The Past Hypothesis is the claim that the Boltzmann entropy of the universe was extremely low when the universe began. Can we make sense of this claim when *classical* gravitation is included in the system? I first show that the standard rationale for not worrying about gravity is too quick. If the paper does nothing else, my hope is that it gets the problems induced by gravity the attention they deserve in the foundations of physics. I then try to make (...) plausible a very weak claim: that there is a well-defined Boltzmann entropy that *can* increase in *some* interesting self-gravitating systems. More work is needed before we can say whether this claim answers the threat to the standard explanation of entropy increase. (shrink)

Are the generalizations of classical equilibrium thermodynamics true of self-gravitating systems? This question has not been addressed from a foundational perspective, but here I tackle it through a study of the “paradoxes” commonly said to afflict such systems. My goals are twofold: (a) to show that the “paradoxes” raise many questions rarely discussed in the philosophical foundations literature, and (b) to counter the idea that these “paradoxes” spell the end for gravitational equilibrium thermodynamics.

In his bestselling work of popular science, Sir Roger Penrose takes us on a fascinating roller-coaster ride through the basic principles of physics, cosmology, mathematics, and philosophy to show that human thinking can never be emulated by a machine.

Suppose that God or a demon informs you of the following future fact: despite recent cosmological evidence, the universe is indeed closed and it will have a ‘final’ instant of time; moreover, at that final moment, all 49 of the world’s Imperial Faberge eggs will be in your bedroom bureau’s sock drawer. You’re absolutely certain that this information is true. All of your other dealings with supernatural powers have demonstrated that they are a trustworthy lot.

Winner of the Wolf Prize for his contribution to our understanding of the universe, Penrose takes on the question of whether artificial intelligence will ever ...

In the last quarter of the nineteenth century, Ludwig Boltzmann explained how irreversible macroscopic laws, in particular the second law of thermodynamics, originate in the time-reversible laws of microscopic physics. Boltzmann’s analysis, the essence of which I shall review here, is basically correct. The most famous criticisms of Boltzmann’s later work on the subject have little merit. Most twentieth century innovations – such as the identification of the state of a physical system with a probability distribution on its phase space, (...) of its thermodynamic entropy with the Gibbs entropy of , and the invocation of the notions of ergodicity and mixing for the justification of the foundations of statistical mechanics – are thoroughly misguided. (shrink)

Two of the world's leading astrophysicists, James Binney and Scott Tremaine, here present a comprehensive review of the theory of galactic dynamics at a level suitable for both graduate students and researchers. Their work in this volume describes our present understanding of the structure and dynamics of stellar systems such as galaxies and star clusters. Nicknamed "the Bible of galactic dynamics," this book has become a classic treatise, well known and widely used by researchers and students of galactic astrophysics and (...) stellar dynamics. Praised for its modern approach, as well as for the rigor and exemplary clarity with which the authors handle the material in this book, Galactic Dynamics includes classic results and data while also reflecting the many recent developments in the field. The authors maintain an effective style of exposition throughout, keeping clear what is present knowledge and what is still speculation, while allowing the reader to grasp an overview of the subject before following through with the mathematical detail. Most of the astronomical community since the late 1980s was introduced to galactic dynamics through Galactic Dynamics, and it remains the most widely used graduate textbook in galactic astrophysics today. No other book gathers together and presents our current understanding of the field in such a clear and concise way. Through this approach, Binney and Tremaine succeeded in creating a classic reference of enormous pedagogic value. (shrink)