Cosmology | Lecture 3

[MrOlenevod]

thanks a lot)

[aqouby]

Crazy Susskind! Always making up words :D

[CaptainImpedance]

Dark Matter is Blackholes of a mass of 10 to the 25th power grams. Lots of them like 10 to the 40th power of them.

[agapitoflores001]

Oh. How I love this lecture. Very interesting!

[DanielARochester]

Hahahaha at "hyperbolic noogie function"

[MrOlenevod]

sorry, what word does he say when he talks adout the sun - hot and opek(g)????

[BagarozziBoi]

@MrOlenevod Opaque .. opposite of transparent, i.e. you can't see through it.

[TheLivirus]

To me it sounds weird that the energy of a photon would decrease over time since it gets stretched. I mean the number of wavelengths and their corresponding amplitudes are preserved right? If a photon's energy was proportional to the wavelength wouldn't it gain energy upon entering a medium with higher refractive index, thus violate the conservation of energy law?

But then again, I'm altogeather uncomfortable with quantum mechanics.

[JAMAC08]

Is it possible that the supermassive Black hole and the scattering of black holes within a galaxy create a galaxy-radial disruption in the space-time fabric which causes dark matter to clump around galaxies since dark matter is weakly-interacting?

[TheLivirus]

Is the velocities of the outer matter in a galaxy relativistic? If so, wouldn't this play an important role when determining the mass of a galaxy?

[mjkr1988]

Not degrees, Kelvin. 3K, 3000K

[SinclairNicholas]

Those damned white board markers, I have the same trouble, Leonard...

[colin0630]

Leonard Susskind: The body of Sly Stallone, and the Brain of Einstein.

[1isaacmusic]

@colin0630 and the hair of a monk.

[dmkramerica]

The expansion of the universe seems a lot like osmotic pressure and thermodynamics. If the ionization layers out in the very distance universe are semi-permeable, and/or the neutrino threshold is semi-permeable, then maybe the expansion is not from within. Think of a tiny sphere or "cell" in an ocean of "universe stuff", perhaps dark matter, and that tiny sphere hits a thermal source (an ocean vent) and rapidly expands, accelerating the osmosis of dark matter, but then cooling and slowing down.

[TrollDicked]

This man he could teach even a rusty nail physics...lol.

[OneWorldHistory]

With a History background, as a mere lecturer, I am often lost in calculus and general mathematics. But to 'see' Dr. Susskind explain these basic formulae and expressions of physics is a true joy.

I may have to watch this a few times to comfortably follow the progression, but one can not help but admire his humor and passion to instruct what is surely rudimentary to his vast knowledge.

He doesn't -have- to do this... but he does.

Wonderful!

Big thanks to Stanford for providing this.

[bunkmasterflex]

1:22:57 there i can stop losing my damned spot

[bunkmasterflex]

it is unbelievable and beautiful regardless of the content that information of this mass let along magnitude is offered in my generation at the cost of internet access i Thank Whole heatedly stanford ucla any of the other universities which provide this intriguing content to those who thirst for knowledge

[joethepro3]

If i were him, all i would seek is respect in the minds of those i taught to continue in this feild of knowledge. Brilliant.

No nobel prize would fashion a wanting with this amount of illustrous brain activity! ; )

Peace

[bunkmasterflex]

@joethepro3 oh i don't know, I think it would nice up there on the mantle between my childhood sport's trophies and my world's greatest dad mug even if purely decorative.

[joethepro3]

@bunkmasterflex

Hahaha yeah, maybe my friend. Though, im very sure that worlds greatest dad is much more important in your eyes ; )

Peace

[raayinrahman]

Ofcourse he is brilliant..He is a professor n have a ph.D in theoretical physics.. He is one of the Godfather of string theory...In fact I was predicting he would be awarded Noble Prize this year for Physics.

[Pastafarealist]

@raayinrahman I doubt string theorists will be getting Nobel prizes anytime soon. Guys like Susskind are likely to win the Fields medal or Abel prize, however. Some may say the Fields medal is better than the Nobel prize since it's the top award in mathematics which is the purest field.

[sidexwalk]

Susskind is brilliant. Is he Ph.D in physics?

[Pastafarealist]

@sidexwalk I'm pretty sure most, if not all, physics lecturers in youtube videos have Ph.Ds.

[unemployedfreak]

If the expansion of the universe causes photons' wavelengths to increase, can't this explain the redshift associated with photons that took longer to reach us? (Without having to invoke the idea that the further objects are receding from us with greater (or any) velocity))

[unemployedfreak]

Wait a minute... it's the same thing! He's just blowing my mind: EVERY point in the universe is "the edge" of the universe-- so the universe's expansion causes the wavelength of a photon that connects any two points to increase. The red shift is just a boundary condition.

[sidexwalk]

Very astutely deduced.

[joerondan]

@unemployedfreak I don't understand what you mean with "every pion in the universe is "the edge". The expansion is everywhere, of course at the large scales!

[joerondan]

@unemployedfreak Well what happens is that we do have a combination of facts. Because of the receding the wavelength is red-shifted then during the time the photon is traveling to reach us the space expands and adds of the wave length shift. That is the reason that distant galaxies are much dimmer than you would normally expect .

[frenkhuijzen]

@joerondan

[gausstein]

I Thank for these lectures to the Stanford University!!!

[BrunswickHeadsHotel]

When constructing the FRW equation he uses a sphere of radius 'a' and gets a 4/3*pi*a**3. However, when determining the energy density 'rho' he uses a unit cube to give M/a**3. Why a cube and not a sphere? A sphere would lead to rho being 3*M/4*pi*a**3. The FRW would then reduce to 2*M*g/a**3 - k/a**2

[llana36]

Well he could have done that, but the basic law would still be the same, a const/a**3 ...so only constant would change, and that is not very important, u can have it both ways..it's a matter of personal preference.

[BrunswickHeadsHotel]

Thanks, I just wondered since the sphere method gets rid of the pi elements which just seem to complicate the "look" of the equations not necessarily the result (as you said it only changes the constant portion). Keeping pi around for use in substituting elsewhere because it probably gets cancelled out when simplifying other equations.

[keggerous]

meso confused i like his voice and the small amount i can understand

[Silentsam7532]

Cosmology isnt too bad, the prticle physics and QCD theory get pretty cool.

[2020bane]

i need a brain upgrade