IT'S A TYPICAL Friday afternoon. Junior is plumped down before the television, caught up in the adventures of Optimus Prime, Megatron and the rest of the Transformers. Upstairs, Sis is perched at the home computer, laughing her way through the cosmos while playing the hottest interactive game around: "The Hitchhiker's Guide to the Galaxy."

Big brother isn't home yet; he's next door trading old Superman comics for a hard-to-find issue of X-Men. Mom has just settled down to read "Contact," a recent best-seller by that nice scientist Carl Sagan. Dad is stopping off at a video store to rent the entire "Star Wars" trilogy.

Everywhere you go these days, you're likely to find science fiction. And Washington is a good place to enjoy it. After all, ours is the city where Michael Rennie and his robot pal Gort land in "The Day the Earth Stood Still," whose monuments explode spectacularly in the climactic battle of "Earth Versus the Flying Saucers," and whose Air and Space Museum rivals Disney World in popularity.

All these may be familiar enough, but there is a more exotic aspect to science fiction. That is the phenomenon known as fandom, what might loosely be called the social side of sf. Fandom comprises the international fraternity of people who form clubs, organize conventions, edit amateur magazines and generally care a lot about the subject. Many science fiction giants -- Robert Silverberg, Gregory Benford, and Roger Zelazny, for instance -- were prominent fans first and only later became professional writers or artists. Fandom is the extended family of science fiction.

No one needs to be a fan to enjoy science fiction's infinite variety: swashbuckling space adventure, social satire, visionary epic, political polemic, surreal poem, post-modernist text. You don't have to be a fan to enjoy the Redsins either. But, like Redskin followers, esseffers want to share their enthusiasm with others. Washington happily offers plenty of ways to do so.

So tell Scotty to ready the transporter beam, make sure to bring your towel, and remember J.G. Ballard's words: "The only truly alien planet is Earth."