Apollo 10 Astronaut. NASA       View of Earth from Apollo 10. NASA   Eyes In the Sky Forty years ago we headed into space to study the moon, the planets, and the stars. Astonishingly, the most throat-tightening view of all was looking back at what astronaut Harrison Schmitt called the "beautiful, brilliantly illuminated blue marble that we call the Earth." Against infinite blackness we saw clouds swirling, oceans changing color, hurricanes gathering force, even a seasonal ebb and flow of oxygen and carbon dioxide as if the planet were inhaling and exhaling. We saw Earth as a living entity.      1 of 7