Cosmology | Lecture 8

Lecture 8 of Leonard Susskind's course on Cosmology. Recorded March 16, 2009 at Stanford University.
This Stanford Continuing Studies course is the fifth of a six-quarter sequence of classes exploring the essential theoretical foundations of modern physics. The topics covered in this course focus on classical mechanics. Leonard Susskind is the Felix Bloch Professor of Physics at Stanford University.
Stanford University:
www.stanford.edu
Stanford Continuing Studies
continuingstudies.stanford.edu
About Leonard Susskind:
www.stanford.edu/dept/physics/...
Stanford University Channel on KZbin:
/ stanford

[@jamesbentonticer4706]

Who would have the sheer unmitigated audacity to hit dislike for any of these videos?

[@joetavish]

[@waynedarronwalls6468]

James Benton Ticer someone who only has the mental capacity to understand the Kardashians and the Biebers of this world...

[@hasanhelal9474]

Flat earthers

[@ritemolawbks8012]

People who hate blue chalkboards.

[@petergreen5337]

❤Thank you very much Professor and class.

[@daujok2827]

# Great lecture by great physcist!! couldnt be more thankful for such physics lectures with respect to mathematics and its beauty!! Thank you Dr. Susskind!

[@lukegratrix]

Leonard Suskiind is the best teacher on the planet and he has exceptional competition.

[@lukegratrix]

If there are two to choose from, consider Ramamurti Shankar at Yale. Both are geniuses! Celebrate them when you find them. Let the rest of the world catch up! Celebrate Dirac, Heisenberg, Planck, Einstein, De Broglie, t'Hooft, Bohr, Suskiind, John Bell, and so many others. These are the geniuses of our time and they are exceptional human beings. I like that they are humble enough to admit when they are under informed. The genius is detectable in the eyes of the inflicted. They can't help themselves. Their eyes show and look the part. They are gifted and perhaps don't realize the extent to which they are gifts to humanity

[@lukegratrix]

I don't want to leave people out. Count among our geniuses Penrose, Witten, Eric Weinstein, so many particle theorists, so many cosmologists, so many other scientists of so many other disciplines. I'm discouraged about many mundane things but I remain hopeful and encouraged by our collective potential. Don't ever give up on science and mathematics. Our modern existence is almost entirely attributable to their accomplishments.

[@hasanshirazi9535]

The students should have the respect and courtesy for that Prof. that they should let him finish what he is saying before asking their questions.

[@hasanshirazi9535]

Isn't it amazing that due to infinitesimal quantum fluctuations within the first 10^(-33) of a second of the creation of the universe, we ultimately got galaxies, stars and life itself!

[@hasanhelal9474]

Yes

[@airforcemax]

Impressive.

[@NutsKleerofski]

a very nice course

[@emasolie4135]

Did you first calculate what happened before the BB, or did you read about it? "You stretch out the heavens like a tent cloth." Ps.104:2.

[@naimulhaq9626]

The hyperbolic De Sitter's contraction and expansion seems to imply big crunch theory that enabled Lee Smolin to even be able to identify "natural selection" in De Sitter space !!!

[@Onoma314]

Haha, I kept getting an image of him trying to write equations with a cookie.

[@mindoxy7452]

Thank you

[@while_coyote]

Oh god, stop asking questions and let him give a lecture for once!!!!

[@johnfraser8116]

Really. I was thinking the same thing. Leonard's patience is one of the things that make him great.

[@ibreakkidslegs]

this scalar field business barely deserves the label of an explanation

[@RenatoCosta1]

there is a TASI lecture note on arxiv 0902.1529 that explains it more quantitatively...

[@joabrosenberg2961]

Omega zero and Omega matter; Is space flat; Inflation and Quantum effects 34:00; Disipation by expansion of the universe, Hubble Friction 52:00; Scale invariant Spectrum 1:17:00;

[@MikeRoePhonicsMusic]

4:57 - He gets riled up & flips the bird to the chalkboard. ;)

[@Metallurgist47]

Does not the V(thi) potential energy element of this proposed scalar field require the presence of an external , interacting force to produce it -- but where does that come from ? Anyone?

[@SpencerMoleda]

As Leonard Susskind said in another set of lectures, "The final exam is buying me lunch". :)

[@okieoneshinobi]

well that was fun

[@ianmathwiz7]

Well, he's a professional physicist, so that's a start.

[@Onoma314]

One of these days he's going to forget which hand has the chalk and which hand has the cookie O:

[@dougruth4296]

What would Roger Penrose say?

[@borispopovich]

What's in those cookies?

[@jacobvandijk6525]

Dark energy!

[@mrazrad]

Yeah, I almost thought I clicked on the wrong link. No accidentally grabbing markers that have ran out of ink but haven't been thrown away?!? That is 1/2 the fun of the videos!

[@hasanhelal9474]

Thought this was from 2012

[@MikeRoePhonicsMusic]

Would you mind explaining to the class how a nuclear reactor works?

[@ethanjahan780]

He probably would mind

[@GuerrillaForce]

Whoa! Unexpected change of venue. After watching this series of lectures I'm almost uncomfortable seeing him in front of a board that's not white ;) Much respect for Dr. Susskind.

[@hasanhelal9474]

I tried to invert the screen but it is invariant under these transformations. I wonder what conservation law is that, chalk?

[@kris6591]

he teaches and eats at the same time, what does that mean

[@Horwellston]

I missed where the limit of 62 e-foldings came from, if anyone notices or remembers when he introduces it i'd be very grateful... off to google to see what I can find there.

[@hasanshirazi9535]

Don't know whether it will be of any benefit to you after so many years, but I just calculated that if 1 Planck length of space is to be expanded to 10^(-6) m then it requires 66 e-foldings. This is based on the assumption that the Universe started with a size of 1 Planck length and the light wavelength at the time of first scattering was 10^(-6) m (after compensating for today's CMB red shift factor of 1100). @1:56:00 Professor explains that for a initial negatively curved universe, if the universe had less than 59.5 e-foldings, space would not have flattened out and would have been so much negatively curved that galaxies could not have formed - hence no life.

[@ianmathwiz7]

Or eating a piece of chalk.

[@MARILYNANDERSON88]

If the cosmos appears to be fluctuating about like a big wave pool bubble, perhaps it appears flat at the point of observation due to "surface tension".

[@shyamvijay8985]

That's an interesting idea!

[@mrkvamaster]

Why couldn't gravity create "lumpiness" out of a universe that is perfectly smooth? I mean, the quantum fluctuations are still there, so it is not PERFECTLY smooth at all...

[@hasanhelal9474]

If there are fluctuations it is not perfectly smooth

[@Eldooodarino]

that is the standard mechanism that is used to account for the observed features of the universe: 10^-5 level fluctuations that are probably due to quantum fluctuations that were then magnified by gravity. He describes this starting at around 16:45

[@Fritzybedeek]

Who doesn't believe inflation? Roger Penrose, Neil Turok, Lee Smolin, to name some. kzbin.info/www/bejne/eF6ooXuHbN6fb8U

[@DerMacDuff]

"scientific dogma" lol

[@succytash]

seriously, listen to yourself. (so the rest of us don't have to.)

[@nurlatifahmohdnor8939]

Page 779 muti = n S. African inf. medicine, esp. herbal. [from Zulu umuthi tree, medicine]

[@nurlatifahmohdnor8939]

Page 778 mutant = [C20: from L mutare to change]

[@jamesthenabignumber]

I like Susskind. However, unfortunately for me, I noticed that he often starts the next sentence with the end of the previous sentence. This occurred to me around lecture 5, and has been a irritant ever since.

[@philosophicalleo405]

Susskind teaching cosmology, testing conformity? Delivering hypothetical constants in order to make mathematical abstractions appear tangible? Make data agree with points of scientific dogma by factoring equations designed specifically to hide facts anomalous to a cannon of thought. Comparing sensory inputs under meditation all principles will become apparent. The nomenclature to describe these principles is best described using condensed or vocal imagery, possibly dance, never mathematics.

[@hasanhelal9474]

Yes but there are experiments that validate these hypothesises.

[@jacobvandijk6525]

I did like the content of the lectures. Obviously mr Susskind is an intelligent man, but too old for lectures of this length. His behaviour was sometimes shocking. Old or not.

[@jacobvandijk6525]

Haha, I really hope he still can ... on the toilet!