The ancient Greeks believed that the Earth was the center of the universe. The great astronomer Ptolemy mapped the solar system and stars, locating each heavenly body in a crystalline sphere, the spheres forming a concentric series that progressed in an orderly fashion outward from the earth. Celestial Matters is a startling novel of hard SF, set in an alternate, ptolemaic universe in which these beliefs are literal scientific fact. The greek empire of Alexander the Great has lasted for a thousand years, and for a thousand years it has been at war with the Empire of the Orient. Now, a spaceship has been built to voyage through the spheres to the sun and return with the ultimate weapon: a fiery piece of sun matter. Aias, a distinguished scientist of the Delian League, is set to command the first, secret expedition to the sun. The ship, Chandra's Tear, sculpted whole from moon matter, is ready to depart on its epic voyage. But as Aias is returning from his final shore leave to Athens across the Mediterranean, his ship is attacked by enemy soldiers flying deadly self-propelled battle kites. Aias's death seems certain, until the arrival of the Greek navy and, more surprising, Aias's new bodyguard, a tough Spartan warrior woman called Yellow Hare, who has been sent by the ruling Archons to protect their valuable captain.