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                                                                                                                                                                                  NETWATCH                               edited by Mitch Leslie




                                                                                                  WEB TEXT                                                                                           RESOURCES

                                                                                                  The Science of Sight                                                                               Find the True Path
                                                                                                  Do you see faint blobs where the white                                                             Whether you want a succinct statement of
                                                                                                  "avenues" cross in this diagram (below)?                                                           Zipf's law or a synopsis of the British Muse-
                                                                                                  You're not losing your eyesight; you've                                                            um algorithm, visit the Dictionary of Algo-
                                                                                                  simply fallen for the Hermann grid illu-                                                           rithms and Data Structures from the
                                                                                                  sion, one of the tricks that help re-                                                              National Institute of Standards and Tech-
                                                                                                  searchers deduce the workings of the                                                               nology in Gaithersburg, Maryland.Aimed at
                                                                                                  visual system. For a clear view of how                                                             mathematicians and computer scientists,
                                                                                                  we see, check out The Joy of Visual                                                                the site is packed with definitions, handy
                                                                                                                           Perception, an un-                                                        functions, descriptions of famous problems,
                                                                                                                           dergraduate-level                                                         and algorithms. According to Zipf's law, for
                                                                                                                           Web text by pro-                                                          example, a few words such as "a" and "the"
                                                                                                                           fessor emeritus of                                                        are common, but most are rare. And the
                                                                                                                           psychology Peter                                                          thorough but tedious British Museum algo-
                                                                                                                           Kaiser of York Uni-                                                       rithm involves checking all possible solu-
                                                                                                                           versity in Toronto,                                                       tions to a problem one by one, beginning
                                                                                                                           Canada. Students                                                          with the smallest. The listings include links
                                                                                                                           can start by focus-                                                       to a wealth of backgrounders, Java applet
                                                                                                                           ing on physiology                                                         demos, papers, and other resources. Read-
                                                                                                                           and anatomy, in-                                                          ers can help build the site by filling in in-
                                                                                                                           cluding the struc-         D ATA B A S E                                  complete entries.
                                                                                                  ture of the eye and the transmission of                                                                           www.nist.gov/dads
                                                                                                  messages across the gaps between neu-               Where Eagles--and
                                                                                                  rons. Other sections let us peer into sub-
                                                                                                  jects such as how we perceive contrast,             Sparrows--Dare                                 E D U C AT I O N

                                                                                                  size, motion, and distance.                         A male resplendent quetzal (Pharo-
                                                                                                     The text also reveals the secrets be-            machrus mocinno, above), whose iri-
                                                                                                                                                                                                     Space Q&A
                                                                                                  hind a long list of fun and instructive illu-       descent plumage once adorned Aztec                 What color is Venus? Did time really run
                                                                                                  sions. The shadows on the Hermann grid,             royalty, can sport tail feathers more              more slowly just after the big bang? Are
                                                                                                  for instance, result from the arrangement           than four times his body length. You'll            stars and galaxies
                                                                                                  of inhibitory and excitatory receptors in           find data on this Central American                 made of dark matter
                                                                                                  the retina.                                         denizen and more than 10,000 other                 lurking in the uni-
                                                                                                                www.yorku.ca/eye                      bird species at Avibase, a taxonomic               verse? Teachers, stu-
CREDITS: (TOP TO BOTTOM) MICHAEL AND PATRICIA FOGDEN/CORBIS; PETER KAISER/YORK UNIVERSITY; NASA




                                                                                                                                                      clearinghouse hosted by the nonprofit              dents, and space
                                                                                                  TO O L S                                            organization Bird Studies Canada. Ac-              buffs can look up an-
                                                                                                                                                      counts cover all the world's avian                 swers to these and
                                                                                                  Just the Right Words                                species and provide the latest informa-            other questions at
                                                                                                  Genome aficionados rely on the well-                tion on nomenclature, classification,              Curious About As-
                                                                                                  known BLAST search to find matches for a            subspecies, and conservation status,               tronomy?, a Web site
                                                                                                  particular DNA sequence in gene data-               along with range maps at the country               from Cornell Univer-
                                                                                                  bases. A site called eTBLAST from the Uni-          level. Visitors hungry for more can mi-            sity in Ithaca, New
                                                                                                  versity of Texas Southwestern Medical               grate to linked sites such as the U.K.-            York. The site's crack
                                                                                                  Center in Dallas lets you use the same              based BirdLife International, which of-            team of mainly as-
                                                                                                  idea to scan MEDLINE for germane arti-              fers details on threats to species.                tronomy graduate
                                                                                                  cles. Enter a sentence or paragraph--say,                   www.bsc-eoc.org/avibase/avibase.jsp        students has already
                                                                                                  from your latest paper--and you can                                                                    answered hundreds
                                                                                                  search for abstracts with similar language.                                                            of reader queries.
                                                                                                  You can fine-tune the search by giving more weight to particu- Submit your head-scratcher, and they'll try
                                                                                                  lar words. The results, delivered by e-mail, can take several min- to respond within about a week. For exam-
                                                                                                  utes to arrive.                                                               ple, pictures of Venus, such as this purple-tinted ultraviolet image
                                                                                                                  invention.swmed.edu/etblast/index.shtml                       highlighting cloud patterns (above), rarely show the planet's true
                                                                                                                                                                                colors. From space, Venus is yellowish-white because of its murky
                                                                                                                   Send site suggestions to netwatch@aaas.org.                  atmosphere, whereas from the surface, its rocks appear dull red.
                                                                                                                    Archive: www.sciencemag.org/netwatch                                       curious.astro.cornell.edu/index.php



                                                                                                                                          www.sciencemag.org      SCIENCE     VOL 304     14 MAY 2004                                                  935