Cover Credit: PHOTOMONTAGE FOR TIME BY BONNIE DAY; PHOTOS-EARTH: PHOTODISC, L TO R: STEPHEN ALVAREZ FOR TIME, BILL KURTIS-KURTIS PRODUCTIONS, CORINNE DUFKA-REUTERS FOR TIME, JEFF SCHULTZ-ALASKA STOCK FOR TIME, JEFFREY AARONSON-NETWORK ASPEN FOR TIME
Cover Credit: PHOTOMONTAGE FOR TIME BY BONNIE DAY; PHOTOS-EARTH: PHOTODISC, L TO R: STEPHEN ALVAREZ FOR TIME, BILL KURTIS-KURTIS PRODUCTIONS, CORINNE DUFKA-REUTERS FOR TIME, JEFF SCHULTZ-ALASKA STOCK FOR TIME, JEFFREY AARONSON-NETWORK ASPEN FOR TIME