@dbob1048 nerdy? why nerdy? it's called; interested in the world in which you live! And you can follow this lectures to understand the world around you. I study psychology, I'm 18 and I hate it. I love physics but I made the wrong choice by dropping physics in highschool (I live in the Netherlands so I can drop subjects, not sure how that works in America).
Slow paced, but gives a very solid foundation for the topic. Very thorough. Seems like accelerating reference frame comes from the non-zero divergence of the field. Otherwise what sense does it make to say it's accelerating , but nothing is really moving or gaining velocity. Is space accelerating into the mass? How can we have acceleration without velocity change? Maybe future lecture will address this...
@stenniswood if space itself is converging into point masses then where is it going to? Another universe? As raw material for the expanding edges of our universe?
@MrAlutchman76 - well the first thing that comes to mind is 'time'. It's the other variable which is affected by acceleration. So it would seem that matter is a converter of space into time. Whatever matter is, it somehow eats space and turns it into time. And it must take a lot of space to insert a little bit of time. Time slows down (dilation) in gravitational fields and space disappears. Reminds me of 'yeast' which converts sugar into alcohol.
@stenniswood if space itself is converging into point masses then where is it going to? Another universe? As raw material for the expanding edges of our universe?
Awesome... Anyone else here wanna mail him a thankyou letter? Help me find his e-mail... What an amazing theorist<< I promise I'll keep your work alive Professor Susskind!
What??? i've los almost 4 hours watching the first lecture and this one and when he finally stops talking about Newtonian Gravitation and is suposed to begin talking about general relativity, he says "Idon't wanna talk about relativity, I wanna talk about geometry!" ..... I mean, don't make me waste my time.
I don`t mean to dksrespect, specially when it's about Prof. Susskind, because I admire him.... but come'on
@tonyxon You can't understand general relativity without a deep understanding of geometry. Don't criticize if you don't know anything about this subject
@tonyxon general relativity is the disturbance of fourth dimensional spatial dimensions that make up space-time in the presence of mass, i would take time to listen to the fundamentals.
I didn't read through all of the comments, so I apologize if this has already been addressed. He gets the surface integral right, but not the volume integral. That integral is still the integral of del dot A, which is still -4piGrho. -4piG is constant, and the volume integral of rho is just M. Now the 4pi cancels and the R^2 from the other side makes A=-GM/R^2, as it of course must. The actual mistake happens around 45:00 when he's writing the right side of the equation.
I guess I should have said that M is the mass enclosed by the Gaussian surface. You really only have to find that equation once: if R is less than the planetary radius, the only contribution to the acceleration is the mass "below" (ie within R) the test mass, and if R is greater than the planetary radius, the mass enclosed is the total mass, so the whole planet contributes to the acceleration.
THE DARK MATTER IS THE QUANTUM PARTICLE OF FOTONS IN DESSACELERATION , THE ENTROPY IS THE QUANTIC-DISSIPATION OF FOTON THAT TRANSFORM LIGHT IN SHADOW ??? THE SPARKS OF FIRE WHEN PLUG OUT DISSAPEARENCE WHEN DIEN !!! MATTER = LIGTH AND/&/UND ANTI-MATTER SHADOW ??? - LANAROARTESANO@GMAIL.COM
Hola. Yo necesito tu correo electrónico para yo enviarle a usted una nueva idea acerca de una posible nueva ecuación para la energía cinética relativista. Gracias por tu atención. Atentamente: José Gregorio Guevara Pérez desde la ciudad de Valencia, pais Venezuela. Mi correo electrónico es JGGP36@Yahoo.com.
English language, translated from the Spanish language by Babel Fish.
Hello. I need your electronic mail I to send to you a new idea about a possible new equation for the relativistic kinetic energy. Thanks for your attention. Kindly: Jose Gregorio Guevara Perez from the city of Valencia, Venezuela country. My electronic mail is JGGP36@Yahoo.com.
I honestly don't know how these students go to Stanford, and how Dr. Susskind has the patience to answer them. He deserves better students with significantly SMALLER egos!
Dear Stanford Admissions, give me a chance to revolutionize the scientific world!
The first time I watched this, I immediately took that question at 13:45 to be the usual confusion between DE and DM. That *seems* to me to be the way Professor Susskind took it. But this time through, it occurs to me to wonder if he's also saying that even the graviton is not involved in the repulsive force.
I am amazed by the thousands of scientists and students who (to varying degrees), since 1915, learned and mastered all the subtleties of Einstein's Theory of General Relativity.
It just make me smile every time Prof. Susskind call the white board "black board". Other than that he's such a great educator. I wish i can attend his classes one day.
I don't really see the simplicity of Gauss's Law over Newton's equations... it seems the only benefit is in being able to calculate accelerations inside of spherical masses? But once outside the sphere, they both treat masses at point sources, and Newton's equation allows you to sum up any number of particles... whereas I don't see how you would do this with Gauss's Law / Theorem? i.e. It seems the integral of mass density over a sphereical volume would only work for one particle?
When he is approximating the angle the light ray gets deflected, why does he not take the inverse tangent of the y-comp velocity over the x-comp velocity? Is it because the values are almost the same?
@babashroud for small angles tan^-1(O/A) is approximately equal to just O/A, where O is the opposite side length to the angle and A is the adjacent side length to the angle, for angles less than 17 degrees this is accurate to 2 decimal places, and the smaller the angle gets the more accurate the approximation is
@rollingstoneblues These students aren't regular college students. They're old people taking night classes. I guarantee you that the average Stanford student taking a GR course is orders of magnitude smarter than any of the 'students' in this video.
D: Thank you so much! I've been struggling with my GR course at the moment because the lecturer, lovely as he is, doesn't explain things as well as he should. Now I understand what the metric actually is and as a result why there's two indices on it and why it's used in finding the lengths of things. "to bring the indices up and down" was the explanation given which left me frustrated. Thanks again! :)
Free energy can change the world!But Millions are spend in supressing that information,Get a real free energy motor at LT-MAGNET-MOTORdotCOM ,Be a part of the energy revolution!
Mr.Boarder we cant use planetgravity for spaceshipacceleration to mars !
. the reason is you have to leave our planet to mars like you have to leave our planet into space short above our atmosphereboarder similar to a flight to our moon. We only have time and little bonus !
SOMETIME our lectures goes slower. do we have slowmotion for youtube ?
Mr.Boarder we cant use planetgravity for spaceshipacceleration to mars !
. the reason is you have to leave our planet to mars like you have to leave our planet into space short above our atmosphereboarder similar to a flight to our moon. We only have time and little bonus !
SOMETIME our lectures goes slower. do we have slowmotion for youtube ?
i got a question: when he talked about the gravitational field inside the earth, he said that the acceleration grows linearly with the distance (as the equation shows), but shouldnt the acceleration get smaller with the distance since the mass (to reasons unclear to me) isnt a factor? (only the tensity was and we took that as constant)
if the question is unclear pls let me try to rephrase it, im not a native speaker...
@gulaschsuppm ah, i think i got it. i wrote befor really thinking about it. the force grows when you get closer to the earth but the acceleration decreases.
Acceleration because of mass grows with density times the new volume as you go out (which goes as the radius cubed), but the acceleration falls off with the radius squared (from Newton's equation). After all these things are taken into account, as you go out from the center of the sphere, you gain acceleration equal to the density times the volume (r^3) divided by the r^2 falloff, for a total gain of r^1 while you're moving outward from the sphere and gaining mass as the density.
Take note that in the discussion of the gravitational field at some radius R inside the earth taken from the center of the earth, that Leonard had dropped a 4pi. Perhaps you may have caught this. So, the g field at radius R inside the earth is actually: G*p*pi*R*4/3
the cosmological constant may not, itself, increase with time. however the force it exerts on the universe obviously does as the universe increases in size. dark energy has created the increase in expansion for only 2 billion years- it could very well be a 5th fundamental force that is decoupling from the gravitational force. if this is true then, eventually it should increase with time exponentially for a brief time, t => 0,causing a second inflation.it will then become a true constant.
i got this book called A BRIEF HISTORY OF TIME BY STEPHEN HAWKING ALL HIS LECTURES ARE RELATED TO IT VERY DEEPLY MANY PHRASES THAT THIS PROF USES ARE IN THE BOOK I THINK HE READ IT OR MEMORIZED IT BUT STILL WHEN I HOLD THE BOOK IN MY HAND AND START READING AS I HEAR HIM IT BECOMES MORE CLEAR.
At 47.39 time to reach earth's centre is t = sqrt(2r/g) where r = radius of earth. Assumes no terminal velocity due to wind resistance and acceleration constant at 10 m/s2. If r is 5 miliion metres, this gives over 4000 seconds - periodic time is thus 16000 sec or about 5hrs. Without the 2 (unreallistic) assumptions of course period is much longer
It isn't difficult to get the eqn without calculus
@BRAIDERMAN The questioning students were right. The first time he did it, with the gaussian sphere outside the earth, -4piGM=A4piR^2 was simplified to -GM=AR^2. Good. But both times he does the gaussian sphere inside the earth, he takes the left side of the equation post-simplification, and the right side of the equation before it's simplified. Giving him -G(M)=A4piR^2. He skips that step I just wrote, instead writing out the mass: -G(4/3 * pi * R^3 * p) = A4piR^2.
We're coming into a new era with the internet education. Susskind is one of the greatest teachers available, togehter with a handful others, and I'm very grateful that his lectures are freely available online.
I'm 40 yo, regrettably didn't find physics back in the school days, but I've had an exploding interest in physics the last 3-4 years. Now there's the math barrier - luckily, I've taken all the required maths during my education, so some refreshment is needed.
In my reasoning..There could not had been a true 100 per cent birth or beginning of the universe! Because..that would mean that there would be a time of neverness! Neverness can't be because in order to have a neverness the universe can't be here today. So that means the big bang was only a beginning of a new cycle. Before it, it was the finishing of an older prior universe..
This is great! I always wanted to get into the math part of The theorty but I"m not keen in math. I find it easy here to follow the Pro teacher and I like the way he presents his instuction. Yes these students should wait until break to ask questions or when the prof asks them for any..This bit of pestering is probberly the cause of his little typo re-do's mishaps! Anyway He knows his stuff. and.Thanks You tube.
I think it would be better if the students hold their questions to submitted notes to be later answered by the Prof's assistants. Too much waste of his time answering lame questions by students who haven't done enough pre-study.
Think of the underlying law of nature. The way of all things.
Consider its astounding inferences and implications.
The single, underlying law ... of nature! Not merely of physics, chemistry, psychology, biology, etc., but of all known fields of inquiry. The law we can all relate to, identify, understand and apply.
Ask yourself. What is the underlying law of nature?
Delight in the question. Have fun in the process of finding the answer firsthand for yourself.
This comment has received too many negative votesshow
A small amount of Dark Energy can supply massive amount of energy. In a New Atomic process. Wm Andrews Discoverer of a Vacuum Universe. and Hydro-Magnetic fission energy. Your wrong !
@Ykoahi Yeap, these guys have difficulties understanding divergence, etc. concepsts from the first year university, however they want to ask "very fancy" (popular) questions about dark energy, etc. It is hard to discuss basics with adults, 'cause they survived professionally without these concepts (left far in the past), and they do not want to go through them (if they barely didi it as kids, it will not be this time...).
It's a privilege to see this man teach. Sure I learned all this at my university, but it's only now that I can say I'm beginning to understand any of it.
Thanks to Google, YouTube and the internet technology researchers who made this possible to watch these videos. Otherwise I had no chance to see this lecture series.
@snaveedimran In a lot of European countries University is free. But perhaps you're from the US. So you'll have to rely on the generousity of private companies. That's a shame in a rich country like the US.
@pi05pm3 Education is never free, even if the government provides it. It's economically naive to say otherwise. Also, private companies are the *reason* the US got rich in the first place.
@fermista Well for me free is free when something doesn't cost you anything. Then of course the government pays the Universities and the taxpayers pays the government through taxes. But on an individual level it is free.
Further, the *reason* might as well be the people who's been working for the companies.
Anyhow, it's great that they post videos like this for free :)
@pi05pm3 It is! It's extremely helpful to have free open-courseware like this available, especially since I'm planning on doing my PhD in theoretical physics next year ;)
both of you are correct but if you listen (or interpret ^_^) correctly Prof. Susskind's argument he is comparing the velocity of the accelerated light ray moving at speed:
v=g.t
to the unaccelerated light ray moving in a straight ("horizontal") line at velocity c.
Both arguments are approximated but do give the same "order" result: which is all that matters, numerical constants do not matter since they can be absorbed by scaling.
The reason the student is getting confused in this lecture is because Susskind uses big R on both the left and right board, but they are not the same, R is < than the one on the right because the shell is inside the earth, when you break the rho for density down, that brings out the actual earth radius that is used on the right board.
It is the sin(x) = 2MG/Rc^2 with x=2MG/Rc^2 that is used for the aproximation, also there is other aproximation, that for the elapsed time delta t, it is taken as the horizontal component of speed of light is the same c, that can be appear as a logic circle (that is not), since for this is used the a posteriori known fact that the angle is too small, and in the former the use of values of G and c are used to aproximate sinx =x.
The "replusive component" of gravity he's talking about is described in MOG, modified gravity theory by John Moffatt. He wrote a book on it called, "Reinventing Gravity," and he proposes all of the characteristics professor susskind is describing.
I Love this Video and also I checked out your Channel. Very interesting! If you need any help getting this Video and your Channel exposed to were it is top in all the search I found this site called tubeviews.(net) that has took my breath away. I'm working on my 4th Channel now, this one I just made. My Videos are getting so many hits now. Check it out and keep in touch.
Since the theory of relativity allows for time travel, understanding that the technology doesn't exsist yet but may in the future, if the rip will occure could you escape it if you continued to go back in time when the unvirse was more suitably for life?
Here's all you need to know about Einsteins General Relativity (I feel like he's channeling through me to say this). You sit with a beautiful woman for 1 hour and it seems like one minute , you sit on a hot stove for 1 second and it seems like an hour..THAT's Relativity :)
Time really does relatively fly when you're having fun
You don't have to argue that statement!!! That's how General Relativity tries to give an easy concept to everybody...So, about the disease or pain or whatever you wrote, It'll just mess up this page...
I dont get it
chris69calderon 1 month ago in playlist More videos from StanfordUniversity
Think the theorization of time is due to space constantly expanding?
RonaldRichardson3 1 month ago in playlist Course | Modern Physics: Einstein's Theory
im an engineer but watching this stuff kinda makes me wish i chose physics, as nerdy as it sounds this stuff is fucken cool! thankyou lenard susskind
dbob1048 1 month ago
@dbob1048 nerdy? why nerdy? it's called; interested in the world in which you live! And you can follow this lectures to understand the world around you. I study psychology, I'm 18 and I hate it. I love physics but I made the wrong choice by dropping physics in highschool (I live in the Netherlands so I can drop subjects, not sure how that works in America).
Jipzorowns 1 month ago
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Great video! More please!
grunder20 2 months ago
Slow paced, but gives a very solid foundation for the topic. Very thorough. Seems like accelerating reference frame comes from the non-zero divergence of the field. Otherwise what sense does it make to say it's accelerating , but nothing is really moving or gaining velocity. Is space accelerating into the mass? How can we have acceleration without velocity change? Maybe future lecture will address this...
stenniswood 3 months ago
@stenniswood if space itself is converging into point masses then where is it going to? Another universe? As raw material for the expanding edges of our universe?
MrAlutchman76 2 months ago
@MrAlutchman76 - well the first thing that comes to mind is 'time'. It's the other variable which is affected by acceleration. So it would seem that matter is a converter of space into time. Whatever matter is, it somehow eats space and turns it into time. And it must take a lot of space to insert a little bit of time. Time slows down (dilation) in gravitational fields and space disappears. Reminds me of 'yeast' which converts sugar into alcohol.
stenniswood 2 months ago
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@stenniswood if space itself is converging into point masses then where is it going to? Another universe? As raw material for the expanding edges of our universe?
MrAlutchman76 2 months ago
Damn, it is reaaaally slow paced Oo"
Is it supposed to be adressed to Bachelors students ?
55Icarus55 3 months ago
thank u so much for the videos..:)
meena2r 3 months ago
so hes a jew? interesting how his life now and e=mc² are connected in many ways then. O.O
oooodaxteroooo 3 months ago
Awesome... Anyone else here wanna mail him a thankyou letter? Help me find his e-mail... What an amazing theorist<< I promise I'll keep your work alive Professor Susskind!
aqouby 5 months ago
What??? i've los almost 4 hours watching the first lecture and this one and when he finally stops talking about Newtonian Gravitation and is suposed to begin talking about general relativity, he says "Idon't wanna talk about relativity, I wanna talk about geometry!" ..... I mean, don't make me waste my time.
I don`t mean to dksrespect, specially when it's about Prof. Susskind, because I admire him.... but come'on
tonyxon 5 months ago
@tonyxon You can't understand general relativity without a deep understanding of geometry. Don't criticize if you don't know anything about this subject
asierraalta7 5 months ago
@tonyxon That little round button at the bottom of the Flash display does something called "seeking". Try it out.
csmcmillion 4 months ago
@tonyxon general relativity is the disturbance of fourth dimensional spatial dimensions that make up space-time in the presence of mass, i would take time to listen to the fundamentals.
xXGoDxiSxdEaDx666Xx 4 months ago
Respond to this video... i meant spatial geometry*
xXGoDxiSxdEaDx666Xx 4 months ago
I didn't read through all of the comments, so I apologize if this has already been addressed. He gets the surface integral right, but not the volume integral. That integral is still the integral of del dot A, which is still -4piGrho. -4piG is constant, and the volume integral of rho is just M. Now the 4pi cancels and the R^2 from the other side makes A=-GM/R^2, as it of course must. The actual mistake happens around 45:00 when he's writing the right side of the equation.
zjak8 7 months ago
@zjak8
I guess I should have said that M is the mass enclosed by the Gaussian surface. You really only have to find that equation once: if R is less than the planetary radius, the only contribution to the acceleration is the mass "below" (ie within R) the test mass, and if R is greater than the planetary radius, the mass enclosed is the total mass, so the whole planet contributes to the acceleration.
zjak8 7 months ago
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zjak8 7 months ago
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Freedomloveandtruth 7 months ago
he lost a 4pi.
hasuchObe 9 months ago 5
just don't bother my pink pig in class he'll get mad.
timeisthekiller 9 months ago
May I bring my farm pig to science class?
timeisthekiller 9 months ago
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THE DARK MATTER IS THE QUANTUM PARTICLE OF FOTONS IN DESSACELERATION , THE ENTROPY IS THE QUANTIC-DISSIPATION OF FOTON THAT TRANSFORM LIGHT IN SHADOW ??? THE SPARKS OF FIRE WHEN PLUG OUT DISSAPEARENCE WHEN DIEN !!! MATTER = LIGTH AND/&/UND ANTI-MATTER SHADOW ??? - LANAROARTESANO@GMAIL.COM
lanaroartesano 9 months ago
Spanish (Original).
Hola. Yo necesito tu correo electrónico para yo enviarle a usted una nueva idea acerca de una posible nueva ecuación para la energía cinética relativista. Gracias por tu atención. Atentamente: José Gregorio Guevara Pérez desde la ciudad de Valencia, pais Venezuela. Mi correo electrónico es JGGP36@Yahoo.com.
jggp444 10 months ago
English language, translated from the Spanish language by Babel Fish.
Hello. I need your electronic mail I to send to you a new idea about a possible new equation for the relativistic kinetic energy. Thanks for your attention. Kindly: Jose Gregorio Guevara Perez from the city of Valencia, Venezuela country. My electronic mail is JGGP36@Yahoo.com.
jggp444 10 months ago
This lecture sponsored by: TD ameritrade
JesseLH88 10 months ago
I honestly don't know how these students go to Stanford, and how Dr. Susskind has the patience to answer them. He deserves better students with significantly SMALLER egos!
Dear Stanford Admissions, give me a chance to revolutionize the scientific world!
leeamsi 10 months ago
@leeamsi it's a continuing education class. They are not students.
Fand421 10 months ago
The first time I watched this, I immediately took that question at 13:45 to be the usual confusion between DE and DM. That *seems* to me to be the way Professor Susskind took it. But this time through, it occurs to me to wonder if he's also saying that even the graviton is not involved in the repulsive force.
sbergman27 11 months ago
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We hit it off so well after another visit busizz4me.info
sasinihsani 11 months ago
I am amazed by the thousands of scientists and students who (to varying degrees), since 1915, learned and mastered all the subtleties of Einstein's Theory of General Relativity.
mphello 11 months ago
i love susskind lol
paulojunior201 11 months ago
Comment removed
DaneAlexTV 1 year ago
It just make me smile every time Prof. Susskind call the white board "black board". Other than that he's such a great educator. I wish i can attend his classes one day.
quantomic1106 1 year ago
The person wondering about the 4pi that doesn't cancel is correct. The equation should have been:
A 4pi r^2=(-4pi G)(4/3 pi rho r^3)
which means A = -4/3 G pi rho r
elfmotat 1 year ago 4
Why do the people ask so many stupid questions? They aggravate me!
FunnyGeese 1 year ago
I don't really see the simplicity of Gauss's Law over Newton's equations... it seems the only benefit is in being able to calculate accelerations inside of spherical masses? But once outside the sphere, they both treat masses at point sources, and Newton's equation allows you to sum up any number of particles... whereas I don't see how you would do this with Gauss's Law / Theorem? i.e. It seems the integral of mass density over a sphereical volume would only work for one particle?
jamesdowns72 1 year ago
Excellent lecture. Very understandable and very thorough. What a treat to be able to access this.
jdtoellner 1 year ago
Einstein Made a Mistake... Fabric of Space and Time is only a Fabricated theory.. there is no Dark Energy.. it's only a Force of Space Compressions.
UnifiedPhysics 1 year ago
When he is approximating the angle the light ray gets deflected, why does he not take the inverse tangent of the y-comp velocity over the x-comp velocity? Is it because the values are almost the same?
babashroud 1 year ago
@babashroud Exactly right; probably also because the angle expressed as a simple ratio is a more intuitive number than a number involving a tangent.
Mattprole 1 year ago
@babashroud for small angles tan^-1(O/A) is approximately equal to just O/A, where O is the opposite side length to the angle and A is the adjacent side length to the angle, for angles less than 17 degrees this is accurate to 2 decimal places, and the smaller the angle gets the more accurate the approximation is
bendelafrance 9 months ago
Does Dark matter have dark energy? is it related in some ways?
DeadBodyOutline 1 year ago
haha
less than a quarter made it to the next video
bluewhale18 1 year ago
"I guess I should elaborate on what I mean by relative" lmao, you don't even understand what you're asking? dear god keep your fucking hand down then
ibreakkidslegs 1 year ago
@rollingstoneblues These students aren't regular college students. They're old people taking night classes. I guarantee you that the average Stanford student taking a GR course is orders of magnitude smarter than any of the 'students' in this video.
shadycharacter 1 year ago
To me this "dark mater" sounds very similar to the luminiferous ether. What evidences we have about it?
anonimoculto 1 year ago
Mrmig I guess you're a pathetic american! Yet another online loser! Get back to jackin off over online porn and your pathetic life. Loser!
rollingstoneblues 1 year ago
D: Thank you so much! I've been struggling with my GR course at the moment because the lecturer, lovely as he is, doesn't explain things as well as he should. Now I understand what the metric actually is and as a result why there's two indices on it and why it's used in finding the lengths of things. "to bring the indices up and down" was the explanation given which left me frustrated. Thanks again! :)
SeraphWolf 1 year ago
Heartfelt thanks to Professor Susskind and Stanford for making these beautiful ideas available to me. I am following all of the series.
mynyddwrglas 1 year ago 44
And the comments relating to the student questions seem a bit boorish too, don't you think?
jamesmongo 1 year ago
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Free energy can change the world!But Millions are spend in supressing that information,Get a real free energy motor at LT-MAGNET-MOTORdotCOM ,Be a part of the energy revolution!
hungarylnnjsd 1 year ago
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Xinroka 1 year ago
These students are low calibre! They can't even re-arrange a simple equation. My grade 9 have a better understanding about simple mathematics
rollingstoneblues 1 year ago
@rollingstoneblues your mom is low calibre in bed
MrMig3 1 year ago
These students are low calibre!
rollingstoneblues 1 year ago
omg wtf is with these questions?
Myster36 1 year ago 2
you can give us feedbacks and resolutions.
Ramy82ify 1 year ago
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Mr.Boarder we cant use planetgravity for spaceshipacceleration to mars !
. the reason is you have to leave our planet to mars like you have to leave our planet into space short above our atmosphereboarder similar to a flight to our moon. We only have time and little bonus !
SOMETIME our lectures goes slower. do we have slowmotion for youtube ?
type me a link
Ramy82ify 1 year ago
This has been flagged as spam show
Mr.Boarder we cant use planetgravity for spaceshipacceleration to mars !
. the reason is you have to leave our planet to mars like you have to leave our planet into space short above our atmosphereboarder similar to a flight to our moon. We only have time and little bonus !
SOMETIME our lectures goes slower. do we have slowmotion for youtube ?
type me a link
Ramy82ify 1 year ago
i got a question: when he talked about the gravitational field inside the earth, he said that the acceleration grows linearly with the distance (as the equation shows), but shouldnt the acceleration get smaller with the distance since the mass (to reasons unclear to me) isnt a factor? (only the tensity was and we took that as constant)
if the question is unclear pls let me try to rephrase it, im not a native speaker...
thanks
gulaschsuppm 1 year ago
@gulaschsuppm ah, i think i got it. i wrote befor really thinking about it. the force grows when you get closer to the earth but the acceleration decreases.
gulaschsuppm 1 year ago
@gulaschsuppm
Acceleration because of mass grows with density times the new volume as you go out (which goes as the radius cubed), but the acceleration falls off with the radius squared (from Newton's equation). After all these things are taken into account, as you go out from the center of the sphere, you gain acceleration equal to the density times the volume (r^3) divided by the r^2 falloff, for a total gain of r^1 while you're moving outward from the sphere and gaining mass as the density.
Iamallthatisman08 1 year ago
@gulaschsuppm anwser us! the gravity seems to be a pig.
Ramy82ify 1 year ago
Take note that in the discussion of the gravitational field at some radius R inside the earth taken from the center of the earth, that Leonard had dropped a 4pi. Perhaps you may have caught this. So, the g field at radius R inside the earth is actually: G*p*pi*R*4/3
charliepontecorvo 1 year ago
shit, he's the slowest teacher i've seen in my life
jimmykilledkeith 1 year ago
@jimmykilledkeith
Who taught you? light?
TheSaintPain 1 year ago
the cosmological constant may not, itself, increase with time. however the force it exerts on the universe obviously does as the universe increases in size. dark energy has created the increase in expansion for only 2 billion years- it could very well be a 5th fundamental force that is decoupling from the gravitational force. if this is true then, eventually it should increase with time exponentially for a brief time, t => 0,causing a second inflation.it will then become a true constant.
SpecterReflector 1 year ago
Thanks for posting these lectures by Dr. Susskind
TexasWorldMusic 1 year ago
Thanks Stanford University for posting these lectures
TexasWorldMusic 1 year ago
saw when he messed up....he canceled out the 4 pi's
momez86 1 year ago
calculus 3 makes sense now ;)
karolCalculus 1 year ago
18:04 never forget
karmatik1 1 year ago
Thanks a lot to Standford University, it's dificult to find the RG theory...
thanks from Peru. Greetings
JKARSKYFULL 1 year ago
i got this book called A BRIEF HISTORY OF TIME BY STEPHEN HAWKING ALL HIS LECTURES ARE RELATED TO IT VERY DEEPLY MANY PHRASES THAT THIS PROF USES ARE IN THE BOOK I THINK HE READ IT OR MEMORIZED IT BUT STILL WHEN I HOLD THE BOOK IN MY HAND AND START READING AS I HEAR HIM IT BECOMES MORE CLEAR.
baaroodii 1 year ago
hey where is the closed captioning??
karmatik1 1 year ago
the clip stalls at 0:45:14
007MOORER 1 year ago
At 47.39 time to reach earth's centre is t = sqrt(2r/g) where r = radius of earth. Assumes no terminal velocity due to wind resistance and acceleration constant at 10 m/s2. If r is 5 miliion metres, this gives over 4000 seconds - periodic time is thus 16000 sec or about 5hrs. Without the 2 (unreallistic) assumptions of course period is much longer
It isn't difficult to get the eqn without calculus
F=MmG/R^2 a=F/m=MG/R^2=4Pi*R^3*density/3
'Accn Density' = a/area = a/4PiR^2 = R*density*G/3
zoroastra999 1 year ago
Thanks to Youtube and Stanford for posting these awesome videos :-)..........really worthwhile!.....oh and thanks to Prof Susskind for his lectures
muaztrek 1 year ago
@BRAIDERMAN The questioning students were right. The first time he did it, with the gaussian sphere outside the earth, -4piGM=A4piR^2 was simplified to -GM=AR^2. Good. But both times he does the gaussian sphere inside the earth, he takes the left side of the equation post-simplification, and the right side of the equation before it's simplified. Giving him -G(M)=A4piR^2. He skips that step I just wrote, instead writing out the mass: -G(4/3 * pi * R^3 * p) = A4piR^2.
SigFigNewton 1 year ago
We're coming into a new era with the internet education. Susskind is one of the greatest teachers available, togehter with a handful others, and I'm very grateful that his lectures are freely available online.
I'm 40 yo, regrettably didn't find physics back in the school days, but I've had an exploding interest in physics the last 3-4 years. Now there's the math barrier - luckily, I've taken all the required maths during my education, so some refreshment is needed.
waperboy 1 year ago
Susskind is the next Einstein!!!!!!!!!!!!!
I say it to him now since Susskind hoped they would of have said that about him many years ago when he wrote the paper on String Theory.
necrom666 1 year ago
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In my reasoning..There could not had been a true 100 per cent birth or beginning of the universe! Because..that would mean that there would be a time of neverness! Neverness can't be because in order to have a neverness the universe can't be here today. So that means the big bang was only a beginning of a new cycle. Before it, it was the finishing of an older prior universe..
JoeyMars1 1 year ago
This is great! I always wanted to get into the math part of The theorty but I"m not keen in math. I find it easy here to follow the Pro teacher and I like the way he presents his instuction. Yes these students should wait until break to ask questions or when the prof asks them for any..This bit of pestering is probberly the cause of his little typo re-do's mishaps! Anyway He knows his stuff. and.Thanks You tube.
JoeyMars1 1 year ago
Ive seriously been looking for real lectures, msg me if u find em!
loamobn 1 year ago
4pi is the most important thing in this whole lecture!!!! geez they need to chill
weweallthewayhome 1 year ago
Good lecture. Easy to follow. Btw, as the student said , it missed the 4pi in the equation. :>
AndyKong51 1 year ago 2
why no subtitle :( :( :( i can't hear all the words he said.
jteik 1 year ago
I think it would be better if the students hold their questions to submitted notes to be later answered by the Prof's assistants. Too much waste of his time answering lame questions by students who haven't done enough pre-study.
BRAIDERMAN 1 year ago
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Think of the underlying law of nature. The way of all things.
Consider its astounding inferences and implications.
The single, underlying law ... of nature! Not merely of physics, chemistry, psychology, biology, etc., but of all known fields of inquiry. The law we can all relate to, identify, understand and apply.
Ask yourself. What is the underlying law of nature?
Delight in the question. Have fun in the process of finding the answer firsthand for yourself.
Google it, as a start.
TedDGPoulos 1 year ago
just like a dream , attending prof. Leonard SUsskind lecture
nickeyae 1 year ago 2
Stops at about 40 minutes no matter how many times I reload :(
ekid2k 1 year ago
@ekid2k
If you click after this 40 minutes on the bar the video load.
I don't now if you can understand what I mean but if you don't please reply and I try to explain in a better way.
Sorry my english is not the best one.
portuguesnanet 1 year ago
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all this will be changed because of global warming
weightSndrumS 2 years ago
( Vacuum / Space / Energy ) Thank God it eneded up in America.
profwmandrews1 2 years ago
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profwmandrews1 2 years ago
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A small amount of Dark Energy can supply massive amount of energy. In a New Atomic process. Wm Andrews Discoverer of a Vacuum Universe. and Hydro-Magnetic fission energy. Your wrong !
profwmandrews1 2 years ago
A Planets mass was never putting pressure on space !.
profwmandrews1 2 years ago
You should learn the difference between your and you're if you want to sound smart on the internet.
akangell 1 year ago 4
Actually no one cares about that ....
XjyujX 1 year ago
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excellent work!
1888junkteam 2 years ago
i love the random questions people ask to try to sound smart during these lectures.
Ykoahi 2 years ago 76
If they are taking a course in general relativity at Stanford I think it's safe to say that they ARE smart.
md65000 2 years ago 2
@Ykoahi
Trying and terribly, terribly failing. :)
LeMegasandwich 1 year ago
@Ykoahi i really hate people like that, there are guys in my physics class who always do that.. omfg. its annoying.
jwliang09 1 year ago
@Ykoahi They aren't trying to sound "smart" by asking questions. They are trying to find the truth.
TokenMatch 1 year ago
@Ykoahi i'm scared of the knowledge of these students... are they really don't GET IT?
junior90210 1 year ago
@Ykoahi Yeap, these guys have difficulties understanding divergence, etc. concepsts from the first year university, however they want to ask "very fancy" (popular) questions about dark energy, etc. It is hard to discuss basics with adults, 'cause they survived professionally without these concepts (left far in the past), and they do not want to go through them (if they barely didi it as kids, it will not be this time...).
zer0s0und 1 year ago
@Ykoahi Yeah they just make themselves sound stooooopid.
cuallito 1 year ago
@cuallito He who asks a question is ignorant for a minute; he who does not ask a question remains ignorant forever.
TheSaintPain 1 year ago
@Ykoahi Yeah, its also always that one white kid. He probably is an arrogant dick too.
idricool 1 year ago
@Ykoahi He who asks a question is ignorant for a minute; he who does not ask a question remains ignorant forever.
TheSaintPain 1 year ago 40
@TheSaintPain
Yes your right, but a question , not random words, somes questions have nothing to do with whats he's saying.
By the way if someone is having trouble understanding this videos take a classical mechanics book, I would suggest the grainer
WShinning 1 year ago
@TheSaintPain He who asks an ignorant question annoys everyone else.
mynameisfingers 4 months ago
@Ykoahi you have never gone to college, right??
marts1233 10 months ago
@marts1233 I made that post a year ago when I was in high school, I've been to college a few times since then.
Ykoahi 10 months ago
It's a privilege to see this man teach. Sure I learned all this at my university, but it's only now that I can say I'm beginning to understand any of it.
karkkilakko 2 years ago
Must be quite an honor to actually be on lectures of that guy.
LapinPete 2 years ago 4
Thanks to Google, YouTube and the internet technology researchers who made this possible to watch these videos. Otherwise I had no chance to see this lecture series.
snaveedimran 2 years ago 79
@snaveedimran In a lot of European countries University is free. But perhaps you're from the US. So you'll have to rely on the generousity of private companies. That's a shame in a rich country like the US.
pi05pm3 1 year ago
@pi05pm3 Education is never free, even if the government provides it. It's economically naive to say otherwise. Also, private companies are the *reason* the US got rich in the first place.
fermista 1 year ago
@fermista Well for me free is free when something doesn't cost you anything. Then of course the government pays the Universities and the taxpayers pays the government through taxes. But on an individual level it is free.
Further, the *reason* might as well be the people who's been working for the companies.
Anyhow, it's great that they post videos like this for free :)
pi05pm3 1 year ago
@pi05pm3 It is! It's extremely helpful to have free open-courseware like this available, especially since I'm planning on doing my PhD in theoretical physics next year ;)
fermista 1 year ago
@sapienmm
both of you are correct but if you listen (or interpret ^_^) correctly Prof. Susskind's argument he is comparing the velocity of the accelerated light ray moving at speed:
v=g.t
to the unaccelerated light ray moving in a straight ("horizontal") line at velocity c.
Both arguments are approximated but do give the same "order" result: which is all that matters, numerical constants do not matter since they can be absorbed by scaling.
TristanTheSaint 2 years ago
thank you. if i had only known about these videos years ago!!!
ravaabyee 2 years ago
it was uploaded this year...
twiistaaa 2 years ago
i absolutely appreciate your videos they are amazingly useful
TheGreenCommunity 2 years ago 6
Thriller moment 1:18:57 :D
618361 2 years ago 2
The angle alpha is wrong by a factor of 2!
One should first calculate the y displacement
y=1/2gt^2 where t=2R/c then take the ratio of
y/x (x=2R) ==> alpha~y/x=MG/(Rc^2) !!
sapienmm 2 years ago
May no so relevant... but is it not funny that he stand before such a big white board and calling it a black board! Sorry, could not resist...
viswas04 2 years ago 4
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What's funny about it? Tell me please, I wanna laugh too! :-)
Charodeiski 2 years ago
woooooooooooooooot i was so excited when he said Cosmological Constant
HeyHeyHarmonicaLuke 2 years ago
The calculation of the gravitation inside of the Earth results in the equation:
4πρGV = A (4πR^2)
4πρG [(4/3) πR^3] = Ap (4πR^2)
(4/3) πρGR = A
Substituting for M = ρV or ρ=M/V makes the gravitation the same at the surface of the Earth.
smh5417 2 years ago
sorry 4pi not 4
johndobson01 2 years ago
the student who was confused was right susskind was off by a factor of 4. because -4piMG=A4piR^2. susskind started his equation as A4piR^2=-MG
johndobson01 2 years ago
The reason the student is getting confused in this lecture is because Susskind uses big R on both the left and right board, but they are not the same, R is < than the one on the right because the shell is inside the earth, when you break the rho for density down, that brings out the actual earth radius that is used on the right board.
ApeOfGod1 2 years ago
It is the sin(x) = 2MG/Rc^2 with x=2MG/Rc^2 that is used for the aproximation, also there is other aproximation, that for the elapsed time delta t, it is taken as the horizontal component of speed of light is the same c, that can be appear as a logic circle (that is not), since for this is used the a posteriori known fact that the angle is too small, and in the former the use of values of G and c are used to aproximate sinx =x.
noelgrade 2 years ago
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this is dumb he cant explain stuff at all and i think he is wrong
JohnRutherford92 2 years ago
So you can do better???
thantheman2010 2 years ago
the only reason that you think that is because you can't understand even this.
iamawesometoo 2 years ago
This series of lectures all flow together. This will be needed when he derives Einstein's tensor. The lectures all flow togeather.
These lectures seem random but they are not. They flow nicely. This lecture series was well thought out. Thanks !!!
russelljbarry15 2 years ago 6
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Revivalist77 2 years ago
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Revivalist77 2 years ago
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Revivalist77 2 years ago
start it about an hour into the video if you aren't interested in a newtonian analysis and just want to get to the general relativity
jc0ng 2 years ago 6
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I know of some courses at Stanford, but will cost you some money for the information
pluyiberto 2 years ago
If anyone know of some Stanford lectures on the Quantum Eraser or Biocentrism, please kindly direct me to them.
mrdandrea 2 years ago 3
The "replusive component" of gravity he's talking about is described in MOG, modified gravity theory by John Moffatt. He wrote a book on it called, "Reinventing Gravity," and he proposes all of the characteristics professor susskind is describing.
deadbaby86 2 years ago
He made a mistake at 1:27:00 , the angle is not equal to 2MG/Rc^2 , the cosinus of the angle is equal to 2MG/Rc^2
sorcerxl 2 years ago
NO...
its --> tangent theta = 2MG/Rc^2
Germosmash 2 years ago 3
and he uses the small angle approximation, in which cos(x)=1,sin(x)=x and tan(x)=x and since tan(x)=2MG/Rc^2 x=2MG/Rc^2
sikory 2 years ago 4
the idea is to look at the taylor series of tan(x)
sikory 2 years ago 5
wow i like this. he's very cognizant of everything, doesn't take anything for granted.
andrew11235 2 years ago
does anyone else think that he sounds a little like Christopher Walken?
ludiavolo 2 years ago 4
Maybe a more buff version. Probably have the same accent...
Devourer09 2 years ago
Yeah, I notice it a lot.
If they ever make a movie about Professor Susskind, Walken would be perfect to play him.
HMiste 2 years ago
I had noticed this, but I thought I was the only one that did.
juanm429 2 years ago
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Balamanifgh 2 years ago
...same with a big crunch.
jas03000 2 years ago
Since the theory of relativity allows for time travel, understanding that the technology doesn't exsist yet but may in the future, if the rip will occure could you escape it if you continued to go back in time when the unvirse was more suitably for life?
jas03000 2 years ago
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LapinPete 2 years ago
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Here's all you need to know about Einsteins General Relativity (I feel like he's channeling through me to say this). You sit with a beautiful woman for 1 hour and it seems like one minute , you sit on a hot stove for 1 second and it seems like an hour..THAT's Relativity :)
Time really does relatively fly when you're having fun
sn1pe352 2 years ago
what if you don't like girls and have that disease where you don't feel any pain?
murderedboy 2 years ago 6
You don't have to argue that statement!!! That's how General Relativity tries to give an easy concept to everybody...So, about the disease or pain or whatever you wrote, It'll just mess up this page...
perrtimo 2 years ago
:D i made you look silly o.o
murderedboy 2 years ago 2
Feel like he's channelling through you?
What you put is a direct quote from Einstein - not your own thoughts.
nietzsco 2 years ago 2
That was an analogy thought up for Special Relativity, on the subject of 'time dilation, not General Relativity.
Entropy3ko 2 years ago
Re: suboreo
Susskind did not use a particular textbook. He's working from his long experience and giving a unique presentation.
General Comment
As of this comment, the next two lectures (3 and 4), which are not on YouTube, are freely available through iTunes U.
Just install iTunes, go to "iTunes store", find "iTunes U", and go to Stanford Continuing Studies where you can find the next two lectures.
meichenl 2 years ago
Oops, never mind. The next two videos are on YouTube. They just aren't on the playlist. They should show up in the "related videos" view.
meichenl 2 years ago