Classical Mechanics | Lecture 2

(October 3, 2011) Leonard Susskind discusses the some of the basic laws and ideas of modern physics. In this lecture, he focuses on some of the incorrect laws of motion that were first proposed by Aristotle. While they are invalid they provide some insight into how modern physics has developed to the state it is at today.

This course is the beginning of a six course sequence that explores the theoretical foundations of modern physics. Topics in the series include classical mechanics, quantum mechanics, theories of relativity, electromagnetism, cosmology, and black holes.

Stanford University

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[joabrosenberg]

Aristotle's laws of motion; Aristotle's law is irreversible 13:00; Newton's law 17:00; momentum 31:00; phase space 33:00; Newton Oscillator is reversible 37:30; Conservation laws 52:00; Newton's 3 laws 55:00; Conservation of momentum 1:02:00; Energy conservation 1:07:00; Harmonic Oscillator 1:33:30

[AlexTrusk]

The quality of this video may be bad, but its still great content from a good campus. Im glad you put it online regardless of the sound quality. Stanford does its part in giving everyone in the world informative, yet enjoyable, ways to enhance capeabilities to unterstand and form the world. Please accept a humble "thank you very much".

[EdSmiley]

I've often reflected on the fact that p stands for "pomentum" and B for the "bagnetic field" sounds like a physicist had a cold some time.

[bradyp]

53:35 Annotations: "Different orbits of different radii correspond to different tentacles." Physics is full of beautiful surprises.

[KeePassDownload]

Thanks for putting subtitles, made it easier to follow along.

[yourlocalclosetedgaybestie]

53:53 *Different orbits of different radii corresponds to different tentacles*
I love the guy who added the subtitles lmao

[jsh]

Here's something odd: In the book The Theoretical Minimum, which is based on these lectures and follows them very closely, Susskind makes the opposite point: he shows that Aristotle's law *is* reversible (p. 62)! It seems a much more clear argument than the argument presented in this lecture that they are not. In this lecture, he seems to be mixing in the issue of sensitivity to initial conditions with this question of reversibility, in a way that I found very confusing. Anyway, to quote his own book:
"The conclusion is clear: If Aristotle’s equations of motion are deterministic into the future, they are also deterministic into the past. The problem with Aristotle’s equations is not that they are inconsistent; they are just the wrong equations."

[rajsinghbani]

I love how he is so casual with his knowledge

[mmaannaann]

The portion where Prof.Susskind mentions that Aristotle's law are not reversible didn't seem very satisfying. Indeed the Aristotelian 'force' is actually momentum(=mv) of the particle. In a closed system, if we know the momentum as well as the initial position of the particle, doesn't the Aristotelian law actually become generally reversible? I guess this is infact the very basis of Lagrangian and Hamiltonian formulations.

[essamhassan]

عظيم الشكر للعالم الجليل على هذه المحاضرة الاكثر من رائعة 

[atrumluminarium]

He takes a break from the lesson and what seems to be the Schrödinger equation suddenly appears on the board... What the hell happened during the break?!

[pocok]

There is a very misleading error in the subtitles at 19:12. The correct sentence is: The laws of physics are that there exist inertial frames.

[SUONIndustry]

Professor Suskind is the first to know the shape of string in string theory.

[OfficialEnman]

He takes a lunch break and suddenly a wild Schrodinger Equation appears. What did I miss?

[flamurbedrolli]

He is a BOSS . They dont call him a rebel of physics just like that . He proved Hawking wrong once

[meetghelani]

Hilarious scene in the last few seconds of the lecture and a great lecture as always in general, thank you stanford and professor leonard susskind for this!!!1

[netrapture]

There's a subtitle/caption error at 02:15 where the caption says "He thought that velocity was a natural consequence, of course" when Susskind is actually saying "He thought that velocity was a natural consequence of FORCE".

[LeavingCertMaths]

He is the first person I have come across who says that Newton's first law is really just a special case of Newton's second law (set a = 0), so Newton's first law is essentially redundant.

[netrapture]

At 06:42 "We can solve this equation very easily and p plus delta, the two graphs, right over" [here] is actually "We can solve this equation very easily for x at t plus delta, let's do that, right over" [here]

[jsh]

Note: the orbits in phase space that Susskind draws for simple harmonic motion should be moving *clockwise*, not counter-clockwise, as he suggests. (If he had drawn momentum as the x-axis and position as the y-axis, they would have been counter-clockwise.)