(1) That both should be at rest is impossible; for, if the earth is at rest, the hypothesis does not account for the observations; and we take it as granted that the earth is at rest. It remains1 either that both are moved, or that the one is moved and the other at rest.
(2) On the view, first, that both are in motion, we have the absurdity2 that the stars and the circles move with the same speed, i.e. that the arc of every star is that of the circle in it moves. For star and circle are seen to come back to the same place at the same moment; from which it follows that the star has traversed the circle and the circle has completed its own movement, i.e. traversed its own circumference3, at one and the same moment. But it is difficult to conceive that the pace of each star should be exactly proportioned to the size of its circle. That the pace of each circle should be proportionate to its size is not absurd but inevitable4: but that the same should be true of the movement of the stars contained in the circles is quite incredible. For if, on the one hand, we suppose that the star which moves on the greater circle is necessarily swifter, clearly we also admit that if stars shifted their position so as to exchange circles, the slower would become swifter and the swifter slower. But this would show that their movement was not their own, but due to the circles. If, on the other hand, the arrangement was a chance combination, the coincidence in every case of a greater circle with a swifter movement of the star contained in it is too much to believe. In one or two cases it might not inconceivably fall out so, but to imagine it in every case alike is a mere5 fiction. Besides, chance has no place in that which is natural, and what happens everywhere and in every case is no matter of chance.
(3) The same absurdity is equally plain if it is supposed that the circles stand still and that it is the stars themselves which move. For it will follow that the outer stars are the swifter, and that the pace of the stars corresponds to the size of their circles.
Since, then, we cannot reasonably suppose either that both are in motion or that the star alone moves, the remaining alternative is that the circles should move, while the stars are at rest and move with the circles to which they are attached. Only on this supposition are we involved in no absurd consequence. For, in the first place, the quicker movement of the larger circle is natural when all the circles are attached to the same centre. Whenever bodies are moving with their proper motion, the larger moves quicker. It is the same here with the revolving6 bodies: for those that are intercepted7 by two radii8 will be larger in the larger circle, and hence it is not surprising that the revolution of the larger circle should take the same time as that of the smaller. And secondly9, the fact that the heavens do not break in pieces follows not only from this but also from the proof already given of the continuity of the whole.
Again, since the stars are spherical10, as our opponents assert and we may consistently admit, inasmuch as we construct them out of the spherical body, and since the spherical body has two movements proper to itself, namely rolling and spinning, it follows that if the stars have a movement of their own, it will be one of these. But neither is observed. (1) Suppose them to spin. They would then stay where they were, and not change their place, as, by observation and general consent, they do. Further, one would expect them all to exhibit the same movement: but the only star which appears to possess this movement is the sun, at sunrise or sunset, and this appearance is due not to the sun itself but to the distance from which we observe it. The visual ray being excessively prolonged becomes weak and wavering. The same reason probably accounts for the apparent twinkling of the fixed11 stars and the absence of twinkling in the planets. The planets are near, so that the visual ray reaches them in its full vigour12, but when it comes to the fixed stars it is quivering because of the distance and its excessive extension; and its tremor13 produces an appearance of movement in the star: for it makes no difference whether movement is set up in the ray or in the object of vision.
(2) On the other hand, it is also clear that the stars do not roll. For rolling involves rotation14: but the ‘face’, as it is called, of the moon is always seen. Therefore, since any movement of their own which the stars possessed15 would presumably be one proper to themselves, and no such movement is observed in them, clearly they have no movement of their own.
There is, further, the absurdity that nature has bestowed16 upon them no organ appropriate to such movement. For nature leaves nothing to chance, and would not, while caring for animals, overlook things so precious. Indeed, nature seems deliberately17 to have stripped them of everything which makes selforiginated progression possible, and to have removed them as far as possible from things which have organs of movement. This is just why it seems proper that the whole heaven and every star should be spherical. For while of all shapes the sphere is the most convenient for movement in one place, making possible, as it does, the swiftest and most selfcontained motion, for forward movement it is the most unsuitable, least of all resembling shapes which are self-moved, in that it has no dependent or projecting part, as a rectilinear figure has, and is in fact as far as possible removed in shape from ambulatory bodies. Since, therefore, the heavens have to move in one place, and the stars are not required to move themselves forward, it is natural that both should be spherical-a shape which best suits the movement of the one and the immobility of the other.
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1
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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2
absurdity
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| n.荒谬，愚蠢；谬论 | |
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3
circumference
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| n.圆周，周长，圆周线 | |
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4
inevitable
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| adj.不可避免的，必然发生的 | |
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5
mere
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| adj.纯粹的；仅仅，只不过 | |
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6
revolving
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| adj.旋转的，轮转式的；循环的v.（使）旋转( revolve的现在分词 )；细想 | |
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7
intercepted
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| 拦截( intercept的过去式和过去分词 )； 截住； 截击； 拦阻 | |
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8
radii
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| n.半径；半径（距离）( radius的名词复数 )；用半径度量的圆形面积；半径范围；桡骨 | |
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9
secondly
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| adv.第二，其次 | |
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10
spherical
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| adj.球形的；球面的 | |
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11
fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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12
vigour
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| （=vigor）n.智力，体力，精力 | |
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13
tremor
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| n.震动，颤动，战栗，兴奋，地震 | |
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14
rotation
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| n.旋转；循环，轮流 | |
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15
possessed
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| adj.疯狂的；拥有的，占有的 | |
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16
bestowed
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| 赠给，授予( bestow的过去式和过去分词 ) | |
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17
deliberately
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| adv.审慎地；蓄意地；故意地 | |
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