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The Planet Saturn

October 1882 —Tenth Annual Congress of the Association for the Advancement of Women, Portland ME

 

The specialist can never believe that his subject is narrow: to him it widens and widens. When the theological professor said to the astronomer that his department was the Old Testament, the astronomer replied, ” So is mine, with the difference that mine is older.” On the other hand, when the astronomer boasted to the entomologist that his department covered the whole earth, the entomologist said, “ Insects do.”

I have perceived, in studying the planet Saturn, how many incidental questions come up in other departments of physical science; I must know something of chemistry, of natural philosophy, and especially of celestial mechanics and mathematics. Saturn alone showed itself a universe made up of systems within systems. To the eye, Saturn is far less conspicuous than Jupiter. It is smaller; it shines with a pale, white light; it might be mis taken for one of the countless stars. The first look with a telescope is a revelation. Like Jupiter, it has its satellites; like Jupiter, it has bands crossing its surface nearly parallel to its equator; but, unlike every other planet we see, it is surrounded by a ring generally so inclined that it stands out like a plateau in front of the planet. It is not a ring, it is a bottomless placque.

Why is Saturn thus girded about, like a high-priest, among the hosts of the firmament? This ring is so posited around the ball that permanence of relative position of ball and ring is secured. ln a few hours, ball and ring turn around on their axes and show to us different faces; but another change is going on slowly in years, that of the inclination of the ring to our line of sight. From this change of inclination the ring is now a broad. flowing river of light surrounding the ball; the position of earth, Saturn, and sun changes. and anon it is a silver thread crossing the glowing disk, and. once in the average life of man, it defies the power of ordinary glasses; it presents its edge directly to us, and we can not see it.

We say “ Ring,” but the ring is made up of many. An ordinary glass will show that this broad, flat ring is divided, and dark bands of sky show through the opening rifts. A narrow ring seems to have separated from the original one, as if parting the close companionship; the most powerful telescopes show other separations. We detect these changes mainly at the extremities of the longer axis of the plane of the ring.

Separating from the inner edge of the plane of the ring is what is called the dusky ring — seeming to tend toward the ball. Reflecting little light, it extends a wide surface toward the ball, seemingly shelving like the sea-shore toward the ocean; and, when seen obliquely, it ap pears to lie upon the ball. and was long talked of as shadow, although no light was there on sea or land to cast shadow in that direction. There can be little doubt that this crape-like, dusky ring has changed in the last century. Are these changes the result of the action of the ball upon the substance of the ring? When the ring is so tipped that the bright edge toward us is projected upon the ball, dark markings appear upon the ball ; they border the ring on one side as the dusky ring does on the other; we call them shadows, but are they shadows? They do not follow the curve of the ring; they do not follow the usual law of light and shade. So, too, upon the brilliant ring are very black irregular spots ; we call them shades thrown by the ball; but the ball shows no prominences which, by intercepting the sunlight, could throw such shadows.

The astronomical observer is fortunate if he can call in some inexperienced friend, if possible an artist, to assist his judgment in lights and shades. Above all other combats, the experienced ob server has that with his own perceptions and favorite prejudices. If he has conceived an hypothesis, it becomes his tyrant and oppressor, warping judgment. Minute objects which will bear no illumination of the telescope, but must be seen in intense darkness. are detected by the eye, but can not be measured with apparatus. To these, different eyes must be called in place of micrometer, and the opinion of the novice as to which is larger and which is brighter is a wholesome correction to the prejudiced observer with his pet bias.

If we look at Saturn only for its picturesque interest, it is wonderfully beautiful. Its variations from uniformity add to its charm. It is not a sphere; it is perceptibly flattened at the poles. Surrounded by the broad, bottomless placque, it is not centrally posited within it, but is visibly on one side. Accompanied by eight satellites, these circle around it in such different orbits, at such different distances, with such different rates of motion, that the configuration of ball, ring. and eight moons never repeats itself. Now, the moons range themselves in n straight line on each side of the ball as sentinels; now, they cluster around one point of the ring as jewels dropped from the circlet; and again, they form a curve as a coronet above the central body.

Like the traveler in mountain regions who tries to think, “Given the mountains, could I gather them together into the picturesque slopes and hills and dales of the vista,” so the astronomical observer learns his impotence when he attempts to conceive the outlines of beauty in the arrangement of points of light. You will never see the same combination a second time. If you changed the grouping of moons in one line only, you would make tens of thousands of changes ; if you con sider the changes of inclination and of distances of these eight moons, of their combinations with Saturn, and Saturn’s changing position of ball and ring, you can never exhaust the variety of the celestial kaleidoscope.

Let us consider the little moons them selves. They pass and repass one an other; Titan, with its orange light, comes between us and the pale Rhea; Tethys, with its peculiar sparkle, is followed by the faint Dione; Euceladus and Mimas cling for a while close to the ring, then shoot out with hasty step and quickly re turn; while afar off, distant many times the diameter of the planet. shines Japetus, now brilliant as Titan, now faint as Dione. Hyperion, the last discovered. is seen only with the largest glasses.

We might think these names absurd; but some nomenclature is necessary; we acquire a habit of speaking of them as members of a family, and so familiar do we become with their peculiar features, that if the family of Saturn passes in its orbit near a star, we know at once the stranger in its solitary fixedness.

Modern scientists consider the rings and the moons to have had a common origin; that the rings are made up of crowded moons not yet separated. If the satellites have, in different ages, separated from different portions of the rings, it seems likely that the rings are not homogeneous. The rings show lighter and darker shades, but scarcely the variety which is so marked in the moons. Titan and Rhea are so unlike in color that any ordinary eye would see it at once.

l know of no telescope which shows other than a smooth edge to the ring; roughness may be indicated by the shadows. Larger telescopes in more favor able climates may lead to the detection of inequalities of surface; new moons may be found; the eight known moons may develop duplicity, as they seem now to show variability.

There is always work for small telescopes, and into this work women should come, and especially young women. The very faults of a girl’s education should lead her into the study of nature. She is trained to observation of minute detail; her eyes and her perceptive faculties are always developed; she is learned in shapes and forms, colors and positions. Her very needs should lead her to the study of Nature, for Nature must be studied out of doors, in good air. The most thoughtless girl is awed when she first looks through a telescope and sees Jupiter or Saturn, and the step from the beauty of the vision to the question of cause underlying it is quickly made. For beyond all scenic effect is the beauty of the law by which permanence and stability are secured. Where fancy fails to depict. mathematical computation traces the curves of beauty. If the earth shows His handiwork, if the sea is His, the heavens declare the glory of God.

 

 

Source: Papers Read Before the Association for the Advancement of Women at its Tenth Annual Congress Held at Portland Maine, October 1882, pp. 5-7.