Lecture 1 | Topics in String Theory

[@WorldBurial]

It's really great that Stanford puts lectures as these online. And as a bonus we're being taught by a great teacher and physicist as Susskind.

[@MnM4516]

Susskind and Feynman are the best lecturers I've ever listened to, IMO.

[@joabrosenberg2961]

Reductionism philosophy; Fermions and Bosons fields 6:30; Electric and Magnetic monopoles 14:15; D-Branes and F-Strings 27:00; S (Strength)-duality 32:00; String is not the right theory of the world but teaches us a lot 1:17:30;

[@scorpionsdangle9]

Hello, I am 14 years old and im approching 9th grade and i dream of being a physicist. Currently i stay home and and studdy physics on the down low because my parents are too religious to understand science. I would just like to say how impressed and how outstanding your videos are, i could watch them all day. Thank you for making these lecture videos.

[@channel-ug9gt]

physics is not bad... I have PhD in it... I like to watch videos like this before falling asleep... it gives me a "feel" for something...

[@Zoro-fl2mn]

Where are you now?

[@Bounty6Gulf]

Wonder if this comment lead to someone staring on Chris Hanson’s show

[@sfsoma]

What a great treat to have this entire course to watch. Professor Susskind is one of the best lecturers.

[@Aiden057]

Leonard Susskind is such a brilliant lecturer. Thank you for posting this series.

[@SeanMauer]

Another Illuminating Lecture from One of Today's Top Thinkers.

[@Amanpreetkaur-cp4fs]

Father of String Theory 🎉🎉🎉 teaching string theory

[@wafikiri_]

Among the few facts that we know for sure about reality, the following stands: things (objects, events, whatever) are not the same everywhere and everywhen. We call a (distinguishing) feature whatever thing that makes two things different. Then features of features must exist to distinguish the latter among themselves. This all leads to a lattice of things. Here Prof. Susskind tells us that sometimes we should consider some nodes in the lattice as more fundamental, others as more complex, and sometimes the other way around. The lattice becomes a network. The root of a lattice can be any node of the network: pull it up (conceptually), the rest will go underneath; the relationships between them will not vary but the view of reality we get will do.

[@wafikiri_]

What is most fundamental, the feature that a table's cell belongs in a column or the feature that it belongs in a row? I would say both are.

[@OskourDuservo]

What a great lecture and what a brilliant lecturer!

[@DanielFBest]

I love you Professor Susskind

[@GreaterDeity]

That's because it is made up. But not 'made up' in the way you are thinking. Verified data can support but not really give credence to this material. This lecture is about ideas. No one said you had to adhere to it. But... you are right to a point.

[@GreaterDeity]

Yes, they are ridiculous. You are the only one that has made a comment worth reading. Susskind knows this; but his job is not to give an opinion, only present the information in these type of lectures.

[@LLorfa]

These are just models for description purposes. A 4th dimensional shape cannot be drawn. Imagine the end of a rod moving around on the world of a 2-dimensional flatlander. What they see is a particle moving in their 2 dimensions, and are oblivious to the rod stretching into the 3rd. If you live in 3 dimensions, a 4th dimensional rod would appear as a particle moving in 3 dimensions, but you would be oblivious to its 'rod' character because it stretches into a 4th spatial dimension.

[@rv706]

"My guess is that SUSY will really be discovered at the LHC" - Hello from 2020 ;-)

[@iOnline72]

Ok, I have to be honest here. Didn't get half of what was trying to explain, but couldn't stop listening.

[@soulskies]

@scout6686 the parameters are the constants which cannot be derived inside the theory but must be put from outside by experimental measurements.

[@Dilaton100]

@jpacemen01 Hi all of Prof. Susskind s Lectures are available from the lower part of the Wiki page about him (search for Leonard Susskind) including the SUSY lectures I mentioned. For some reason I`me not able to post any link here :-/ ... All of the Theoretical Minimum courses are very good, I`ve checked them up to SUSY by now :-) Cheers

[@mathemystician]

Dude absolutely loves cookies.

[@otonanoC]

Has anyone else noticed that this material is more fascinating than science fiction?

[@soulskies]

In general relativity you have a set of differential equations which gives the local geometry=physics at every point. But there is no restriction on the global geometry. We put the global topology by hand (ex: we make the phi coordinate periodic in Schwarzschild solution to get a reasonable interpretation). Reductionism may also end in this case. Which is our priority? global or differential topology of our universe? according to reductionism local laws must completely determine the global laws.

[@yurivolkovich]

Listening to Susskind from Kenya.

[@WhatIsGod]

10:43 "rotate this end around by 2 pie"..... love it. not 360 degrees but 2 pie.

[@MckenzieAndy]

23:12 my respects, those people are really lucky to have it as a teacher

[@LLorfa]

The sandwich example is to describe a 2-dimensional reality encountering a third. One way to imagine that they only see this at small sizes is to imagine a field of cylinders, each with some small spacing between them. They form a 2d plane, and flatlanders could only see the 3rd dimension if they could examine their reality at a distance small enough to "see" between the cylinders. You just have to kind of abstractly extrapolate this to a 3d world and imagine what its consequences would be.

[@boomclan5163]

6:29 is when the lecture starts.

[@imegatrone]

I Really Like The Video Leonard Susskind gives a lecture on the string theory and particle physics From Your

[@samsamhuns928]

Prof Leonard Susskind looks like Mike Erhmanntruat from Breaking Bad

[@justingreen1887]

Who?

[@lazarivkov879]

+Sam Samhuns Agreed

[@owenpeter3]

+Sam Samhuns Actually, he looks like me!

[@lidan9805]

And the example of fermions and bosons refers, i agree fermions and bosons are the same thing. The reason of only Fermions obey Pauli Exclusion Principle (for electron case) is the numbers of available extra plane for wave functions. Since electrons (fermions) "circulate" around a massive nuclear, they are trapped in the 3d world with limited planes for motion, (i.e. 2,8,16....). For photons (bosons), they don't "circulate" around a massive nuclear, so they are not trapped in 3d world, and therefore can travel in the same energy state in higher dimensions. My point is the universe itself is (not yet proved) already a multi-dimension spacetime.... Thanks for reading =)

[@JamesCarmichael]

Well in most cases science fiction is built on real science, but its often exaggerated and theoretical material is used. A lot of science fiction (expecially these days) has to be explained to the viewer and that is when this /\ /\ /\ kind of material is very useful as it is just as or as you pointed out more fascinating than science fiction.

[@williamotule]

So much the teacher I wish I had had!

[@Dilaton100]

A ha, cool :-))) Thanks @ Lenny Susskind and Stanford for this new Lecture Series. I`ll come back here to see all of the videos later. (still busy with the SUSY-Lectures at the moment ...) Cheers :-)))

[@williamvanleuven2645]

When you go to the top of the sandwich, you come out in the bottom. IMHO, this is because the extra dimensions are curled up like the famous calabi-yau manifold, some kind of knot. You keep moving in circles.

[@soulskies]

@soulskies But this is not the case in general relativity. Neither of differential laws and global topology completely determines the other. This may be the problem of gr or any field theory. Otherwise reductionism does not make sense. I wanted to point out that the reductionism may not break only for the fundamental constituents of the universe, they also could break in the way we formulate the physics: local laws.

[@jpacemen01]

@Dilaton100 Excuse me for being curious, but which lectures are you talking about? :-)

[@MrDevin666]

As a high school student, I really don't understand most of it because you really have to know your stuff.

[@karabomothupi9759]

How about now?

[@chrishawk93]

I'm so happy I stumbled upon this, while watching something very unrelated.. :P

[@VishalSharmavish121989]

I enjoyed the lecture. Can I get the mathematical equations explaining the reason why string theory need more dimensions ?? Thank you.

[@lidan9805]

theoreticalminimum.com/courses/string-theory-and-m-theory/2010/fall/lecture-5

[@flixerstudios1862]

What is the difference between this lecture series and the other one on String Theory?

[@hackerisslv]

Thinking that you understand something doesnt mean that you really understand it!

[@FeederForLife]

I love the contrast between the two top comments at the moment: a critique of ignorance and retroactive reasoning among philosophers followed by "pehnut buttah sandwich".

[@frankfrancia2053]

So Great Professor. Thanks Stanford

[@rav9993]

Excellent Lecture....Thank you....

[@eereths]

you do understand that classifying philosophical terms is almost completely subjective with regards to many factors

[@TheShenergy]

Hi Brendon! I So wonderful to hear a youth discovering physics in an era where YOU very well could be another Newton! Keep dreaming! and doing you own homework! The library can teach you as fast as you want! Have fun! Does theory perhaps stems from dreaming?- there is no box... just keep thinking and dreaming... Have you discovered Prof Walter Lewin "For the love of physics" Have fun! I'll be watching for your theories sooner than 'they' think. Peace from Canada :)

[@FirstRisingSouI]

I can picture a 4-brane. It helps to understand that we naturally see in two dimensions, but think in 3. We naturally apply strategies to expand our 2D experience to 3D thought, and we can apply similar strategies to expand to 4D thought.

[@CPLains]

rofl. i paused to get a peanutbutter sandwich, and then as i unpause it he mentions peanutbutter sandwich within 5 seconds x)

[@nurlatifahmohdnor8939]

What is a contour map?

[@MatthiasBehrends]

IMHO the guy asking at 1h 11m:30s has a point that the cyclic nature of the extra dimension gives "a kind of infinity". Moving in a circle requires a (constant) change in direction, which in the first case is not necessary. Probably this is being resolved mathematically, but nonetheless a beautiful thought.

[@jomen112]

+Matthias Behrends It is not "probably" explained. It is a explained and was so by Susskind as well. Susskind said, but in other word, on a circle you can travel an infinite distance but the actual distance is bounded by the circle. Did you not pay notice to that?

[@newtonrhodes7093]

Always a theory taught as fact. Here's a fact...water is LEVEL. No theory changes that.

[@XCyclonusX]

Could we just be going down a mathematical rabbit hole? That the simple math leads us to more complex math to more complex until we're trying to shape reality simply to please a mathematical equation. What if the is a particle we can go down to say a quark, and that 3 dimensional quark is made up of nothing smaller. Its simply a pure quark, and when we break it apart we're not freeing smaller particles just shards of quarks. BTW, I love string theory, and totally believe it.

[@ThatsTooSmall]

i accidentally started playing this and Take Five by The Dave Brubeck Quartet. it's sounds cool and artsy.

[@MangaFood]

"here's a 3-brane.. Ha! This isn't a 3-brane it's a 2-brane, too bad!"

[@abhishekchowdhuri9129]

great lectures.......

[@trajtemberg]

What does the D stands for?

[@deanrubine2955]

This is a great lecture series, perhaps the capstone of the Theoretical Minimum idea, bringing in ideas from statistical mechanics, quantum mechanics, special and general relativity and string theory to study black holes and the expanding universe. The focus is mostly on event horizons of black holes and expanding spacetime. They're very neatly illustrated by Penrose diagrams. We learn Dark Energy = Vacuum Energy = Constant Hubble Constant = Cosmological Constant = Exponentially Expanding Universe. Unfortunately, this series is misnamed. The only parts about string theory are in Lectures 1, 6 & 7. This one here, Lecture 1, should really be Lecture 11 String Theory and M-Theory, as it continues the ideas of Lecture 10 of that series. You could safely skip it as it doesn't have anything to do with Lectures 2 through 10 in this series. Lectures 6 & 7 derive the entropy of a black hole from string theory by considering a black hole a string and adiabatically increasing gravity, but that's about it for string theory in this series. Also be careful not to confuse these with some similarly named lecture series by Dr. Susskind.

[@GreaterDeity]

Well, he's right. Do you disagree with him? Just a question.

[@matharoofmaths]

I was the sixty-fourth person to like this. 64 is my lucky number.

[@BrotherWoody1]

Superb! Thank you.

[@williamcottrell72]

I love how wanna-be philosophers try to retroactively act as if everything that physicist discover is "obvious". Susskind is not the one confused here - his very point is that reductionism runs into difficulties and that this is a property of the particular models which physicist have been led to through research. It is not 'a priori' or obvious, since this kind of reductionism works in certain theories and not in others. Thinking that this is obvious just displays real ignorance.

[@knightsofempathy6768]

Can we not agree that reductionism is also fractal in nature??

[@HigherPlanes]

Many highly intelligent people have little quirks like that in common.

[@scorpionsdangle9]

your great sir

[@alphalunamare]

Calculus and reductionism ... how on earth did he keep a straight face?

[@WhatIsGod]

you don't understand it. you think you do, but you don't. I started studying thins stuff at 12 when hyperspace came out. i am now 30 and after 3-5 hrs of this level of study a week, every week.... it is almost like i know less now then i did then. there is no understanding it there is only understanding what happens.

[@tariqxl]

You did 2 paragraphs i something I know and now my brains numb lol. If you read my comment again maybe you'll pick up on the humour, maybe not. It was an attempt at mimicking the string theory in-joke, don't know if you've heard it Michio Kaku's told it plenty of times. Thanks for the reply though aim to educate and all that :)

[@isedairi]

Lenny,at the LHC you will discover what!? Wrong

[@Dyslexic-Artist-Theory-on-Time]

Could quantum mechanics represent the passage or Arrow of Time? This theory is based on just two postulates, 1.The first is that the quantum wave particle function explained by Schrödinger’s wave equation represents the forward passage of time or Arrow of Time itself photon by photon, quanta by quanta or moment by moment. 2. The second is that Heisenberg’s Uncertainty Principle that is formed by the wave function is the same uncertainty we have with any future event.

[@glasswalker82]

THANKS

[@darrylwillard2419]

According To Professor Lewin the magnetic monopole doesn't exist.

[@dodecapusrex]

Oh good, we still can't explain existence. I thought so!

[@kn123able]

he defines reductionism wrong. A theorem is reductionist if for example its supposes that the genetic determinism is to be explained only by quantum mechanics and the biology has to be excluded.as an explanatory tool --> such a theorem would reduce the biological level to the quantum physical level.

[@Dyslexic-Artist-Theory-on-Time]

Not spam! In the mathematics of Hugh Everett Many Worlds interpretation the different universes or dimensions are all at right-angels to each other! In this theory they are just future possibilities in our one three dimensional Universe of continuous creation or energy exchange. The mathematics remains the same! They are at right-angels to each other because EM field are always at right-angles to each other as a process of continuous change as time unfolds.

[@mamjuzinnekonto]

mike?:D

[@sterbenthanatos8549]

Bosons are more fundamental....how is that even a question?

[@JasonDeveau]

Or maybe they could zoom out a bit...

[@Dyslexic-Artist-Theory-on-Time]

This is an invitation to see an alternative view! Where the different dimensions of String Theory are just future possibilities in our one 3D Universe Based on: 1 Is that the quantum wave particle function Ψ or probability function represents the forward passage of time itself photon by photon 2 Is that HUP ∆×∆p×≥h/4π that is formed by the w-function is the same uncertainty we have with any future event within our own ref-frame that we can interact with turning the possible into the actual!

[@kurosenchou]

i was wrong, watching TBBT does not make me understand this

[@Onoma314]

What does a Zombie String Theorist say ? " Braaaaaaaaaaannneesssssssssss "

[@Dyslexic-Artist-Theory-on-Time]

This is an invitation to see an alternative to String Theory! Where the different dimensions are just future possibilities in our one 3D Universe. Based on the postulates: 1. The Ψ probability function represents the forward passage of time with the future coming into existence photon by photon. 2. Is that HUP ∆×∆p×≥h/4π that is formed by the w-function is the same uncertainty we have with any future event within our own ref-frame that we can interact with turning the possible into the actual!

[@davidwilkie9551]

Suffixes ist and ism, "when I attended School" meant "a tendency towards", so very much like "prone to Opinionated, unsubstantiated Assumptions and Pronouncements" in the vernacular. Eg "Quantum Mechanics is weird and mysterious", is just plainly ill-informed. Speculation reduced to the minimum observation of what, how and why the Universe is as it is, was the theme of Henri Bergson in regard to Time Duration Timing phenomena. So Reducing observables, a pure-math activity in Thought Experimentalist's Intuitions is a recognition of Euler's Intuitions and Conjectures that were left open for Physicists to Research in conjunction with Mathematical Disproof Methodology.., recognising Logarithmic Time, in Evidenced Communication universally by AM-FModules of temporal mechanics wave-packaging formation, as Dr Disney has stated, (Theoretically) The self-defining sum-of-all-histories here-now-forever observational statements in Theoretical observational research corresponds to discovery of the Holographic Principle Imagery projection-drawing Actuality.., Logarithmic quantization coordination-positioning in Quantum-fields of Temporal continuity Fluxion-Integral, Superposition-point Superspin, "Mathemagical" Calculus.

[@Onoma314]

That's a pretty thin sammich. I want my money back.

[@homekatsushi]

I want to study the “M theory”! But, Wait, I like a little different idea because I don’t like the basic idea of the “STRING”. Everything from physical universe, galaxy, our solar system, earth and moon, to molecules, atoms, subatomic particles, elementary particles, and quantum world have(there is a notion of spin) notion of rotating or spinning in common. Why we can’t express in the term of spinning or rotation, not sting. Considering the idea of spinning (rotating) leads naturally to a concept of spins (classical mechanics). I feel like more natural direction than going with the string. Can anyone develop a new little different theory from the string( or M-theory)?

[@Dave78214]

Peanut Butter with Jelly Sandwich

[@amany247]

No god but Allah Islam way for peace and real monotheist Search about the truth with honest heart And first ask Allah to help you to find the way

[@sterbenthanatos8549]

I'm confused as to why the question of "usefulness" is being discussed in the context of developing fundamental physical models - this attitude strikes me as being a significant stumbling block to theoretical physics in the modern era. The founders of quantum mechanics were able to make such genius breakthroughs because they cared about developing elegant and simple models of Nature. There is a very practical reason why the primary goal of theoretical physicists should be elegance - a simple and elegant model at the core of a theory acts as a guidepost in developing more useful models, so physicists can branch out and be creative without losing their bearings. Without a well-defined foundation physical model that one can point to and say "that's what Nature _really_ is," (again, by definition) the physics community is doomed to wander around in the dark always just groping for a slightly more useful model. In this process, a lot of _really good ideas_ will go unnoticed because the community lacks a coherent framework of terminology with which to evaluate exactly how newly proposed models fit into the overall theory. The theoretical physics community has turned into a stampeding mob of half-baked mathematicians who are more interested in playing with big shiny "super" toys (SO(10), E8xE8, etc.) than they are in understanding Nature's secrets.

[@TJae1]

I can't b-lieve this appeard on pier-ro's channel ~ soberity suxs & can b boring ~ thus ~ pyrrho314 is attempting to bridge the invigorating world of intoxication w/ boring yet enlightening wrld of science all w/ camtwist effects w/ sound effects 2 match ~ chck it out

[@MarcoAurelio-vb9hl]

If my math is right then you should already be 15 years old or become 15 soon enough. How are your physic studies going? Did you stick with it? :)

[@tariqxl]

And this is why I've never quite got string theorists... The mathematics tell them the universe has to have 11 dimensions the observers say well I only see 3 so one scientist tries to cheat and says well if i have this 3d piece of bread and put some 3d filler then another 3d pieces of bread on the top we have a multidimensional universe... No u have a 3d sandwich

[@gogoteca]

Funny how most of the comments for this video have nothing to do with physics.

[@kn123able]

you dont have to be einstein in order to classify philosophical terms properly. ironically you are the one declaring her/himself as the authority of physics.

[@computergenius365]

when did mike from breaking bad get a physics degree?

[@111tato]

I have the same jacket, he has. Imma scientist

[@CHeCKEyE5]

Camera has to stop following him every where on every move. Almost nauseating.

[@eereths]

Ok Einstein... When you disprove one of Stephen Hawking's theories and become a physics professor fluent in string theory come back to me...

[@functiontopacket339]

God doesn't play spillikins ... ;-)

[@apburner1]

Nice troll you did there.

[@wolfpack9425]

im 15 years old and understand this but when i showed this to my science teacher at school he was totally lost lol

[@Roccdrummer]

What if none of it exists?

[@newtonrhodes7093]

He teaches fairy tales and is praised for being good at it.