Penetrating yet farther out into the hinterland of space, we come to Saturn, the last of the five planets known to the ancients. Indeed, Saturn was known to be a planet in the Solar System before it was known that our Earth was one. As long ago as the time of Christ the Greek mathematicians had arrived at the conclusion that our Earth was not a central fixed body, the hub of the universe. The priesthood and the later Church, with all of its great, despotic power, commanded this latter belief, and for centuries few dared think differently. Thus the straight thinking of the Greeks was of no avail. As recently as the year 1600, after settlements actually had been made in our Western Hemisphere. Giordano Bruno was burned at the stake because he insisted that Earth was only one of "endless particular worlds" a star similar to the Moon, the planets, and the other stars. The Pole Copernicus about 1550 got himself into difficulties by pointing out that there were the best of reasons for believing that the Earth and the planets all revolved around the Sun.
It was Galileo, along in the early sixteen hundreds, who threw the final intellectual bomb. When he got his deadly-truthful telescope working, he made the astounding discovery that Venus had what we call "phases." Like the Moon, it was not self-illuminating, but rather it shone by reflected light which came from the Sun. When the illuminated surface was mostly turned away from the Earth, only a narrow crescent was visible. We call this gradual shift from narrow crescent to full moon and back again to narrow crescent the "phases" of the Moon.
When Galileo noticed that Venus went through similar phases, he "let the cat out of the bag" and Mercury, Venus, Earth, Mars, Jupiter, and Saturn were revealed in their true status. They were all seen to be non-self-illuminating bodies, traveling in different orbits around the Sun and also revolving upon their axes. There was no longer anything supernatural or mysterious about them. Everything that had been observed down through the centuries checked up, and no unprejudiced mind could escape being convinced.
But this made things bad for the Church. It was absolutely contrary to everything it had been teaching. Galileo had shown that Earth, instead of being the Deity's chosen center of all things, was nothing but an inconsequential bit of cosmic dust amid untold millions of far more important bright stars. Of course, it would not do at all for this belief to spread, so Galileo and those who believed as he did were led to see the wisdom of keeping their mouths shut. Pressure was brought to bear upon Galileo to induce him to recant, but he would not. He was thrown into prison, and his life probably would have been taken, as was customary in the case of such recalcitrants, had it not been feared that it might make him a martyr and strengthen his followers rather than weaken them. The strength of the Church of those times and the perfection of its organization may be appreciated when it is recalled that well into the seventeen hundreds the University of Paris dared not teach that Earth revolved around the Sun; instead it explained that this was one of the hypotheses that was used by some to account for the actions of the stars, but it was not the true explanation.
Even our own Harvard and Yale originally taught both the Church concept and the scientific concept of astronomy, leaving it to the student to select which one he preferred to believe. But time, although a lot of it was required, straightened the matter out, and men and women came to be brave enough to assert their confidence in ascertained fact rather than superstition and the super- natural. Even to-day remnants of the prejudice in favor of what the Church teaches persist, as witness the recent lawsuit in Tennessee over the right to teach the theory of evolution.
Saturn appears to the naked eye as an ordinary star. But when the telescope became available, only a bit over 300 years ago, it became the most sensational of them all. This was because of its spectacular ring, easily seen in a telescope and easily photographed later, when astronomical photography came into use. Figure 15 is one of the finest of recent photographs of Saturn.
The mysterious ring, when its presence became known, precipitated all manner of explanations. We now believe that it is analogous to the asteroids, composed of the fragments of a tenth and very large moon which once revolved around Saturn. There are now nine of these moons, and the tenth was the innermost. In the course of events it became dragged inside the Roche limit, and the enormous gravitational pull of Saturn caused it to burst. It can be shown mathematically that in such a case the fragments would slowly be drawn into a ring around the equator of the parent body. This is what we see to-day.
The ring is seen on close inspection to be made up of several rings which are separated from each other. Again it can be shown mathematically that these separate rings represent a balance of the complex gravitational forces exerted by the nine remaining moons. It is probable that the rings are made up mostly of small fragments, such as, gravel, rocks, and bowlders. All of the rings are inside of Roche's limit, which is a highly satisfactory check on the accuracy of the latter.
Saturn is big. He is nearly ten rimes the diameter of our Earth. Jupiter only is larger among the Sun's children. To indicate the size of these two planets: if we exclude Jupiter, Saturn is five times larger than all the other planets put together, while if we include Saturn, Jupiter is nearly twice as big as all the rest of the family put together. The fact that these large planets appear in the center of the family, and that as we proceed toward either end, the sizes grow smaller, has led to a confirmation of the theory of their birth out of the Sun which we shall look into as we proceed.
Saturn weighs about 95 times as much as Earth: The Sun weighs 31150 times as much as Saturn. Saturn's largest moon has been named Titan, and some believe they have seen evidence of an atmosphere of some sort on it. The temperature on Saturn must be away below where life can hope to exist. We must cancel it from the list of places where we may hope to find living organisms, not to speak of intelligent creatures.
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