Notes: Libraries and Black Holes

May 19, 2009

I started re-reading a book by Matthew Battles a librarian at the Houghton Library at Harvard University this evening called The Library: An Unquiet History. I especially like this passage from the beginning of the book:

But the library–especially one so vast [as Harvard’s Widener Library]–is no mere cabinet of curiosities; it’s a world, complete and uncompletable, and it is filled with secrets. Like a world, it has its changes and its seasons, which belie the permanence that ordered ranks of books imply. Tugged by the gravity of readers’ desires, books flow in and out of the library like the tides. The people who shelve the books in Widener talk about the library’s breathing–at the start of the term, the stacks exhale books in great swirling clouds; at the end of term, the library inhales, and the books fly back. So the library is a body, too, the pages of books pressed together like organs in the darkness.

I’ve also been reading about black holes and Einstein’s theory of relativity, of spacetime:

Within days after formulating his equivalence principle, Einstein used it to make an amazing prediction, called gravitational time dilation: If one is at rest relative to a gravitational body, then the nearer one is to the body, the more slowly one’s time must flow. For example, in a room on Earth, time must flow more slowly near the floor than near the ceiling. This Earthly difference turns out to be so miniscule, however (only 3 parts in 10 to the 16th power; that is, 300 parts in a billion billion), that it is exceedingly difficult to detect. By contrast, near a black hole gravitational time dilation is enormous: If the hole weighs 10 times as much as the Sun, then time will flow 6 million times more slowly at 1 centimeter height above the hole’s horizon than far from its horizon; and right at the horizon, the flow of time will be completely stopped. (Imagine the possibilities for time travel: If you descend to just above a black hole’s horizon, hover there for one year of near-horizon time flow, and then return to Earth, you will find that during that one year of your time, millions of years have flown past on Earth).

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