Hold on to your seats, folks. You've just crossed over into the Twilight Zone.

Michael Williams, a Republican candidate for Alabama's 5th Congressional District seat, has a proposal to funnel new revenue into the National Aeronautics and Space Administration.

He wants to place a 1-percent "NASA tax" on all science-fiction books, science-fiction comic books and "space-related" toys, puzzles and games.

This is the point at which humorist Dave Barry says, "I'm not making this up."

Of course, most people take Williams' proposal about as seriously as they do his futile congressional campaign. He is the underdog in a two-man race to determine who gets to be crushed by entrenched incumbent Bud Cramer, D-Huntsville, in November.

Already, some have dubbed Williams' nutty scheme the "Star Trek tax."

But just because an idea is stupid and bizarre doesn't mean it won't eventually find its way into law.

How dumb is the Star Trek tax? Well, as Mr. Spock would say, it is highly illogical.

NASA already owes a huge debt to the science-fiction community, which has done more than anyone else to promote interest in space exploration. Ask NASA's scientists and astronauts, and most will tell you that science-fiction books and movies are what inspired them to join the space program.

The SF community did its part, and all it got in return was a glorified jobs program and taxpayer-subsidized re- search and development for the aerospace industry.

A tax on SF is not just unfair; it's impractical. How do you tax something that no one has ever defined? Science fiction isn't cigarettes, after all.

Fans have spent decades trying to decide what is and what isn't science fiction, and there is still no generally accepted definition. SF is like pornography; people know it when they see it.

Or do they?

Most people think the "Star Wars" movies are science fiction, but "Star Wars" has more in common with King Arthur than with hard SF like "2001: A Space Odyssey" or the works of Isaac Asimov.

Are Edgar Rice Burroughs' Martian tales science fiction even though the Mars he describes never existed? Or what about Ray Bradbury's Mars of "The Martian Chronicles"? Where is the dividing line between science fiction and science fantasy?

It isn't hard to imagine publishers trying to get off the tax hook by classifying SF novels and stories as fantasy. (In most cases, they wouldn't be far wrong.) And if we try to tax fantasy, too, where does it stop? Are we going to tax stories about wizards and unicorns in order to finance space exploration?

The boundaries between science fiction and other genres are fluid. Is "Alien" a sci-fi movie, a horror movie or both?

In a few short steps, we go from Williams' proposal to tax science fiction to taxing ghost stories. And what have ghost stories to do with NASA?

If Williams thinks he can define science fiction precisely enough to tax it, he must also think he is smarter than three generations of SF fandom.

But you can't accuse Williams of lacking vision. He also wants Congress to call for a constitutional convention as soon as 30,000 colonists live "on the moon, Mars or any other celestial body besides the Earth."

After all, we want our off-world descendants to have just as wonderful a political system as we have, don't we?