Stanford University

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:

Stanford Continuing Studies:

About Leonard Susskind:

Stanford University channel on YouTube:


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  • Teachers don't spend enough time on the particulars of the slit experiment. What EXACTLY is used to measure the photons on the back screen? What EXACTLY causes the slight randomness of the photons going thru ONE slit? Is it the frequency shift of photons coming out of the "laser", is it the human error in designing a perfect laser shooter? Is it the photons knicking the inner sides of the slit? And then in the advanced notion of the slit experiment which talks about measuring WHICH slit the photon goes thru, which alters the results (from quantum mechanical, back to mechanical expected results), how is the slit-choice ACTUALLY measured, perhaps the device is affecting the result?
    Also I think the fluid physics dudes should always chime in on slit experiment presentations with talk about carrier-waves, which after many many decades STILL hasn't been proven wrong.
    Physics teaching is so bad, and so one-sided, new students get bad education, thinking they know something, when in fact due to being presented the questions and solutions wrongly, the education system has actually created a barrier for those trying to ADVANCE human knowledge.
    If teaching sometehing, do it right, do it completely, and spend some actualy time on it, rather than trying to get to a pre-determined endpoint.

  • Physicists like to say that Einstein was wrong that "God doesn't like to play dice", bc of the Uncertainty Principle. Physicists are wrong. Just because it is true that quantized physics doesn't allow anyone or any being to know with precision the location AND the velocity at zero error, DOES NOT MEAN that the particle doesn't actually HAVE an EXACT Location AND an exact velocity. It only means that for PHYSICISTS and even GOD, niether can tell you the informatin about the particle better than Heisenberg's law. HOWEVER, that ASSUMES God isn't all-knowing. If God is all-knowing, he doesn't need to subscribe to the BOUNDARIES which quantum mechanics present (that of light's quantum nature), thus he/she could actually tell you both measurements bc those measurements ACTUALLY exist. Physicists like to tell you what I'm saying is wrong, but that's bc Physicists belive the Wave Function IS the physics. It is not. The Wave Function describes the MEDIUM, not the particle. Again, see fluid dynamics for better understanding. A Photon will have a Wave Function associated with it, but it doesn't mean that a photons particle doesn't have an exact set of quanta (location, speed etc…).

    one thing Physicists DO do correctly, is tell you that they go in wrong directions sometimes, for VERY long times. I believe this to be the case with Heisenberg's Uncertainty principle. HUP is a VERY good tool, but the tool is not reality. The reality is the reality, in spite of the limitation of quantum mechanics to determine the reality.
    The Wave Function ONLY describes the probabilities, NOT the realities.

    Einstein, AS USUAL (see his "biggest mistake" term in his Gravitation Equation is a term that ends up describing what we now call "dark matter/energy" which explains the acceleartion of the Universe outwards) will end up being correct (is there ANYTHING he got wrong?) again, and we'll one day determine that "god (indeed) does NOT play dice".
    I believe the Fluid Mechanics guys are helping us all see this, but the Physics community is VERY slow to move, and hasn't recognized it yet bc Quantum Mechanics is such a nice comfort zone bc the math works out (we know how to do Wave Functions, and we know the quantized nature of physics prevents us from getting beyond the Wave Function– so Physics stubbornly refuses to accept that certain people in Physics history that talked about carrier waves were indeed correct).

    Heisenberg was a great man, but Einstein was Divine.

  • Possible explanation to the wave particle duality:

    1. Charged particles have an associated magnetic field with them.
    2. Protons and electrons are charged particles and have an associated magnetic field with them.
    3. Photons have both an electric and magnetic component to them.
    4. Whenever a proton, electron, or photon is shot out of a gun, it's respective magnetic field interacts with the magnetic fields of the electrons in the atoms and molecules of the gun itself, the medium the projectile is traveling through (ie: air), and/or from around the slits themselves.
    5. Via QED (quantum electrodynamics), newly generated photons might occur.
    6. The projectile goes on it's own way and the newly generated photons go on their own way.
    7. Gives the illusion of a wave particle duality, but is not that way in actual reality.
    8. As far as having detectors involved, they probably have an energy field that is one way when on and is a different way when off.
    9. The interaction between this energy field, (or lack thereof), with whatever is passing through it, gives the indication that is observed.

    Utilizing the scientific principal of Occam's razor, (whereby the most probable scenario is most probably the correct scenario; it might not be truly correct in actual reality, just that it is most probably correct), which way is most probably correct? This way as stated above, or what modern science teaches today that the projectiles "know" what other projectiles are doing and that wave particle duality truly exists?

  • Electron moving through the single slit:

    It's respective magnetic field interacts with the magnetic fields of the electrons in the atoms and molecules surrounding the slit. The interaction of magnetic fields causes the electron to go where it goes.

  • Been watching these lectures on YouTube since I was 19! Really helped me grasp a bigger picture and more general view of things while working through the minutiae of specific homework problems and whatnot while doing physics in college. Thanks for making these!

  • I LOVE this dude, keeps it simple, explains it like Im 5 😛
    [insert reddit plug} xD
    And that's all thats NEEDED.

    good gravy, and here my professor is practically speaking cling on in class.
    keep it simple like we're NEW to the topic, which, we ARE.
    dont muddle high profile words when it can be explained like THIS.

    Complicated concepts broken down into SIMPLE terms. thats how teaching SHOULD be.
    not YOU ciphering what the teacher has to say and then you going off to LEARN the other 80% of the material 😐

    SO I like this guy ! ♥♥

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