Monday Science Links

This week's science:

• Jen at Cocktail Party Physics talks about Hokusai and woodblock printing and copying of a more modern kind: Woodblock printing first made its appearance in China sometime between the fourth and seventh centuries AD, possibly deriving from the ancient Babylonian seals used to stamp impressions into wax or clay as authenticating marks. By the end of the ninth century, printed books are quite common all over China, at a time when most of Western Europe was stuck in the comparatively illiterate Dark Ages, waiting for Johannes Gutenberg to get around to inventing the printing press in 1455. You might be surprised to hear that Gutenberg did have a predecessor in China: an alchemist who lived in the mid-11th century named Pi-Sheng, who invented his own form of moveable type. He fashioned small blocks from an amalgam of clay and glue, and carved a Chinese character in relief on each, then baked the blocks to harden them. He could then glue each individual piece of type onto an iron plate, coat it with a mix of resin, wax and paper ash, then hat and cool the plate to set the type. It was then a simple matter to detach the type when done by reheating the plate. Pi-Sheng's invention might even have caught on, if there weren't some 30,000 individual ideograms required to make a complete font.


• Bee at Backreaction on the black hole information loss paradox: The evolution laws in quantum mechanics are time-reversal invariant. (That does not include the measurement process, which does set limits to our knowledge). Initial states evolve into final states, the evolution is given by a Hamiltonian and is unitary. You can turn it back around. If you start with something it will go into something with probability one. The evolution is a one-to-one map. Unitarity is a fundamental property of quantum mechanics. Now consider you have some matter distribution (e.g. a pressureless gas) and let it collapse (for simplicity assume it is spherically symmetric). That what you need to specify the precise state I will call information. The collapsing matter forms a horizon and becomes a black hole. The black hole no-hair theorem says that a black hole can carry only three parameters: mass, angular momentum, and electric charge. After the collapsing matter has settled down, this is the only information you can get from examining it. What happened to all the other information of your gas? All the details of that initial state?


• Judith at Zenobia: Empress of the East looks at the the Zenobia romance:Tabari's life of Zebba (= Zenobia) is so deeply imbued with folklore that it is hardly possible to take the story seriously on any level. Besides, he makes her a member of a mythical tribe, the Amlaqi, and gives her a nomadic lifestyle so unsuited to the city of Palmyra that it's easy to dismiss his tale as a hotchpotch of epic proportions. Once we clear away the fantastical and obviously legendary elements, what -- if anything -- is left in this Arabic version of her history? Quite a bit, actually. And there are inscriptions to prove it.


• Female Science Professor has a two-part look at an Atlantic article about 'morality' of expanding college: There are of course major differences between Professor X's experiences teaching as an adjunct instructor of introductory writing and literature classes at these colleges (in one case, a community college) and my experiences as a tenured professor of science at a research university. There are, however, fewer differences than Professor X supposes, at least in terms of how we interact with students.... There will always be some students who can't succeed at the 'college level'. But is it immoral to let them try (again and again)? It is immoral if the educational system is dysfunctional and consists primarily of an accounting office to take your money so you can hurl yourself at impossible tasks taught by an implacable instructor.
  


• And finally, Dr Astropixie has several posts about manned space exploration: i think there are clear benefits to space exploration, and i think the major problems us earthlings are facing is how we are treating each other, our children and our earth. those things should be evaluated, but not by putting on hold the one task that currently keeps us all together and reaching for the same goal.