Lecture 1 | Modern Physics: Quantum Mechanics (Stanford)

Lecture 1 of Leonard Susskind's Modern Physics course concentrating on Quantum Mechanics. Recorded January 14, 2008 at Stanford University.

This Stanford Continuing Studies course is the second of a six-quarter sequence of classes exploring the essential theoretical foundations of modern physics. The topics covered in this course focus on quantum mechanics. Leonard Susskind is the Felix Bloch Professor of Physics at Stanford University.

Complete playlist for the course:
http://youtube.com/view_play_list?p=1...

Stanford Continuing Studies: http://continuingstudies.stanford.edu/

About Leonard Susskind: http://www.stanford.edu/dept/physics/...

Stanford University channel on YouTube:
http://www.youtube.com/stanford

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[HikaruYamamoto]

even the greatest minds can make typos... xp

[origamiview]

Definitely one of the most comprehensible explanation I've ever seen. I'm so grateful for this lecture, it's really nice there is someone who is able to combine together great passion with something what's certainly may be defined as a useful.

[projekcja]

What's the F word used to describe the third possible state of coins?

[fcmilsweeper9]

Math is just a way of describing something we see; I see what you are saying, but from a qualitative perspective, the standard presentation still stands...

[Opethfullcovers]

Prove it...........

[Mark Halperin]

He's from New York!

[thrunsalmighty]

(1) I hate the ponderous description of the two slit experiment such as this.

It encourages what I call peek-a-boo physics in which the quantum world somehow depends on human consciousness. Blame John von Neumann. It leads to absurdities like dead-and-alive cats and the splitting of universes.

There is NO connection between human consciousness the behaviour of the quantum world (apart from the fact that the brain is part of that world).

[thrunsalmighty]

(2) The usual presentation of the two slit experiment is that Nature just does not want to tell us which slit an electron passes through when forming the interference pattern. However carefully you try to sneak a peek at which hole the electron passes through, if you succeed, you f*** up the pattern. So you can never know.

Is this Nature being bloody minded?

No.

[thrunsalmighty]

(3) Here is my explanation.

We understand what happens to quantum things (like electrons) by solving Schroedinger’s equation. Nature, too, needs to “solve” Schroedinger’s equation. When the electron has a choice of holes to pass through, that solution is degenerate (not fully determined because of the symmetry of the two holes). It could do one thing or the other.

[thrunsalmighty]

(4) It is that degeneracy which produces the interference pattern

As soon as one hole is identified (howsoever that may be) as the preferred hole,

then that symmetry no longer applies. Then the degeneracy is removed from the corresponding solutions to Schroedinger’s equation. So there is ipso facto no interference pattern.

[thrunsalmighty]

(5) It is NOT a game of peek-a-boo in which Nature manages to outwit the observer. It’s just in the maths.

[Collective239]

Yeah when I watched it, less people had viewed it