"Before the Big Bang?" (2005), the original lecture by Roger Penrose (part 3 of 9)

[givemeblowjob69]

Penrose is an inspirational human.

[manucalrad]

hmm true.

[huntmatuk]

Penrose was my twistor theory lecturer at Oxford. We all read his book, it was easier to understand. Spinors still give me the shakes...

[ImperatorAquila]

@huntmatuk "Spinors & Spacetime"? I've got both volumes at home, but for an amateur like me, that's pretty heavy stuff.

[huntmatuk]

@ImperatorAquila I have both volumes of the book, signed as well by Penrose. It was those books we looked to when we couldn't understand his lecture course.

[albedoshader]

@ImperatorAquila: I like his "Road to Reality" very much. It's very nice to see all of his diagrams drawn with a felt pen :)

[commodoreherring]

@huntmatuk i wormed and wriggled a lot about twistors (spinors aren't scary though methinks you exaggerate..). i also attended penrose's lectures. i'm interested in what you think about his cosmology (he's written a book due for september). is it really a true statement that conformal symmetry held in the early universe? and would the same hold true after all black hole evaporation? this is the crux. i do not have a firm conviction, simply would like to hear intelligent people's opinions...

[huntmatuk]

@commodoreherring I did the MSc in Gemetry, Mathematical physics and Analysis in 96, I had done nothing like this up to that point only to be confronted with Penrose's style of lecturing. If you have a good book or a good teacher then nothing is scarey, but sadly during those times we had neither.

[HappyBirthdaySANTA]

not to affend any1 but this is just so far from the point... its a paradox it's like asking a baby what was it like inside the womb... wrong question to ask.. mathematics is the key.........Infinity always was always will..... the human brain has been institutionalized for to long that we forgot how to simply live...

[Craighill9]

Evidence and experiments show that if matter is exploded out from a singularity in a vacumn, the matter doesn't tend to clump together but its mass tends to drive it along its own path. We also find that the nuclear fussion reaction needed to create one star requires more energy than the energy produced by every star in an entire galaxy.

[commodoreherring]

@Craighill9 there has never been an experiment exploding matter from a singularity because we are unable to create singularities. not only is the energy to do that far beyond our means, but "naked" singularities (i.e. unshielded by a relativistic horizon) cannot exist in nature, as stated in the famous penrose-hawking theorems. therefore no matter could escape from the singularity since it could not cross the horizon. i don;t know where you are getting your information from.

[commodoreherring]

@commodoreherring the activity of gravitational mass is to cause matter to clump together whereas inertial mass resists any change in its momentum. the question of which of these opposing tendencies wins out on the cosmological scale is the point of the earlier diagram he drew (different k-values). on a local scale, however, clumping clearly does happen, that;s why we have the sun and the planet earth. his argument is about the consequences of this behaviour for the system's entropy.

[commodoreherring]

@commodoreherring finally, a star begins to shine (due to nuclear fusion) when the wavefunctions of the nuclei overlap strongly enough that the strong attraction overcomes the electromagnetic repulsion. how do they get close together enough to do this? it is precisely because of the "gravitational clumping". so the energy needed to ignite a star comes from the gravitational field. it happens everywhere in nature. just look up at the night sky.

[Craighill9]

@commodoreherring So you have observed this precise star ignition process and were able to calculate the wave function and you were able to observe the strong attraction as it overcame the electromagnetic repulsion? I doubt it

[Craighill9]

@commodoreherring The sun is not evidence for clumping the sun is evidence that stars are nuclear fussion reactions. And since we find that the nuclear fussion reaction needed to create one star requires more energy than the energy produced by every star in an entire galaxy. Its preposterous to say that gravitaional clumping causes stars....its not observed.

[commodoreherring]

@Craighill9 you have repeated that statement but it's simply untrue. i am trying to understand what you meant in your original post. you don't believe in gravity? 1. gravity causes masses to attract each other. This is OBSERVED. 2. This happens according to well defined laws, so the gravitational force on hydrogen atoms inside the sun is KNOWN. 3. Nuclear fusion then occurs due to tunnelling when the wavefunctions overlap. This is OBSERVED in experiments. None of this is preposterous.

[commodoreherring]

@Craighill9 you make two foundless statements: 1) experiments have been done on matter exploding out from a singularity; and 2) the energy needed to ignite a star exceeds that of a galaxy. Answers: 1) no such experiments have been or can be performed; 2) the stellar gnition process in the presence of gravity is exothermic not endothermic, i.e. it gives out energy and does not require it to be fed in. i'd add that the truth is much more profound and beautiful than your theological dogmatism.

[commodoreherring]

@commodoreherring apologies, i meant to say the stellar "ignition" process, not "gnition". for clarification, you may have read that the classical energy required is huge: the answer for seriously interested people (rather than dogmatists) lies in tunneling due to overlapping wavefunctions. sorry for filling up this page, i just don't like obscurantists injecting falsehoods in order to justify their own dogmas (see craighill's page). enjoy the lecture!

[nickharvey7]

I see no symmetry or beauty in is diagrams and drawing I feel there should be beauty. He says that it is not important that the light is really spheres but it must be important

[JFriday123]

I am in college for physics, and I must say - these kinds of talks are what drives me towards wanting to become an astrophysics researcher.

[Tolstoievsky]

amazing how these people think

[ImperatorAquila]

Yeah. :) I don't think I had many childhood heroes, none that lasted anyway, but Penrose was one of the few.

[albedoshader]

@ImperatorAquila: "The Road to Reality" gives more explanations and better insights than any of Hawking's books, even if one doesn't understand the mathematics.