Want to build your own world? It's only $69.95.

That will get you 40,000 virtual acres in cyberspace, where, using computer graphics, you can build any sort of world you like, then invite others to visit. You'll have plenty of neighbors; there are already hundreds of virtual worlds out there on the Internet, offering education, art or just play to hundreds of thousands of regular visitors.

You can find out more about world-building, or get a feel for what's out there, at the Virtual Worlds in Formal and Informal Education workshop to be hosted by the Cornell University Theory Center Thursday and Friday, May 20 and 21. Cornell participants in the workshop will convene in the real world, in Rhodes Hall, but they will meet in virtual worlds with participants in a simultaneous workshop at the University of California at Santa Cruz and with a few other special guests located in other parts of the country.

The workshop is aimed primarily at the Cornell community, said Margaret Corbit, communications manager at the Theory Center and organizer of the event, to make teachers and students aware of the educational possibilities of the new technology.

Virtual worlds are a mix of video gaming technology, the World Wide Web and chat rooms. When you visit a virtual world by using a special browser, your computer screen displays a three-dimensional space in which you can move around using your mouse or arrow keys. You can choose to walk, run or sometimes fly through the space. Occasionally there are opportunities to "teleport" or "warp" to get somewhere in a hurry, the equivalent of clicking on a link on an ordinary web page.

Others who are in a world with you will appear as graphic figures called "avatars," which the user may choose to have appear as humans, animals, robots or almost anything else. When you're near someone else's avatar, you can talk to the other person by typing messages in a window at the bottom of your screen. The word "avatar" comes from Hindu tradition, where it refers to the form a god takes to walk on the Earth.

Many virtual worlds have been built by universities and other educational institutions. Others are devoted to games or to re-creating scenes from popular culture. There are, for example, worlds containing scenes from the "Star Trek" universe and the "Ringworld" stories of science fiction writer Larry Niven. A number of worlds are museums displaying digital art. There are virtual roller coasters and virtual shopping malls. The Theory Center is building a virtual science center, a museum that will contain interactive exhibits teaching scientific concepts.

Participants in the virtual worlds workshop will get hands-on experience in visiting virtual worlds and can attend advanced classes on creating their own worlds.

The keynote speaker will be Bruce Damer, founding director of the Contact Consortium, a group of 35 institutions and corporations promoting the use of virtual worlds. Damer is the author of two books on interactive cyberspace, Avatars (Peachpit Press, 1998) and Virtual Worlds (Perseus Press, 1998). Damer will attend in person.

The technology and virtual space used in the conference will be supplied by Activewords.com Inc., a Massachusetts company that leases server space for virtual worlds and provides one of the software systems that make them work. Much of their programming, Corbit says, is done by Roland Vilett, a 1991 Cornell computer science graduate. The Active Worlds browser, which requires a Pentium PC, is available free from the company.

The workshop is co-sponsored by the Theory Center and the Contact Consortium and is receiving additional support from the Cornell Council for the Arts and from the University of California-Santa Cruz.