Children of the Giant

Brighter than any star, Jupiter dominates the sky tonight. It gleams low in the southern sky.

But Galileo, training his primitive telescope on Jupiter in January, 1610, saw more: he saw four bright specks lined up in a row on either side of Jupiter, changing position as they slowly rotated around it.

These were the moons of Jupiter, moons that would come to bear his name: the Galilean moons. Each about as big as our own moon, they can be seen with any small telescope. (They may even be glimpsed through a pair of binoculars, if the sky is clear, and your hands are steady. Lean against a nearby building for stability.)

"Common sense" told people then that the stars, the Sun, and the planets traveled around a fixed Earth. But here, in the tiny lens of Galileošs telescope, was a mini solar system: four moons traveling around Jupiter just as Copernicus said all the planets revolved around the Sun. And as Jupiter moved, these moons werenšt left behind, as people thought birds in flight would be if the Earth traveled around the Sun.

It was the beginning of a great revolution in the minds of men and women. We ourselves, our own motion, was reflected in the skies. The stars appeared to move across the sky at night because the Earth itself rotated once a day. The stars we saw changed from season to season because of our yearly journey around the Sun. We were part of the great dance of the universe.

We have spaceships exploring the planets and moons of the solar system. The Galileo mission was designed to explore Jupiter sand its moons. The second moon of Jupiter is Europa. For years, telescopes have revealed that Europa is covered with ice. Now our spaceships report that there is a liquid ocean beneath the ice.

And maybe, just maybe, future expeditions may report that they see in the oceans...signs of primitive life.

(07/23/08)