The Composition of Planets

As to your reasoning of the inconvenience that a centre would become further removed from another centre than from the circumference of his own globe, though centres are of the same species while the centre and circumference are of contrary nature and should therefore be furthest removed from one another, I reply as follows: Firstly, that contraries need not be at the furthest distance one from another, inasmuch as one may influence the other or may be patient of influence therefrom; as we see that the sun is disposed very close to us among the earths which encircle it, since the order of nature causeth an object to subsist, live and derive nourishment from his contrary, as the other becometh affected, altered, vanquished and transformed by the first. Moreover a short while back we discussed with Elpino the disposition of the four elements which all contribute particles in the composition of each globe, one particle being placed within another, one mixed with another. Nor are they distinguished as a containing and a contained body respectively. For where there is dry earth, there also are water, air and fire, either patent or latent. The distinction made by us among the globes, that some, like the sun, are fiery whilst others, as the moon and the earth, are watery, doth not depend on these bodies consisting solely of a single element, but merely on the predominance of a single element in the mixed substance. Furthermore it is a most false belief that contraries are situated furthest from one another. For in all objects the elements become naturally combined and mixed. And the whole universe, both in the principal and secondary parts, consisteth solely of such conjunction and union, since there is no portion of the earth which is not intimately mixed with water, without which it would have neither density, connection of the atoms withal nor solidity. Moreover what terrestrial body is so dense that it lacketh insensible pores? Without them such bodies would no longer be divisible nor penetrable by fire nor by the heat thereof which is, however, sensibly perceived to issue from the substance of these bodies. Where then in this thy body is a cold and dry portion which is not joined to a moist and warm part, no less appertaining to thy body? This distinction of elements resteth then not on nature but on logic. And if the sun be in a region far removed from that of our earth, yet neither air nor dry land nor water is further from him than from our own globe. For the sun, like our earth, is a composite body, though in him there predominateth a certain one of the above-mentioned four elements, and in our earth, another.

And why we do not see them orbiting other suns.