Newton, Fontenelle, Aesthetic Cosmology, and Extinction.

Helen de Cruz shared a draft translation of the fifth evening of Bernard le Bovier de Fontenelle’s (1686) Entretiens sur la pluralité des Mondes (see here). As Helen notes correctly, Fontenelle was drawing on “ Descartes’s notion of vortices, of which Fontenelle was a huge fan.” The scientific timing of Fontelle’s work could not be worse: Huygens and Newton both had developed overwhelming empirical evidence and many conceptual arguments that Descartes’ account could not work by then. And by 1690 (after the publication of the Principia and Huygens’ Treatise on Light, which included his Discourse on Gravity) this was obvious to all informed natural philosophers. It didn’t prevent Fontenelle’s work be a century long best-seller.

Huygens himself defended a modified vortex account (but based on Newton’s evidence, accepted Kepler’s laws for celestial phenomena in our solar system). One important difference between Descartes’ vortex theory and Huygens’ approach is that Huygens insisted that solar systems had to be causally isolated from each other. As Huygens explains in his (1695) Cosmotheoros,

“for I cannot allow [vortices] to be so large as [Descartes] would make them. I would have them dispers’d all about the immense space, like so many little Whirl-pools of Water, that one makes by the stirring of a stick in any large Pond or River, a great way distant from one another. And as their motions do not all intermix or communicate with one another; so in my opinion must the Vortices of Stars be plac’d as not to hinder one anothers free Circumrotations.

Basically Huygens worried that if the solar systems of the universe could interact mediated by a universal vortex (or offshoots thereof) then all solar systems would be fundamentally unstable; there there would be nothing to prevent an eternal return of catastrophic galactic events (as the Stoics clearly thought).

In De Cruz’s translation of day 5, Fontenelle anticipates the worry, and offers a response to it:

all these vortices adjust to each other the best they can, in such a way that each turns around its sun without changing place, each one taking the manner of turning that is most convenient and easiest in its situation. They interlock like cogs in a watch, and mutually aid each other's movements. Even so, they also act against each other. Each World, as they say, is like a balloon that self-inflates and that will expand, if it was allowed to, but it is quickly pushed back by its neighboring Worlds, and so it returns to itself, after it will start again to inflate, and so on.

To what degree aliens always can survive the self-inflation, expansion, and return to normal of solar systems is left unclear.

As an important aside, to the best of my knowledge (and this seems to have been little noticed) it is Fontenelle who, while articulating Descartes’ cosmology, invents the clockwork universe as self-regulating machine here! (It’s often attributed to Newton by his early critics, especially.) [For a fun paper of Fontenelle’s impact on Adam Smith, see Paganelli here.]

Okay, so much for set up. In the same evening, Fontenelle also claims the following:

Nothing is as beautiful to present itself as this prodigious number of vortices, where each center is occupied by a sun that makes the planets turn around itself. The inhabitants of a planet of one of these infinitely many vortices see the luminous centers of the vortices in their neighborhood, but they have to be careful to be able to see the planets, which only have a faint light, borrowed from their sun, never pushing it beyond their World.

This passage is echoed in the General Scholium (added to the second, 1713 edition) of Newton’s Principia. Before I quote that, a bit of a reminder (recall here). In the first (1687) edition of Principia, God is only mentioned once (and somewhat hidden) in the body of the text: “Therefore God placed the planet at different distances from the sun so that each one might, according to the degree of density, enjoy a greater or smaller amount of heat from the sun'' (Book 3, proposition 8, corollary 5; p. 814; all my Newton quotes are from the translation by I. Bernard Cohen and Anne Whitman). In context it’s clear that Newton helps the reader understand that if you know/posit the distance from Earth to Sun, then you can calculate mass and density of Sun (and then all the other planets). This claim was removed in subsequent editions of the Principia.

Despite only being present in the first edition of the Principia, Many readers of Newton — e.g., Huygens (1690) Discourse on Gravity; Maclaurin (1747) An Account; Adam Smith (1795) History of Astronomy; Kant (1755) Universal Natural History — realized and were charmed by the fact that you could, thereby, also calculate the gravity alien life would experience on their home planets. Newton’s readers treat Newton as suggesting that alien life is part of the providential plan of God.

As noted above, Newton removes the mention of God from the body of the text of the second edition Principia, but instead writes the General Scholium and adds it to the end of the book. The first paragraph of the General Scholium attacks Descartes’ vortex theory. The last sentence of that paragraph reads: “Comets go with very eccentric motions into all parts of the heavens, which cannot happen unless vortices are eliminated.” (I have added emphasis, and will return to that below.) Comets are taken to be a devastating problem for vortex theories, because they would undermine the stability of the vortex and the visible planetary orbits.

The second paragraph of the General Scholium argues that space is empty and that planetary bodies and comets do not encounter any resistance. The last sentence of that second paragraph reads: “They will indeed persevere in their orbits by the laws of gravity, but they certainly could not originally have acquired the regular position of the orbits by these laws.” This is the first mention of cosmogony in the Principia.

The third paragraph uses the motions of comets to deny the lawlike origin of the cosmos: “And all these regular motions do not have their origin in mechanical causes, since comets go freely in very eccentric orbits and into all parts of the heavens.” (again emphasis added).

The fourth paragraph I quote in full because it partially echoes the Fontenelle paragraph I quoted above.

This most elegant system of the sun, planets, and comets could not have arisen without the design and dominion of an intelligent and powerful being. And if the fixed stars are the centers of similar systems, they will all be constructed according to a similar design and subject to the dominion of One, especially since the light of the fixed stars is of the same nature as the light of the sun, and all the systems send light into all the others. And so that the systems of the fixed stars will not fall upon one another as a result of their gravity, he has placed them at immense distances from one another.

The underlying idea is that natural Beauty/elegance is evidence of God’s design. Among the reasons why we can assume that our solar system is the product of design is that it is beautiful to us, and there is no plausible lawlike cosmogony that can produce our solar system and comets. (As I argue elsewhere (here) Kant’s Universal Natural History and Theory of the Heavens can be read as producing such a lawlike account.)

Newton’s argument relies on the idea that light travels through the cosmos, and is one kind of thing everywhere. (That’s a tacit appeal to his first rule of reasoning: “Nature does nothing in vain, and more causes are in vain when fewer suffice. For nature is simple and does not indulge in the luxury of superfluous causes.”)

Now as is well known, Newton accepted the argument that light has a fixed speed first measured by Rømer with the help of Huygens (in 1676). I wouldn’t be surprised if Newton tried repeating his prism experiments on starlight to show that it had same degree of refrangibility as Sunlight. (But I don’t know of any evidence.)

So, lurking here are two important commitments.

1. There seem to be infinite solar systems that will also have similar beauty as ours and so ruled by God.

2. God’s benevolence puts solar systems sufficiently far apart to keep them safe from each other.

From 1-2 it seems to follow (3) that there are infinite (astronomer) aliens who can experience beautiful starry nights (governed by God’s providence). So, while Newton very much disagrees with Fontenelle’s cosmogony and cosmology—they seem to agree on (3.)

If you lack time you can stop reading here.

But there is a two-fold problem lurking in Newton’s argument. First, for Newton, light is made up of particles with mass. And if light is everywhere the same and traveling among solar systems then solar systems are, thus, not causally isolated but exchange mass! And so with enough time they will move toward or away from each other.

Second, light is not the only interstellar mass-containing traveler. Recall the following two passages that I quoted from the general scholium:

• “Comets go with very eccentric motions into all parts of the heavens”

• “Comets go freely in very eccentric orbits and into all parts of the heavens.”

It is quite explicit that Newton also thinks comets are at least capable of interstellar travel, and do seem to do it. They also play a non-trivial role in what one may call the “economy of nature.’

I have the following in mind. Here’s the very last sentence of main body of (2nd and 3rd edition of) Principia: “the vapors that arise from the sun and the fixed stars and the tails of comets can fall by their gravity into the atmospheres of the planets and there be condensed and converted into water and humid spirits, and then—by a slow heat—be transformed gradually into salts, sulphurs, tinctures, slime, mud, clay, sand, stones, corals, and other earthy substances.” This is not an isolated closing flourish. A few pages before, Newton writes: “I suspect that that spirit which is the smallest but most subtle and most excellent part of our air, and which is required for the life of all things, comes chiefly from comets.” (bk 3, prop 41, p 926, emphasis added)

Now, there is a way to read these two last quotes (that are not in the general scholium) as restricted to intra-solar-system cometary activity. And without the General Scholium arguments, I would not be tempted otherwise.

But the more expansive claims of the General Scholium clearly suggests that the orbits of comets can depart so far from a solar system that, in principle, they can escape the gravity of the Sun they orbit and — given enough time — be captured by other solar systems and even bring the necessary ingredients of life there. (Newton is clearly on team-possible-alien-origins-of-some-life.)

But that’s to say that the Principia offers two kinds of reasons (light and comets) for thinking that the actual causal isolation among solar systems need not be absolute. And so leaving aside the question over the intrinsic stability of the planetary orbits of a solar system, there was always lurking in Newton’s project a question over (what we may call) the extrinsic stability of a solar system. The possible, catastrophic — extinction level — interactions among solar systems cannot be ruled out with the tools Newton has and must rely on providential faith.