Einstein's General Theory of Relativity | Lecture 5

[sssandhu78]

I get a kick everytime he says "everwheres"

[adelle0001]

nice one! thanks

[agapitoflores001]

Einstein id my idol. I bet he's the professors idol too. LOL

[EinsteinsApprentice1]

I got an A- in this course.

[necroforest]

Susskind drinking game: take a shot every time he says "everywheres"

[gikiian]

Views decrease as the no. of lecture increases!

[gikiian]

Which textbook does he use?

[csmcmillion]

@gikiian None. He gives the class copies of his notes.

[jpknie]

Ha ha, the crowd is still. That's Funny :) (in some way)

[StudyAcademic]

what is gamma? 

[StudyAcademic]

General Relativity is all about Calculus and Tensor Calculus...no relativity at all

[floopsie666]

@StudyAcademic You obviously don't understand relativity then. The fact that GR distinguishes between proper time and coordinate time is one of its central relativistic features. All of SR applies in local inertial frames in GR.

[StudyAcademic]

@floopsie666

I know but it's 5th lecture and all he talks is some tricky mathematics. He doesn't talk about relativity at all.

I've got a question: why time slows as you move faster? how can time slow down or stop?

[bigbobgotu]

@StudyAcademic it slows to protect the cosmic "speed limit" what is the speed of light, so it slows down so u cant go over that

[ClamCrunchy]

Do they have lectures past Lec. 7?

[ozkansafak]

why is the ordinary derivative of a tensor not a tensor ?!? Didn't get it..

[SpiritualAtheist]

@ozkansafak I'm not sure if I've got this right, but I think the ordinary derivative describes the change of a tensor relative to a particular coordinate system. The gammas describe how that coordinate system changes relative to the metric. So if the metric causes the coordinates to change, that will change the tensor, which should remain invariant. So you have the gammas to account for any change to the coordinates due to the metric.

Of course, I could be totally wrong about all that.

[floopsie666]

@SpiritualAtheist The christoffel symbols account for the change in the bases for the particular coordinate system. In Euclidean 4 - space one does not need to worry about this because the bases are orthonormal but this is not true in general such as in spherical polar coordinates. Therefore, the covariant derivative accounts for the relative change of the basis vectors and/or dual basis vectors.

[GammahooX]

@ozkansafak Because its the change of the Tensor's components relative to the coordinates. If it was a Tensor then it should be 0 in all coordinate systems if its 0 in one. However a Tensor that is constant in one coordinate system could be varying in a different coordinate system simply because the axes are varying.

[wizardofmadness]

If the theta component is 0, the (unit) vector should lie on the x axis.

[gur0004]

lol How these students concentrate for almost 2hrs sitting in a Lecture. A BIT TOO MUCH I Recon.

[bhigr]

He's a fantastic teacher!

[oringent]

lol 5 lectures on general relativity without any general relativity

[floopsie666]

@oringent You can't jump into maxwell's equations without knowing what divergence and curl are. You can't jump into quantum mechanics without knowing what wave equations are. You can't jump into general relativity without knowing how tensors work.

[lukequixotesanjose]

@floopsie666

Well said. To study general relativity usually means one has to study tensor calculus first.

[SpecterReflector]

most questions asked are not really questions.

[keycomedy]

omg this is the longest video i ever seen!

[fermista]

@keycomedy You mean you've never seen The Return of the King? You poor thing! :P

[EsatBrahimLodi]

He might have been operating with affine connections which are the negative of the ones you would normally see. However at 1:10:00 he uses the usual sign for the Christoffel Symbols. Therefore I guess Susskind made a small error. All the same he is a great lecturer.

[ExhumedANDConsumed]

All of my tensor calculus books state the covariant derivative of a covariant tensor has a negative sign in front of the gamma and the covariant derivative of a contravariant tensor has a positive sign. So did Susskind make a small error when he wrote down that version or am I just misunderstanding?

[grootkanoniek]

@ExhumedANDConsumed

So your connection coeffincents are minus his coefficients;). That doesn't change the math;)

Cheers

[ShootBigBird]

And mathematics isn't reality either! Of course they're not THE forces.

[ibreakkidslegs]

lol that dude asking questions is a total tard

[mizantrop12]

There's always one tard asking stupid questions.

[ibreakkidslegs]

yea i noticed. im auditing a GR course this year and we have an old tard asking stupid questions

[greg5566]

This guy is a fucking great teacher.

[ibreakkidslegs]

hes brutal at putting equal signs where they shouldnt be

[ShootBigBird]

FYI. Whats important to note here is that the Christoffel symbols represent the forces, not just gravitation, ergo the many different symbols with set values attached to each. So the symbols (values) may remain constant, even though spacetime (the metric) around it may be changing. The term connection symbolizes the constancy whether in flat space or curved space. Laws are universal, gravity fields change.

[ShootBigBird]

Just so you know, over the 5 lessons so far, we have covered Gauss (extrinsic geometry), Riemann (the metric), Minkowski (d(tau)^2 products), Ricci-Curbastro/Levi-Civita (covariant calculus) and now Christoffel (forces in tensors). Einstein has yet to rate a mention. The field equations (later) came from Hilbert who was himself working on gravitation.

[winfriedstar]

the staement fucks up.

i can it better

[forgotaboutbre]

Anything we don't understand is boring. It's the same reason that a lot of women don't like football.

[12elza12]

women understand football. they just don't see any sence in watching it.

[forgotaboutbre]

True but my case is not against women but rather my case is that we often dismiss what we do not understand as "boring". We value what is instantaneously stimulating more than patience and learning and self discovery.

[listminusv]

wow....these are most excellent!!! I wish I saw these at the beginning of the year....sitting my relativity exam next week!! thankyou prof susskind!! excellent.....everyone should know about these lectures!!!

[sodiumcrapolate]

I'm confused about one point. He says that the word covariant in covariant derivative has nothing to do with covariance as in covariant tensor. But I understand that taking the covariant derivative of a tensor yields a tensor with one more covariant indice; increasing the rank of the tensor by one. He has totally avoided this notion by using del ?? I am used to the comma notation.

[listminusv]

methinks del is the same as using the comma

[KinStrategy]

This is really a very generous gift to the community of those interested in learning. Thank you for posting these videos, professor!

[djwalsh101]

mez lernd lots tank ya vry moch!

[xCookiex3]

lol...I thought the tracker was broken...o.o Because the video is so long. xD

[EuroCarfan00]

Is it true, that you can actually represent any visual object as a mathematical equation???

[cr3rzemJest]

i think this is stupid question...

[elmeromero123456789]

THANKS FOR THESE VIDEOS

[SixFt12]

He sounds like Christopher Walken!!!

[irfaanfr9]

thanks 4 postin' these videos

[dickbeck]

Thank you for giving me a view into a world I've had an interest in since my undergraduate days but have never had the time to study seriously. Your Physics Videos are a real joy and I might add, a powerfull motivator. Thanks again.

[rusurazvan]

are you nuts?there is a on hour video!

[russelljbarry15]

Thank you for posting these. I have been learning this on my own and missed some of the basic ideas. Please post the rest, I really thank you for posting these.

The few ideas I missed by learning on my own were conceptual Ideas that really make a big change in how I Understand GR.

Thanks again !!!!

[clearview007]

thank you for these videos, could you please please please please upload the rest. thanks once again

[1234spankymc]

I'm looking forward to seeing the remaining videos once they get uploaded!

[1234spankymc]

Can you please upload the rest of the lecture series? I am really enjoying these videos. Thanks.