HOLLYWOOD -- When the concluding chapter of "Roots" aired on ABC on Jan. 30, 1977, the United States seemed to come to a standstill.
More than half of all homes tuned in, and the historical TV miniseries provided a common experience for almost 77 million viewers, spurring discussion of slavery and race in schools and offices.
"They changed the times of the shows in Vegas because they were afraid nobody would show up," executive producer David L. Wolper recalled of the last night.
The final episode of "Seinfeld," which NBC will broadcast Thursday night to an expected audience of more than 75 million people, promises to be a similar kind of event -- a shared American cultural milestone sure to be gabbed about over water coolers and Starbucks counters Friday morning.
In that sense, saying fond farewell to a situation comedy renowned for being about nothing has broader implications, for "Seinfeld" may be the last hurrah of the huge broadcast event that knits us as a nation.
In an age in which the average viewer receives dozens of channels and people tote water around in individual bottles, television's ability to forge such communal bonds is fast diminishing. Few TV shows on the air now seem destined to approach the cultural impact of "Seinfeld."
During its nine-year run, "Seinfeld" has provided fodder for conversation, introducing phrases like "Yada, yada" and "Not that there's anything wrong with that" (Jerry and George's disclaimer in saying they're not gay) into the national lexicon. The series even prompted a much-publicized lawsuit after Miller Brewing fired an employee for discussing a racy episode with a co-worker. The executive, Jerold Mackenzie, sued Miller and won a $26.6 million judgment from the company last year.
"Seinfeld" has helped bring people together, serving as "a provender of words and images that became a kind of cultural shorthand between people, providing a sense of community," said cultural critic Neal Gabler.
But "Seinfeld" is also one of the few weekly programs still reaching such a vast audience, as viewers turn to cable channels and upstart TV networks. The three major networks, which still accounted for 90 percent of prime-time viewing in the 1970s, have seen their audience share dip to 47 percent this season, the lowest-rated year in their history.
Even "Seinfeld" and NBC's medical drama "ER" -- the two most-watched series, each averaging in excess of 30 million viewers each week -- attract less than 12 percent of the U.S. population, according to ratings service Nielsen Media Research.
And for all the hoopla about the end of "Seinfeld," the show has held scant appeal for large segments of the population. Based on Nielsen figures, the comedy fails to register among the top shows in black households or among people over 55, many of whom prefer CBS' time-period competitor "Diagnosis Murder," starring Dick Van [filtered word].
"This is a culture of dispersion, and it's dispersed in television as in other forms," said Todd Gitlin, a New York University professor and author of "The Twilight of Common Dreams: Why America is Wracked by Cultural Wars." "`Bonanza' belonged to a time when culture was more conglomerated and focused -- there were three networks, and three car companies. In a larger sense, the significance is that the culture no longer has a common story."
The challenge facing the networks will become more difficult as the spectrum of options expands. An explosion of choices promises to follow once the industry solves the technological and marketing puzzle of how best to wed digital television, computers and the telephone to disseminate information and entertainment.
In a society increasingly connected through the media, cultural common ground could be one of the casualties as the number of widely seen programs declines.
"This is the new ersatz community," said Vicki Abt, a sociologist at Pennsylvania State University. "We're desperate for community, (but) it's virtual reality. We feel like a community because we watch television."
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An unavoidable aspect of the "Seinfeld" finale is also the enormous media attention showered on the program since December when Jerry Seinfeld announced his intent to end the series.
Gabler, whose upcoming book "Life: The Movie" explores the way entertainment values permeate American life, described the months leading up to Thursday night's finale as "a national Irish wake."
To writer Larry Gelbart, who developed "MASH" as a TV series for CBS and skewered the media in the Home Box Office movie "Weapons of Mass Distraction," the outpouring of "Seinfeld" coverage says as much about the information age as the program itself.
"It is a case of another kind of media frenzy that is self-perpetuating, (naming) a winner of the moment," Gelbart said. "I think virtues are being attributed to the show (that) the people involved don't even claim for themselves. It's a show about a bunch of spiteful, mean-spirited people. It's fun, but it's hardly statue material."
Gelbart nevertheless sees value in the public send-off "Seinfeld" is receiving. "Anything that brings us together -- God knows there are enough things that keep us apart -- is good for the family that we are as a nation," he said.
Not everyone would agree.
"Everybody likes ice cream. They just have different flavors," said NYU's Gitlin. "I'm not nostalgic for the days when we all talked about a common show. It didn't make us a better or a happier society."
Television officials concede it may be a long wait for another program to rival "Seinfeld." "Cheers" prompted prime time's last major public funeral in 1993, preceded by "MASH" (whose finale remains the highest-rated program ever) a decade earlier.
Even so, within the industry, hope continues to spring eternal, with producers and executives stressing that one can never predict when and where the next hit program will arise.
According to Chuck Lorre, executive producer of the ABC comedy "Dharma & Greg," which paid homage to "Seinfeld" in this week's episode, the water-cooler show will merely lie dormant "till somebody does something remarkable. The medium fools you. It still has the capacity to bring people together."