Lecture 2 | Topics in String Theory

(January 17, 2011) Leonard Susskind describes the special theory of relativity and focuses on showing how it connects to string theory. He considers concepts such as space-time and some of Einstein's original concepts.
In the last of course of this series, Leonard Susskind continues his exploration of string theory that attempts to reconcile quantum mechanics and general relativity. In particular, the course focuses on string theory with regard to important issues in contemporary physics.
This course was originally presented in Stanford's Continuing Studies program. Leonard Susskind is the Felix Bloch Professor of Physics at Stanford University.
Stanford University:
www.stanford.edu/
Stanford Continuing Studies Program:
csp.stanford.edu/
Stanford University Channel on KZbin:
/ stanford

[@ZacharyXAE]

Leonard Susskind works so hard on these lectures, he deserves some thanks. Greetings from New York!

[@joabrosenberg2961]

Cosmology and String theory; Rehearsal Special Relativity; Metric Tensor 7:00; Schwarzschild Metric 19:30; Quantum Mechanics of Black holes 35:00; Entropy and information (=Yes/No Q&A process) 41:30; Temperature is the change in Energy if you add 1 bit 53:40; Entropy in a Black Hole (Bekenstein) 1:04:30; Hawking Temperature 1:18:00; Planck area = change in 1 bit in BH 1:24:00; Bekenstein equation 1:29:30

[@bushje]

Amazing. Fascinating. Thanks for making these public.

[@imbertemmanuel8259]

About enthropy, I learned that entropy is opposed to information. So if we take a bit and put it to the atmosphere, we decrease the entropy to one so we cool the atmosphere isn'it?

[@nurlatifahmohdnor8939]

Page 263 .25 cm = .1 in apium graveolens = celery

[@ericmelton4186]

The definition of temperature is the relative motion of more than one atom to another. Atoms that don’t move are at 0. Everything else is heat.

[@MikeRoePhonicsMusic]

Super cool projection, bro.

[@miklysenko]

Does anyone have some notes/a short summary on what was covered in the missing sections?

[@SeanMauer]

Does this mean if the universe is expanding it's doing so because the increase of information?

[@francoboggi9542]

It seems like the materia falls on the horizon increasing it, like gentle snow, but what about the materia inside the horizon? does it falls alike up on the massive horizon?

[@oscarheath5507]

1:17:00 there's also two powers of 'c' missing (T ~ c^3 not ~c), because the complete formula for the Schwarzschild radius is R = 2GM / c^2

[@sherlockholmeslives.1605]

What is Pi Squared Time D by DA? Cheers - Mike

[@sherlockholmeslives.1605]

To be honest Oscar, not trolling but I don't understand a word of this!!! It is so nice to be put into perspective by far superior minds than my own!!! I know that Nelson's column in London is 169ft 3inches high from the based on it's plinth to the top of Nelson's hat on the statue, but that is about all I know!!! I love watching all this really juicy, brainy stuff!!! And feeling free and happy that I am not as clever as these guys!!! I have an I.Q. of 124! But I am by no means a Physics' Ph.D.!!!!!!!!!!!!

[@commodoreherring]

@commodoreherring the apparent slowing down is just an artefact of the coordinate system, like the fact that there seems to be a singularity at r = 2MG. this is only a consequence of our using the frame of reference of an inertial observer who is far from the black hole. an observer falling in would not even notice when she had crossed the horizon. in the same way, light rays in this region DO NOT slow down. it's just an apparent effect, like a optical illusion.

[@davidwood4488]

i ĺike him he qàntifies uncertainities delivers good structure

[@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.

[@SalvatoreIndelicato]

Lezione chiara e brillante

[@commodoreherring]

@luzzie9 the speed of the light ray is the same for inertial observers and those in accelerated frames. it is the PATH of the light ray that changes: observers in accelerated reference frames see light rays following curved trajectories. it's not true that light slows down near horizons; the curvature of the ray becomes so great that it turns back in on itself and never reaches the observer on the other side (like the earth's horizon: we can't see past it!)

[@oscarheath5507]

1:18:44 can someone who knows more about the rigorous derivation explain this step to me: I was under the impression that the effective mass of a Schwarzschild source was only additive for very weak fields, which would obviously not apply here.

[@PMaldeev]

AFAIK since Schwarzschild metric is the EXACT solution of Einstein's field equations no weak field assumptions are involved.

[@oscarheath5507]

PM I didn't mean weak field assumptions applied to the schwarzschild metric (its in fact an extremely strong field solution, unless I'm mistaken); the complication is in the relationship between the parameter M and kinematic mass Schutz describes M as "not in any sense just the sum of all the proper energies of the fluid elements" because "total energy is not localisable in GR" and "the integral is over the volume element 4πr^2 dr which is /not/ the element of /proper/ volume [in curved space]". He goes on to mention that the difference can be interpreted to an extent as gravitational potential energy, which may address my concern, although GPE isn't a very solid concept in GR I was mainly wondering wether someone with more expert knowledge than I could give a slightly more rigorous perspective - maybe I should take this to physics stack exchange instead

[@PMaldeev]

>>maybe I should take this to physics stack exchange instead Well, I think you should.

[@while_coyote]

He's so high in this one!

[@oscarheath5507]

He looks high in all of them to be honest

[@justingreen1887]

I am too

[@coulhillcoulhill4470]

Thanks be

[@sherlockholmeslives.1605]

Am I right in thinking area of a sphere or is it the area of a black hole is Pi Squared Times D by DA? Cheers - Mike

[@sherlockholmeslives.1605]

Prof Malcolm Parry mentions on it on an Astronomy video I have as he wanders through Cambridge, UK. Cheers - Mike

[@matthewlemon2832]

That has more to do with hawking radiation and the relation to the area of a black hole than just the area its self. DA in relation to delta A

[@cesarjom]

keeps saying "polar coordinates" where he is using and also must mean to say "spherical"

[@Nazim1495]

@grunder20 all the fundamental particles you see in this world is made out of strings,2d strands of energy that vibrate, depending on the vibration and shape of those stings in can correspond to a different particle, including gravitons,photons,electrons, higgs boson, etc. these strings could only exist in an 10-11 dimensional space. we live in 3 dimensions. the other 7 dimensions allow for parallel universes, time travel, M-THEROY, paradoxes are solved, black holes make sense.

[@wresing]

The East Pole?

[@justingreen1887]

Was someone really arguing with him whether or not there is a T in Schwarzchild!? 😳

[@matthewlemon2832]

Physics students tend to do that. In a early video they argued with him about dna base pair......completely missing the point it is an analogy not a exact representation.

[@BiophysicalChemist]

matthew lemon It's called lightening the mood and giving your brain a rest. In most of my upper division courses we used to spend at least 10-15% of our class time just cutting up or arguing over random things (professor included). The ones that had lame professors with no personality who just lectured the entire time usually just left everybody zoned out and disinterested

[@grunder20]

what does STRING THEORY really mean?

[@brendawilliams8062]

Looks like 1001035 has friends. 🤷‍♀️ I don’t know

[@surjendu_bhattacharyya]

no question is stupid's question!!!

[@albertgerard4639]

Surjendu Bhattacharyya only stupid people

[@rammozs]

POTATO

[@apburner1]

Having spent more than 20 years in the US military, with many of those years as an instructor, I can assure you that you are wrong.