I've watched RI lectures since I can't remember (I'm 64). Jim carefully talked his presentation through in such a way that I heard and could digest every word. Perhaps the sound effects weren't necessary, but otherwise he managed to avoid any other dramatic concessions. For an interested layman, I've never seen a better lecture on this or any other subject. Thank you.

If you already listened countless talks about general relativity you can skip to 38:00

As a layman, I found your lecture fascinating. The sound effects were quite alarming; especially for someone who's profoundly deaf in one ear. What sounds I can hear, are extremely distorted and Dalek like. Needless to say, I jumped quiet a few times 🤣. I'll have to watch the video a few more times. Some of the concepts you introduce, are really hard to get one's head around. They simply don't comport to our everyday perception of space and time. As I said, the lecture was fascinating, thank you for sparking my curiosity 😀.

He has a wonderful talent for making these extremely difficult concepts (somewhat) understandable while putting the listener at ease about not totally understanding it.😊

Someone somewhere is working hard to truly push this information into a new era of experience and conductivity! We can help by learning and pushing toward our own goals, no matter how small or large they may be! Cheers to the Roaring 20’s as they happen! So excited to see where all of this information heads 🧘🏽‍♂️🕰❤️

The closed captions (subtitles to you Brits) are great and error-free! Thank you, Royal Institution, for the captions, and the caption representation of the sound effects is helpful. Nothing wrong with those sound effects if they make the lecture interesting.

I guess the first half rehash is unavoidable, but the second half was highly effective in guiding me towards a better understanding of the big picture. Cheers to all involved in producing this little gem !

The first time I could follow a scientific explanation from start to finish and able to understand it all the time.

Thank you for this; I've been looking for years for a clear explanation of LQG and now I've found it!

This was such a fantastic explanation. I've watched several videos on loop quantum gravity and I believe this one to be the best so far.

Really enjoyed the way Dr Baggot covered all this. Very interesting.

"...have you heard the new album of Cosmic Metronome, Jim..." Brilliant! Thank you mr Baggott and RI for another excellent talk.

Loved this presentation, I put it at 1.25x speed like the other comments suggested, not sure why everyone is griping about the SFx, I can’t watch regular science shows anymore, I only digest lectures from theoretical physicists. Loop quantum gravity is an alternative to string theory , I recommend Brian Greene’s “the elegant universe” for more on gravity and quantum mechanics. Thanks for posting this RI.

If there's one thing that gets me mad, Jim, it's 'Don't worry about ...', since usually, that's exactly where I do want to go. Not understanding it, means it's what I need to find out about. That aside, an interesting and well-presented talk; thanks. And yes, Jim, I've bought several of your books, the latest included. Be bold, bloody and brave with the next one - and put the damn math in!! I'm sure I'm not the only one with that feeling. Hawking's editor who said every equation halves the sales, was an - ok, let's just say, was misguided.

WOW Dr. Baggott, thank you so much for the crystal clear explanation. I see Smolin changed his mind about Time, much to Professor Rovelli's annoyance, I suppose. Furthermore, as a layperson, I just hope one day to see string theorists and LQG supporters publicly confront each other, comparing ideas instead of filling square meters of blackboard with math....as I must confess I'm still unable to understand the substantial differences between the two approaches to the problem.

Can we do an experiement like projectile using Quantum Gravity/Space ? it seems fun to trace the path of a particle on the Quantized Space :)

RI is a great institution! Humanity at its finest :) I was never really good at physics in high school, but I feel I have gained great insight and understanding by watching these really intuitive lectures. Brian Cox had similar great lectures and TV series. SciShow and similar UKposts shows are similar great resources. I wish I had them when I was in high school in the 90s. Then again it's never too late to learn. I'm currently pursuing a master's in public health and I love it though it would be even better if I had scholarship :) It is nice to see how biology, physics, chemistry and psychology intersect. To understand the universe and use that understanding to make a difference. I would love to see a lecture live in person someday.

I almost wanted to hit the desk for him at least once! hahaah, I love this talk. thanks so much for sharing.... love it.. again and again....

"To see a World in a Grain of Sand And a Heaven in a Wild Flower, Hold Infinity in the palm of your hand And Eternity in an hour." William Blake

LOVE ALL THIS STUFF ..GREAT VID....

Excellent lecture! I loved every minute of it. A hearty thank you to Dr. Baggott and the RI. I can't recall ever meeting a RI lecture I didn't enjoy.

This guy officially melted my brain.

Fascinating and kept making me think fundamentally matter, energy are all comprised of momentum from the big bounce. (like the idea of a bounce instead of a bang) The particle/wave paradox seems like a clue. Nice to see that the singularity and it's associated mathematical infinity's are bogus (irreducible quanta). That always bugged a friend of mine and turns out he was right.

Excellent explanation of where physics stands and how we got here.

His melancholy is delighting.

At one point you mentioned that the loops are not in space but are space. 2 questions - what is in between each loop, and what is in between from where you are looking and the loop you are observing?

Stunning. Absolutly stunning. The way you do the trick Sir is excellent. This is how you recognize a great mind!!! I'm a physicist myself as a graduate years ago and must say some ideas I' ve never even heard of.

Beautiful lecture, storytelling, narrations - very engaging.

55:24 'a single proton contains about 10^65 quantum of volume'. Quite a lot. And proton is small as hell.

This is unimaginably awesome lecture where things I could not understand in the past were described so simply and clearly that I understood them all. Woah, just wow!

This is no surprise to me after all I have read about quantum mechanics and fields, etc.. Physicists have been working towards this for years. Nice to see it getting explained.

To continue your research, I have impression particles maybe are made by gravity-loops, because mass is making deficit of space-time around it. However, does it consuming or restructures gravity knots when moving through the space as Earth around the Sun? How then the space curvature is constructed and have acceleration effect?

I'm dying for some lectures that cover the subject from something higher than high school level. If he was my professor I would really fall out with him for telling me numerous times not to try to conceptualise important things.

wish there was more context and explanation -- for example, its clear as mud how Einstein concluded space-time was curved based off his thought experiments involving relative motion....

15:24 jeeez thanks for scaring my dog LOUD

god damn those audio fx effects

15:50 The thunder effect is pushing the words of the speaker into the noise floor. Needs subtitles badly. There were missed words. (Edit: On second thought, it might not have anything to do with the noise floor; it could just be a software thing. But the point still stands.) (Edit2: Clarification: There are subtitles available, but it looks like they're based on the audio from the video, and are therefore useless, as they include the sound effect as well.)

Lord of the Rings reference was spot on. Sadowfax was like a force of nature, riden by Gandalf one of the Ainur a race of beings from before the creaton of the World, also a fundamental power. J.R.R Tolkein was a master story teller.

Regarding the lightning bolts experiment, it's easier to imagine you staying at first in the middle between them, and starting to run the same time they hit. Think about the fact that photons are speeding away from the left bolt, and you are trying to run away from them (towards the right bolt) at a fraction of their speed. This means you have time to cover some small distance before they hit you. On the contrary, the photons from the right run in the opposite direction, thus they will reach you a lot faster. I stopped for a while to think about this - because I'm not that bright (pun intended) - and I hope that this will help some other people as well.

For those familiar with history of physics, loop quantum gravity starts at 36:00

Really great video and explanation of LQG !! Thanks for this clear and helpful video.

Great lecturer who knows about microphones and good audio.....brilliant !

A sidenote. It seems to me that particle physics is the real interpretation of the universe, while relativity is an approximation on the macro scale. Just like Newton's theory of gravity was a more imprecise approximation before that. I think we need to abandon relativity and try to extrapolate new macro theories from quantum mechanics.

Jim mentions the Queen Elizabeth Engineering Prize as being awarded 'today'. The award to Parkinson, Spilker, FrueHauf, and Schwartz was announced 12 February 2019. This lecture and that announcement were simultaneous -- unless you're moving very fast.

Jim “Don’t look for them, you won’t find them” Baggott

Great talk, excellent speaker and summary of the current state. Basically we still need to convert spacetime from a continuous to a quantized geometric space.

Space-time & energy-matter... Got it! Good talk!

If I were to take the diplomatic route, I'd say that as a speaker this guy is a great writer.

Try Milo Wolff Wave Structure of Matter.

I'm not expert on this and don't know how the super computer works mathematically but didn't we quantize the space ourselves when we put the gluons and quarks on a lattice for lattice quantum chromodynamics which could give the appearance of quantified space?

The explanation that the gluon network holding the colored quarks together "snap" doesn't explain why quarks can't be separated. The explanation that the force needed to separate quarks would be enough to create a similar particle kind of does.

As usual, excellent treatment with all the depth you can get without going numerical (or symbolic). Good job Jim. By the way I could do without the sound effects - it cheapens the exposition and may startle some.

We need an audio peak compressor.

Fascinating. The immediate problem that springs to mind with this theory is the apparent expansion of the universe. If space is quantum in nature, what is expansion? It can't be the increasing in volume of one quantum of space, otherwise Planck's constant isn't so constant. So are new quanta of space being created? Another question I have is... if space is quantum in nature, does energy occupy space, or displace it?

Equivalence of gravity and acceleration: In picophysics first we explain formation of particles with its constituent space and Kenergy, and consequent interaction among themselves and space and quants.

if space has gravity waves, space would be like a 3d ocean's top in my head. those waves should overlap even over themselves. would that create a "void" inside space? since the "void" would be "empty" it would not be able to break through the "fabric" of space, creating a outward expanding pressure inside the void. the void could still be shaped by gravitational effects causing it to be lumpy, smooth or both. could this be "dark energy" or "dark matter"?

47:00 knot quantum gravity could possibly be the greatest misleading physics term if they went with that.

Is this video quantumly linked with the other one you just posted? Are any changes I make here shown there instantly too?

If Alan Partridge studied physics...

Extremely good explanation! Thank you so much! I would love to see more lectures with Jim.

Greatest lecture ever heard. Brings everything into perspective!!:)

Glad I found this youtube channel. This was great to listen to

Thank you for giving me an intuitive model for loop quantum gravity - and for delivering that model in excellent banter!

A WORK IN PROGRESS: I've listened to so many scientific lectures and enjoyed them thoroughly. I find that the majority readily admit that they don't have *absolute* answers, but they do know how to reason. The people who are obnoxious are the non-scientists that support science (as if it is infallible). Nothing is infallible, bc the human mind is imperfect. So, I take it as it is, an impressive work in progress (that often makes life better).

Clarity where I have never seen it before!

Incredible lecture , RI is fantastic

If Eo and uo can give us the viscosity of space and plank is the minimum membrane thickness it makes total sense. casimir forces at the quantum level along with frame drag from the spin. neutrinos serve as spin un/coupling mechanism and since they have 3 axes/flavors of spin they have some mass. but all true mass has both chage and spin combined.

some horrific sound effects there

Definitely one of the best RI Talk I've heard!

13:22 my favorite bit

If there is an analogue to photons, called gravitons, that transmit gravity the way photons transmit electromagnetism, and a black hole is a place where light can not escape from, then how can gravitons escape from it, so that its presence can be felt by other objects in the universe?

Very interesting, thanks! ** LOUD AND UNNECESSARY SOUND EFFECTS WARNING TO HEADPHONE USERS **

Save yourself a half hour and skip ahead to 35:46, if you already have a cursory understanding of special relativity, general relativity and the inception of Quantum Mechanics.

wonderful ... can't help but absorb every single word in this lecture. Trigger my imagination further into the realm of quantum physics.

what is the mechanism that the photon triggers that causes the movements of 2 electrons moving appart? HOW does the repulsion work,where is the lever? is it the spins that the electrons have, so they are like reaction wheels...gyros,if this spin is interupted, that causes motion?

No need for the sound fx/ naive graphics. but otherwise excellent.

Jim Baggott, many Thanks: Great lecture!

At the quantic level, time is undistinguishable from space since every particle moves at speed c, that is, the amount of Planck's length units displaced equals the amount of Planck's time units required.

59:34 Dividing by such a small number means that _S_ is *GINORMOUS.*

Thanks for the great video. What impact might be impressed by LQG on the topic of quantum entanglement ?

It certainly explains Xeno's paradox perfectly.

Very insightful lecture. After listening this lecture one idea bothers me that matter has gone so lower scal like from atom to quarks bt space time is yet not. How come this possible? I think there must be deeper parts of space time as well.may be just a thought

Lovely lecture and a lovelier idea about the bounce back hypothesis of the big bang. However, wouldn`t blackholes "bounce back" as well? I mean, once they reached that quantum limit of smallness? Maybe a blackhole would need a certain critical mass to reach that quantum smallness? I have an idea that may help with this issue of blackholes in our current universe not bouncing back, but getting increasingly large. Possibly Space is more like a pressure and gravity is a measure of that pressure. The pressure is created from the displacement of Space. In other words, space is trying to reoccupy the displaced area of the mass that creates the displacement. Also, space would not be subject to the limits of GR of relative speed because space is not mass. In theory it has a particle to account for the mass of other particles, but itself does not have mass. So, the idea is that if a fissure opened in the original "songularity" =) at the beginning of our universe, the space around it would rush in so fast that it would blast all of that matter back out into the universe. Initially it would move faster than the speed of light because of the pressure of the space refilling the void created by the original mass. Then the recombinations would occur and slow the matter below the speed of light. There is a way to test for this in our universe where there are current extraordinary events surrounding blackholes and active galaxies. Just look for spectrums of much higher amounts of hydrogen and helium than would be expected. I have spoken with a physicist at my work and his response was, "that is exactly what would happen, if the mass from a blackhole was suddenly released back into the sourrounding space". Anyway, I think about this stuff quite a bit and am back in school to see if I can aquire the skills to prove myself wrong. Thanks for reading, if anyone reads this post.

at 52:51 "Fluctuations in quantum space create the appearance of time." How can you possibly have fluctuations without having time to begin with?

20:40 tough crowd

While considering the center of gravity for quantum particles it struck me, how do you define the center of gravity of a quantum particle that is showing super positioning? if you are not able to point the center due to super positioning then general relativity should also not be able to predict the precise motion since it cannot fix the center point gravity originate. In essence center of gravity would be smeared to a region of space of probability reducing the total gravitational force which should reduce the total equation of force between two masses since neither masses has a center of gravity in a quantum sense, only a region dictated by super positioning.

I've been working on a hypothesis to try to nail down why we can't get this right. it seems to me that space itself is not quantized, but finite. As energy enters a given plank volume, that volume size should expand and flatten, up to a certain point, based on the amount of energy provided in said space. Time is just the perception of energy moving through space. As energy passes through space it flattens and expands creating a lower potential energy location at the center of the coordinate and sense energy takes the path of least action, that would be the most probable, but not only, path energy can move thru that space. a black hole is just merely the maximum capacity that space can flatten and we perceive the 6 dimensional object as a 3 dimensional shadow of fully flattened and expanded plank volumes of space filled with energy. Although they tested the idea for loop quantum gravity space being quantized, I believe the assumption that they use for that experiment was that those quantized bits are not malleable. However relativity has shown us that space dynamic. It would seem to me that if we could figure a way to see how much energy it takes to expand and flatten space per unit of energy, we may be able to extrapolate why relativity works. Matter and energy do not tell A spacetime how to curve but how to flatten and expand inside a three-dimensional framework... Well at least that's what I'm working on

Relativity from the perspective of the British Empire: "I don't have a goofy accent, you have a goofy accent!"

Thanks to all life forms to bring us knowledge. Time is a stream of unchangeable changes that propagate in all dimensions.

If space is quantized, then wouldn't time have to be quantized as well? It seems impossible that there could be a unit of time below which change is unobservable because you can always move closer to the change, since light has no 3rd dimension. Light should always be able to reflect off an object no matter how close the observation is. How, then, could there be a unit of space-time below which change ceases to be discernable?

Mr. Baggott is rather gifted at explaining QM -- I suggest picking up his book, The Meaning of Quantum Mechanics. Very good expositor of QM--

Best Ri lecture ever? Certainly a contender.

To anyone complaining for little details as the sound effects... Why don't you just say Thank you Jim for your time and the lecture? Those people who ONLY criticize instead of being grateful are usually the ones that never contribute with anything in this world, but are always ready to find mistakes and wrong in what the other are doing. If you are so perfect, why don't you do a presentation as this one? It is very easy to criticize, but hard to recognize the effort and contribution of others... Very sad reality :-( Please, do not criticize now my English, it is my third language :-)

I loved it! I need to investigate these knot theories. Find the Logos in them!

Does the Penrose spin network look eerily similar to the universe network that connects and creates spin of our galaxies?

He says "there are no infinities in nature." Then he says "maybe the universe began with a bounce rather than a bang." Pardon me if I am missing something, but the bouncing universe cosmology implies an infinity of Time... right?

i will come and pick that up XD hahah

@33:45 if recombination should be called combination, then the fotons are leased in this act, not released. ..coat..

if the Pauli exclusion principle holds I wonder if the diameter of Sagittarius A* would be a more human scaled object? Edit: I first have to convert it's mass into moles of hydrogen. then each quark of the same proton can overlap, but the set can't overlap a separate set. so each proton takes up a cube that is very roughly the plank length squared on each side. But then it is spinning and that would flatten it into a disk.

If time exists then is it also quantum in nature? A time particle ? A time wave? A time field?