"I have emphasized what I consider the two most remarkable features that I have learned in my research on space and time: (1) that gravity curls up space-time so that it has a beginning and an end; (2) that there is a deep connection between gravity and thermodynamics that arises because gravity itself determines the topology of the manifold on which it acts".

In “The Nature of Space and Time by Stephen Hawking and Roger Penrose” by Stephen Hawking in the lecture "Quantum Cosmology"

"We should think of twistor space as the space in terms of which we should describe physics."

In “The Nature of Space and Time by Stephen Hawking and Roger Penrose” by Roger Penrose in the lecture "The Twistor View of Spacetime"

"These lectures have shown very clearly the difference between Roger and me. He's a Platonist and a positivist. He's worried that Schrödinger's cat is in a quantum state, where it is held alive and held dead. He feels that can't correspond to reality. But that doesn't bother me. I don't demand that a theory correspond to reality because I don't know what it is. Reality is not a quality you can test with litmus pap. All I'm concerned with is that the theory should predict the results of measurements. Quantum theory does this very successfully. It predicts that the result of an observation is either that the cat is alive or that it is dead. It is like you can't be slightly pregnant: you either are or you aren't."

In “The Nature of Space and Time by Stephen Hawking and Roger Penrose” by Stephen Hawking in the lecture "The Debate"

Can I write a review on such a book? Hawking and Penrose... It's staggering...I don't even know what day the mailman comes...After having re-read this oldie after Hawking's passing, I'd say it depends on where you are in the universe, whether you're on/near some sizeable object (of mass), its rotation, distance from other masses, or whether you live in my neck of the woods...When in doubt I always follow "the flat earth" rule (Medieval behaviour is so "in" now). The world is the centre of (my own)) universe that you/I live in and it's getting flatter everyday. Which hopefully means you can see further and observe when others perform the same behaviour. Or ask them. Preferably in a suit of armour while riding a horse. Possibly a lance too. (Until you understand the society you live in). I'm all for a flat and cubist planet! Our time is here! And it'd be easier to fence. And we could launch spaceships off the corners. Uncannily, the mailman knows when I'm on the phone, asleep or having a quiet moment on the throne...I sniff a time conspiracy here (*It'll End in Tears theme music*)

When it comes to Quantum Theory, the math in the book includes every possible outcome, and the predictions it makes are simply probabilities - e.g. there's a 1% chance X will happen, 90% chance Y will happen and 9% chance Z will happen. How you choose to interpret this is still up for grabs, if you go with Everett's "Many Worlds Interpretation" idea then all possibilities are equally real and actually happen in different universes; if you go with the Copenhagen Interpretation then the wave-function of "possibilities" collapses down to one single result. On a fundamental level, whichever way you choose to interpret it (there's about 8 main contenders for interpretation) the math remains unchanged, and the possibility remains that the math itself is the "truth" and there is no further interpretation, usually called the "shut the fuck up and calculate" interpretation (my favourite).

Bottom-line: This is not a book à la Smolin, i.e., it's not for laymen. I still remember some of the reviews I read in 2010 when the second edition of the book came out. Hilarious! E.g., "Clearly the work of two great minds" (possible Translation - "I didn’t understand the bits I speed read, but they looked dead clever and I have to say summat"...). ( )

Vent'anni fa Stephen Hawking e Roger Penrose hanno tenuto una serie di conferenze per raccontare come loro pensavano si potessero mettere insieme la teoria della relatività generale e la teoria quantistica dei campi. Non che ci si sia riusciti nemmeno ora a farlo, intendiamoci. Ad ogni modo questo libro raccoglie il testo di queste lezioni. Ve lo dico subito: se non avete studiato fisica a livello universitario non ci capirete molto, o almeno io non sono riuscito a cavarci molto, anche perché la versione epub che ho letto (e che tanto per dire ha un ISBN errato nel colophon...) ha perso dei caratteri una volta letta con Aldiko che è tra i pochi programmi che permettono di leggere un file protetto da DRM; una versione pdf sarebbe stata migliore. Penrose si fa capire un po' di più, Hawking è davvero tosto. Stranamente in un paio di punti mi è parso che Libero Sosio si sia perso: solo che non sono riuscito a copiarmi il testo, sempre per colpa del DRM :-( ( )

Too much advanced mathematics for me, but, it still all comes down to that stupid cat ~ ( )

Too much advanced mathematics for me, but, it still all comes down to that stupid cat ~ ( )

This delightful little volume is essentially the transcript of a series of lectures given by Stephen Hawking and Roger Penrose at the Isaac Newton Institute in Cambridge. While given to a technical audience, the book is fairly readable. Still, the more you know about general relativity, the more you will get out of it. I read it when I was a teenager and enjoyed it, even if I was often pretty puzzled. Even now, after obtaining a PhD in physics, I can still enjoy it and I am only a little bit puzzled. ( )