The secrets of Einstein's unknown equation - with Sean Carroll

Did you know that Einstein's most important equation isn't E=mc^2? Find out all about his equation that expresses how spacetime curves, with Sean Carroll.
Buy Sean's book here: geni.us/AIAOUHn
KZbin channel members can watch the Q&A for this lecture here: • Q&A: The secrets of Ei...
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This lecture was recorded at the Ri on Monday 14 August 2023.
00:00 Einstein’s most important equation
3:37 Why Newton’s equations are so important
9:30 The two kinds of relativity
12:53 Why is it the geometry of spacetime that matters?
16:37 The principle of equivalence
18:39 Types of non-Euclidean geometry
26:26 The Metric Tensor and equations
32:22 Interstellar and time and space twisting
33:32 The Riemann tensor
37:45 A physical theory of gravity
43:28 How to solve Einstein’s equation
47:50 Using the equation to make predictions
51:05 How its been used to find black holes
The real Einstein's Equation is part of general relativity, which relates the curvature of spacetime to the mass and energy distributed within it.
Sean explains why the geometry of spacetime has anything to do with gravity, and how this famous equation expresses the way that spacetime curves.
Sean Carroll is Homewood Professor of natural philosophy at Johns Hopkins University. He won the Royal Society Winton Prize for his book about the search for the elusive Higgs boson, The Particle at the End of the Universe, and The Big Picture was an international bestseller. His most recent book is Something Deeply Hidden. He lives in Baltimore.
Copies of Sean's latest book, 'The Biggest Ideas in the Universe 1: Space, Time and Motion', are available from Amazon and all good bookstores.
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[@TheRoyalInstitution]

The Q&A for Sean's talk is available exclusively for our KZbin members here: kzbin.info/www/bejne/qYCYkpeYi8Sgq5o Despite our fancy name, we're actually a charity that relies on donations to keep going. If you sign up to become a Science Supporter on our KZbin channel, you'll be helping us connect more scientists with the public, so we can bring you more incredible lectures like this one. You can sign up here: kzbin.info/door/YeF244yNGuFefuFKqxIAXwjoin

[@ShonMardani]

In the formula F=ma, a has a time variable which means F = 0 when time = 0 and Force can not be calculated unless you provide time duration. The parameter a Acceleration is due to the Gravity and Gravity has a set vector / direction, 0 to 180 degree, in other words there is NO Acceleration if there is NO Gravity, and in Gravity direction and Time needed. Force is 0 (zero) unless you give a non zero time. This is what scientists have been hiding and the space time scam is to explain a flawed formula using the gang leader einstein. E=mc2 is also False since you can change the constant 2 to 3 or any other number, it has no effect because E has no Unit. Also all the formulas mentioned as the successor to E=mc2, has the Time variable with the value 0 (zero) which makes all the calculated Forces, Energies and Vectors Zero. Additionally einstein never wrote and published any of these formulas and no other scientist wanted to claim Fallacy.

[@davidfarrar4993]

Òòòòòò ll òo 2:40 😮go gl4r6

[@Michael-cf9lf]

Would Ri consider a series of videos with Michio Kaku with the Ri giving him a series of topics to discuss without interruption or others on stage just him by himself..

[@superalex7880]

​@ShonMardani maybe this is why Einstein never got the Nobel for his Relativity😢

[@kwimms]

Einstein was an bad actor who had relations with both of his cousins, hence his equation... Einstein = Married Cousins x2 .

[@stephenhicks826]

I'm 70 year old retired Physics teacher and was mesmerised by Carroll's wonderful presentation. The best teachers have a way of bringing clarity and simplicity to very difficult concepts. Brilliant, thank-you.

[@whirledpeas3477]

Mesmerized, Wow

[@TheFrewah]

Veritasium on youtube is fantastic. Math and physics. Outstanding

[@candidobertetti27]

This man made advanced physics accessible to the masses. If there is something similar to the Nobel Prize for science communication then he truly deserves one.

[@davidhand9721]

If you ever find yourself saying "made advanced physics accessible to the masses", you're working with an inaccurate definition of either "advanced physics" or "masses".

[@candidobertetti27]

@@davidhand9721 I'd like to know what's wrong with my comment as English is not my first language. General Relativity (and the whole series called "The Biggest Ideas in the Universe" by Sean Carroll) is not exactly basic physics, that's why I used the word "advanced". By "masses" I mean ordinary people, those who don't have a high degree of education in physics, or any other field of science for that matter.

[@ImrePolik]

@@candidobertetti27 Then you just need to define accessible :-)

[@fabiocaetanofigueiredo1353]

I understand the comment and maybe could be better expressed by "comprehensible by the average individual"

[@candidobertetti27]

@@ImrePolik My bad then, I thought my comment was clear. By "accessible" I mean, as explained in another user's comment, that he made understandable to the average people essential points at the foundations of certain theories. In the series of videos by Sean Carroll that I mentioned earlier, he covers topics that, until now, only a student of a master's degree in Physics would hear about. For instance, he talks about field quantization, renormalization, the work of Kenneth Wilson, as well as symmetry groups, general relativity and so on. But he goes beyond words and provides heuristic, yet correct, mathematical descriptions. The main prerequisite to understand the level of those lectures is basically high school mathematics. In my opinion, this work deserves more media attention because these are very specific topics that rarely find a place in popular science.

[@thomasdaniel100]

I suffered a brain injury a few years ago and it is sometimes difficult to understand simple concepts, nevermind complex concepts. Thank you Sean Carroll for simplifying subject matter for those of us who want to understand the science we love so much. Thank you RI for the same. I may not be able to do the math and I may never be an engineer again but this video makes me feel like im included again.

[@helifynoe9930]

I had a head injury at the age of 10. So the side effects dropped me from the top of the class, to the bottom, and eventually had me dropping out of school altogether. Teachers basically thought of me as the dumbest person in the class, due to me now having difficulty retaining long term memories. However, despite me having no physics education what so ever, I still managed to independently discover the special relativity phenomena, and how this phenomena is created, along with deriving the special relativity mathematical equations at the same time. Have a look at how I did it, if interested. Anyhow, never let brain injuries hold you back.

[@kwimms]

It's all bs... maybe you are a zombie and don't realize it.

[@thomasdaniel100]

@@kwimms meaning?

[@optimism_of_will]

@@thomasdaniel100 he's an asshole, ignore him and always believe that you will make a comeback. Sometimes as they say reality is stranger than fiction

[@mavelous1763]

Keep up the good work. The brain is always working to overcome injuries. Be vigilant, and your brain will respond

[@daxramdac7194]

This was the best presentation I've seen on this subject. And I'm not at all surprised that it was given by Sean Carrol with his brilliant ways of explaining things, his clear voice, and keeping your attention. The historical context shown behind the equation, and the motivation behind its construction over time was not only fascinating, but so excellently and expertly presented, without having to go off on any tangents or use too many analogies. And without insulting the intelligence of the audience with things like "imagine the swing you played on as a kid" or "imagine the strings on a guitar", just straight build up of the logic behind going from the Newtonian formulation up to the final Einstein equation, and all the players involved along the way. Perfect.

[@andrewgormley2958]

Always fantastic to see a Sean Carroll lecture, especially at the RI. Day one of the membership has started well!

[@TheRoyalInstitution]

This is great to hear! And a huge thank you to you for joining our KZbin channel membership and supporting science 😀

[@peterspiker9960]

As I get older I find the admiration I used to have for my favourite musicians is fading (only a little) and I’m becoming more fascinated by what people like Sean M. Carroll have to teach me. I may be too old for out-and-out hero worship, but I am definitely a big fan of these big thinkers. Hooray for RI, Mindscape and Sean Carroll!

[@JRush374]

Read QED by Richard Feynman and watch his lectures and videos. The video Fun to Imagine is great.

[@stephenbarrette610]

@@JRush374 Totally agree, it’s a great book and you really have to concentrate - well I did! Feynman is a hero of mine and I think I have all his books. I remember the BBC Horizon documentary when it came out and have a VHS copy somewhere. But thanks to KZbin anyone can see this extraordinary man talk about jiggling atoms and flowers.

[@kiers1970]

I agree totally too. I'm not daft or particularly intelligent.. I can think like this now too, appreciate possibly more than understand incredibly brighter minds more than ours. I wonder how many possible, probable almost genius minds have been missed, shunned or ignored at schools? Young men especially, develop and mature intelligently years after Girls...

[@stephenbarrette610]

Actually I totally agree with you being an old person, very old person.

[@robertwood9984]

Wow!!!👍 Thank you!!!

[@myopenmind527]

One of the best communicators in science. I’ve never failed to be equally entertained and educated by listening to his talks.

[@250txc]

Maybe on your words but 99.99% of us did not understand ANYTHING he said ... Most of us were just amazed any human could dream this up...

[@kwimms]

One of the best liars in Science.

[@migfed]

This is clearly the next step: start explaining the math in a friendly way. Sean Carroll at his best. Thank you so much.

[@stylis666]

The step that follows is teaching the basics of relativity and quantum mechanics to 10 year olds. And start teaching the accompanying maths at about 14yo, when there's a little algebra and geometry knowledge. Maybe :) And maybe that's not for all children, but my youngest nephew of 10yo loves it and has a very quick understanding of complex abstract physics because of his intuitive and creative mind that has no problems with thinking of spacetime as four dimensional curving geometry or how probability would lead to a particle to potentially end up on the other side of a barrier. He just sees the barrier as a wall that holds back part of the probability wave as it would a water wave, but if the wall is thin enough some of it might leak through, especially if you consider that most of the wall is empty space. But the point is that children can understand a lot more than we think they can. I'm guessing that we think that they can't because the maths is difficult and we're usually taught such things when we can understand the accompanying equations and maths, but that's entirely unnecessary for the basics of physics. You can easily show a relation between push and acceleration without making a child calculate it. If you push harder, there's a larger acceleration. A child can see that easily. We don't have to know the exact ratio to understand the principle.

[@Chaobai]

I really like the way Sean Carroll presents all the scientific concepts. He always explains how they evolve over time and that really helps me understand how we get where we are in science for a certain topic. Most worthy membership I have ever had.

[@TheRoyalInstitution]

Thanks so much for joining as a member! We're very glad you liked Sean's latest video, he's definitely one of the best when it comes to explaining scientific concepts.

[@gordonspond8223]

Agree. I wish my college professors would have spent a bit more time on the history of science as well, rather than endless formulas. It (1) would have helped put things in perspective / allowed me to connect the dots better and (2) I would have realized that certain concepts didn't just pop up one day in someone's super-smart brain, but literally took centuries to be developed / discovered.

[@MI-qj6xr]

There’s a certain similarity between Sean Carroll and James woods. James woods has a 180 iq (or so the internet says) and I would bet Sean Carroll is near that . He’s great at illustrating his point on complex subjects in a simple and understandable way.

[@JohnnyComelately-eb5zv]

I agree. He's great. Fantastic communicator and such a nice guy with a sense of humour. Pity he's wrong about quite a lot! For example, his Many Worlds Interpretation is complete nonsense.

[@joje86]

​@@MI-qj6xrJames Woods definitely does not have an IQ of 180 (at least not in any meaningful sense). This for a multitude of reasons. Mainly because no well established IQ tests have any reliability in that range and a score that high on a typical IQ test (which are unreliable outside 2 standard deviations of the mean, i.e. outside 70-130) is basically meaningless. Part of the same rumors was that he was a member of MENSA, or that MENSA was the source of this oft quoted score, something that MENSA quickly denied (they were also stonewalled by Woods and his publicist when they tried to reach them about the rumors, since some sources implied that Woods himself might be the original source of the claims). He did supposedly score very high on his SAT, but his score was not on par with the 1 in 20 million that an IQ of 180 is (I couldn't verify his SAT score either, but it's a far less extreme claim and the guy did supposedly get into MIT based on his SAT and I couldn't find any repudiation of this from MIT). Basically, nobody seems to know where the 180 figure really comes from (and it's often quoted as 184 or 160 as well). It seems to have started as tabloids, gossip bloggers, and clickbait sites bouncing the rumor back and forth, though the rumor also seems to have had a resurgence in right-wing media in the last couple of years. The guy might at some point in time have taken a test that gave him a score of 180, but so did most everyone who has access to the web in the early 2000s. I remember that I scored over 200 on some of those ridiculous tests floating around the web back then. Another popular claim is that Woods has an IQ higher than Leonardo Da Vinci, and this one might actually be true. However, this is not really a meaningful claim either. If we extrapolate the Flynn effect that far back, a lot of us probably have an IQ higher than Leonardo, maybe most of us. And even if we ignore the Flynn effect, there is basically no reliable way to estimate the IQ of someone living that far back. And since we do know that the Flynn effect is at least true in the last century and thus that IQ scores change significantly over time, someone living that far back can't be meaningfully compared with someone living today. Don't get me wrong, the guy might be super smart. There's just no reason to believe any specific claims that high unless there is very strong evidence from a reputable source.

[@willemvdk4886]

Yes! A new Sean Carroll lecture! This man is such a good presenter and spokesperson for science.

[@meacadwell]

He is, hands down, one of my favorite presenters. He can make a droll topic interesting.

[@gcewing]

Plot twist: After this lecture was over, the audience tried to leave the hall and found they were in a rocket ship far out in space accelerating at 1g.

[@BikeArea]

You are fully blown away by this guy's rhetorical talent and the uninterrupted talk. He never stutters, hangs or uses filler words. By the way: Great to hear a german word he uses (Ansatz). 😀

[@erikfinnegan]

Prof. Carroll is the only science communicator who can pull off this feat of educating the general public about Maths. So vivid. So approachable.

[@cougar1861]

And so profoundly desperately needed!!!

[@miinyoo]

Sean is a great communicator and a sweetheart. I think equations are fun but they often look misleading largely for short hand reasons. Unpacking equations and looking at all the knobs hidden by symbols really is the only way to understand them. Having Sean break them open and show their inner working bits is an enormous help.

[@joestitz239]

Indeed. On the enterprise in engineering they turned knobs =ing the short hand way to communicate to the computer the shorthand of what to do; as the computer could read the equation showing also people who built it knew from us today that Eventually, man did figured how to be as smart as the equation itself :)

[@phillupson8561]

Always love a Sean Carroll lecture, just think without the Internet we'd have to smart enough to get into his class and I suspect many of us wouldn't make it, what a time to be alive.

[@IvanMorenoPlus]

Sean Carroll is a joy to read, but he is way funnier and more to the point in a lecture! Perhaps the best explanation of Einstein's field equations I have seen. Thank you!

[@cyclonasaurusrex1525]

Absolutely stunning. To be a master both of the subject AND of how to convey it is remarkable.

[@amritsharma5373]

What a great lecture. Thanks to Sean and the Royal Institute for making it accessible.

[@marcosfreijeiro8763]

Fantastic talk as usual from Sean Carroll and his books are worth reading. Great content thanks RI

[@davidwilder7542]

One of the best lecturers on KZbin. Makes me want to study physics again. On a note, his books are great 👍. Thank you.

[@grahamwilson8843]

This is perhaps my favorite RI lecture I've seen yet. I really love getting a better look at these more complex ideas about physics, and I hope to see now like this. Really nice work, Sean and RI!

[@beln33]

You're wright. A well deserved 'excellent too' second is the one on quantum fields. Try it.

[@andremaccarini1656]

Wish we had more professors like this guy.

[@paulscott2502]

Sean Carroll has an astounding gift for explaining very complex concepts into much simpler terms.

[@rayoflight62]

This is the best lesson on General Relativity I have attended, ever. Compliments to Prof. Carroll for his unequalled ability in explaining such complex matter with simple words. Regards Anthony

[@everythingisalllies2141]

A bit too simple.. He forgot to explain why the theory, like all Einsteins theories are nonsensical. He forgot to mention that little gem.

[@candidobertetti27]

@@everythingisalllies2141 A "little gem" that only science deniers could say, which he's not.

[@everythingisalllies2141]

@@candidobertetti27 I'm not "denying science", that is real science, I'm calling out liars who spread nonsense dressed up as science.

[@candidobertetti27]

@@everythingisalllies2141 Yeah, because of course you know better than Einstein.

[@everythingisalllies2141]

@@candidobertetti27 I don't need to be "better" than Einstein or anyone else, I only need to examine his claims in his hypothesis and weight them up to the accepted standards of rational analysis and Logic. And unfortunately for Einstein his claims do not make the grade in any way. In fact, it would be fair to say that he seems to have based his hypothesis in a purposeful deception, in other words he lied by telling half truths mixed in with truths in order to deceive. It worked well on you is seems, because you have never bothered to read his hypothesis with a scientific mind set, that of being skeptical. If you did read his paper, it would have been form the point of view of a fawning, awe struck worshiper.

[@deanmindock5020]

Sean's enthusiasm and deep knowledge is what makes his talks informative and entertaining. Never disappoints.

[@walnutclose5210]

Absolutely brilliant, inspirational lecture. Thank you RI and Sean Carrol.

[@chaoslab]

Wonderful talk, breaking things down piece by piece and eloquently explaining them. Thank you Prof Sean Carroll.

[@AmanSingh-lv9qp]

Equations are too special I remember in highschool gauging at the Archimedes' principle for quite a lot of time and when you finally understand the mathematical realations between the symbols / quantities, it's amazing

[@JamesSarantidis]

That happened to me almost 10 years ago when I finally figured out what the symbols of differential equations meant. remember solving the same physics problems again and again in that summer at the beach struggling with all the d's and coming up with my own boundary condition problems. Up until then I was performing terrible at math courses. Then, it finally clicked. From that moment I fell in love with math again.

[@as-qh1qq]

What an accessible lecture! Brilliant exposition - simple, no simpler.

[@DelbaKV]

Sean is the best. I was so happy to see you guys with a new video! Time for me to watch it and I am sure ir’a gonna be epic. Thanks for sharing :)

[@apngeram]

Absolutely fantastic! Looking forward to his quantum mechanics talk next!

[@TheSearchPodcast]

Heck yeah!!! Always love listening to Sean Carroll.

[@thomasmogensen1]

What a great lecture and what a great teller he is 👍🏻👌🏻 Great work.

[@Haroldus0]

Absolutely first rate explanation . thanks so much. Much better than my professor in 1969. I get it!! I must say I bought Hawkins book about black holes and that made a lot of sense at the time, but this whole subject does require a light touch, otherwise is so easy to get lost in the woods. Your introduction of the various tensors was brilliant.

[@allenaxp6259]

This is the best presentation I have ever seen that explains General Relativity in very straight forward manner. Excellent!

[@benyram5357]

Thank you for great conversation.

[@GrouchierThanThou]

Sean Carroll truly is one of the greatest treasures of science communication.

[@littleboy437]

Gravity is NOT a Force at All Einstein Said Sean is totally lost Very disappointing He says Gravity is a Universal force🤣🤣🤣

[@conradleonard]

This is really one of the best RI lectures available on KZbin! Great stuff.

[@recurrencetheorem4264]

Thank you so much Sean Carrol. Greatly enjoyed this one.

[@tahititoutou3802]

The simplest and easiest explanation of Einstein's tensors I have ever seen. Crystal clear exposé by someone who not only masters this stuff but has integrated it into a unified coherent concept. Kudos!

[@JRush374]

More of this, please. It would be great to have a quantum mechanics version of this, maybe to understand the Schrodinger equation.

[@mondop5270]

Meow

[@jakeduff5677]

He's done on on this channel before exploring and explaining that

[@thisisfyne]

A new appearance from Sean Carroll is always welcome! Love this guy

[@sethjchandler]

One of the best lectures I have ever heard. A fantastic mixture of math, science history and humor.

[@dylwhs]

Excellently explained. Thank you!

[@as-qh1qq]

He is a phenomenal orator.

[@joyecolbeck4490]

Thoroughly enjoyable.

[@DrVolkerRedder]

One of the best lectures I've ever seen on these topics. Sean Carroll is a great teacher. Thank you very much.

[@josephpazar]

That was an Amazing example of an awesome explanation.

[@Epoch11]

I would love to see a similar lecture by Sean explaining the Schrodinger equation in the same level of complexity and detail. Not everyone is a physicist but many people have an interest in the equations used and how they are attained.

[@maxproph]

Definitely check out his biggest ideas in the universe podcast series, it's excellent

[@anonymes2884]

That'll be the next book (this lecture is based on his latest book in case you weren't aware, with the second book in the series, "Quanta and Fields", due in May of 2024). And as @maxproph says, the books themselves are based on a set of KZbin videos he did over the pandemic called "The Biggest Ideas in the Universe" - a bit less polished but still utterly fascinating (and available now on his KZbin channel). (or if you're comfortable with some not _too_ crazy maths you could also check out either "A Student's Guide to the Schrodinger Equation" by Daniel Fleisch or "The Quantum Cookbook" by Jim Baggott in the meantime)

[@garydecad6233]

Brilliant as usual

[@MendeMaria-ej8bf]

Good to see and listen again to Sean Carroll. It's always a great pleasure.

[@808bigisland]

Great lecture! Thx!

[@ryanbaker7404]

I love it any time Sean Carroll lectures, and most especially when he does so at the RI! His wife publishes some of my favorite articles on Ars Technica as well!

[@RubALamp]

Was there a Q&A for this talk? Could you share it please if that's the case? Thank you! And great talk!

[@TheRoyalInstitution]

So glad you enjoyed the talk! The Q&A for this event is available as a KZbin channel member exclusive here - kzbin.info/www/bejne/qYCYkpeYi8Sgq5o

[@RubALamp]

@@TheRoyalInstitution Got it. Thank you.

[@Good13man]

Wow. Brilliant summary. Thank you.

[@alexwilli]

This is by far the most beautiful lecture featuring tensors that I’ve ever seen.

[@Erik-rp1hi]

He is great at explaining. Was fun to watch his home series during covid lock down.

[@User-jr7vf]

I remember that

[@user-om6kd6mp3r]

Melina meric 1:25

[@user-om6kd6mp3r]

Maliva meric 2:09

[@kkandola9072]

8:22 to me the fact that gravity acts equally on different mass objects was actually quite intuitive. Not that I’m some genius who intuited the math lol. But the way I saw it, gravity was acting on each bit of mass equally, so regardless if it’s 100K atoms or 100 trillion atoms, each atom is accelerating at the same rate so more mass doesn’t change how fast something falls.

[@gregjones2217]

Thank you for sharing your knowledge.

[@andraslang96]

Excellent presentation on a difficult but brilliant topic. Thank you!

[@beardcat]

Sean Carrol is a genius. I can listen him for hours and hours. Wish I had him as a teacher ❤. PS. Thank you Royal Institute

[@AradijePresveti]

He's a clown that believes there are more than two sexes in humans.

[@TheWeatherbuff]

Hi Sean! Since listening to a few of your lectures and podcasts, this stuff doesn't seem quite so scary to me anymore. Keep in mind, I am just a lowly meteorologist... but it's still useful to hear your explanations, which help put these concepts into perspective for me. Question... Is any of this going to be on the test? 😊

[@DrDeuteron]

Weather is pretty hard.

[@TheWeatherbuff]

@@DrDeuteron Yes, it can be. But for some reason I understand weather way better than this material. Which is one reason I enjoy Sean's presentations so much.

[@User-jr7vf]

@@TheWeatherbuff "for some reason"--- the reason is that you haven't been exposed to it enough. Once you get familiar with all the stuff, it becomes easy.

[@NandishA]

Brilliantly explained. Thanks Professor . Kudos to KZbin which enables access to high quality education for free across the globe.

[@makoyoverfelt3320]

Always good to see Mr. Carroll, I am an avid listener of the Mindscape podcast so video format Sean is a treat

[@temptemp563]

Good to see Sean Carroll again. He used to be everywhere. Then he went quiet. Now he's back.

[@ishaansingh6973]

He runs his own podcast: Sean Carrolls Mindscape, where he comes to speak every week.

[@MaarioneteSR]

As someone who studied General Relativity from Prof. Carroll's excellent book 'Spacetime and Geometry', it feels like betrayal seeing the (+ - - -) metric signature! And excellent lecture as always!

[@nadamuchu]

thank you for the captions!! 🤟🏼

[@h.i.5280]

Thank you, always a pleasure to hear Sean Carroll. And to read his books.

[@joestitz239]

What are names of his books ? I dont see on ebay

[@dreamingwolf8382]

So I'm slightly confused anytime someone refers to gravity as a "force", because it was my understanding that gravity is merely an emergent property of the geometry of space-time being warped locally by mass.

[@LordMarcus]

Yeah, it seems like that we call "gravity" has more to do with how we are given the illusion of acceleration through each 3D "slice" or "moment" we experience, even though the universe described would seem to indicate a static 4D spacetime where everything has already "happened".

[@BlazeOrangeDeer]

It's the same way centrifugal force and coriolis force are not technically forces. We still call them forces sometimes because they act like forces if your reference frame is spinning. Likewise, gravity looks like a force if your reference frame is accelerating. A reference frame fixed to the ground is really accelerating upwards, so it looks like there is gravity accelerating downwards. It's useful to think of it as a force because it's useful to use a reference frame fixed to the ground, it matches how we usually experience the world.

[@thstroyur]

The confusion lies within GR's particular framework, and the way Newton is 'carved out' of the geodesic equation and Poisson's law out of the EFE; however, this is far from an universal necessity: yours truly, for instance, has constructed a theory in which gravity is simply viewed as a force in the traditional sense, and yet one can still draw observational conclusions comparable to GR's. Oh, and before you dismiss that as some ramblings from a rando who doesn't know what they're talking about: currently under peer-review - in a fancy journal and everything 😉

[@DrDeuteron]

@@BlazeOrangeDeerthe coriolis and centrifugal forces are just gravity in GR.

[@dreamingwolf8382]

@@thstroyur Ooooh neat! What's the journal, I wanna read it when it comes out!

[@barefootalien]

Outstanding as always!

[@robertthacker495]

That was an amazing talk. Just incredible. You are right, the equations, mixed with words from someone who understands them, is magic.

[@themcchuck8400]

Most of the weirdness of spacetime comes from the more basic principle that time (the fourth dimension, at 90 degrees to all others) is imaginary. You still use the Pythagorean theorem, but when you square the imaginary time element, it becomes negative, converting the Euclidean function (a^2 + b^2 = c^2) into a hyperbolic one (a^2 - b^2 = c^2). The principle is simple. The implications are profound.

[@alexleibovici4834]

> basic principle that time ... is imaginary It is not, in fact.

[@themcchuck8400]

@@alexleibovici4834 It is, in fact. That many don't know or understand it does not negate its truth.

[@alexleibovici4834]

@@themcchuck8400 You confuse the nature of the time variable with the fact that a pseudo-Euclidean metrics can be transformed in an Euclidian one by substituting -t^2 with (it)^2

[@themcchuck8400]

@@alexleibovici4834 And yet the math works out the same, while my version has explanatory power. I believe the equivalence principle applies to this discussion. If it walks like a duck and quacks like a duck...

[@alexleibovici4834]

@@themcchuck8400 > And yet the math works out the same Oh, I see: you don't know what is a pseudo-Euclidean metrics !

[@KennethiSlite]

The rest of the world are really wondering why not Trump is in jail yet. So, for the best for US and the rest of the world, make that happen!

[@mehulyogi925]

This session just clarified my understanding in multiple ways. Thanks a lot.

[@palodoxaliqua5809]

Great lecturer and interesting topic

[@PlanetXMysteries-pj9nm]

Your videos have ignited a passion for science and the mysteries of the universe within me. Thank you for being such an incredible source of inspiration.

[@sitisabrina1426]

Never clicked on a video so fast! I love his talks and super stocked that he is giving a talk at the RI again

[@hotcols1171]

That was fantastic - I really like science communication like this - the deep dives into the history and mathematics with what it can show us we didn't know at the start - Maxwell's equations from Faraday's work showing to (an unaccepted) lack of the ether leading to space time. Have just ordered Sean Carroll's book - hopefully filled with a similar level of insight!

[@tigerhuey4051]

I’ve watched This three times now. It’s amazing to have this come into focus. Can’t wait to buy his book!

[@mollylundquist9145]

Whenever I feel discouraged about the U.S. and our mess...seeing/hearing/watching Sean Carroll gives a boost to the spirit. Thank you RI for hosting him...again.

[@hahahasan]

sublime. Love the way he explains things.

[@TonyTheTerrible]

Sean Carroll is so eloquent. thank you!

[@josenegrete]

Wonderful, brilliant, comprehensible at last :)

[@iaov]

What a great teacher!!❤️

[@JohnnyMarauder]

This will have been the best hour of my day today. Thank you!

[@timdintinger9037]

I will look out for Sean Carroll's books now... A long time since I studied physics but this talk made me interested again. Thank you

[@Zamicol]

Excellent lecture! Well done Sean.

[@Roddy1965]

Very good presenter for general public on a profound subject. That's a real art.

[@boxvism]

Great explanation! I almost understood. 🙂

[@stephenbarrette610]

I so wanted to get a ticket for this lecture. The RI is such a special place and Sean Carroll is always brilliant and engaging and witty. But it’s great to see the video. Science is cool!

[@TheRoyalInstitution]

We've got some incredible lectures coming up, that can be watched online from anywhere in the world - www.rigb.org/whats-on?type=6

[@stephenbarrette610]

@@TheRoyalInstitution Thank you so much for your reply and the link. I really appreciate that. Yours truly, a 70-year-old science geek!

[@Joseph-dd7iq]

Sean Carroll's explanation of Einstein's equation makes reading about cosmology more exciting. I was always curious about how such a simple looking equation can be so foundational. ...feels like a grand epiphany. Thanks Sean😊

[@schmetterling4477]

That is not a simple looking equation by any means. It just hides the complexity to those who don't know what the symbols mean. He pointed that out in the talk, by the way. Whether it's foundational is not known. It's just one version of an infinite number of similar equations that nature may also follow in the classical approximation. It just happens to be one of the most simple versions of all possibilities. We have, so far, not found any deviations from it, but that's mostly due to the measurement errors that we are limited by. The bigger issue is that it has a distinct thermodynamic form... which may be an indication that gravity is a thermodynamic remnant (rather than a quantum mechanical one). Or that's just coincidence. People have been wondering about that for the better part of a century. The limited success with direct quantization of gravity might be a hint that we are missing a thermodynamic layer there.

[@robertingliskennedy]

best hour I've spent in ages sublime chapeau

[@gordonfraser5448]

Sean Carroll, Brian Greene and Neil Turok are great explainers. Love' em.

[@MatteoMarconiDaVerona]

I appreciate the enthusiasm of Professor Carroll. The capacity to set the discussion at a level that isn´t too low or too high, and the logical thread that makes it clear and enjoyable. Not least the vein of irony that put the public at ease. Would be possible to have a link to the Riemann´s paper? Or the title? That one where he makes funny comments because it wasn´t his favorite subject? Thank you.

[@thomassag]

Mr. Carroll is on fire in this one. Excellent lecture

[@brucerosner3547]

One of the best science lectures I've ever seen.

[@philfox8377]

Amazing lecture

[@DenkyManner]

His podcast is really great, been listening to it for years.

[@thiagoabsc]

as always... amazing and inspiring...