Posted on Thursday 16 November 2006 to unknown

It took Copernicus to revolutionise our understanding of the universe, Kepler to make it work and Newton (many years later) to explain it but it took the heretical monk Giordano Bruno to understand what it meant.

Bruno, who was born five years after the death of Copernicus and who himself died nine years before Galileo first peered through a telescope, was more philosopher than scientist but he had a powerful intuition and could see what none of his contemporaries or immediate successors were able to.

Copernicus replaced the earth with the sun as the center of the universe for some very classical reasons. Ptolemy had broken with Aristotle and introduced a concept of non-uniform motion in order to explain the observed behaviour of Venus and Mars. This had bothered astronomers ever since and Copernicus decided to create a model which would consist purely of uniform circular motion but the price was to reject the common sense view that the world was at rest and instead he argued that it was in circular motion around the sun. Nevertheless, despite the revolutionary (in ever sense) potential of this innovation, Copernicus continued to accept the majority of the Ptolemaic dogma. He continued to think of the so-called fixed stars of the firmament as merely equidistant points of light which lay upon the inside of an invisible sphere (but one that didn't rotate as Ptolemy had believed). Copernicus in the process of rejecting geocentrism simply replaced the earth with the sun as the central point in the universe while holding all things else in Ptolemy as the truth.

Bruno went much further this. He agreed that earth was a planet just like any other (in fact he referred to all planets as "earths") but he also denied that the sun itself was in anyway special. Far from placing it at the centre of the universe, he argued that it should be considered just a star amongst an infinity of others and that stars were not fixed to an outer sphere but rather were separated from one another by vast stretches of open space. Furthermore, he considered the possibility that all of the planets were inhabited (and even the sun!) and that every star in the universe was orbited by inhabited worlds.

In his work, On the Infinite Universe and Worlds, he expounds his theory in the form of a dialog

Philotheo. [The whole universe] then is one, the heaven, the immensity of embosoming space, the universal envelope, the ethereal region through which the whole hath course and motion. Innumerable celestial bodies, stars, globes, suns and earths may be sensibly perceived therein by us and an infinite number of them may be inferred by our own reason. The universe, immense and infinite, is the complex of this [vast] space and of all the bodies contained therein.

Elpino. So that there are no spheres with concave and convex surfaces nor deferent orbs; but all is one field, one universal envelope.

Philotheo. So it is.

...


Elpino. There are then innumerable suns, and an infinite number of earths revolve around those suns, just as the seven we can observe revolve around this sun which is close to us.

Philotheo. So it is.

Elpino. Why then do we not see the other bright bodies which are earths circling around the bright bodies which are suns? For beyond these we can detect no motion whatever; and why do all other mundane bodies (except those known as comets) appear always in the same order and at the same distance?

Philotheo. The reason is that we discern only the largest suns, immense bodies. But we do not discern the earths because, being much smaller, they are invisible to us. Similarly it is not impossible that other earths revolve around our sun and are invisible to us on account either of greater distance or of smaller size, or because they have but little watery surface, or because such watery surface is not turned toward us and opposed to the sun, whereby it would be made visible as a crystal mirror which receiveth luminous rays; whence we perceive that it is not marvellous or contrary to nature that often we hear that the sun hath been partially eclipsed though the moon hath not been interpolated between him and our sight. There may be innumerable watery luminous bodies ? that is, earths consisting in part of water ? circulating around the sun, besides those visible to us; but the difference in their orbits is indiscernible by us on account of their great distance, wherefore we perceive no difference in the very slow motion discernible of those visible above or beyond Saturn; still less doth there appear any order in the motion of all around the centre, whether we place our earth or our sun as that centre.

...

Elpino. Therefore you consider that if the stars beyond Saturn are really motionless as they appear, then they are those innumerable suns or fires more or less visible to us around which travel their own neighbouring earths which are not discernible by us.

Theophilo. Yes, we should have to argue thus, since all earths merit the same amount of heat, and all suns merit the same amount.

Elpino. Then you believe that all those are suns?

Philotheo. Not so, for I do not know whether all or whether the majority are without motion, or whether some circle around others, since none hath observed them. Moreover they are not easy to observe, for it is not easy to detect the motion and progress of a remote object, since at a great distance change of position cannot easily be detected, as happeneth when we would observe ships in a high sea. But however that may be, the universe being infinite, there must ultimately be other suns. For it is impossible that heat and light from one single body should be diffused throughout immensity, as was supposed by Epicurus if we may credit what others relate of him. Therefore it followeth that there must be innumerable suns, of which many appear to us as small bodies; but that star will appear smaller which is in fact much larger than that which appeareth much greater.

Elpino. All this must be deemed at least possible and expedient.

Philotheo. Around these bodies there may revolve earths both larger and smaller than our own.

...

Burchio. We, however, maintain that the earth should always be regarded as central, as hath been believed by so many highly learned personages.

Fracastoro. And hath been confirmed by fools.

Burchio. What do you say of fools?

Fracastoro. I say that this opinion hath not been confirmed either by sense or reason.

...

Burchio. Quickly, your conclusion!

Fracastoro. I would conclude as follows. The famous and received order of the elements and of the heavenly bodies is a dream and vainest fantasy, since it can neither be verified by observation of nature nor proved by reason or argued, nor is it either convenient or possible to conceive that it exist in such fashion. But we know that there is an infinite field, a containing space which doth embrace and interpenetrate the whole. In it is an infinity of bodies similar to our own. No one of these more than another is in the centre of the universe, for the universe is infinite and therefore without centre or limit, though these appertain to each of the worlds within the universe in the way I have explained on other occasions, especially when we demonstrated that there are certain determined definite centres, namely, the suns, fiery bodies around which revolve all planets, earths and waters, even as we see the seven wandering planets take their course around our sun. Similarly we shewed that each of these stars or worlds, spinning around his own centre, hath the appearance of a solid and continuous world which taketh by force all visible things which can become stars and whirleth them around himself as the centre of their universe. Thus there is not merely one world, one earth, one sun, but as many worlds as we see bright lights around us, which are neither more nor less in one heaven, one space, one containing sphere than is this our world in one containing universe, one space or one heaven. So that the heaven, the infinitely extending air, though part of the infinite universe, is not therefore a world or part of worlds; but is the womb, the receptacle and field within which they all move and live, grow and render effective the several acts of their vicissitudes; produce, nourish and maintain their inhabitants and animals; and by certain dispositions and orders they minister to higher nature, changing the face of single being through countless subjects


...

Burchio. Then the other worlds are inhabited like our own?

Fracastoro. If not exactly as our own, and if not more nobly, at least no less inhabited and no less nobly. For it is impossible that a rational being fairly vigilant, can imagine that these innumerable worlds, manifest as like to our own or yet more magnificent, should be destitute of similar and even superior inhabitants; for all are either themselves suns or the sun doth diffuse to them no less than to us those most divine and fertilizing rays, which convince us of the joy that reigneth at their source and origin and bring fortune to those stationed around who thus participate in the diffused quality. The innumerable prime members of the universe are then infinite [in number], and all have similar aspect, countenance, prerogative, quality and power.

...

Burchio. In this way, you would put the world upside down.

Fracastoro. Wouldst thou consider him to do ill who would upset a world which was upside down?