Nobody covers television worse than television does, but now and then the almighty tube casts an insightful eye on itself -- as with "The Television Explosion," a fascinating edition of the industrious "NOVA" series, tomorrow night at 8 on Channel 26.

"Before we understand the age in which we live, we have to understand television," says George Gerbner, dean of the Annenberg School of Communications at the University of Pennsylvania. "Explosion" offers a thorough, fast-moving crash course on the great big mess of technologies transforming not just television but all the lives it touches.

This isn't just a program about what's going to be on TV in the next few years. It's an introduction to the rest of the 20th century. Although not aimed at children, it should be seen by just about every kid in the country, because they're going to have to deal with the ominously expanded TV Monster lurking around the corner.

There is more to this, too, than a glossary of new services and technological refinements -- though the show will lead viewers through the acronymical new world of VCRs and STVs, SPN and HBO and CNN and dishes you don't eat off of but receive satellite TV from. Beyond all the seeming wonders at hand, there are spooky and troubling issues.

For starters, we have to try to get a grasp on what the first wave of television, the past 30 years of it, has done to us. "NOVA" traces the history of the medium from Marconi's wireless to early appearances of Felix the Cat as a test pattern for experimental TV, on to TV's unveiling at the 1939 New York World's Fair, a Paramount newsreel offering moviegoers "First Actual Movies of Television!" and into the '50s with those elfin immortals Kukla, Fran and Ollie.

What effects have three decades of exposure had? Gerbner, a pioneer in TV research, notes that TV's warped view of the world, on which most Americans depend, severely underrepresents the very old and the very young in our culture. Heavy viewers of TV violence, it has been found, overestimate the likelihood of enountering violence in the real world. In fact, says Gerbner, research suggests that heavy viewers of TV may be conditioned into such paranoia that "they will welcome repression, if it comes in the name of security."

The new television will be, essentially, "more of what we have now," says Gerbner, but there is one huge new wrinkle: two-way TV, which enables a viewer at home to interact with programming. This could mean participating in a public opinion poll from one's living room or ordering up a recipe from a cooking show by pushing a button.

Potential abuses and side effects of this technology are on the chilling side. Les Brown, editor of Channels magazine -- and the man who succeeded, for a brief time, in moving TV coverage in The New York Times out of the Dark Ages -- warns of the risks. Instant polling could turn out to be a high-tech form of mob rule. The high costs of new services could divide society into two classes: "the information haves, and the information have-nots."

And as people depend on it for more and more services, Brown fears TV will become government, "an oligarchy controlled by large corporations."

We get an inkling of things to come not just from dire predictions but also from a visit with a Qube family in Columbus, Ohio. Qube is Warner-Amex's experimental two-way cable TV system. Viewers sit at home and, with a button on a console in their hands, vote on which play should be tried next during a Columbus football game; in the excerpt we see, the majority votes for an end run, and, presto, a touchdown is scored when the play is used.

But there are other less festive aspects. The head of the household notes that "we haven't gone out to movies for almost two years," because movies now come to them, on pay-cable. The mother says of her small child, "My son Robby won't sit still for me to read a story for him." But he will sit still for hours watching animated stories on television.

Television is "mainly an isolating experience in American society," says Cornell sociology professor Rose Goldsen on the program; it could grow much, much more so if we are going to bank, shop, even vote by TV. The great danger is that we will sit there watching in silence and not think about how TV is affecting us. "The Television Explosion" asks no less important a question than whether the tube will rule us, or we will rule the tube. 'Love Tapes'

A grim but haunting Valentine: Wendy Clarke's "Love Tapes," a half-hour, black and white PBS special at 5 and 10 p.m. tomorrow on Channel 26.

Producer Clarke assembled about a dozen soliloquies on the subject of love made on video tape by New Yorkers in a little room with just them and a camera. Some of the tales are heavy-laden, others almost desperately joyful; the tapes are a set of doodles on a variety of human conditions, and even when the participants seem to be embellishing reality to suit their own fantasies, there's a sweet directness to what they say and to how willing they are to say it.

Each was given a three-minute limit, and for one woman with nothing but misery to report (she says she has "lived without love" all her life, that her mother withheld love after the family dog died and that "I've always been suicidal, too"), three minutes is too little. "God, that went fast," she says in a chipper way when interrupted. But a 31-year-old man trying to maintain romantic optimism finally says, "Three minutes is a long time," not long after addressing the camera this way: "To all who say they need someone to love, I say, 'Love me. I'm lovable.' "

A blond woman says she's in love with a fellow called Anton: "I think it's a fantastically glorious name in itself." Another woman says, a bit frighteningly, "Being in love with another person for me means wanting to be that other person . . . I want to lose myself in that person." And a little girl says, "I love my stuffed animals" and "I love myself."

It may not break your heart, but it does bend it here and there. There is television, there is good television, and there is real television; "Love Tapes" we would have to call true television. 'Twilight Theater'

Holding out the promise of a Ton o' Fun and then delivering only a Heap o' Fun is certainly not the most heinous crime committed in the name of television. Steve Martin's "Twilight Theater" special, at 11:30 tonight on Channel 4, may not be the daffy departure one would hope for, but it is, in that persistently relevant phrase, good for a few laughs.

The program -- a pilot project that will probably get no further than this one installment -- is also a welcome change (as almost anything would be) from NBC's "Saturday Night Live," a brain-dead creation now being kept alive by artificial means. "Twilight Theater" is a mythical TV show -- "The most honored program in televison history," intones the host, Roddy McDowall -- that offers a genuine but sometimes numbing variety of comic sketches by various writers.

McDowall makes a surprisingly funny, deadpan, pipe-toting host, introducing one segment by saying, suavely, "As part of our distinguished series of hiding cameras in the bedrooms of celebrities . . ." The show borrows, from "La Cage aux Folles," the character of a black male maid, who attends to McDowall in his upholstered study and meticulously trills the program's mockingly pretentious theme song.

Bill Murray appears briefly, and too quietly, as the star of an old-time prison movie (at a table in the mess hall, he shouts out, "You call this quiche?"); Martin stars with Michael York, Pam Dawber and YOU, the viewer, in "Playhouse Minus One"; Shelley Duvall appears in a speechless, bittersweet vignette about the breakdown of a relationship from the viewpoint of a fly on the bedroom wall; and Paul Reubens, a Pinky Lee for our times, offers a radically condensed version of his space-age kiddie show, "PeeWee Herman's Playhouse."

That very fine singer, Rosemary Clooney, makes a felicitous appearance during an otherwise labored sketch called "Party in My Pants." On the far flip side of the coin, Devo, the rock group, contributes "It's a Beautiful World," a facetiously sardonic protest ballad. The group continues in its defiantly singular way to pretend to be attempting to be art.

Martin is very funny as the driver in a car pool who hears on a radio talk show that all the other men in the pool are sleeping with his wife and closes the program with an illustrated version of his "What I Believe" monologue, delivered Patton-like in front of a huge U.S. flag. "I believe that Ronald Reagan can make this country what it once was," Martin says. "An Arctic region covered with ice."