Special Relativity | Lecture 6

(May 14, 2012) Leonard Susskind dives into topics of electromagnetism and how it relates to quantum mechanics.

In 1905, while only twenty-six years old, Albert Einstein published "On the Electrodynamics of Moving Bodies" and effectively extended classical laws of relativity to all laws of physics, even electrodynamics. In this course, Professor Susskind takes a close look at the special theory of relativity and also at classical field theory. Concepts addressed here include space-time and four-dimensional space-time, electromagnetic fields and their application to Maxwell's equations.

Originally presented in the Stanford Continuing Studies Program.

Stanford University:

Continuing Studies Program:

Stanford University Channel on YouTube:

[xSeiZmikx]

I've listened to this man speak for over 100 hours and haven't once gotten bored of him.

[hasanshirazi]

@0:00 Vector Notations.
@26:17 Tensor Notations.
@49:39 Electromagnetism Tensor Notation.
@51:10 Electromagnetism.
@1:49:21 Three Principles of Physics

[santiagoerroalvarez]

That was simply fantastic, thank you very much, Dr. Susskind.

[KipIngram]

5:38 - it's called "contra" variant because if you change coordinates you change the component in the inverse way. For example, if you switch from meters to inches, you have reduced the size of the unit, but the numerical value of components of length have to become larger. 1 m --> 39.37 inches. On the other hand, covariant vectors have the component change in the same way as the unit - to change a power density from watts/m^2 to watts/in^2 you have to make the component value smaller (by a factor of 39.37^2). The component "covaries" with the change of the unit.

[KipIngram]

42:30 - Just consider vector V which is a velocity, and vector P which is a power density. They transform in different ways. V is contravariant and P is covariant. The subscripts and the superscripts give you a way to denote in the notation which way a quantity transforms.

[rgudduu]

Notation: upto first 50 mins.
Emag: after that.

[luckymmez]

i fell aleep, randomly woke up on this vid, now a nigga mad smart

[devanshnangia]

Accidently skipped lecture 5 and came here directly. Was so confused.

[alhobbel]

I'm the same. I've watched the original course on relativity and now this one again and I'm still transfixed.
If you're after other good lecturers, I can highly recommend the Stanford course on the Fourier transform and its applications (by Brian Osgood, he talks fast but he's quite good) and the MIT courses on basic physics and electrodynamics (by Walter Lewin, he has a heavy Dutch accent, but he sure loves physics and he's really enthusiastic).

[stupidpdj]

Dr. Susskind has eaten a relativistic quantity of cookies. This was a tough one.

[KipIngram]

1:26:33 - The question is valid. It feels like you GUESSED at an answer, worked it out, and then said, "Ah, this explains the experiments!" But WHY did you guess THAT? What principle of physics led you to that particular guess? This all feels like you know the answer ahead of time. It doesn't feel like you are DERIVING the theory. Maybe that's the best we can do, and if so, so be it - but you should say at the outset, "We don't KNOW HOW to derive this - someone guessed it and we can do some math to show how to compare it to experiment." Don't make it sound like it's painfully obvious why you should have done that, because it's NOT.

[brainstormingsharing]

Absolutely well done and definitely keep it up!!! 👍👍👍👍👍

[PetraAxolotl]

At about 1:23:40, it should be (x_super_0)_dot, instead of (x_sub_0)_dot.

[redpunk]

I had a physics professor who thought he was better than the students (who were mostly biology majors) for the fact that he knew how to use tensor notation.  The first day of class he told everyone that "physics is hard" and then assured us that we'd never be able to understand physics like he does.  Everyone used to think that he was edgy.  I always figured him as an asshole and wondered whether everyone was just too stupid to realize when someone was insulting them.

He also seems to have plagiarized his lectures.  He actually copied, damned near word for word if not word for word, a sequence from Cosmos.

[patriciaheil]

I don't know who did the camera work on lesson 6 but it didn't keep up like on ALL the other courses and lectures.

[KipIngram]

1:30:12 - Shouldn't that x[n] dot over at the far right of the board, on the bottom, be a superscript? I understand that in special relativity the upper/lower doesn't matter, but in general relativity it does, so shouldn't we get that right? The terms in the parentheses have downstairs n's, so the one outside should have an upstairs n if you want to contract them. Plus the one outside is a velocity component, so it should be contravariant.

[TwinsOfJune]

I taught this guy everything he knows

[ThorRidder]

the Corleones' personal physics teacher

[YouGenie]

With good instructors you should never have to pretend to understand. He's merely communicating in another language. The TIME component is indeed the key.

[Sintaxx]

What kind of language is this? :0 Me no understand.