument that that time travel should be considered metaphysically impossible. Randy LaMonda Randy LaMonda 2 years ago Is gravity an effect of the universe expanding or just the cosmological constant or matter resisting the flow of the expansion? Raymond Luxury-Yacht Raymond Luxury-Yacht 2 years ago With Newcomb's paradox, if the boxes are already set, aren't you then predicting the past? The answer lies in the observers future, but the quantifiable reality is already determined. Timothy Mc Timothy Mc 1 year ago Would a flip picture book be an effective analogy for the question of "block universe unchangingness" The book is the block but each page is different from the one before and after but still a part of a unified whole. Eric Eric 2 years ago Sean explains complex topics in a way that everyone can understand it. Fascinating stuff, as always. Thanks for the content! 2 Barefoot Barefoot 2 years ago (edited) There's a line I read today in Something Deeply Hidden that said, to paraphrase, that the laws of physics as a description of reality, should lead to outcomes that are consistent with our exerience of the world. It's okay if it speaks a different language, but at the end of the day, the undeniable elements of our experience should be able to emerge or be derived from those laws, whatever the language in which they are written. I think you are underestimating those who object to the block universe on the grounds that it is "static". You put it down to a semantic argument and assumed that they (we) simply don't understand what words like "static" or "change" mean in the block universe. I assert that we do (at least some of us). The way you defined each of those terms in terms of the block universe is precisely as I had understood them, but my objection remains. Yes, there is change from "frame to frame" within the block universe, but the whole four-dimensional shebang is static. This goes completely counter to a very fundamental, undeniable experience that every single person, and indeed every single creature ever to have existed has just known , in the same sense that you describe us knowing things like "self" or that we never "feel like" we are in a superposition state. In elucidating Everettian QM, you did a wonderful job of convincing me that you can fully account for those "known" things, like never feeling like we're in a superposition, or having a strong sense of "self" in spite of the clear reality described in quantum language that guarantees no such thing. For me, at least, in communicating the block universe concept, you have failed to convince me of any such thing. Like everyone else, I feel like I have free will, like I can make decisions about what to do next, and have made decisions about what I have done in the past. In a static four-dimensional block universe, this is necessarily an illusion, is it not? And while I will concede that it is possible that it is an illusion, and that the future is just as set and real as the present and the past, it fails, for me, to pass Occam's Razor. Rather than assuming myself and others like me are simply misunderstanding the block universe concept (for surely if we did not, we would be converted, seems to be the implication?), what if we flipped the assumption around? What if it is eternalists who do not understand what presentists mean by the word "now"? The block universe seems to me to be a sort of a crutch, a means to cling to a notion of reality that isn't really necessary anymore, or indeed, in my opinion, particularly compatible with Everettian QM. It's very difficult to wrap one's mind around the concept of time and light cones on a scale at which the speed of light is terribly slow, and so thinking of time as a fourth coordinate, as a "thickness" to the universe that "now" scans through creating only the illusion of change and free will becomes easier than imagining instead that the wave function of the universe can evolve perfectly well through time despite the limitations of light speed and light cones. You've drawn a number of times now, a comparison between a block universe with a slice of time that is "now", and a presentist universe in which you draw the same slice of time that is "now" , and act as if those are the only choices. But what if there's a third choice in which the presentist "now" is more akin to the rippling waves along the surface of a pond? In this view, there would only be one universal wave function, that is everywhere at once, and only exists instantaneously. Just as field theory allows for "action at a distance" not to be "spooky" because each infinitesimal volume of spacetime affects only the volumes around them, and are affected by only those volumes as well, why can't time be the same? Embedded within the instantaneously existent wave function would be all the information necessary to "chug forward or backward through time" using the laws of physics for prediction and retrodiction, as well as for reality itself to chug forward through time in a fundamental way. Is there an existing view on time that treats it this way? Sort of a "temporal field theory"? If not, it seems like a far more interesting and promising line of thought to me than deciding whether the same slice of time exists on its own or inside a block of Jello, at least to my mind... 1 Tom Lakosh Tom Lakosh 2 years ago Dear Doc; Time and entanglement are mutually exclusive as superposition precludes acceleration and the time function. That's why we need a dual membrane electromagnetic field with an antimatter half that doesn't have a time function and this brane produces entanglement through strings that are paired with matter strings to form 1 to 3 aspect ratio tori that we call gravitons. The circuit or conduction tesor formed keeps these strings from annihilating as does the conduction tensor holding graviton clusters together, (looks like a barbell). Time just renders these antimatter strings to a recessive manifestation in the graviton and subsequently more complex structures incorporating gravitons. Gravity is just the electromagnetic processes applied to the flow of graviton and graviton clusters around and through Standard Model particles. The clusters are actually gluons that were formed en mass during the GUT Epoch and are continually formed in SM particle cores. These gluons/clusters act like a dipole gas subject to condensation via Feshbach resonance and BCS field effect, and this condensate is formed in the electromagnetic field of galaxies as dark matter that is scattered by cosmic rays . The dipole gas is spin and charge coupled on the surface of leptons and baryons to form the Higgs field operating as an electromagnetic rectenna generating space-time viscosity as it captures the momentum of gravitons and clusters flying through the field. The gas is also the working fluid for a gravitational propulsion system operating as an “ion thruster” through the core of the leptons and baryons. Dark energy is just the increase in quantum friction of the propulsion system in barren space where the Higgs field drags the particle backwards toward even less dense space. Anex_ Anex_ 2 years ago Oh gosh, i forgot to ask in the previous video, but ive wanted an answer for this for a long "time" now. I was thinking, what is the rate at which time passes or the speed of time itself (lets say we are looking at one observer. Do we believe time passes at the same rate for everyone (excluding, obviously, relativity) or the notion of time over time would be an erroneous way to think. For example, if we were in a simulation, it could take years in the real world before one moment of this world passes, yet we can only precieve time passing at one "time" that we know. I realize that comparing our clocks to other observer clocks are useful but it says nothing about how the time itself progresses on. I hope my question is sound and I am not saying crazy stuff. Thank you for reading. ecsciguy79 ecsciguy79 2 years ago Question: If 'change' technically means 'change with respect to time', then what is the meaning of 'x warps space-time', since to warp means to change. 1 Jasmen coelho Jasmen coelho 5 months ago For some reason, in my head, I imagine Block universe as a block of cheese. you cut a hole through the block, if you slice that block up you will still have a hole in each slice Pavlos Papageorgiou Pavlos Papageorgiou 2 years ago Honestly I didn't know you'd written a book on it! The Knowledge. The Knowledge. 6 months ago I don’t think that we could travel in to the Past without reversing the Expansion of Space / Space-Time. Alexis Trudel Alexis Trudel 10 months ago In Newcomb's Paradox, could you choose box A and disprove the predictor (because if B has 100000, you could have choose both and he would have been wrong or if the box B has 0, you could have choose just B and he would have been wrong) ? clavo clavo 1 year ago (edited) Jimminy Sean, Wonderful enlightening video! It gives me to understand that: Knowledge can violate the laws of physics. E.g. you cannot go back in time to "effect" change in the past but you can "change" the probabilities of the future by gaining knowledge that is only available in the past. Is this not so? In your discussion you do not distinguish between bodily time traveling and mentally time traveling. Mikkel Mikkel 4 days ago (edited) Will Time Dilation depends on direction if the one-way speed of light is individuel per direction? Up/Down Time Dilation depending of directional velocity relative to where one is at a xyz-velocity that equals the one-way speed of light, likely as the CMB? And so also defines a lowest possible time dilation relative to all surroundings? Dean Batha Dean Batha 2 years ago In Special Relativity, time for any observer is dependant on their own inertial frame of reference and can be quite different for different observers. In General Relativity, time, along with space (spacetime) can be curved. Both of these seem to take the Humean view of time. The Big Bang theory shows space expanding as time advances. We can identify a point in time (about 14 billion years ago) for the Big Bang, but not a point in space; we can find a point in time and say, "it happened then," but we can't find a point in space and say, "it happened there." This is more anti-Humean. Where the beginning of the universe is concerned, time seems to be independent of space, and likely existed before it, and perhaps time even brought space into existence. Have I missed something? Saint Burnsy Saint Burnsy 1 year ago 12:40 My intuition about presentism is that reality might feel to be only the present moment as a result of how our brains/ perceptions work... we perceive only a part of the whole, for whatever reason (perhaps evolutionary?) Pablo Ledesma Pablo Ledesma 1 year ago This is a great format (Y) Tony D'Arcy Tony D'Arcy 2 years ago Gosh where did those 51.10 minutes go ? Throughly enthralling stuff Sean. See you again last week. 1 Ali Karimi Ali Karimi 2 years ago Thank you so much Sean for answering my question about time travel to the past. The Newcomb's paradox is very thought provoking too. Can't wait to see the next video 🙌🙂 mandar khadilkar mandar khadilkar 2 years ago I need a clarification - Electrons do have a mass then it should experience time. If an electron is left to its means then, after a period of time (well it could be very long), quantum properties should change over time (statistical probabilities) . Right? What am I missing? Tommy Grändefors Tommy Grändefors 2 years ago Well, we still get older Sean 🙂 The arrow of time. 1 Denis Daly Denis Daly 2 years ago I made time to watch this. Time well spent. 32 Naimul Haq Naimul Haq 1 year ago (edited) Is CPT proved beyond doubt? Multiverse seems to make Sean vacillate between block universe and multiverse, with his paradoxes. beefcurtainz69 beefcurtainz69 2 years ago If I’m sitting on earth and my twin brothers both leave and one goes to the moon at a fast average rocket speed and the other brother goes in a futuristic rocket that can go near light speed and he flies around the solar system and then eventually they both come back to me, aren’t they both still the same age? I mean they both were still born at the same time no matter what happened to them along the way. ytinformes2 ytinformes2 1 year ago What I liked about this Lost time travel theme, the ''What happened, happened''', this was because the universe was self-correcting. In other words, if you change the past, the universe has laws that will bring the events as they used to be. For instance, you go back in time to make sure that your girlfriend doesnt get in the car in which she died in a car crash. She does get in this particular car and she is saved. Well, she might die two days later, hit by a bus. So, she will die anyway to keep the time-events coherence of the universe, to keep the future events linked to her death synchronized with her death. It is like a tv serie version of the entropy or the least action principles. What happened is what has the highest probabillty to happen. You can come back in time to bring a stupid rock uphill, but it will come down to the bottom as soon as it has an opportunity. Christopher R Chociey Christopher R Chociey 2 years ago @Sean Carroll. Have you been watching the series "DEVS" about quantum computing using Everett's model as framework . 2 ed o ed o 2 years ago Sean thanks for the videos, your floating head at the start makes you look like the science wizard of Oz 46 Viral Patel Viral Patel 2 years ago I believe time is same for everything and it’s not relative. When we say gravity or speed slows down the time.. it is really not slowing down time but it’s slowing down the atomic/molecular activities of every particle. It’s the slowness of activities of particles creates the effect of time slowing down. Time flows the same regardless where you are in the universe or how much gravity or high speed the thing is traveling at. It’s just at different gravity or speed... the molecular activities slow down or speed up for every single particles in that situation. Hope I can somehow express it better what I mean. D1N02 D1N02 2 years ago The past and the future are just different presents in my view. So if you go to the past you will be in the present and you can make choices about the future, but it will not be the future you came from because that didn't have you in it's past. eefaaf eefaaf 1 year ago Newcomb's Paradox isn't one at all. Of course you take box B, and if it's empty, you pick up A not to leave empty handed. If it has a million, who cares about the other box, that would just be greedy. So, yes, very predictable that when you take 2 boxes, B is empty, and if you take just B, you have your million! :) Niloy Mondal Niloy Mondal 2 years ago So I realized why Newcomb's Paradox is a paradox. Its because even though the predictor already knows the future, it still gives us 2 possibilities. Having 2 possibilities is incompatible with the block model of universe, there should only be 1 possibility. The predictor should just say 'this is what you are gonna do' and the universe will somehow conspire to make it happen. The paradox is ill-posed. Bill Garthright Bill Garthright 2 years ago (edited) Wormholes? Forget time travel. I'd be happy enough to use wormholes to zip across space. :) Please tell me this... might not be pure fantasy. Oh, I don't need a practical demonstration right now. I'll give you a little time to build a starship. But could it be possible,... maybe? My science fiction book club will be very interested! :) CorwynGC CorwynGC 2 years ago Can you predict whether your friends are one-boxer or two boxer? IF you can, why would you think that a predictor couldn't? Pierre Houston Pierre Houston 2 years ago The time-traveling historian fiction of Connie Willis should be mentioned (try to ignore the first novel's use of telephone tag as a plot device, time travel exists in future Oxford, UK but mobile phones don't). Definitely portrays a one-timeline, or "whatever happens, happens" universe. The mechanism for avoiding paradox is the time travel portals which don't always work reliably. If a traveler would change the past, the portal will not open to that place and time. I won't mention whether the other case ever occurs, portals instead working reliably and travelers contributing to known history. Spoiler for Avenger: Endgame ... but it instead portrays a multi-timeline universe, with its own wrinkle that's portrayed fairly consistently. Their technology works such that after changing the past (though they try not to), traveling forward again takes them not to the new future created by those changes, but the unchanged timeline they left from. Lots of other fiction instead freely mix-up their rules to serve the story. Dustin King Dustin King 2 years ago Knowing the workings of the Predictor is probably worth a billion dollars or more, so maybe we should capture and reverse engineer it. atf300t atf300t 2 years ago Accordingly to the Wheeler–DeWitt equation, the universe is timeless for any external observer. Thus, though time is a real emergent phenomenon for internal observers, it is absent for external ones. In this regard, the block universe picture (with time being one dimension) is misleading as it gives an impression of time as something that exists independently from an observer. Ullrich Fischer Ullrich Fischer 2 years ago What about this idea? Wouldn't that also be taking you back in time? You're locally changing the shape of space to go faster than the speed of light. Search Results Web results Alcubierre drive - Wikipedia en.wikipedia.org › wiki › Alcubierre_drive The Alcubierre drive, Alcubierre warp drive, or Alcubierre metric (referring to metric tensor) is a speculative idea based on a solution of Einstein's field equations in general relativity as proposed by theoretical physicist Miguel Alcubierre, by which a spacecraft could achieve apparent faster-than-light travel if a ... Warp-field experiments · Miguel Alcubierre · Casimir effect · Exotic matter LiteratiCircle LiteratiCircle 2 years ago So let's say Quantum, dark energy is the female and Mass is the Male; and like life itself, the process of birth, conception- then would it be possible to conceive a similar dynamic, say these two entities joined and exploded into Universe, as we know it? Just a theory. Thanks to you, now I feel way smart right..so don't blame me if this sounds absurd :) Awesome shows amazing lectures Bravo rautibo rautibo 1 year ago Fun comment, as economist, it depends on your propension to risk to decide which box you choose. Without additional information, like the probability of each outcome, I'd chose $1000 cash, because the other box doesn't exist for me (even with one quadrillion dollar inside). I'm wired that way, I was born like that. And that is not actual free will! Go Away Go Away 2 years ago For the "whatever happened, happened" stuff, I think a better way of looking at it is that the past becomes your personal future as a time traveler, so you have factual information about your own future. The question is, if you know baby Hitler is not going to be killed by you, do you give up trying? If you give up trying, is THAT why baby Hitler never died? Abhay Chacko Abhay Chacko 2 years ago Time travel paradox works only if the consciousness of self is preserved, so if the past is unique about all the particles that makes our body and all of the universe, time traveler's particles could end up in the same past,since it already happened could resume it's history in the present, so time traveler may always reach the present may be Yoda Jimmy Yoda Jimmy 1 year ago 37:00 but then there is a present of me which experienced something before. If i have such an information, the kid me of past could commit suicide, but then there is me alive as an adult. Whatever happened happened might be a good theory, but it would mean the universe is a function of constant space and time arguments, which violates certain basic observations in quantum mechanics. The better explanation is I can alter the past, but it would not be mine, as while sitting in time machine and going to past, all i am doing is travelling in my future. This would be the standard multiple timeline theories. And it would only curve space-time in a way that it can be plausible, which is all this theory needs is the validation of worm-holes. Mark G Mark G 2 years ago Sean, you should watch the German show "Dark" on Netflix, it has a really wonderful time travel paradox............it is one of the best shows about time travel I have seen. I don't know what your taste is in movies or TV, but I have a feeling with your great intellect you might enjoy the show. You got to butter'em up first before you try to get them to do something......wink wink ks ks ks ks 2 years ago (edited) Sean: if a person (or energy) is sent into the future or past that energy must be accountable. Which version of "time" pays for you being there or spent energy displacement. Unless the universe "borrows" said energy and either repays later or gets a credit. Unless time doesn't exist, so who cares when you get what it's owed. And if you disagree, then you'll just have to accept the fact destiny exists. Lol. Sean literally just stole what I was thinking as I typed out. 😂 mani mohamed mani mohamed 1 year ago TIME is real and emergent in nature .its flowing with no stop .not passivating and always active whether existing in past or present or future damyr damyr 2 years ago PUN 1: I'm no boxer man. I prefer German shepherds. PUN 2: I'm no boxer. I'm a karateka. Which one is fundamental and which is emergent? Which one is passive and which is active? Are they both paradoxes or none? you have 42 units of time to answer or not 1 Furbs Furbs 2 years ago Sean sporting the lockdown haircut to the max! Ron Andrews Ron Andrews 2 years ago I don't find Newcomb's paradox to be very compelling. It's easy enough to create a contradiction with language, it doesn't mean that it has anything to do with the real world. I can say that I have a computer that is 100% accurate but when you input 2 + 2 it returns 5. All it means is that I have created a nonsensical premise. Similarly, a 100% accurate predictor would not make a statement like the one in Newcomb's paradox. Ankerman Nermon Ankerman Nermon 2 years ago if we could stop moving in space what would happen with time. if you traveled near light speed age slowly so if you stop moving in space would you age quickly CaptainFrantic CaptainFrantic 2 years ago A thought just struck me while Dr Carroll was talking about gravity being a one way street. It occurs to me that galaxies very far away are moving away FTL because space is expanding. So I wonder if there is a long distance force (repulsive "anti" gravity") which is created because of this relational speed over huge distance. Just spit-balling. hughJ hughJ 2 years ago A compatibilist might say "free will exists" in the same way that "a table or chair is 'solid'"; the fact that nothing is truly "solid" doesn't change how we use tables and chairs. The rub here, imo, is that the operational belief that chairs are solid is not something people use to validate the pursuit of retributive justice, nor does it substantiate medieval metaphysical intuitions of an immortal soul and the threat of damnation in the afterlife. If free will is as real as tables and chairs then it becomes almost impossible to make an objective argument against "eye-for-an-eye", capital punishment, vengeance, not to mention all the needless anxiety people carry everyday for "what could have been". Communist Hippie Communist Hippie 2 years ago (edited) Sean i hope you are aware that, you mess my head up.. in a good way :). Now im cursed being in my head, with having that 100 yard stare, tomorrow at work while i try to figure this shit out. 2 Piotrekk99 Piotrekk99 2 years ago The box at any point in time is either empty or has money in it. Unless the rules specifically say that the content can be changed later based on your choice, the predictor can not make a statement like that about the future. It is equivalent to saying that if you choose A I already put the money in the box, if you choose B I did not, as if you were to transfer the information about my future choice into the past. It is just another time travel paradox. C B C B 2 years ago (edited) If I walked into a restaurant today serving a dish called "what the universe has determined I'm going to have", it would be a shit sandwich. 2 lisa monalisa lisa monalisa 1 year ago 48:00 If the predictor knows the future, it should not give an "if" claim, because it suggests a choice on my end, which is against its ability to predict perfectly. Ron Fisher Ron Fisher 2 years ago the anti-Humean view is that of Kant....even why Kant started writing! Nobby Stuler-Bålzak, Esq. Nobby Stuler-Bålzak, Esq. 2 years ago I don't believe in the 'Many Worlds Theory'. I believe it's the same Universe creating time. So every so called alternative universe is actually this Universe moving into a newly created time. Don't mind me, I have a vivid imagination. Mgenth bjpafa Mgenth bjpafa 1 year ago (edited) Time travel, Determinism and Freewill (Liberum Arbitrium Indifferenciae) are a mix of Ideas where Roman, Christian, Jewish thought converge, and are now important to all grounds of organized knowledge , from Computer Theoretical Science to Epistemology, from Quantum Mechanics to Pure Mathematics, Game Theories, 7th Art, performing arts, Engineering, and dominated by good Philosophy. Psychology and delusion of free will, psychiatry and spectrum diagnosis, and, ultimately, affect the Zeitgeist. Opine, avoid options on a matter that has legal implications, decisions of Life and death. Let them be wrong, avoid involvement. Since Augustine to Doctor Angelicus, William of Occam, till Der Grundlehre und both Kritics von Rheine und Practische Vernunft from Kant, forgetting all in the middle. From structuralism to Derridas, Rorty to Daniel Dennet. It is, respectfully speaking, to much baggage to a physics opinion, Although you are entitled to have one, I suppose it is not stable....As time travel, it is tainted by vulgarization. Just saying... Alex Tritt Alex Tritt 2 years ago Not sure if you even read these comments Sean, but have you seen the TV show “Steins; Gate”? If not, it’s about these students accidentally discovering ways to time travel (and getting way out of their depths when doing so), and you follow them along during all of this. But it also involves swapping between different branches of the wave function (which they call world lines), and CERN also plays a big role in it. Would recommend. Barefoot Barefoot 2 years ago (edited) 19:52 this is simply not true. If you throw a ball in the air in idealized "spherical cow" Newtonian physics, yes, time is reversible, and if you reverse the ball's velocity, it will retrace the same path. But that's only an idealization. Even without invoking anything quantum at all, and treating the air through which the ball flies as a fluid, if you truly applied all of the elements of Newtonian Mechanics (especially including friction!), the ball would not retrace the same path, because air friction would always act to slow the ball, in either direction of time, and the reverse-time ball would not end up in the same place at all. The only circumstance in which you could legitimately claim that the laws of physics truly do not distinguish the directionality of time would be if you mean in a block universe you would simply scrub time backward rather than forward as if watching a video in reverse... but in that case, then things no longer make much sense. Sure, you can reverse the velocity of the ball, but if it truly would retrace its trajectory backward, that would mean that it would necessarily somehow be spontaneously gaining energy from the air around it, which in this time-reversed world is now somehow conspiring to rush in behind it and push it along... in other words, it is no longer physics. It's magic. I wonder if on some level, this isn't the result of too much time steeped in the world of academia, in which physicists' equations on the chalk board start to take on an almost mystical quality. Go to your Engineering department, and ask an aerospace engineer if the laws of physics do not distinguish between the directions of time, and I think you'll get the same response I've given here. Once you get rid of all the idealizations and simplifications, there are an awful lot of things conspiring to make sure things don't look quite right in a video played backwards, and you'd have to be very, very careful indeed to set up a demonstration or experiment that could be viewed in reverse without it being completely clear which direction time went in the real thing. Apsteronaldo Apsteronaldo 7 months ago So if I understand correctly the only force in the block universe is that time moves forward? And there really is no concept of physical law, it is an illusion? Andrea Paolini Andrea Paolini 1 year ago Newcomb's paradox solution: take ONLY box A! XD A Kumar A Kumar 2 years ago (edited) Wow how lucky we are to get to watch your video. I just love how you plug your book, I will definitely be ordering. I would be very grateful if you could give your view on Roger Penrose CCC theory, I really find this concept exciting, look forward to your value view point. 3 zebionic zebionic 2 years ago "Whatever happens, happens" only works if there is a "pre-existing" loop. Not being able to change macroscopic historical events is a red herring, since the presence of your future self in the past at all would violate WHH if it hadn't happened already. So the history you remember before traveling back in time must include your time traveling self having been part of it, whether the pre-travel you knows about it or not. ag ag 2 years ago I was thinking potentially Box A has an invisible monster that likes to eat money from opaque boxes before you've opened them. 1 Go Away Go Away 2 years ago (edited) An additional point about there not being free will is that "now" in your brain is a construction. If you clap your hands, the sound and the image seem synchronized, but hearing is a much faster sense than sight. Your brain does a ton of processing to recognize faces, create stereoscopic vision with distances, etc. Yet your brain syncs it up after the fact. I also remember a study where an fMRI showed that the brain sends signals to move muscles before the decision part of your brain "decides" to move those muscles. Conscienceness feels just like the brain creating a story to tell itself to make sense of what it just did and of whats happening on the other side of your skull. Sed Na Sed Na 2 years ago Thank you. Trebor Heminway Trebor Heminway 5 months ago If quantum particles can be both a wave and a particle or waveicles, why can't time be both passive and active? Kind of a background time that maybe infinite, and a local changing/passing time? John Guilfoyle John Guilfoyle 2 years ago it's about time! 2 Theo Schijf Theo Schijf 2 years ago Why make things so complex? Time does not exist in the quantum world, nor does space. Therefor, yes, both time and space (spacetime) are emergent. It explains nicely why entangled particles stay entangled when moved apart. They only move apart in our world, not in the quantum world. They might even be the same particle there. Helcio Felippe Jr Helcio Felippe Jr 7 months ago 41:58 Newcomb's paradox. Hobbies Hobo Hobbies Hobo 2 years ago Time, more fun than anyone can imagine, John Titor was here! Ha Ha Ha Shalkka Shalkka 2 years ago Block u niverse doesn't imply static time. There is a computer game Achron that has an ontology that is a growing block dynamic universe. As a person deep enough into time to write a book about it you might be interested in that and talk to doctor Hazard about it. One of the frases used to refer to the staticness property is game of thrones with "the ink is already dry". If we live in a universe where we visit a page only once it doesn't matter a whole lot whether the ink is dry or wet as the page will read something when we visit it. If you can revisit pages and the ink is dry then it is possible to concive of THE CANONICAL HISTORY of the universe. The dynamical option is somewhat theorethically messy. And a lot of thinkers are only comfortable assuming some kind of staticness. One good formulation is Novikovs self-consistency princple (becomingness can't change the probability of any events). However there doesn't seem to be good reasons to rule out or against the dynamical option. In a dynamical block universe a demon might have to do more computation. The dynamical view also has the issue/feature that the change can't be in respect to time (need another time dimension or some addition like that). But if the laws of physics are primarily consistent in this "wetness" sense then they are also approximately consistent in clock progression sense. In principle some facts could depend on which "revision" of the history books is in effect but if there is local connection between cause and effect there is a (potentially very long) uninterrupted story that spans all the revisions. John Goldman John Goldman 2 years ago If information is taken from the future and added to the present then the present information would be increased which contradicts the conservation of information ie QM 1 TheyCallMeNewb TheyCallMeNewb 2 years ago The kind of quote that, in its original form, one does not walk away with all that there is present to glean upon just one viewing: "Given for one instant an intelligence which could comprehend all the forces by which nature is animated and the respective situation of the beings who compose it - an intelligence sufficiently vast to submit these data to analysis - it would embrace in the same formula the movements of the greatest bodies of the universe and those of the lightest atom; for it, nothing would be uncertain and the future, as the past, would be present to its eyes". I guess Laplace was trying to be clear. bestape bestape 2 years ago I like to think of machines that can tell if something changed been exist or not exist but not which one. It could have changed from exist to not exist or it could have changed from not exist to exist. Then, create information out of those machines. In other words, imagine our experience as one step removed from full reduction. Always have one remaining process that's unsolved. Hofstadter's "Godel, Escher, Bach" grapples with a Zeno recursion version of this kind of thought experiment. Prime numbers do not allow space for it. mike barrett mike barrett 1 year ago What if anything do you believe has oomphiness sean? K C K C 2 years ago #science #physics #ideas The Biggest Ideas in the Universe | Q&A 4 - Space 58,166 viewsApr 19, 2020 Sean Carroll 154K subscribers The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is the Q&A video following Idea #4, Space, the video for which can be found here: https://www.youtube.com/watch?v=77LM_... My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/p... The Biggest Ideas playlist: https://www.youtube.com/watch?v=HI09k... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: https://wallpapercave.com/w/Pr9hNhy #science #physics #ideas #universe #learning #cosmology #philosophy #math #space #dimensions 133 Comments rongmaw lin Add a comment... Matthias Kaufman Matthias Kaufman 2 years ago (edited) I rarely comment but I just wanted to say thanks a bunch for these videos Sean, they’re great! You’re a great educator; wish I could same the same about more of my professors. 36 Žiga Tretjak Žiga Tretjak 2 years ago I love it, even though it is way over my knowledge. Great masters know how to present complex topics. 12 Varinder Bains Varinder Bains 2 years ago Amazing how Sean Carroll can cover such deep, technical discussions in an understandable way. A great teacher, educator and of course genius! Thank you... 16 Bigmike Beebee Bigmike Beebee 2 years ago Thank you so much for this series, it's fantastic! Question: If we postulate that space is quantized and nothing can be smaller than a Planck Length, does that solve the problem of gravity and quantum mechanics clashing in singularities and producing nonsense numbers? If so, do we still need string theory to unite gravity with the Standard Model, or is quantized space sufficient? 1 Frank Calabria Frank Calabria 2 years ago Thanks Sean. I've been trying tu understand partial derivatives and Hamiltonians for years and you nailed it in the first ten minutes of this Q&A! 3 NickRR NickRR 2 years ago Thanks for this series - definitely a silver lining in these strange times. At the risk of using terminology I don't fully understand, can the extra curled up dimensions be thought of as a fibre bundle? 2 R C R C 2 years ago (edited) Thank you, Professor. These Q&A videos are fantastic and this series of videos is the very best content for me during the current events. I appreciate the effort and time you have devoted, it is like a free gift for us all. 1 Cooldrums777 Cooldrums777 2 years ago Oh boy. Just when I think the last video you did in the series was really good, you go ahead and produce one that's even better!!!!! I especially enjoyed the way you tied the concept of the Hamiltonian with ways to explore deeper insights into nature and reality. I am now officially addicted to this video series. Long live the Biggest Ideas !!!!!! 1 Archie Lundy Archie Lundy 2 years ago Many thanks professor for this wonderful series. Combined with the Mindscape podcasts you're providing some of the most compelling content extant. Benjamin Zand Benjamin Zand 2 years ago Sean thank you for these lectures. As always they are brilliant. Ministry Of Arguments Ministry Of Arguments 2 years ago Thank you for the series. You've piqued my curiousity now that you mention 10 or 11 dimensions. Knowing that we traditionally have time as one dimension plus 3 dimensions of space making the 4D universe. In these extra dimensions that you mention could there be extra dimensions of time or is that always restricted to the one? Professr Frank Professr Frank 1 year ago 21:55 I like the explanation very much for small dimensions. Another example would be a very thin wire, which for us big things is practically a 1D thing, a single line, but a tiny insect would see 2D because it can go around it. 1 DeltaXY DeltaXY 1 year ago In the Q&A videos, I believe more examples would be great! Thank you again for your work. rage rage 2 years ago I could listen to Sean all day long thanks for this new series. Jan Gregrowicz Jan Gregrowicz 1 year ago (edited) Thank you Sean for the amazing series! Neither Laplace nor Leibniz invented ∂ (curly d; del). There are many "L-men" in the history of mathematics and curly d is attributed to Legendre. In fact, it was Condorcet who used it first and Jacobi (after Legendre) who made it popular (hence sometimes called Jacobi delta). 2 Lautaro Kinalczyk Lautaro Kinalczyk 2 years ago (edited) Hopefully someday we get to the symplectic structure of phase space :) 2 Umbranic Umbranic 1 year ago Professor will be great if you do a video explaining your paper on the compactification of dimension. I have tried to read it but it is still difficult as a student to understand some parts. Thank you!! 1 Chris Stewart Chris Stewart 2 years ago Thanks for answering my question about "disappearing" dimensions. I originally thought you meant disappearing was literal :) Now I get it. H. I. H. I. 2 years ago Just yesterday discovered this. Immediately subscribed. Thank you, Dr Carroll, for this and for the books. Daniel Karbach Daniel Karbach 2 years ago Could other branes' gravity leaking into ours explain, in part or in whole, the effect we currently attribute to dark matter? 2 Atakan Gökeer Atakan Gökeer 1 year ago Before sleep i watch this brilliant lectures. Dr. Carroll is such a great teacher. Shoopaah Shoopaah 2 years ago Suggestion: maybe you could use the screenspace in the video more efficiently. For example extending the part where you write towards the bottom of the screen. Or using the space above your head, maybe with a second screen for short notes, however that would maybe be overkill. Great series btw ! A Kumar A Kumar 2 years ago Looking forward to watching this video, I have to watch at least twice to grasp the topics. DoVaBoVa DoVaBoVa 1 year ago Professor Carrol, there are no words to describe our gratitude to your great efforts! Think about how many people would love this subject, at least change their minds about it, and many would like to pursue it to become our future great scientists, as yourself, and they will carry on the torch of science further! pipertripp pipertripp 2 years ago The Hamiltonian bit was great. I'm curious to learn more about that formulation of mechanics. I'm still working my way through introductory Newtonian mechanics so it will be a while perhaps. Ken Yo Ken Yo 1 year ago Great contents! Absolutely love it!! HCLeft HCLeft 2 years ago As a matter of fact the symbol of partial derivative is indeed a letter in "some language" and that language would be Greek ;) It's a small (as in non-capital) theta. Not that it is of any significance at all but just mentioning it. What is of a major significance though is that you are doing a spectacular job something that makes me (and i am sure many- many others) deeply grateful for. And i am not referring just to this project alone but in general; As I've been following your lectures and books for quite sometime now. Consider even, that you have me "almost" convinced that the "Many Worlds" - an idea that i was holding as one of the most absurd things i had ever been exposed to - might actually be the way to go :P 1 Brent Brent 2 years ago “And why is it negative? Because trust me.” Thank you for doing these, they are saving me from rotting my brain watching Marvel movie update videos. 1 Jan Neggers Jan Neggers 2 years ago notability has a red-dot (laser point) feature, i like to use it to highlight when i'm talking to class. It's the rightmost icon of the group of drawing options at the top. Alex Madeira Alex Madeira 2 years ago Sean - there's nothing else like this series on the web. These are wonderful! I know it's probably a little obscure but I'd love to understand more the concepts behind the theory Lee Smolin discussed a few years ago about time being fundamental and space being emergent and dependent on a multi-dimensional network or graph - the implications of this seem to me to be quite significant at a foundational level. - Thanks, Alex Geoffrey Byers Geoffrey Byers 2 years ago Fantastic series. I've not seen this amount of accessible description of arcane concepts like Hamiltonians and extra dimensions. You are really making a series for those that half understand mathematics and physics but were previously unable to relate all the concepts. Thank you. Jainal Abdin Jainal Abdin 1 year ago Can entangled particles be connected by compactified smaller dimensions? John Długosz John Długosz 2 years ago In quantum mechanics, the position and momentum together is, in some sense, a single thing that can have different classical aspects revealed. (position and momentum are conjugate variables, thus the uncertainty principle that the combined knowledge of both is limited by Planck's constant) So, x and p are different shadows on Plato's Cave wall, of a singular true reality. The difference in nature between x and p are keyed with the difference between space-like and time-like dimensions. Look at how you apply operators to the wave function to obtain them. 1 Mike Mike 2 years ago Sean has some legit hockey flow. 2 MadderHat MadderHat 2 years ago Can we view uncertainty as a feature of and by itself ? A tool just not for quantum mechanics? 1 In Coath We Trust In Coath We Trust 2 years ago Hey Sean, what are your thoughts on guys like Eric Weinstein and Stephen Wolfram each developing their own version of a "Theory of Everything"? Do you think they have any chance of succeeding? They're both highly capable individuals. 3 peksi peksi 2 years ago IT&T - imagine this and that theory :) I so want us to prove anything new "soon", let's hope the major construction of any future supercolliders won't be halted and hindered. Get well, America! Josef Angeria Josef Angeria 2 years ago 38:45 PLEASE prof explain further, this is the only thing in the universe I don't understand (ignorance is bliss..), how can something with a gravity that lets nothing escape, even light, let radiation (light) to escape? I saw a PBS space time episode and I guess either I cant remember or I still did not understand after their attempts to explain.. Thanks for these videos 💖💪👍👍 Liam McCarty Liam McCarty 2 years ago Not sure if it was my comment about locality or someone else’s you were addressing, but thank you Sean! Your answer helps tremendously Dylan Allen Dylan Allen 2 years ago Thank you keep them coming!! Pineapples Pineapples 1 year ago Flying through space surrounded by dweeble brands reminds of a story I wrote in sixth grade must of had old physics books available somewhere about 37 years ago apper cumstock apper cumstock 2 years ago Might get used to such cool and concise teaching! Alex Tritt Alex Tritt 2 years ago it's past 2am, I've been programming a random map generator for a video game I'm starting designing. about to go to bed cause I'm making mistakes Sean Carroll uploads something Well, looks like I'll be up for a bit longer 18 common sense common sense 2 years ago Math is the law of science written down, the thought we can use math presumptuously by itself to make sciences like quantum mechanics is totally preposterous because the laws of nature are already set. The fact they are unchanging allows us to do science. 1 Barefoot Barefoot 2 years ago (edited) I would be interested in more on the Hamiltonian formulation... specifically how the Hamiltonian for simple harmonic oscillation leads to trigonometric functions. I suspect the actual movement over time has something to do with the integral of the hamiltonian rather than the derivative, and that an i comes into it at some point and then gets used as an exponent in an e^i(something)? Or at least a "something^i(something)" that then gets normalized to e? Actually, I'm getting hazy memories of this maybe having been done in college... <.< Humphrey Chimden Earwicker Humphrey Chimden Earwicker 4 months ago If there's one thing Ive learned watching and listening to Sean M Carroll, is that he loves Laplace and his demon. Josh Hickman Josh Hickman 1 year ago A dabble of math might answer the 'is this entangled?' questions better -- talking about whether you can factor things isn't too much, I think, for this audience. Flying Arts Flying Arts 7 months ago Do you have a discussion about dark matter hidding in extra dimensions? Clorofila Azul Clorofila Azul 2 years ago Design tip: don't cut your image (body) under your chest ;) :D Thank you very much for your videos! judy churley judy churley 2 years ago (edited) Does an object moving displace space as it distorts it? 2 Glen Orchy Glen Orchy 2 years ago I thoroughly enjoyed that. Joshua Pasa Joshua Pasa 2 years ago Is there a symmetry that preserves locality, in Noether's theorem? Tony Bowen Tony Bowen 2 years ago Thank you so much! Stewart Hayne Stewart Hayne 1 year ago Thanks for the math example! Dave Brosius Dave Brosius 2 years ago Why couldn't there be 3 spatial dimensions and 7 time dimensions? Shoopaah Shoopaah 2 years ago This is great stuff Nathan R. Nathan R. 2 years ago I believe in regards to the entropy of the black hole violating the hamiltonian and Laplace deamon of where the energy goes it may very well be that 3 dimensional space simply doesn't exist in a black hole and instead those extra tiny dimensions that are so small are allowed to form and suck up that energy and retain it for some time; like a periodic table of dimensions would form and there could be more than the posterized based limit of 10 or 11 that could support the symmety in supermassive black holes like Matthias Kluge Picksalot Picksalot 2 years ago (edited) @Sean - Your Partial Derivative "funny d" symbol looks a lot like the the letter "d" used in English Lute Tablature in the very famous 1610 publication of the "Varietie of Lute Lesssons" by Robert Dowland. Here's an example: https://walterbitner.files.wordpress.com/2015/09/earleofessexgalliard.png There are a couple in the first measure (an elsewhere), and indicate the the 3rd fret for a particular string. I so know you play music, so I thought you might find this trivia interesting. John P John P 2 years ago Thanks Sean for another good video. I'd like to suggest the next Biggest Idea: universal constants. 1 Richard Rodfar Richard Rodfar 2 years ago Thanks for your work please give the name of application that you use for blackboard on the screen 1 Wafikiri Wafikiri 1 year ago Another way to have undectable extra dimensions of space: they might be big, but movements through them might be so slow or so inertial (i.e., constant velocity) that we haven't ever developed any senses to detect them. This is to mean p vectors mightn't sway enough in such directions or their components in such directions mightn't vary fast enough to be of any use to animal survival. Would you sense a speed of a metre per millenium? Would you have muscles that would take ages to move anything in such dimensions? Michael G Michael G 8 months ago The Simple Harmonic Oscillator is ‘Super famous’. Well it is more famous now for sure! SubEthaEngineer SubEthaEngineer 2 years ago Great content Paul C. Paul C. 1 year ago Reminder : Hamiltonian / Phase space discussed + example. SHO. Calculus, D, delta & del. Xtra dimensions, Locality, Holographic Principle. All in 48 mins !! Spirinsola Spirinsola 2 years ago Can twins be quantum entangled? Anshuman Sahu Anshuman Sahu 1 year ago Is "mass" considered a dimension in the extra dimension that is mentioned here?? Even in Newtonian mechanics why isn't "mass" considered as an parameter to describe where as momentum does. Patrick McHargue Patrick McHargue 2 years ago Give the shut-down a few more weeks, and your hair will get as wild as my university calculus professor's hair. (he was also quite good) 1 kapsi kapsi 1 year ago "Take a brain and wrap it around" - I'm trying! Zero One Zero One 2 years ago Is a black hole a thing, or the absence of something? They appear to hold a spherical shape. Yet to my knowledge they aren't comprised of something, if they were, shouldn't those 'somethings' experience instant spaghettification? Thereby vanishing from existence entirely and instantaneously? So why do they have the appearance of a shape? Larger/heavier bodies are spherical due to their relationship with gravity. That force is equally applied evenly to the entire surface-area of said object, resulting in a spherical shape. Black holes don't have surfaces, right? When I think about a star collapsing into an anti-star (BH), shouldn't the near infinite gravity just pull the remaining material into oblivion instantaneously? How could a field of any kind remain after the collapse? Anti-stars shouldn't leave anything behind, let alone a light consuming spherical field that decimates matter. Just the fact that anything remains after such a collapse doesn't make sense to me. My conjecture: Unless these anti-stars are actually antimatter fields, whereby matter that gravitates too close to the field are annihilated upon contact. The Hawking Radiation could be matter converted into out-gas after making contact with said event. Vincent Randal Vincent Randal 11 months ago "Particles" whose mass changes over time? That's a rocket that burns its fuel. Paco 6335 Paco 6335 2 years ago Merci beaucoup pour votre travail de vulgarisation Soul DFS Soul DFS 2 years ago Can you post something special when we reach 100K subscribers legend? You make Carl Sagan look like Arnold Schwarzenegger in Kindergarten Cop. Exhibit Express Evidence Exhibit Express Evidence 2 years ago Feynman student, You're my professor now! 1 Beena Plumber Beena Plumber 1 year ago We talk about hiding dimensions in smaller scales, but shouldn't the inverse be true? What if our 3D space is like that 2D tube that vanishes to a fiber as we move away from it. If we can move away from a 2D tube and make it look 1D, might we be on a 3D space that is seen as a 2D surface to a 4D observer at a great distance? Or maybe all of our dimensions are small to a large enough observer living in large space? Is there anythi9ng wrong with that? Fergus Fergus 1 year ago Got left in the dust at branes being related to strings. Phew! David James Bolger David James Bolger 2 years ago (edited) Once Sean gets into the stringy stuff. Physics is getting funky somehow. Likes its moving away from reason and knowing to an unknowing madness. The more we open the intricate clock. The more it confounds us but just keeps us interested enough to stay in the maddening game. The answer will never be what we expect. The future is gonna seem crazy if we knew it. But it will overall over time be good. Heart somehow trumps head. Even in physics for me. 1 Ron Ron 2 years ago Hey, 130 videos would be great :) I got plenty of time right now. 3 Артём Завидеев Артём Завидеев 1 year ago Haven't understood getting the "yellow" equality at 9:35, can anybody explain? Hamoud Alwardy Hamoud Alwardy 2 years ago Thank you pizzacrusher pizzacrusher 2 years ago These are wonderful, but getting very ‘mathy’ and not as accessible for the casual listener/watcher. Yoda Jimmy Yoda Jimmy 1 year ago What about M-theory? Eliézer José da Silva Rios Eliézer José da Silva Rios 1 year ago If the information in the book is written in Chinese, for me me is zero information because I don't know Chines language, so this paradox might be false. The information written in Chines carries zero energy for me, so wouldn't radiate from the black hole. Yoda Jimmy Yoda Jimmy 1 year ago I loved it when he said funny d 8:40 GroovyVideo2 GroovyVideo2 2 years ago nice show - maybe try Rule of thirds - will make show look better Exhibit Express Evidence Exhibit Express Evidence 1 year ago Thanka! David James Bolger David James Bolger 2 years ago Thank you Seany boy. 5 Boris Petrov Boris Petrov 2 years ago Space episode was very difficult to follow... ;-(( -- especially Hamiltonian ;-))