On the 21st day of August, 2017, the moon will slide between the Earth and the sun, painting a swath of darkness across North America. The Great American Eclipse. An exercise in cosmic geometry. A reminder that we live on one sphere among many, all moving to the laws of Kepler, Newton and Einstein. The moon’s orbit around the Earth is slightly tilted, so the shadow of the new moon usually passes above or below us. About twice a year, the three bodies briefly align, and the moon’s long shadow cuts across our planet. The day dies and is reborn. The sun is replaced by an inky hole, feathered with the pale corona, a million degrees hotter than the sun itself. Staring up into the cone of blackness you can feel the cosmic gears grinding. Two minutes of beauty and terror. But while most humans will be looking up, a few will be looking down. For astronauts on the International Space Station, an eclipse is a shadowy stain on the planet. A dark blur among swirling clouds. Even farther above the Earth, weather satellites keep pace with our spinning world, watching the moon’s shadow slide from sunrise to sunset. Other satellites look outward, staring up at our nearest star. Their view of fire interrupted by the passing moon. From the moon’s perspective, the Earth never rises or sets. It just wobbles back and forth in the sky. From its orbit around the moon, the Lunar Reconnaissance Orbiter will look back at Earth to photograph our shadowed home. A million miles away, the Dscovr spacecraft faces perpetual noon. The spacecraft can watch the moon’s dark face pass behind the globe or slip across it. A dull gray orb on a sphere of white and blue. From this far out, an eclipse is a passing shadow after months of brilliant sunlight. But the moon is not the only object moving between sun and Earth. Winged Mercury has no moon of its own and no eclipses. But seen from Earth it crosses the sun about 13 times a century. A tiny dot, slightly larger than our moon, backlit by fire. Transits of Venus are much rarer. These images from 1882 were the last for over a century, until Venus returned to double-cross the sun in 2004 and 2012. Our descendents will not see another transit of Venus for a hundred years. The next one is in 2117. Mars has two moons. Phobos, the largest, is a potato-shaped rock only 16 miles long. Martian rovers have looked up to capture Phobos passing in front of the sun. A partial eclipse seen from the dried-out surface of another world. Jupiter has so many moons that the giant planet may have several eclipses at same time. Three shadows, sliding at different speeds, falling on rippled cloud. Beyond our solar system, astronomers have found thousands of planets by playing a game of shadows. Looking for slight drops in starlight when a planet moves in front of its star. Distant eclipses on alien worlds. But is anyone out there to cry or cheer or shudder? Or see the shadows cast by our own lonely planet? Or are we alone in the long night. Do the shadows and the spheres dance only for us?