An example of an analogy used to explain development in science:
"The obsession on the subject of circular motion was disappearing at this time [when Kepler was working out his model of the Solar System], however, for other reasons, and chiefly because the existence of the hard crystal spheres was ceasing to be credible. It had been the spheres, the various inner wheels of the vast celestial machine, that had enjoyed the happiness of circular motion, while the planet, recording the resultant effect of various compound movements, had been realised all the time to be pursuing a more irregular course. It was the circular motion of the spheres themselves that symbolised the perfection of the skies, while the planet was like the rear lamp of a bicycle – it might be the only thing that could actually be seen from the earth, and it dodged about in an irregular manner; but just as we know that it is really the man on the bicycle who matters, though we see nothing save the red light, so the celestial orbs had formed the essential machinery of the skies, though only the planet that rode on their shoulder was actually visible. Once the crystal spheres were eliminated, the circular motion ceased to be the thing that really mattered henceforward it was the actual path of the planet itself that fixed one's attention. It was as though the man on the bicycle had been proved not to exist, and the rear lamp, the red light, was discovered to be sailing on its own account in empty space. The world might be rid of the myth of circular motion, but it was faced with more difficult problems than ever with these lamps let loose and no bicycle to attach them to. If the skies were like this, men had to discover why they remained in any order at all – why the universe was not shattered by the senseless onrush and the uncontrollable collidings of countless billiard-balls."
Herbert Butterfield (1957) The Origins of Modern Science 1300-1800 (New Edition: Revised and enlarged). G. Bell and Sons Ltd., London.
Read examples of scientific analogies
The extract discusses the model of the universe in which each of the visible planets (and the Sun and Moon) was mounted in its separate crystalline sphere – the concentric spheres being centred on Earth. This model was widely accepted for centuries in much of the world. Today we would consider these ideas alternative conceptions (if not too fantastic to entertain).
The reference to the spheres 'enjoying the happiness' of circular motion can be sen as an anthropomorphic metaphor.
Read examples of anthropomorphism in science
