The impending encounter between Earth and a cloud of particles ejected from comet Tempel-Tuttle is likely to produce a dazzling meteor shower, visible over North America in the early morning hours of Nov. 18. Bill Cooke of NASA's Marshall Space Flight Center provides forecasts and viewing conditions for this year's Leonid storm.Go to: http://see.msfc.nasa.gov/see/Leonid_Forecast_2001.html and http://leonid.arc.nasa.gov/.

The National Oceanic and Atmospheric Administration offers an amazing library of more than 16,000 spectacular images, organized into a variety of topical sets. You can browse image collections devoted to coastlines, fisheries, ships, polar regions, severe storms, undersea research, nature reserves, flight, geodesy, coral reefs, and many other subjects.Go to: http://www.photolib.noaa.gov/ .

There are reasons that terrorists have been sending anthrax—and threatening anthrax exposure—to people around the United States: It’s scary (and deadly). Understanding that, the Medical Library Association has put together a Web page to help physicians, parents, teachers, and others learn more about anthrax, smallpox, botulinum toxin, plague, and other bioterrors—and the extent to which government agencies and medical organizations are ready to cope with outbreaks. Moreover, it offers readings and citations to books that suggest how adults might work at soothing a young child’s or even a teen’...

Ready to party? If you're familiar with Avogadro's number, 6.02 x 1023, you can join the celebration of Mole Day on Oct. 23 from 6:02 a.m. to 6:02 p.m. Check out the Web site of the National Mole Day Foundation for a history of this event and other tidbits from the not-so-furry realm of chemistry, where 1 mole of any substance contains Avogadro's number of atoms or molecules. This year's theme is "2001: A Molar Odyssey."Go to: http://www.moleday.org/

Once you've seen the White House and the Washington Monument, either in person or virtually, spare a minute for another national treasure: the United States Algal Collection. The Smithsonian Institution's National Museum of Natural History offers a bite-size introduction to the collection's tens of thousands of specimens. The Web site describes each of the major groups of algae and offers a variety of images and links to other great cyber-algal hot spots, many at the University of California.Go to: http://www.nmnh.si.edu/botany/projects/algae/Alg-Menu.htm

Interested in playing around with some mathematical knots? Manuel Arala Chaves of the University of Porto in Portugal has created a table illustrating all 75 knots with up to 9 crossings in their standard representation. If your computer can handle LiveGraphics3D, you can manipulate the knots in three dimensions and look at them from different angles. The instructions are in English and Portuguese.Go to: http://www.fc.up.pt/atractor/nos/

Should researchers be allowed to tinker with our genetic codes, or create copies of human beings? Could we somehow be harming future generations by aiding sick people today? Public Agenda Online offers a nonpartisan guide to these and other policy issues related to medical research.Go to: http://www.publicagenda.org/issues/frontdoor.cfm?issue_type=medical_research

Want to know more than just selenium's symbol, atomic number, and atomic weight? Created by chemist Mark Winter of the University of Sheffield, WebElements provides information on each chemical element's history, uses, reactions, bulk and thermal properties, and more.Go to: http://www.webelements.com/

View the tip of a snapped towel (which moves faster than the speed of sound), then take a look at a bursting water balloon, a collapsing water drop, a tennis ball in mid-collision with a racket, and many other amazing images in this gallery of high-speed photos snapped by high school students.Sorry! This Web site is no longer available.

Did you miss last month's National Academy of Sciences workshop on scientific and medical aspects of human cloning? You can listen to the recorded presentations via RealPlayer (use the links at Workshop Agenda) and view the accompanying slides (see Speaker Presentations).Go to: http://www7.nationalacademies.org/COSEPUP/Workshop_Agenda.html—updated 8/26/03—VM.