Earth Day. Today. Good idea. Now let's move on.

And why not? For most people, most of the time, Earth Day has become just that. A thought. An idea.

And a fleeting one at that.

Details surrounding the first Earth Day, founded in 1970 by U.S. Sen. Gaylord Nelson of Wisconsin, seem from another time and planet.

Nelson primarily organized the event as an environmental teach-in, with classes nationwide in universities, high schools and grade schools.

Declaration of this first day dedicated to the Earth followed a decade or more of ecological catastrophes, including those noted by Rachel Carson in 1962 with the publication of her book, "Silent Spring," which detailed the deleterious effects of widespread use of DDT.

But more than schools and schoolchildren were involved in the first Earth Day. The front page headline of the New York Times read "Millions join Earth Day observances across the nation."

A few excerpts:

"For two hours, except for crosstown traffic, the internal-combustion engine was barred from Fifth Avenue between 59th and 14th Streets. … Union Square saw the kind of crowds it had rarely seen since the turbulent days of the '30s when it was a favorite area for leftists. Around the square, particular causes were stressed — clean air and peace, urban planning and voluntary sterilization, conservation and wildlife preservation."

Addressing the Manhattan throngs, New York City Mayor John Lindsay said, "Beyond words like ecology, environment and pollution, there is a simple question: Do we want to live or die?"

The first Earth Day also was feted in Minnesota, where at the U, the event morphed into a weeklong jamboree called the "Festival of Life."

In a retrospective edition of the U's alumni magazine, writer Tim Brady reported that the festival featured "workshops on nutrient pollution and the fate of the Boundary Waters, the building of a geodesic dome, the screening of the documentary 'Who Killed Lake Erie?', a reading of a 'Declaration of Interdependence' and an 'Environmental Bill of Rights,' a mock ceremony to present awards to local polluters, and a Jazz Funeral Bicycle Caravan from Northrop (Auditorium) to the General Electric stockholders' meeting at the Minneapolis Auditorium downtown."

U President Malcolm Moos kicked off the festival with a speech, followed by the planting on campus of a "tree of life." An accompanying plaque read:

"On this day, representatives of the human race planted this tree symbolizing their hopes for an environment in which humanity could survive. This plaque has been placed here as a service to future archaeologists — of whatever species or planet — in case our hopes prove vain."

Perhaps more predictably than ironically, the tree and plaque ultimately succumbed to a campus building project.

Important as organization of the first Earth Day was, viewed through a 2016 lens, some fears aired at the time were far-fetched.

Nelson himself predicted that by 1995, some 80 percent of animals would be extinct. Life magazine warned that by 1985, air pollution could reduce the Earth's sunlight by half. Still others foresaw an imminent global ice age.

Hyperbole, yes. But perhaps some of these or other calamities were averted because the U.S. Environmental Protection Agency was established by Congress soon after the first Earth Day, or perhaps because Congress passed the Clean Water Act, the Clean Air Act, the Endangered Species Act and other legislation.

Sound public policy, after all, represents the best collective shot we have at a sustainable future. Yet such policies don't congeal from thin air. Most often they're the outcome of agitation by an informed citizenry — a fact that hasn't changed much since 1970.

So, what are you doing on this Earth Day? Probably nothing. Because for most people, most of the time, Earth Day has become just a thought — and a fleeting one.

But change doesn't require most people to act. Just you. Worry, if you will, about the big picture — say global warming.

But act locally.

Join a conservation or environmental group. Get outside more. Take a friend of family member along.

Cultivate, as it were, a deeper appreciation of the Earth. Not for a day, but a lifetime.

Agitation on its behalf will follow naturally.

Dennis Anderson • danderson@startribune.com