(October 15, 2012) Leonard Susskind moves the course into discussions of gravity and basic gravitational fields. The Fall 2012 quarter of the Modern Physics …
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26 Responses to “General Relativity Lecture 4”

  • Elliott X:

    America….as it is…not the ramblings of the uneducated no matter where their country of origin

  • Raymond K Petry:

    And for a little more clarity I’ll bi-clarify that last clarification and point out that before the stretched string breaks it emits heat F×D=W by Hook’s Law which has to be an interesting result from SR that accelerated objects heat-up…. 2. Only if accelerating the string in the co-moving frame converts, its rest mass, to kinetic energy, and thereby lengthens its momentum wavelength, should it stretch without breaking; But such ‘affectation’ is not expected, of the greater mass pulling it….

  • Raymond K Petry:

    I’d agree but only in a minor way because it’s basically Riemannian geometry considerations… I’d fix the notation and move the counterclockwise “upstairs” contravariant superscript to the base symbol leftside evenly with the rightside.

  • Raymond K Petry:

    To complete that statement about the string breaking or-not, Note that time in the relative frame, by SR-calculation, remains zero-offset: so, at a given time, the string is, being stretched the greater distance… Then, the only question is whether or not the string might ‘stretch’ due to ‘spooky action at a distance…’ But the answer to that is, QM requires the stretched atom to want to fall back and so break the string; Also constant acceleration changes wavelengths to lock-in possibilities.

  • Raymond K Petry:

    1. “Flat” applies also to 8-ary space (“octonion”), in which case it’s not limited, but for convention, to just-1-or-3 negative-1′s, but to 1-or-7 negative-1′s… Or any other n-ary.

    2. To suppose that the string would not,-break because it’s merely a Minkowski space transformation, would be comparable to saying the returning-relativistic-Twin was not-younger… Some of the SR results are going to yield “true” changes, others virtual… (I know, Susskind says we don’t-say “SR” but do-say “GR”.)

  • Gazmend Ceno:

    I think relativity should be revised in order to survive the next 20 years.

  • Jeesubmyunu:

    No. If there your coordinate system is curvilinear whilst describing a flat space then the christoffel symbol can have nonzero values that still imply there is a flat space. He went over this.

  • Alec Brady:

    No, it just means your coordinates aren’t Cartesian. Try it – work out the Christoffel symbols in 2 dimensions for ordinary polar coordinates.

  • Adam Francis:

    The origin represents the centre of a gravitating object or the point around which an accelerated frame is moving. For large R the acceleration of the frame tends to zero.

  • therealjordiano:

    starting to make sense :) thanks for these

  • interstellarmonkey:


  • Santosh kumar:

    yea heres my doubt ! – well apart from R being equal to 1 over A, isnt R physically the distance of “something” from Origin ? if so what is that “something” and what does a really large R mean ??

  • emdeth:

    Leonard Susskind=I+M+N/nirvana 

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  • ctressle:

    OK I was hoping at the end when he asked that question, I would get an answer. I know that A = 1/R, to get a modest A = g (w/ c = 1) we should use very big R. But what is the inuition of a big R? If modest A correlates to our everyday feel of g, what does R correspond to in such experience? An alien very far away seeing the effects of our gravity? Because the radius of the earth isn’t that big!

  • thebaltbaby:


  • steven antal:

    Love your lectures.

  • MooseIce:

    No no no! He forgot to account for the relationship between gravitational rationalism and quantum special mechanics where the vector(regardless of its coordinates) affects only object in non association to the laws of kribergs third set of universal formulas..

  • Umar Khan:

    Aspiring to learn more

  • Test channel. failure.:


  • On3Thought:

    Sleep, Party and get your GED. And you shall be endowed with knowledge.

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