Contact

by Carl Sagan

“But beyond its being one of the brightest stars in the sky, is there anything special about it?” Joss wanted to know. “Or anything that connects it up with the Earth?” “Well, in terms of stellar properties, anything like that, I can’t think of a thing. But there is one incidental fact: Vega was the Pole Star about twelve thousand years ago, and it will be again about fourteen thousand years from now.” “I thought the polestar was the Pole Star.” Rankin, still doodling, said this to the pad of paper. “It is, for a few thousand years. But not forever. The Earth is like a spinning top. Its axis is slowly precessing in a circle.” She demonstrated, using her pencil as the Earth’s axis. “It’s called the precession of the equinoxes.” “Discovered by Hipparchus of Rhodes,” added Joss. “Second century B.C.” This seemed a surprising piece of information for him to have at his fingertips. “Exactly. So right now,” she continued, “an arrow from the center of the Earth to the North Pole points to the star we call Polaris, in the constellation of the Little Dipper, or the Little Bear. I believe you were referring to this constellation just before lunch, Mr. Rankin. As the Earth’s axis slowly precesses, it points in some different direction in the sky, not toward Polaris, and over 26,000 years the place in the sky to which the North Pole points makes a complete circle. The North Pole points right now very near Polaris, close enough to be useful in navigation. Twelve thousand years ago, by ...