Until now, I believed that the smallest unit of time was between the moment the traffic light turned green and the car behind you honked. I was wrong. The shortest unit is actually between the moment you win the Nobel Peace Prize and someone asks if you're running for president.

This is the story of Al Gore. It's wrapped succinctly in the Time magazine headline: "Gore Wins the Nobel. But Will He Run?" The best answer came from congenitally sardonic congressman, Rahm Emanuel: "Why would he run for president when he can be a demigod?"

Indeed, if the man who is free at last from politics has learned anything, it's that becoming a candidate means open season on his weight, his wit, his wisdom and his son's arrest record. Besides, which would you rather do, save the Earth or dial for dollars in Iowa?

The attention on Al Gore's trajectory from loser to laureate misses something about this second act and second actor. As he approaches 60, Gore's staking out something of a new path for his generation.

Consider the new sixtysomethings. On Monday, 61-year-old Kathleen Casey-Kirschling, the first baby boomer and a retired teacher, signed up for early Social Security benefits. Next Friday, Hillary Clinton turns 60 and her second act is running for president. And when the new Harvard president, Drew Faust, 60, met with her Bryn Mawr classmates last summer? Many were talking about leaving their "extreme jobs" just as she was installed in hers.

Baby boomers are the first generation that can look forward to such a lengthy and (fingers crossed) healthy stage of later life. They are as likely to be talking about what they want to do next as about where they want to retire. Never mind all those declarations that 60 is the new 40. In fact, 60 is the new 60.

The stage of life called adolescence was only invented a century ago. Today, says Rosabeth Kanter, Harvard Business School professor and a founder of the university's Advanced Leadership Initiative, "we have a chance to invent another stage of life that doesn't have a name yet."

But Gore is its poster child, the model for what Marc Freedman calls the "encore career." The head of Civic Ventures, a think tank promoting civic engagement as the second act for boomers, Freedman says, "Gore found himself by losing himself — literally losing — and being liberated from ambition, the idea that there's a particular ladder you have to scurry up and if you don't make it to the top it's all over. Essentially he found a different ladder."

Alas, Gore's "liberation" came with a little help from the Supreme Court. But he spent time in the wilderness — bearded and academic, rested and restless — before reconnecting with what he cared most about. It was there, all the time, in the huge satellite photograph of the Earth that hung on the wall of his office.

There's an inconvenient hole in "An Inconvenient Truth." Gore never confronts his failure to accomplish more on climate change while vice president. But elsewhere he has implied that he'll be better at "creating that sea change in mass opinion" to force this agenda from the outside. This, says Freedman, "is the classic baby-boomer pattern of returning to an earlier dream unclouded by the compromises of midlife."

We have a roster of famous second actors, from Jimmy Carter to Bill Gates. The transition is a lot easier for folks not worrying about 401(k)s and pharmacy bills. Nevertheless, many in what Kanter calls the "Al Gore population" approach their 60s with a different set of values ... and, it must be said, urgency.

I cannot forget one more second actor, Niki Tsongas, who became the newest member of Congress this week. At lunch last month, she talked of feeling rejuvenated, young at 61 as she started a new career. Just hours later, her younger sister unexpectedly died. The 60s come with sober reminders as well.

As a country, we are at the beginning of an enormous transition. Under the old compact, sixtysomethings were supposed to get out of the way and out of work. They were encouraged by financial incentives and prodded by discrimination. Now we are drawing blueprints for people who see themselves more as citizens than seniors.

"We used to say that the choices ran from A to B&B," says Kanter, author of "America the Principled." Today, she says, "we have an opportunity to define it as a time when your wisdom gets put to work on complex problems."

Demigod or demographic? Al Gore may not have invented the Internet, but the "Al Gore population" is reinventing this altogether new stage of life.

Ellen Goodman is a columnist for The Boston Globe. Reach her at ellengoodman@globe.com.