Ringside seat: sometimes, in science as in boxing, you want to be up close; sometimes you want to keep your distance

Natural History, Oct, 2004 by Neil deGrasse Tyson

Imagine you're strolling along a boulevard on a crisp autumn day. A block ahead of you is a silver-haired gentleman wearing a dark blue suit. It's unlikely you'll be able to see the jewelry on his left hand. If you quicken your pace and get within thirty feet of him, you might notice he's wearing a ring, but you won't see its crimson stone or the designs on its surface. Sidle up close with a magnifying glass and--if he doesn't alert the authorities--you'll learn the name of the school, the degree he earned, the year he graduated, and possibly the school emblem. In this case, you've correctly assumed that a closer look would tell you more.

Now imagine you're gazing at a late-nineteenth-century French pointillist painting. If you stand ten feet away, you might see men in top hats, women in long skirts and bustles, children, pets, shimmering water. Up close, you'll just see tens of thousands of dashes, dots, and streaks of color. With your nose on the canvas you'll be able to appreciate the complexity and obsessiveness of the technique, but only from afar will the painting resolve into the representation of a scene. It's the opposite of your experience with the ringed gentleman on the boulevard: the closer you look at a pointillist masterpiece, the more the details disintegrate, leaving you wishing you had kept your distance.

Which way best captures how nature reveals itself to us? Both, really. Almost every time scientists look more closely at a phenomenon, or at some inhabitant of the cosmos, whether animal, vegetable, or star, they must assess whether the broad picture--the one you get when you step back a few feet--is more useful or less useful than the close-up. But there's a third way, a kind of hybrid of the two, in which looking closer gives you more data, but the extra data leave you extra baffled. The urge to pull back is strong, but so, too, is the urge to push ahead. For every hypothesis that gets con firmed by more detailed data, ten others will have to be modified or discarded altogether because they no longer fit the model. And years or decades may pass before the half-dozen new insights based on those data are even formulated. Case in point: the multitudinous rings and ringlets of the planet Saturn.

Earth is a fascinating place to live and work. But before Galileo first looked up with a telescope in 1609, nobody had any awareness or understanding of the surface, composition, or climate of any other place in the cosmos. In 1610 Galileo noticed something odd about Saturn; because the resolution of his telescope was poor, however, the planet looked to him as if it had two companions, one to its left and one to its right. Galileo formulated his observation in an anagram, smaismrmilmepoetaleumibunenugttauiras, designed to ensure that no one else could snatch prior credit for his radical and as-yet-unpublished discovery. When sorted out and translated from the Latin, the anagram becomes: "I have observed the highest planet to be triple-bodied." As the years went by, Galileo continued to monitor Saturn's companions. At one stage they looked like ears or handles; at another stage they vanished completely.

In 1656 the Dutch physicist Christiaan Huygens viewed Saturn through a telescope of much higher resolution than Galileo's, built for the express purpose of scrutinizing the planet. He became the first to interpret Saturn's "ears" as a simple, flat ring. As Galileo had done half a century earlier, Huygens wrote down his groundbreaking but still preliminary finding in the form of an anagram. Within three years, in his book Systema Saturnium, Huygens went public with his proposal.

Twenty years later Giovanni Cassini, the director of the Paris Observatory, pointed out that there were two rings, separated by a gap that came to be known as the Cassini Division. And nearly two centuries later, the Scottish physicist James Clerk Maxwell won a prestigious prize for showing that Saturn's rings are not solid, but made up instead of numerous small particles in their own orbits.

By the end of the twentieth century, seven distinct rings, lettered A through G, had been identified. Not only that, the rings themselves turn out to be made up of thousands upon thousands of bands and ringlets. In the most recent photographs available at the time this article went to press--taken this past July by the Cassini spacecraft from a mere 4 million miles away--some ringlets look braided, and others have mysterious kinks. Some are opaque; others are translucent. Some are pinkish; others are ivory; still others are gray.

So much for the "ear theory" of Saturn's rings.

Several Saturn flybys preceded the one by Cassini: Pioneer 11 in 1979, Voyager 1 in 1980, and Voyager 2 in 1981. Those relatively close inspections all yielded evidence that the ring system is more complex and more puzzling than anyone had imagined. For one thing, the particles in some of the rings are corralled into narrow bands by the so-called shepherd moons: teeny satellites that orbit near the rings. The gravitational forces of the shepherd moons tug the ring particles in different directions, sustaining numerous gaps between the rings.