Special Relativity | Lecture 4

(April 30, 2012) Leonard Susskind moves into the topic of fields and field theory. For the most part he will focus on classical field theory, but occasionally will relate it to some of the concepts from 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:

[tobywhite]

Smaller things also deserve praise: Nice job by the video operator in general on this lecture, who was even able to frame & focus the flying bug that briefly disturbed the lecture around 1:32, as well as having to deal with a lot of visually wide equations and quick changes of ... reference frame (as good a term as any, I guess).

[Neueregel]

Dr. Susskind is a science legend. Respect. Thanks for uploading.

[archananaik]

45:00 - why are we putting a minus in front of space derivatives? Please clarify it someone

[pragjyotishbhuyangogoi]

It's incredible how he makes things look so easy.

[Mahebollja]

Starting from 1:41:15, I'm getting confused how he derives the equations of movement. According to the Euler-Lagrange equation he introduced in 38:40, one should first of all compute the derivative of the Lagrangian w.r.t. d*phi/d*x^mu for mu =0, 1, since we are only considering one space direction along x. So we only have mu=0 and mu=1 to worry about. However, the derivative of the Lagrangian with respect to d*phi/d*x^mu are for both for mu=0 as well as for mu=1 equal to zero, since we do not have d*phi/d*x^0 = d*phi/dt = phi^dot or d*phi/dx in the Lagrangian. So what is left is dL/d*phi in the Euler-Lagrange equation. But this would be different from what he has there.
What am I missing here?

Thank you very much in advance for your help! ❤

[neerajgogate]

while calculating the lagrangian of a particle placed in a field, why did he specifically add fi with the mass? I mean he could have done any other thing like multiplying the entire thing by fi etc. Was there a particular reason behind doing that ?

[ThQuietnee]

I’ve woken up to 3 of these lectures wiser

[Denosophem]

Is this answering a large questions broken down into sub equations?

[TwinbornMist]

This was on a auto play and apparently I watched an hour of it

[neelmodi]

Why is the gradient of the scalar field a vector? How can one see that it transforms like one? I thought it was a covector and hence should transform differently?

[UpVade]

I left yt on while I was sleeping and I came back to this

[elias_xp]

I made it 9 minutes in before I lost. This is gonna take a while to digest.

[zack_]

20:17- nice 3D drawing!

This series can be tremendously boosted if presented by videos in real 3D format via collaboration with two great animation channel's:

Physics video:
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One can then imagine the unprecedented teaching efficiency and productivity where the teacher and students are as if walking IN a 3D space.

[cheesechizel]

+sub ... thanks for putting these up here to watch

[SloppyLarry]

He's a WIZARD! But seriously thanks for posting, I am sure if I continue taking math classes I will understand this better.

[Denosophem]

Now when I go back to look again it’s vanished or I keep magically looking over an entire 37 seconds of footage

[Denosophem]

Those minus signs are on ok two separate equations

[ilredeldeserto]

Splendida questa puntata, la mia preferita di questo corso! O:

[manse]

thank you Prof. Susskind, and stanford U

[patrickderp]

if i watch a car video, autoplay shows me car videos

if i watch a guitar video, autoplay shows me guitar videos

if i watch a kurt cobain video, autoplay shows me more grunge

but just when i think i have trained youtubes autoplay to show me crazy outlandish conspiracy videos, it always defaults to stanford courses! thats not an accident lmao