Every now and then, Byron Tapley steps outside with a pair of binoculars and trains them toward the late afternoon sky, hoping to catch a glint of sunlight reflecting from a pair of minivan-sized satellites he has nicknamed Tom and Jerry. Tapley has good reason to be proprietary: he leads the team of scientists who launched the twin satellites in 2002. Working in tandem, the satellites orbit the earth from pole to pole every 90 minutes, recording tiny variations in the earth’s gravitational field caused by the movement of vast amounts of water. The two spacecraft have provided compelling ... Read More