In recent days we have been watching Mercury, Jupiter and Venus in the western sky at sunset, with the crescent Moon moving from evening to evening along the line of planets. Together, planets and Moon slipped one after the other below the horizon as we sped on the spinning Earth at a thousand miles per hour to the east.
The Moon and planets mark the plane of the ecliptic in the sky -- the plane of the solar system -- and night by night they drift among the stars as they and we make our great circuits around the Sun. On the darkest nights we can see a band of faint light reaching up from the horizon, the zodiacal light, sunlight reflected from meteoric dust lying in the plane of the solar system, leftover debris from the pancake of whirling dust and gas out of which the solar system was born.
Another band of pale luminescence, the winter Milky Way, arches overhead from north to south, the light of billions of stars individually too faint to be visible to the unaided eye -- another plane, the plane of the galaxy, another whirling journey.
A spinning Earth, in a spinning solar system, in a spinning galaxy! Wheels within wheels within wheels, like the vision of the prophet Ezekiel.
And my flight isn't over yet. In the northwestern sky, in the constellation Andromeda, I can just make out a blur of light, too fuzzy to be a star, like a smudge on the dark windowpane of night. This is the central part of the Great Andromeda Galaxy, the closest spiral galaxy to our own, towards which we fall in another mutual motion.
I stand in the darkness and try to feel my vertiginous flight. And I think of that blind old man kneeling on the floor of the Office of the Inquisition in Rome in 1633, having renounced his belief in the motion of the Earth, whispering -- as legend has it -- under his breath, "And yet it moves."