It is no accident of history that the first earth day, in April 1970, came so soon after color photographs of the whole earth from space were made by homesick astronauts on the Apollo 8 mission to the moon in December 1968.

Those riveting Earth photos reframed everything. For the first time humanity saw itself from outside. The visible features from space were living blue ocean, living green-brown continents, dazzling polar ice and a busy atmosphere, all set like a delicate jewel in vast immensities of hard-vacuum space. Humanity's habitat looked tiny, fragile and rare.

Suddenly humans had a planet to tend to. Planet-scale perspective on atmospheric health, ocean health and stable climate made strictly national approaches obsolete. Environmental nongovernmental organizations bloomed to set in motion mechanisms for emerging global governance.

Even more important, a new time perspective arose. Such issues as climate, biodiversity and population could be dealt with only in terms of multiple decades, even multiple centuries. Governments limited to next-election thinking had no way to grasp environmental issues. Corporations limited to next-quarter perspective were similarly blinded. Both blundered environmentally because they could not operate on a planetary time scale. Ecological problems were thought unsolvable because they could not be solved in a year or two.

That's changing. Environmentalism is teaching the world's citizens, governments and corporations to think long termÑto realize that lag times and lead times in the dynamics of atmosphere and climate are decades long, and to think of forests, oceans and aquifers as "multigeneration equity." It turns out that environmental problems are solvable. It's just that it takes focused effort over a decade or three to move toward solutions, and the solutions sometimes take centuries. Environmentalism teaches patience.

Patience, I believe, is a core competency of a healthy civilization. I propose that it is useful and realistic to think of a civilization as operating at a number of different paces at the same time. Fashion and commerce change quickly, as they should. Nature and culture change slowly, as they should. Infrastructure and governance move along at middling rates of change.