Today, Earth Day turns 37.

It’s neither old, nor does it fit a demographer’s definition of “young.” According to statistics from the Centers for Disease Control, 37 is about the middle of an American’s life, given our average life expectancy of 77 years.

It’s midlife, a phrase often paired with crisis, which together are used to describe a mindset obsessed with the past. Hollywood just loves it, and serves up bland comedies featuring faded stars buying motorcycles to feed this national neurosis.

Earth Day’s approach to midlife is less funny, because despite pop culture’s groan-inducing jabs, the arrival at life’s midpoints should inspire serious reflection on the past, and on altering the future. It’s an opportunity for perspective, which is growing rare in today’s world.

Sen. Gaylord Nelson of Wisconsin introduced Earth Day in 1970, during a time of political unrest in the United States. A controversial faraway war was polarizing the nation, and advocates were accusing Congress of ignoring obvious degradations of the world’s environment.

Earth Day, the senator said, intended to bring environmental issues onto the forefront of the political agenda, and capitalized on the supercharged political environment surrounding the Vietnam War. “That was the remarkable thing about Earth Day,” Nelson later wrote. “It organized itself.”

By creating a focal point for the environmental movement, Nelson and Earth Day are rightful ancestors for the landmark legislative advances that followed: establishment of the Environmental Protection Agency, strengthening of the Clean Air Act, passage of the Clean Water and Safe Drinking Water acts.

This legacy earned Nelson the Presidential Medal of Freedom in 1995. President Bill Clinton, in describing Nelson as the father of Earth Day, said he was the grandfather of the momentum it started.

Now, Nelson’s grandchild is grownup, and facing unrest similar to the conditions of its birth. Earth Day has sparked remarkable achievements, by demanding attention to air and water quality, and inspiring millions to action.

Yet reality tempers this progress. As before, Congress is an obstacle on environmental issues, as evidenced by some of its members’ tortuous insistence that global warming is a hoax, and the issue’s most eloquent spokesman, Al Gore, oft-derided as an hypocritical diva with a bloated “carbon footprint.”

There’s hope, though. Pressure on federal lawmakers to address environmental concerns is growing, supercharged by the unrest over war in Iraq, and our frightening dependence on foreign oil. This month, the U.S. Supreme Court finally gave the EPA direction to control emissions that cause global warming.

Earth Day brings this together, and as its midlife celebration arrives today, April 22, the holiday can look toward its past accomplishments and smile.

And then roll up its sleeves, because there’s still much to be done.