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SPINNING INFINITY. “Rotating blue supergiants, such as the progenitor of SN 1987A, may also give rise to rapidly rotating BHs. For these stars, neutrino-mediated mass loss will fail to unbind most of the hydrogen envelope, and a rapidly rotating BH will be produced if the AM in the hydrogen envelope is accreted by the BH.” (BH = black hole; AM = angular momentum). https://lnkd.in/dApxk5K View in LinkedIn

BLACK HOLE SPIN. “Spin is one of only three fundamental properties of black holes (BHs), but there are few reliable predictions of natal BH spins. The BH spin is determined by the angular momentum (AM) content of the core of the star that collapses into the BH. Yet our ability to predict internal stellar rotation rates and AM content has been limited by sparse observational constraints and the complex magnetohydrodynamics of differentially rotating stars.” (BH = black hole; AM = angular momentum). https://lnkd.in/dApxk5K View in LinkedIn

EVOLUTION OF BLACK HOLES. “Because so few philosophers have worked on these issues, many questions and problems of great possible interest have not been investigated philosophically at all; others have had only the barest starts made on them; consequently, several sections discussed in this article merely raise questions and point to problems that deserve philosophical attention. The field is wide open for expansive and intensive exploration.” https://lnkd.in/dPXn5gh View in LinkedIn

A Girona artesenal bookbinder who still occaisionally works in velum. Another dying breed. Extraordinary workshop of old tools. View in LinkedIn

LEWIS CARROLL’S THE SNARK. “The poem describes " with infinite humor, the impossible journey of an improbable crew, to find an inconceivable creature ". (Sidney Williams and Falconer Madan: Handbook of the Literature of the Rev. CL Dodgson , cited in Martin Gardner: The Annotated Snark , Penguin Books, 1974.). https://lnkd.in/dCZKzN4 View in LinkedIn

INCREASING ENTROPY? “Finally, the evolution of black holes is apparently in conflict with standard quantum evolution, for such evolution rules out the sort of increase in entropy that seems to be required when black holes are present. Indeed, as purely gravitational entities with striking quantum properties, what we know about black holes lies at the heart of and guides many attempts to formulate a theory of quantum gravity. This has led to a debate over what seemingly fundamental physical principles are likely to be preserved in, or violated by, a full quantum theory of gravity.” https://lnkd.in/dPXn5gh View in LinkedIn

RABBIT HOLE. “This all raises problems about inter-theory relations, in particular about relations between the “same” quantity as it appears in different theories. It also bears on the meaning and status of the Second Law of thermodynamics, with possible implications for characterizing a cosmological arrow of time.” https://lnkd.in/dPXn5gh View in LinkedIn

UNKNOWN CONSEQUENCES. “It is far from clear, however, what it may mean to attribute thermodynamical properties to black holes. At the same time, some of these thermodynamical properties of black holes now seem amenable to direct testing in terrestrial laboratories by observing the behavior of “analogue” systems composed of ordinary material.” https://lnkd.in/dPXn5gh View in LinkedIn

UNEXPECTED NEXUS. “Black holes, however, raise several additional conceptual problems and questions on their own. When quantum effects are taken into account, black holes, although they are nothing more than regions of spacetime, appear to become thermodynamical entities, with a temperature and an entropy. This seems to point to a deep and hitherto unsuspected connection among our three most fundamental theories, general relativity, quantum field theory and thermodynamics.” https://lnkd.in/dPXn5gh View in LinkedIn

SINGULARITIES. “Black holes are regions of spacetime from which nothing, not even light, can escape. A typical black hole is the result of the gravitational force becoming so strong that one would have to travel faster than light to escape its pull. Such black holes generically contain a spacetime singularity at their center; thus we cannot fully understand a black hole without also understanding the nature of singularities.” https://lnkd.in/dPXn5gh View in LinkedIn