I first saw the earth--the whole earth--from the shuttle Challenger in 1984. The view takes your breath away and fills you with childlike wonder. That's why every shuttle crew has to clean noseprints off their spacecraft's windows several times a day. An incredibly beautiful tapestry of blue and white, tan, black and green seems to glide beneath you at an elegant, stately pace. But you're actually going so fast that the entire map of the world spins before your eyes with each 90-minute orbit. After just one or two laps, you feel, maybe for the first time, like a citizen of a planet.
All the colors and patterns you see--the visible evidence of the complex working of the natural systems that make our planet habitable--seem both vast and precise, powerful and yet somehow fragile. You see volcanoes spewing smoke, hurricanes roiling the oceans and even fine tendrils of Saharan dust reaching across the Atlantic. You also see the big, gray smudges of fields, paddies and pastures, and at night you marvel at the lights, like brilliant diamonds, that reveal a mosaic of cities, roads and coastlines--impressive signs of the hand of humanity. Scientists tell us that our hand is heavy, that we are wiping out other species at an unprecedented rate and probably transforming our climate. Will the immense power of global systems withstand the impact of humanity? Or is it possible that our collective actions will change the nature of our planet enough to cripple its ability to support life?
I no longer believe that we can wait for all the scientific data needed to answer these questions conclusively. We must recognize immediately what it means to be citizens of this planet. It means accepting our obligation to be stewards of the earth's life-giving capacities. As homeowners, we wouldn't neglect or damage our houses until they weren't fit to live in. Why would we do that with our planet?
Sullivan, who as a U.S. Navy Reserve captain flew on three space-shuttle missions, is president of the Center of Science & Industry in Columbus, Ohio www.cosi.org