#science #physics #ideas The Biggest Ideas in the Universe | 16. Gravity

#science #physics #ideas The Biggest Ideas in the Universe | 16. Gravity 585,064 viewsJul 7, 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 #16, "Gravity." By which we mean Einstein's theory of General Relativity, according to which gravity is the curvature of spacetime. Since we've already learned about spacetime and about curvature (geometry), this one is a breeze. 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/playlist?list... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: Astronaut Bruce McCandless floating in space, NASA. https://www.nasa.gov/astronautprofile... #science #physics #ideas #universe #learning #cosmology #philosophy #gravity #generalrelativity #einstein #spacetime 805 Comments rongmaw lin Add a comment... Sean Carroll Pinned by Sean Carroll Sean Carroll 1 year ago Couple of errata: Around 48:00, the first entry in the components of the metric should be -1, not +1. And around 1:02:40, I said the Riemann tensor has 128 entries, when of course it's 4x4x4x4 = 256. 173 Kobev3li Kobev3li 1 year ago How you showed the differences and ultimately the relationship between gravity and geodesics to other gauge fields, I thought the explanation was so clear I couldn't help but shed a tear when marveling these concepts. Words cannot express how much this series is appreciated Dr. Carroll, thank you so very much again for all your insights and all the time you devote to this series. Which truly has to be the most wonderful series on youtube today. 92 Rhonda Goodloe Rhonda Goodloe 1 year ago Thanks again for your willingness to put so much time and effort into this project! 210 Michael Hauser Michael Hauser 1 year ago Thank you Sean Carroll! Your series here on YT, the Royal Institution, etc… You conversations on the Mindscape Podcast… is a gift to humanity that I thoroughly enjoy since I found this. Please never stop doing this and consider me a humble fan from Austria. This is all gold and writing history! 15 Matt Litton Matt Litton 1 year ago Saw this posted to reddit, great timing since I just started reading your space time and geometry book. I went and checked out some of the other videos in the series and they are great! Really love this, I think you're one of the best physics communicators out there right now 5 dnavas77 dnavas77 1 year ago OMG I've loved every single one but this is the ONE I was waiting for!!! Thanks a lot Dr. Carroll ❤❤❤ 20 Subhanu Saxena Subhanu Saxena 1 year ago Thank you, one of the best talks I have seen on this. Maybe you could have added one more consequence of the field equations as gravitational waves. A video deriving the wave equation from EFE would be awesome. Thank you 2 Calvin Grondahl Calvin Grondahl 1 year ago Relaxing presentation, I can rewatch this over and over and learn something new every time. I am a retired editorial cartoonist and your drawing is just fine. 9 Tan Vachiramon Tan Vachiramon 1 year ago Absolutely incredible series. The amount of detail is spot on to understand these concepts and not bogged down by details. Thank you! 2 D P D P 1 year ago Holy crap this is amazing. Finally that next level of understanding I can't get from audiobooks and other YouTube videos. A true lecture 3 LeOnIdAs162 LeOnIdAs162 1 year ago Thank you so much Dr. Sean for sharing this amazing lecture with us ! Cheers from Brasil ! EarlWallaceNYC EarlWallaceNYC 1 year ago Once again: I've gotten great insights into a topic I've know for years. Thanks 35 Paul C. Paul C. 1 year ago Dear Prof. Carroll, thank you so much for that. I have known Einstein's Equation of GR for years, but this is the first time that I have actually UNDERSTOOD what all the terms & symbols really mean. That was the most comprehensive & complete explanation that I have ever been able to follow.Thanks again from a lifelong fan. You should stand for President of the USA !! 2 Dr10Jeeps Dr10Jeeps 1 year ago As a university psychology professor, I love these sessions with Dr. Carroll. He is such an engaging person (to say nothing about being brilliant as well). 15 Virtual Moyda Virtual Moyda 1 year ago (edited) Gravity and reverse gravity are truely fascinating subjects. Also thank you for doing such a good job at relaying this stuff to the masses. 1 David Jewell David Jewell 1 year ago Your presentation has finally melded the physics with the supporting math for me. Thank you! 6 Jake Littleton Jake Littleton 1 year ago Sean, thank you so much for creating these. I am someone who missed the boat on physics. I had no encouragement to pursue these topics until later in life. While I'm likely never going get back to school for these subjects, I appreciate you breaking down these big ideas in a very consumable way. Thanks for helping us all think big thoughts. Eric Eric 1 year ago Sean, just wanted to say you are so eloquent and well-spoken, that you deliver complex messages in a way that everyone can easily understand. Thanks for the videos, and look forward to all the content you make in the future. 1 Sanjay Patel Sanjay Patel 1 year ago I love how Sean gets breathless and so excited, must have been a little like what Einstein would have felt at the time when the Eureka moment hit 9 Mesokosmos Mesokosmos 1 year ago (edited) This is what I've been waiting for in these lectures. And worth of waiting it was! I liked the idea of linking integrales and special relativity with GR. C R C R 1 year ago Sean, never ever stop a video short because you think it's too long! absolutely amazing work here keep it up! 3 imaseeker100 imaseeker100 1 year ago There are many brilliant minds among us but few are as articulate and engaging as Mr. Carroll. 4 Jon Wesick Jon Wesick 1 year ago Thanks for another great talk. I noticed two typos. I think you want g00=-1 in your discussion of the expanding universe metric. Also, I think you wanted to define theta as the angle relative to the z axis when defining spherical coordinates in your discussion of Schwarzschild. JC JC 1 year ago He’s arguably the best science communicator out there! Pure brilliance!❤️❤️ John Joseph John Joseph 1 year ago My favourite theory. Thanks Sean for the in-depth explanation 1 Vincent Button Vincent Button 1 year ago This video is the icing on the top of this series... and there are more videos to come. Just brilliant! 1 Howard Moscovitz Howard Moscovitz 1 year ago I took Susskind’s GR video course before watching your video. Now I have a more intuitive understanding. Thanks for making these videos. You are a great teacher. Still, I think you said the Earth’s path around the Sun does not minimize length but maximizes time. I’m close but still I don’t get it. Please consider discussing this in the Q&A. 1 Sgt Aymos Sgt Aymos 1 year ago You're awesome dude, love the biggest ideas in the universe series 👍 Ewur3 .gaming Ewur3 .gaming 1 year ago This video stands out for me as having the right blend of simplicity, complexity and flow to optimize my understanding of the current model of gravity which has always been very mysterious to me. Sincere gratitude Sean, thank you. Carlo Malpensa Carlo Malpensa 1 year ago (edited) Thanks Sean, your videos give truly inspiration and wake up minds. I would have anyway quoted, together with Gauss and Riemann, the Italians Ricci Curbastro and Levi Civita because it is their work (published in Paris quote anonimously) the one that Grossmann suggested to Einstein. It's true that without Riemman and Gauss their work could have not be possible, but still I believe they should deserve a better place in GR history . 1 Benny Bundi Benny Bundi 1 year ago As an introductory physics student I’ve been interested in this stuff all of my life and have spent a lot of time understanding it but this was by far the most clear, intuitive, explaining I’ve heard, with the history and mathematical concepts interlaced gave me such a deeper understanding of what I already thought I understood! Will be binge watching these videos now Francisco A. Camargo Francisco A. Camargo 1 year ago Hi Sean, I enjoy your lessons very much. Thank you for such well thought out material. Can you tell us what is the blackboard software you use? I found it very intuitive and would like to try it... Thank you for your attention. Muttley Muttley 1 year ago These videos are so much fun, thanks Sean! Guilherme Fórnias Machado de Rezende Guilherme Fórnias Machado de Rezende 1 year ago (edited) Hi, Sean. Such a nice lecture, as always! I hope it might be addressed in the Q&A section: Is the principle of equivalence necessary and sufficient (therefore equivalent) to prove the inertial mass equals the gravitational mass in Newtonian Mechanics? Vini Vini 1 year ago (edited) Would really love a video on HN/steady state theory and Mach principle. I find it very hard to find good information on it but superficially it seems like the next step of the equivalence principle. Global Digital Direct Subsidiarity Democracy Global Digital Direct Subsidiarity Democracy 1 year ago (edited) Finally someone gives you a rough idea about the mathematics! Big thanks, Sean! vic summers vic summers 1 year ago These videos are absolute gems. Thanks Sean! Luke A Luke A 1 year ago I just finished my master's degree for which I took an introductory course into general relativity: this captures all the important aspects... I'll be watching each lecture! Thanks! jsstwright jsstwright 1 year ago Great work Sean, may I ask what software you're using for writing? Ok Ok Ok Ok 1 year ago Wish I'd known Sean had a youtube channel sooner. 26 Beena Plumber Beena Plumber 1 year ago Thanks for this, Prof! My goal for this pandemic (still in lockdown) is to understand general relativity, and I'm almost there! But then my head feels like it's full of sticky nougat, & you say with a smile, "Some of you may have never heard of a matrix, and that's ok." College physics was 23 years ago, and short calculus was I think 25. If I actually do get my head around GR, you bet I'm gonna be that nerd who corrects people about gravity being a force. I'll have earned that right! Ok, maybe just for a couple days... albertods611 albertods611 1 year ago This is an amazing video. I am studying the book "spacetime and geometry" , a great book on GR. Lindsay Forbes Lindsay Forbes 1 year ago Just brilliant, thanks, your knowledge and enthusiasm is breathtaking Robin Betts Robin Betts 1 year ago (edited) This makes all the other lectures I've watched on this subject so much more accessible! Fantastic! Undergraduate lecture series should recommend this overview for some folks, like me, before getting down to the number-grinding. Lordie7 Lordie7 1 year ago I don't mind the longer videos, I see it like a lecture, not a PowerPoint. I think it allows you to be more thorough even though I know you like to keep them shorter 28 KAĞAN NASUHBEYOĞLU KAĞAN NASUHBEYOĞLU 1 year ago Great series continues. Thanks a lot Prof.Carroll becomepostal becomepostal 1 year ago This is a fantastic video. I’ve never seen so many ideas clearly explained in so short time. Cloud Room Beacon Place Cloud Room Beacon Place 1 year ago Best description of why gravity is the curvature of spacetime I have ever heard 1 C.J. McELEAVY C.J. McELEAVY 1 year ago This might sound a trifle glib but...I love gravity! And it's not just for the obvious reasons. I've been waiting for this talk for weeks. Cortez Cabret Cortez Cabret 1 year ago This video is so great. And so hard. I didn’t watch any previous ones, just started with this one so I’m not sure if I should watch them in order. But maaaan.... I love this video because for the first time I understand how talentedly-intelligent of a person you have to be to truly understand this in mathematical terms. 1 Travis Travis 1 year ago Thank you for this grest video. Are there any theories as to WHY mass and energy warp spacetime? John at the Falls John at the Falls 1 year ago Sean is so friendly and relaxing he could be the Bob Ross of Physics. It is obvious he tries to teach from the perspective of the student. Amateur GAS Amateur GAS 1 year ago Best one yet, nice to see you still excited by the subject 1 David Sardarov David Sardarov 6 months ago I hope it is like you said: "100 years from now your series will still be on YouTube..." It is golden and for everyone to know! Thank you. JFT241 _ JFT241 _ 1 year ago I read your book The Big picture! Along with other great courses you've done. Had no idea you were here on YouTube. Maybe you weren't here until I looked but either way you've got yourself another subscriber. Thank you for sharing your knowledge with all of us, really appreciated. Yannis Varoufakis Yannis Varoufakis 3 months ago Great presentation! BTW, I just ordered your book "Spacetime and Geometry". I'm certain it will go way over my head, but I want it to inspire me to learn. One question: Einstein's fundamental concept behind GR is that there is no experimental method to tell the difference between gravity and a uniformly accelerating reference frame (the box). But now that there are experimental methods to ascertain the difference, which did not exist at the time Einstein came up with GR, why does this not require a reconsideration of GR? It is my understanding that in a gravitational field, like earth's surface, there is more gravitational force at your feet than at your head, which isn't the case with just acceleration, where the force is the same both at your head and feet. So if, for example, you were in a box that was very tall and there were a bookcase in it that was almost as tall, you could tell whether or not the box you were in was on earth's surface or in space accelerating at a constant acceleration of 1g by placing a scale on the bottom shelf of the bookcase and weighing a 1gm weight and then weighing that same weight with the same scale on the top shelf. A similar experiment would measure the passage of time on an atomic clock at the bottom shelf and the passage of time on an atomic clock at the top shelf. In an accelerating reference frame, there would be no difference. The weights would be the same and the clocks would be precisely synchronous. So acceleration may be reminiscent of gravity, but it is not functionally the same and is not indistinguishable from it. Sound waves propagating through the air also behave almost identically to the way light waves propagate in a vacuum. Does this require that the luminiferous ether be revived? Probably not, since although sound waves behave in ways reminiscent of light waves, they are clearly not the same. luca valentino luca valentino 1 year ago (edited) Thanks for this fantastic and enjoyable lectures!!! SlyFox SlyFox 1 year ago You make Tyson and Nye look like kindergarten teachers 🔥 Thanks for treating us as intellectuals. It's such a departure from the rest of social media. 149 Hays Goodman Hays Goodman 1 year ago I'd appreciate knowing which equations were used in the theoretical formulation of 'frame dragging.' The experimental technique for proof of that was fascinating. If this was addressed somewhere in Dr. Carroll's lessons so far and I missed it, I'd be grateful for a pointer to where it was. Thank you. UNSTOPPABLE-AR UNSTOPPABLE-AR 1 year ago Much love professor. Thank you KAĞAN NASUHBEYOĞLU KAĞAN NASUHBEYOĞLU 1 year ago Great series continues. Thanks a lot Prof.Carroll EK Lim EK Lim 1 year ago Wow, what a timeless piece of lecture Rob Mack Rob Mack 9 months ago Mr. Carroll, thank you so much for taking the time to explain EFE. Everywhere I looked, everyone would give examples for application, and when you have not been ever properly explained where symbols and letters derived from, or why those symbols do what they do, the language of the math in my head was indecipherable. Now I know what is being applied and derived from these equations. Thank you so much. Forrest Neal Forrest Neal 1 year ago Please make more videos educating us Sean! No Bell No Bell 1 year ago (edited) I find myself gravitating towards Sean's videos! 86 John Tamulonis John Tamulonis 1 year ago I always feel very lucky to be listening to Sean Carroll, I think he is one of the great scientists of our day. Hawthorne Hill Nature Preserve Hawthorne Hill Nature Preserve 1 year ago Just the opportunity to listen to you lecture is beyond amazing! Your delivery, humor and passion, make listening to you very easy. Thank you 🙏 John salem John salem 1 year ago You are doing a great job of describing the effects of and the measurement of gravity, but well short of explaining what gravity is Henry J. Henry J. 1 year ago This is the best one so far. Very clear, step-by-step. It did "payoff" btw. Thanks for doing this series. 5 John salem John salem 1 year ago You are doing a great job of describing the effects of gravity, and the measurement of gravity, but well short of explaining what’s Quinn Talley Quinn Talley 1 year ago (edited) Really enjoyed this and many others in your Biggest Ideas series, and Mindscape program. Thanks a bunch for the walk down memory lane. Hoping you have a wonderful 2021. GOOGLETUBE GOOGLETUBE 1 year ago (edited) Can someone help me please? I've been watching Sean for a few months. Some of his videos I watch multiple times as the subject matter is quite dense. My question is this.... How well can I really understand this subject matter, quantum mechanics, gravity, entanglement, cosmos, space-time etc. with my limited mathematical background? Can I come to a certain understanding but just be fuzzy on some details or will I be left in the dark? Some of the lectures place one math theory on top of another while counting on you to know a third theory. Some if the content is beginning to sink in but how shackled am I by my lack of math knowledge? Thank you. mikestabler mikestabler 1 year ago (edited) Thanks for making these videos. Good work! 1 rsin757 rsin757 1 year ago Thanks for the hard work. It was fun until it got a little complicated for me. Even so it was enjoyable to listen. 👍 Robert Shirley Robert Shirley 1 year ago (edited) Question: does simple harmonic oscillator work for gravity in all scales? I believe it should be if we neglect charges and spins. Does it work in large scales like between two galaxies or earth and moon? I believe it must be if the moon was literally falling to earth Omnipotat0 Omnipotat0 1 year ago Wow! I could listen to this guy's science talks all day Jed Gould Jed Gould 1 year ago (edited) 51:30 Sean’s central point in one sentence. Intrinsic property of space time. Michael Hutton Michael Hutton 11 months ago ".... And know you know what it is". Boom. Thank you Sean. Brilliant presentation. Just kept me in awe and wonder throughout. Einstein... What a mind. SLAYERx319 SLAYERx319 1 year ago Love every lecture, documentary or podcast you've done. Is 30 years old too late to start going to school for astrophysics? Jim Graham Jim Graham 1 year ago This is great work, together with Richard Feynman's videos gives a wonderful insight into reality. One error though, as 75yo can assure you t not constant, dt0>dt75 I think due to dark energy. Paweł Wójcik Paweł Wójcik 1 year ago Hi! This is very interesting and well presented. I enjoyed watching the talk but may I have a different question, please? How do you do the writings? Are you doing it in an iPad? Could you please tell me what app you are using for the writing to show on screen? I would appreciate it very much because I think It is brilliant! I would love to use it because COVID-19 is making me work from home and I think it’s a great way to explain thing to my English students when we have classes. Thanks and hope you have a good day! Paweł NEW DAWN NEW DAWN 1 year ago Even after having a master degree in Botany and the research experience of four years in PLANT TISSUE CULTURE I could comprehend the Mathematical formalism of the GENERAL RELATIVITY you just have described in a lucid way . thanks sir !! Ross Petersen Ross Petersen 1 year ago Man, you really know how to attract an audience! 24 Seppo Koivula Seppo Koivula 1 year ago That was so interesting episode. Thanks! DonaldLL DonaldLL 1 year ago Ive learned more in this one video than I have in any/many class(es) at the university attempting to explain the same material Siri Landgren Siri Landgren 1 year ago Something I've been looking for an occasion to ask: So quantum physics seems to be symmetric with respect to (charge, parity and) time. Meaning that we need the past hypothesis to give us an (entropic) arrow of time. But what about the fact that relativity limits is to travel in one direction of time, which happens to be the one where entropy increases? I guess that asymmetry could be resolved by viewing antimatter as traveling backwards in time, thus meaning that there exists both matter that travels in the same direction as the rise of entropy and in the other direction. But do we then start to get into the territory of the question of matter-antimatter asymmetry? Dave Wilson Dave Wilson 2 months ago You are the man. Thank you, Sean. Eric Diamond Eric Diamond 1 year ago Fell asleep listening to this, ended up dreaming I was back in class, and one of my friends was incredibly eruditely and confidently talking about gravity....and I was half listening thinking, shit, he seems to really know his stuff... 6 lashram32 lashram32 1 year ago Thank you so much for putting this out there for the world for free. You are a nerdy hero. ManWhoUsesComputer ManWhoUsesComputer 1 year ago Such a gift. Thank you SC! Marius Myburg Marius Myburg 1 year ago The first half hour of this video has been more informative than any video I have ever watched and any book I have ever read to try to understand what Einstein was saying regarding the curvature of spacetime and its relationship to gravity. Thank you very much for this. No concept is difficult, it is just that very few people are able to explain things well. A good teacher is one that explains so-called difficult concepts properly, making them simple, as they actually are. Explaining concepts well is a real skill, and you do it very well Mr Carroll. Mikkel Højbak Mikkel Højbak 1 year ago 27:26: "So you are accelerating right now unless you just jumped off a building or something like that. So that concludes the truly fun part of our video..." Beautiful transition there Sean. 🤣 1 non participant non participant 1 year ago Love your videos Sean. Thanks. MohPK MohPK 1 year ago Again Mr.Sean, thank you fo much for making these. 13 JP Richard JP Richard 1 year ago Love these! Thank you! Jacek Piterow Jacek Piterow 1 year ago There was an explanation I found on the youtube that gravity is a result of a time difference between points in space around a mass. That was the quickest and simplest explanation easy to imagine. Will that be correct? Joe schmo Joe schmo 10 months ago i bought his books and his courses because i felt guilty getting all of this free knowledge. Reading them after the lectures helped quite a bit Alfredoncio Tmr Alfredoncio Tmr 1 year ago Thanks for sharing sean! Great content. Cheers from Chile Jordan Weir Jordan Weir 1 year ago I've studied this for years with minimal success, and never come across such a clear explanation, thanks so much, I love when someone explains something with the intention of actually teaching the material instead of just looking smart :) Change Gamer Change Gamer 1 year ago 1:46:26 Do two objects orbiting each other cause gravititional waves? Or would their oribit have to decrease in order to send out gravitational waves? 1 Jamian Jacobs Jamian Jacobs 1 year ago We need to be able to see what is actually being observed from a perspective which isn’t our own. Stephen Bryant Stephen Bryant 1 year ago I feel I can relax this week... something I've thought a lot about. Still, I'm prepared to learn something new, perhaps quite a significant something. 1 Cyrus Kalali Cyrus Kalali 1 year ago Thanks a lot Sean. You are great. As a chemical engineer by eduaction, , it has been several decades since I dealt with equations. It is helpful to show us the equations, despite the fear of speakers and scientists, to write any equations, since it scares away the audience. Your sketches and diagrams are very helpful. This is a university lecture and I have to see it several times to digest it all. Thanks again.. Jack CF Jack CF 1 year ago Where is the connection field that predicts the graviton? This is my favorite video so far. I actually understood 95% of it this time. 😀 8 Gurito43 Gurito43 1 year ago Would it be correct to say that gravity is the density of spacetime? Like does spacetime get sucked inn to the mass, decreasing the distance between the original points in spacetime (increasing the density of spacetime), or would they just stretch appart? 1 Cooldrums777 Cooldrums777 1 year ago (edited) when discussing gravitational time dilation, you say that one can't accelerate along a geodesic. However, a satellite in a circular orbit around the Earth is on a geodesic path. One could apply a tangential thrust to the satellite and simultaneously apply a perpendicular thrust normal to the orbit pointing to the center of the Earth. Wouldn't this result in an accelerating satellite that remained on it's original geodesic path? How would this type of acceleration effect the proper time of the satellite with respect to an observer far outside the gravitational well of the Earth? 1 Mike Warot Mike Warot 1 year ago The "Small region of spacetime" you mention at 12:50 is now smaller than a standard physics lab. It's possible to have side-by side optical atomic clocks that can detect altitude differences of 2 centimetres! In a 1 G rocket, there would be no difference between the clocks. Soma Chatterjee Soma Chatterjee 1 year ago Can you please define time in term of mass? Ken Havens Ken Havens 1 year ago This is pretty neat Mr Carroll, been a long long time fan of your ideas and discussions on physics. This is the first one where I get to be involved in trying to understand the math behind the ideas. Doug G Doug G 1 year ago Man I fell asleep with this going and I had a dream Sean was my guest speaker at a party at an old folks home for the wealthy. I was getting treatments for cancer at the party and Sean was feeling sorry for me following me around. Crazy:) Ghan04 Ghan04 1 year ago Gravity seems to be a different beast than the other interactions we've talked about like the strong and weak forces because it is intrinsically tied to the geometry of spacetime, whereas the other fields appear to just go along for the ride. If we predict the existence of the graviton and we've discovered gravitational waves, are we really saying that these features are an intrinsic property of spacetime itself? Or is there a distinction between the gravitational field and the geometry of spacetime? Christian Hujer Christian Hujer 1 year ago This is the first satisfying video that I came across about this topic. Every other video only explains parts of the physics, but never the maths behind it. I love this video. I will watch it a few times. Thank you @Sean Carroll for making this! I'm learning so much from this! Ken Carlo Ken Carlo 1 year ago Holy cow - did you just successfully explain the mathematical underpinnings of general relativity to a doofus like me? I think you did. MAURICE PANERO MAURICE PANERO 1 year ago I was told equivalence was between inertial mass and gravitational mass. Inertial reference frames seem to be at the heart of both kinds of relativity. Farhan Hossain Farhan Hossain 1 year ago Hi sir, how string theory explains gravity in quantum level ? Dave Dave 4 months ago this was so dope! thanks for the video. I thought it was ironic that Schwarzschild died of pneumonia and this video was made at peak pandemic. Likely that pneumonia was the first flu pandemic. Andromeda Andromeda 1 year ago amazing video, thank you very much prof. Nigel Connell Nigel Connell 6 months ago Question: What’s the SMALLEST idea in the Universe? TrumanHW TrumanHW 1 year ago (edited) Of COURSE I stayed until the end, Dr. Carroll. So very generous of you to share. Having been unable to afford college this's truly a wonderful 'gift' to have a favored author / teacher teach courses. Change Gamer Change Gamer 1 year ago 1:24:48 can you explain why the bending of light is two times larger when calculating with GR compared to Newton Gravity? 3 David Griffith David Griffith 1 year ago I graduated in May with a degree in physics and was taught special relativity in modern physics and intro to cosmology. However, I #science #physics #ideas The Biggest Ideas in the Universe | Q&A 16 - Gravity 48,841 viewsJul 12, 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 for Idea #16, "Gravity." We cover some of the inspiration for general relativity (the Principles of Equivalence and Mach), and do quite a bit more on black holes, including the information-loss puzzle. 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/playlist?list... Blog posts for the series: http://www.preposterousuniverse.com/b... Background image: Astronaut Bruce McCandless floating in space, NASA. https://www.nasa.gov/astronautprofile... #science #physics #ideas #universe #learning #cosmology #philosophy #gravity #generalrelativity #einstein #spacetime 113 Comments rongmaw lin Add a comment... Rhonda Goodloe Rhonda Goodloe 1 year ago Sean- thanks for so generously sharing this part of your life with the world, ( well at least this world). 34 Dr10Jeeps Dr10Jeeps 1 year ago Another fascinating session with Dr. Sean Carroll. I can't emphasize enough how much I (we) appreciate your time and sharing of knowledge. 5 Erick Moya Erick Moya 1 year ago Always wonderful elucidations, Prof. Carrol. Thank you for taking time to communicate physics in such a fantastic manner. 3 A Kumar A Kumar 1 year ago I get a incredible sense of excitement watching this video, Professor Carrol is such a great person. 5 Ekain Garmendia Ekain Garmendia 1 year ago (edited) I like the fact that even though Hawking didn't like the 2nd generalized law, in the end he believed in the two best known theories. 1 Adam Albilya Adam Albilya 1 year ago (edited) 48:50 Sean Carroll: "No one in their right mind will ever remember it". Also Sean Carroll: * Remembers it * Man you gotta love him 😄 6 Dean Batha Dean Batha 1 year ago Sean, serious question: can't the Big Bang be thought of as a "white hole" in the past of the universe? Paul C. Paul C. 1 year ago Great. Brilliant. Thanks again Prof. Carroll for another superb Q & A. Will watch it tonight and again in the morning. I have binged watched the whole series this week. (Well, almost.) That was FUN !! Rollo Burgess Rollo Burgess 1 year ago Thanks again for these brilliant videos. Ps minor fact check - Hawking's memorial is in Westminster Abbey not Winchester cathedral. It is where memorials to great artists and scientists are traditionally put in the UK; there is a prominent monument to Newton as well as many others. 2 Benjamin Stone Benjamin Stone 1 year ago As a student completing a PhD in theoretical physics (specifically physics beyond the standard model/quantum gravity), your physical intuition and ability to effectively communicate these ideas is truly inspirational. Please keep doing these videos! 9 James Stewart James Stewart 1 year ago Information-loss might be a good puzzle, unfortunately there's no picture on the box and we're missing a few very important pieces. 1 joy fergie joy fergie 10 months ago (edited) Dr. Sean, I remember your lectures that I was listening to last year. Want to take a moment to say, Thank you~~~♡♡♡ Fixundfertig1 Fixundfertig1 1 year ago I love this series but it would be better if Sean says goodbye in each video, otherwise at the end it seems like if something is missing :o) 10 Michael Wrenn Michael Wrenn 1 year ago For the sake of the future of physics, I think, there is much guidance to be drawn from the fact that in the field of time nature exists as a duality. In view of this fact, a singularity is a useful device, and there is reason to believe it is only half the story. Vitaly Doletsky Vitaly Doletsky 1 year ago Sean, following 35:47, does that imply that the entropy of black hole by itself is lower compared to, say, Jupiter? In your black hole video can you please cast a light on what is going on with the entropy of a black hole - Jupiter system when the prior swallows the latter? Valdagast Valdagast 1 year ago (edited) As a chemist, I know of course that ethers are very real and a bugger to break up. 1:09:00 I now envision a number of theoretical physicists torturing a black hole and saying "we have ways of making you talk!" Vini Vini 1 year ago One incredible lesson by Sean Carrol after my lunch... Perfect! 1 Sam Carter Sam Carter 1 year ago A question I always had is, if there is no preferred velocity, then how could there be centrifugal force due to spin. Is there preferred spin but no preferred velocity? How is that possible? 1 unctarheels27517 unctarheels27517 1 year ago Sean Carroll is awesome. The videos are definitely focused on novice (unlike Leonard Susskind’s lectures) but still wonderful! Thank you Sean Naimul Haq Naimul Haq 1 year ago (edited) Equivalence Principle, Symmetry, In variance are aspects of the laws of nature. Maldacena introduced another aspect called 'duality' (ADS-CFT) as another law of nature, so as Sean explains entropy S is very high and very low for a BH, temperature T is very high and low, time similarly is high and low, information is lost and not lost etc., viewed from inside and outside of the BH, may explain the true nature of BH. Christine LaBeach Christine LaBeach 1 year ago Ok for a spinning black hole wouldn't the angular momentum exceed the actual physical integrity of the black hole? In other words spin so fast it overcomes its own Gravity and rips apart? Stewart Hayne Stewart Hayne 5 months ago I love the part about the book: Singularities in GR!! Tubluer Tubluer 1 year ago A whopping good romp around the block... there's a zillion good ideas in this video. Really good job Sean. Here, let me solve the info paradox for you... Information doesn't really exist anymore than "fourteen pi r squared" exists. Info is just one of those mythologies people made up because we are all inherently story tellers. It's a real as Zeus or Teenage Mutant Ninja Turtles and it's loss is not a meaningful concept. So there ya go :)) George Steele George Steele 1 year ago Time-Symmetry implications. Suppose that reality is time symmetric. The BB happened both ways in time. We "see" a universe collapsing over time to the (1) size -- the smallest possible size, perhaps with a non-uniform distribution of energy. The denizens of the negative-time universe experience entropy away from time 1, too. They, too, see, using their time direction, a universe collapsing into (1). There just is no time 0. The universe likes cause-effect. Okay each causes the other. Interesting questions arise if the directions in time are more than two. These directions are, IMO, probably QM probabilities. 1 Dean Batha Dean Batha 1 year ago (edited) Another serious question, Sean. If I can create information by writing a book, but I can't destroy it by subsequently burning the book, which implies that the total amount of information in the universe increases with time, is information somehow related to entropy? Too Crash Too Crash 1 year ago Wow, never thought Hawking radiation would be overpowered by micro wave background 1 Hunter Bungay Hunter Bungay 1 year ago Thanks Doc. Great stuff. Steve Hill Steve Hill 1 year ago I know I will sound like a terrible pedant, but 48:45 it's Westminster Abbey (between Newton and Darwin). This is a wonderful resource for anyone remotely interested in what modern physics has to say about the world. 1 nosirrbro nosirrbro 1 year ago What about something involving the holographic principle as far as a solution to the information loss problem? Is that seriously respected as a possible idea, or is it too much of a departure from our current understanding? Andre Amorim Andre Amorim 1 year ago (edited) Sean you are the best ever teacher I ever had in physics ... Thanks very much I wonder if you going to review the film TENET and the inversion of time... Jainal Abdin Jainal Abdin 1 year ago Two questions regarding the Time Symmetry talk in the video for White Holes: 1) Before the formation of the Black Hole, at an earlier time on the graph when the star collapses, isn't the Supernova like a White Hole? There'd be a section where nothing can enter it, and the explosion ejects matter from the centre of the star - opposite to the Black Hole. 2) If you extend the graph, such that R is the radius of the entire Universe beyond the observable Universe, the Black Hole in that scale is where everything is accelerating towards, analogous to a 'North Pole' (if you consider the Universe slightly curved like the Earth). And in the earlier time on the graph, the White Hole is a Big-Bang like explosion near the time of creation, leaving the 'South Pole' of such a curved Universe - a larger version of the Supernova from Q1. On this larger scale, you'd get Time Symmetry as well. Marco Senatore Marco Senatore 1 year ago i hope to see in the near future a series on various speculation about quantum gravity Mark G Mark G 1 year ago Isn't quantum teleportation a way to create a perfect copy of something? Paul C. Paul C. 1 year ago SUGGESTION - Dear Professor Carroll, “The Biggest Ideas in the Universe” is a genuinely excellent & inspirational video series, for interest, intellectual benefit & education. Would you consider releasing the whole series (after completion), as a set of DVDs ? This would be of special benefit to those people who are not always able to get on-line and access YouTube. (Such as seafarers, for example.) I know that I would definitely buy the DVD set if it became available. I realise that DVDs may seem very out-of-date and Old Hat to some viewers, but they are still very popular with a significant number of the audience. Thanks again Dr. Carroll, and I hope you will consider this suggestion favourably. Looking forward to the next video. 1 scott miller scott miller 1 year ago do BH really have charge? or is it just seeing the spin friction with the compressed space/time. and the charge building on the horizon? vs the actual "charge" of the hole. the hole itself has spin, and mass. EM and etc is the friction of space and matter falling into the hole. Ray Littlerock Ray Littlerock 8 months ago (edited) At some point I got lost, because I could not figure out any more how metric / connection and curvature behave as functions, that is, what kind of objects these functions take as input and what they send back as outputs. Maybe this would be easier to grasp for non mathematicians like me if it were presented using a sagittal representation ( explicitly stating the domain and the target set of the function). For example, when curvature is identified to a matrix, I cannot see anymore how it can be a function and what it "does" ( so to say). Anyway , these vidoes are absolutely unique and incredibly helpful! Merci à vous Pr Carroll ! Christine LaBeach Christine LaBeach 1 year ago Maybe there is no singularity. Perhaps all 100% of the mass that made up the star was converted to gravity in some as of yet unknown way. So if that's true then perhaps the event horizon is the only physical thing that remains of the original star. Christoph Hipp Christoph Hipp 1 year ago (edited) So, I want a "24 video course just about black holes"! (33:40) 2 fulmarmusic fulmarmusic 1 year ago The equations around Einstein's guess and onward totally lost me. To quote, the British metropolitan middle class elite comedian, Stewart Lee, "like a dog listening to classical music". 3 kapsi kapsi 1 year ago (edited) So the singularity is the moment time stops for you? (Or rather for the elementary particles that were you) Peter Way Peter Way 1 year ago If the smaller a black is the faster it radiates away there must be a minimum size limit of black holes in the universe, cause anything smaller would already have radiated away (unless of course they are being created today, and we see no evidence of that). If relativistic laws break down at the event horizon and quantum laws exist beyond wouldn't the relativistic information in your "book" break down also, or at least be captured or confined or spread across the event horizon. Jon Wesick Jon Wesick 1 year ago Regarding No Hair: Suppose you fed a black hole with baryons, blue quarks, or leptons. Would you then need to label the black hole with conserved quantum numbers like baryon number, color charge, or lepton number as well as mass, charge, and spin? If not, where did these conserved quantities go? Is this related to the information paradox? Steven Mellemans Steven Mellemans 1 year ago I think CCC likes it when entropy is reset by the evaporation of a black hole. Christine LaBeach Christine LaBeach 1 year ago Once you pass the event horizon of a black hole, it's not that you can't escape, it's that you won't escape because all your futures point toward the singularity. The light cone representing your future only points toward the singularity and no longer outside the event horizon. Does that sound right? Marcop Marcop 1 year ago Well, but after all, do they really exist those Big Monsters we call BH? Or are them only our trivial but fancy speculation about something we should be IN PRINCIPLE ignorant? (Hic sunt leones, but then eventually some new more accurate map of the world may came...) TheLeonhamm TheLeonhamm 1 year ago If general relativity etc is a fundamental part of 'reality' ('Quantum' - thingness and 'quanta' - thinginesses) - then Einstein could not have invented it (or even discovered it). As a posited concept presented by him .. resting on the work or ideas of others, of course .. its maths fitted remarkably well with the earlier notions of 'time' as the relationship(s) marked by the (or, a) distance between two passing objects. Gravity, the weight or serious/ imperious majesty aka hefty power of attraction in the relations between material bodies, is, naturally enough, an abstraction from this observable force (i.e. power of attraction at work) specifically considered in terms of 'heaviness' (e.g. the ability to heave/ to have hove/ to be hoven/ to have been hoven) apparently governing two or more material persons/ bodies/ objects. See, it's that simple. Yeah! ;o) shooshoojoon4 shooshoojoon4 1 year ago Love listening to your explorations...imagining if the universe was an infinite ocean with consistency as liquid or jelly substance, with all elements moving within it causing curvatures, variety of formations depending on size, distance and impact......seems incalculable challenge of it's totality! Christine LaBeach Christine LaBeach 1 year ago I'm probably going to get fussed at for all these dumb posts but in regard to Hawking radiation here's a thought: I call this Hawking radiation paradox: If time runs faster outside the event horizon of a black hole than it does inside the black hole, Hawking radiation would evaporate the black hole before enough time has passed inside the black hole for such an event to have occurred. So how is it that a black hole could experience two frames of reference at the same time? There seems to be a real paradox here. If an observer inside a black hole looking out could survive long enough, could she witness hawking radiation evaporate the black hole before enough time in her frame of reference passed for the evaporation to occur? Atakan Gökeer Atakan Gökeer 1 year ago Sean Carroll is gold. Boris Petrov Boris Petrov 1 year ago Can you define the term "manifold"? Many thanks Gareth Williams Gareth Williams 1 year ago How can a BH have a measurable charge? Given that EM force carriers are photons and therefore cannot go beyond the EH. Is the charge entirely contained just above the EH? In that case doesn’t gravitational red shift reduce the effectiveness of the charge? John Długosz John Długosz 1 year ago At 52:00 and just before, you give the lifetime of an astrophysical black hole. Is that taking into account the cooling temperature of the CMB? Or is that as if it were in a zero-K context? A BH that doesn't eat will still grow as long as the CMB is higher than its own temperature. Then, what is the curve of the falling CMB temperature? If it's above the BH temperature due to evaporation, then the in-situ evaporation will be pegged to remaining in equilibrium as the universe cools. 1 Johnson Philip Johnson Philip 1 year ago Requesting a book from you with all the topics in this episode. NoWhereMan NoWhereMan 1 year ago Come on Sean, Boltzmann got more than a little sad, he killed himself. Left his formula on his headstone. Vector Sol Vector Sol 1 year ago 1:43 "when the wise man shows the moon, the fool looks at his finger" 😅 Darth Plagueis Darth Plagueis 1 year ago (edited) Why is it necessary to speak about the charge of a black hole? I understand mass and spin because those properties are visible outside the event horizon. How can one speak about charge when the charge cannot be measured from outside the event horizon? (or can it? If so : How can the electric field escape from the black hole?). nosirrbro nosirrbro 1 year ago 20:44 How exactly does that gel with the fact that an event horizon is, well, an event horizon? I'm sure a single particle wouldn't notice, but a large object such as a person with forces traveling all around it that has partially crossed the singularity would no longer be able to interact with itself across the horizon (and thus would not be able to remain a single coherent object held together by chemical bonding and van der waals forces and whatnot that is all mediated by the electromagnetic and photon fields that necessarily transmit information), would it not? I can't imagine how forces could keep something together across an event horizon without also necessarily transmitting information across the horizon, which should not be possible. Does this actually true for a large object? 3 TheyCallMeNewb TheyCallMeNewb 1 year ago Whoa -- I think i'll need enter into review. Michael Sommers Michael Sommers 1 year ago Does it even make sense to talk about the inside of a black hole? We can't measure anything inside a black hole; we can't get reports of measurements inside a black hole; and we can't see anything cross the event horizon. On the principle that if you can't measure something, it isn't real, should we say that black holes have no insides? Put another way, can an experiment be designed that could distinguish between a universe in which black holes have no insides, and a universe in which they do? Nixon Nixon 1 year ago Thanks for doin, these videos ❗️ John Długosz John Długosz 1 year ago I saw an episode of "60 Symbols" explaining that a new paper explains the Information Paradox. But, his presentation is not elucidating. As of the making of this video, you should have known about this advancement. So what's up? 2 apper cumstock apper cumstock 1 year ago This whole series sets new standards. 2 markweitzman's wannabe a theoretical physicist school markweitzman's wannabe a theoretical physicist school 1 year ago (edited) But Professor Carroll in his book on p.320 does mention and have a problem on the Lense-Thirring effect. Dan Kole Dan Kole 1 year ago Like a steak that was left on the grill too long. That was well done. Cheers. Rick Harold Rick Harold 1 year ago Awesome. ! Oliver van der Togt Oliver van der Togt 1 year ago Is it possible that Dark Energy is in fact caused by the rotation of the Universe? Potonicml Potonicml 1 year ago space isn't curved, it's mass that is charged subatomically that displaces space like an emission of light. Soma Chatterjee Soma Chatterjee 1 year ago Please define time in terms of mass. JRR JRR 1 year ago If you've seen my office- you would know that books collapsing into a black hole is a real possibility. Smoogems Smoogems 1 year ago GWAN SEAN! Bo Zo Bo Zo 1 year ago They had hair in the 70s. Soma Chatterjee Soma Chatterjee 1 year ago Can time be ether? never had a proper course in GR since it wasn't offered at my school, so I decided to find a textbook on the subject and attempt to learn as much as possible about it. I bought your textbook a few weeks ago and have been reading th