It may not surprise people terrified by a visit to the dentist that one of the top pain research groups at the National Institutes of Health is located within the National Institute of Dental and Craniofacial Research. Check out the group's history in NIDCR's fascinating primer on the science of pain.Go to: http://history.nih.gov/exhibits/pain/

Need help in tracking discoveries of planets orbiting stars beyond our solar system? NASA's new Planet Quest Web site offers one-stop shopping for planet discovery news. Check out the latest findings, search an atlas of extrasolar planets, and learn about NASA's proposed missions to search for new worlds, particularly those that might harbor life. Interactive features include a three-dimensional model of an extrasolar planetary system and an extensive multimedia gallery of animations and virtual-reality tours.Go to: http://planetquest.jpl.nasa.gov/

This well-organized Web site introduces visitors to the realm of thermodynamics and the concept of entropy. Originally created by autonomous software agent "Chris Hillman" and now maintained by Penn State's Roland Gunesch, these Web pages start with the Chinese character for entropy, then offer intriguing glimpses of disorder and randomness in information and coding theory, dynamical systems, statistics, economics, biology, and other fields.Go to: http://www.math.psu.edu/gunesch/entropy.html

New maps of data from space-based optical sensors reveal the uneven distribution of lightning strikes across the globe. The NASA maps show that lightning avoids the ocean, but likes Florida. It's attracted to the Himalayas and central Africa. It almost never strikes the north or south poles.Go to: http://science.nasa.gov/headlines/y2001/ast05dec_1.htm

For a winter holiday treat, try the vividly illustrated pages from the American Phytopathological Society on the poinsettia and its history and diseases. The Web site begins with the tale of how a Mexican beauty of limited range grew into the United States' best-selling flowering plant. Subsequent pages document the abundant spots, rots, and other ills that menace a holiday display. Playing doctor has rarely been so colorful.Go to: http://www.apsnet.org/online/feature/xmasflower/

Stimulating scientific curiosity is one aim of questions posed at the "Did You Ever Wonder. . ?" Web page, produced by the Lawrence Berkeley Laboratory. Sample questions: How would you rebuild the surface of a cell, and how can you carve with light? Answers to the questions, colorfully illustrated and presented in language accessible to students and nonspecialists, highlight research performed at the lab. Links lead to sites with more detailed information.Go to: http://www.lbl.gov/wonder/

Mixing live Webcasts with interactive presentations, San Francisco's Exploratorium documents a journey to Antarctica. Team members interview scientists, dive and film underwater, climb a volcano, and visit a vast frigid desert. The Web site also features reference material on a variety of topics, including how fish adapt to icy waters, and views of the continent's spectacular ice formations. In another Antarctic expedition, which just finished, biologist Terrie Williams of the University of California, Santa Cruz, and her colleagues studied the foraging behavior of Weddell seals. Her field no...

The SkyServer provides public access to Sloan Digital Sky Survey (SDSS) data. Learn more about the SDSS project, which aims to map the universe, and browse images and spectra of celestial objects. Take a look at the atlas of "famous places" in the sky.Go to: http://skyserver.sdss.org/.

The National Weather Service has revised its formula for calculating wind chill. These Web pages feature an explanation of the changes, a new wind chill chart relating temperature and wind speed, and a handy wind chill calculator.Go to: http://205.156.54.206/om/windchill/.

In 1502, Leonardo da Vinci made a simple drawing of a great, 240-meter bridge that was to span an inlet at the mouth of the Bosporus River in what is now Turkey. The bridge was never built, but Leonardo's design has been reproduced in a wooden bridge for pedestrians over a highway in Norway. Artist Vebjorn Sand's Web page describes his campaign to get the bridge built and provides images illustrating how it was constructed.Go to: http://www.vebjorn-sand.com/thebridge.htm