The real behind-the-scenes heroes, though, are not the science advisers but the geek experts. The accuracy of the nerd oeuvre — the obsession with superheroes, “Star Trek” and “Star Wars” (before their umpteenth viewing of the movie, Howard, the M.I.T. engineer, says to Sheldon, “If we don’t start soon, George Lucas is going to change it again”), comic books and video games — is sometimes so eerie that I feel as if I’m watching a high- (or low-) light reel of my own life. In one episode, Sheldon goes to a computer store and is soon being asked for advice from tech-illiterate customers, to the point where he hacks into the store’s mainframe to check on the availability of an item. (“O.K., we don’t have that in stock,” he says to a customer, “but I can special-order it for you.”) He stops only when a real salesclerk reminds him that he doesn’t actually work there. Change the date to 1971, the computer store to a record store and the item in question to Judy Collins’s version of “Amazing Grace,” and that could have been me.

Beyond any navel-gazing thrill for me or other current or former nerds, the masterminds of the show — Lorre, Bill Prady, the showrunner Steven Molaro and others — have dared to produce a TV program that plays not a whit to the aspirations of its audience. You might laugh at the characters, pity them or love them, but you don’t want to be them (especially because you might already be them). There are a good amount of pre- and postcoital scenes, but they’re not especially sexy. These are not especially pretty people. A friend of mine who’s also a recent convert to the show says that she has a problem with Howard (Simon Helberg), the gnomish, dickie-sporting mama’s boy. “I can’t look at him,” she says. Even Penny (Kaley Cuoco), the bombshell across the hall, often appears rumpled or with a bottle of cheap wine hanging from her like an extra limb.

By the end of the sixth season, which wrapped last week, the characters had started to mature, while remaining true to their essence. Howard has been somewhat redeemed by living the ultimate nerd fantasy — becoming an astronaut — but even more by the love of a good woman, Bernadette (Melissa Rauch), whose oft-remarked-upon “ample bosom” is overshadowed by the fact that she’s smarter than he is and makes more money. Raj (Kunal Nayyar) finally seemed on the verge of a real relationship with a new character named Lucy (until she dumped him in the season finale last week), even as his sublimated love for Howard continues to surface in spontaneous belches. (In Raj and Amy, “The Big Bang Theory” could very well have two bona fide bisexuals among its characters.) Sheldon appears headed for some kind of revelation — either a Nobel-worthy discovery, his first real sexual experience or a nervous breakdown. The on-again-off-again (currently on) romance between Penny and Leonard (Johnny Galecki) may reach some resolution, but it almost certainly won’t have the fairy-tale ending of Ross and Rachel on “Friends” or Carrie and Big on “Sex and the City.” If they ever do marry, Leonard will most likely have one hand on his asthma inhaler at the ceremony and Penny will have one hand on a bottle of chardonnay. (Or a basic physics text; one roadblock to their relationship has been her concern that she’s not smart enough for him.)

The main direction that all of these characters continue to head in, though, is toward one another. With their social “shields” down (as one character puts it), they have direct access to their own and one another’s feelings — and buttons, especially when formulating the perfect insult. The intimacy that they achieve, and the chemistry among the actors, is certainly on a par with that of long-running sitcoms like “Cheers” or “Will and Grace” and is approaching the territory of maybe the greatest TV ensemble cast of all time, from the show about the Minneapolis TV-news producer and her coterie of kooky, lovable friends and co-workers, people whom you didn’t necessarily want to be but whom you always wanted to be around.

Unlike “The Mary Tyler Moore Show” (29 Emmys in its seven years on the air), “The Big Bang Theory” is a bit underdecorated. Parsons has his two Emmys, but he should have easily won a third for his work in the fifth season, if for nothing else than playing the bongos and singing about the subjunctive mood. Galecki and Bialik have received single Emmy nominations, but the show has never won for best comedy series, and its writing and directing have never even been nominated, having most recently run up against the awards juggernaut of “Modern Family,” an altogether hipper, sexier (if not necessarily funnier or smarter) show.

And while my own proselytizing about “The Big Bang Theory” has earned it a few new fans, many of my would-be converts remain unconvinced. When at one happy hour I lauded the guest appearances of Christine Baranski as Leonard’s mother, one of my buddies sneered, “She’s too good for that show.” When I praised the show in passing in a previous column, one of my editors strongly urged me to reconsider (“Replace it with anything else,” he said). And this from my haircutter: “But isn’t it about . . . nerds?” (She eventually came around.) So even though the show has lately been earning its highest ratings (20 million viewers for one episode in January) and has been regularly finishing at No. 1 on the Nielsen list, it has remained something of a guilty pleasure, an affection that you don’t broadcast too loudly. It’s still a little lonely at the top.

For me, though, true validation came last summer when I was on vacation, walking up a darkened hill in the kind of resort town where the smart TV talk veers toward shows like “Girls” and “Mad Men.” I was wearing a T-shirt emblazoned with the word “bazinga,” Sheldon’s self-satisfied exclamation whenever he thinks he’s got the better of one of his pals. A car crept toward me, a window rolled down and my shields went up: Uh-oh, I thought, here comes some snarky comment. Instead the driver just said the word, Sheldon-like, quietly but rascally: “ba-ZING-a,” and then moved on. It was an acknowledgment of a shared secret, a coded utterance of the sentence that some people wait a lifetime to hear: How cool are we!

Twenty million nerds can’t be wrong.