Descartes' vortices and the plenum are impossible

Descartes supposes an immense mass of insensible particles, which carries the earth along with a rapid movement from west to east, and which, from one pole to the other, moves parallel to the equator.

This vortex extends beyond the moon and which pulls the moon along in its course, is itself embedded in another, even more vast vortex, which touches another vortex without merging with it, etc.

1. This vortex moves around the earth from west to east and so it should drive bodies on the earth, from west to east

But in reality, bodies when falling all go straight down.

Therefore this vortex does not exist.*

2. If the circles of this vortex moved parallel to the equator, all bodies should fall perpendicularly under the circle[1] of this subtle matter to which it corresponds.

A body at A near the pole P (figure 45) should, according to Descartes, fall at R.

But it falls approximately along the line A B, which makes a difference of about 1,400 leagues, for one can count 1,400 common leagues of France from point R to the equator of the earth B: therefore this vortex does not exist.

3. If, to support this novel of vortices, one still likes to suppose that a fluid that is swirling does not turn on its axis; if one imagines that it can turn in circles which will all have as a center the center of the vortex itself;

One only has to do the experiment of a drop of oil or a large air bubble enclosed in a crystal ball full of water: make the ball turn on its axis, you will see this oil or this air arrange itself in a cylinder in the middle of the ball, and form an axis from one pole to the other; for all experiments as well as all reasoning ruin the vortices.

4. If this vortex of matter around the earth, and these other so-called vortices around Jupiter and Saturn, etc., existed, all these immense vortices of subtle matter, rolling so rapidly in different directions, could never let a ray of light darted from a star come to us in a straight line.*

It is proven that these rays arrive in a very short time compared to the immense path they travel: therefore these vortices do not exist.

5. If these vortices carried the planets from west to east, comets which cross these spaces in all directions from east to west, and from north to south, could never cross them.

Even if one supposed that comets did not in fact go from north to south, nor from east to west, one would gain nothing by this evasion, for we know that when a comet is in the region of Mars, Jupiter, Saturn, it goes incomparably faster than Mars, than Jupiter, than Saturn: therefore it cannot be carried by the same layer of the fluid that is supposed to carry these planets; therefore these vortices do not exist.

6. These vortices would be either:

• as dense and massive as the planets

• denser

• less dense

If so, the subtle matter that surrounds the moon and the earth would be as dense as an equal volume of earth.

We would experience, to lift a cubic foot of marble, for example, at least the same resistance that we would have to lift a marble column with a one-foot base, which would have for its length the distance from the earth to the extremity of the so-called vortex of the moon.

In the other two cases, which are, I believe, impossible, we argue with reason about what would happen. But here is something to cut short all difficulty, and to show that no vortex can press on the earth, and cause gravity.

The theory of motive forces show that a body that moves, for example, with 10 degrees of speed, receives no force, no movement from a power that will also have only ten degrees, and which will pursue this moving body.

For this power to add new degrees of movement to this body, it must have more than it; and it only communicates its excess to it. But the power of gravitation of attraction acts equally on bodies at rest and on bodies in motion, and communicates the same degrees of speed to both: therefore this power cannot come from a fluid which can only act according to the laws of motive forces.

7. If these fluids existed, one minute would be enough to destroy all movement in the stars. Newton demonstrated that any body that moves uniformly in a fluid of the same density loses half of its movement after having traveled three of its diameters. This is without any rebuttal.

8. Supposed again, which is impossible, that these planets could be moved in these imaginary vortices, they could only move circularly, since these vortices, at equal distances from the center, would be equally dense; but the planets move in ellipses: therefore they cannot be carried by vortices; therefore, etc.

9. The earth has its orbit which it travels between that of Venus and that of Mars; all these orbits are elliptical, and have the sun as their center; now, when Mars, and Venus, and the earth, are closer to each other, then the matter of the so-called torrent, which carries the earth, would be much more constricted: this subtle matter should precipitate its course, like a river narrowed in its banks, or flowing under the arches of a bridge.

Then this fluid should carry the earth along with a much greater speed than in any other position; but, on the contrary, it is at that very time that the movement of the earth is more slowed down.

When Mars appears in the sign of Pisces, Mars, the earth, and Venus, are in approximately this proximity that you see (figure 46): then the sun seems to be delayed by a few minutes, that is to say that it is the earth that is delayed. It is therefore demonstrated impossible that there is a torrent of matter there that carries the planets: therefore this vortex does not exist.

10. Among more sought-after demonstrations, which annihilate the vortices, we will choose this one. By one of Kepler’s great laws, every planet describes equal areas in equal times.

By another no less certain law, each planet makes its revolution around the sun in such a way that if, for example, its average distance from the sun is 10, take the cube of this number, which will make 1,000, and the time of the revolution of this planet around the sun will be proportional to the square root of this number 1,000.

If there were layers of matter that carried planets, these layers could not follow these laws: for it would be necessary for the speeds of these torrents to be at once reciprocally proportional to their distances from the sun, and to the square roots of these distances, which is incompatible.

11. To top it all off, everyone sees what would happen to two fluids circulating opposite one another.

They would necessarily merge, and form chaos instead of sorting it out. This alone would have cast a ridicule on the Cartesian system which would have overwhelmed it if the taste for novelty and the little habit then of examining had not prevailed.

The plenum is where these vortices are supposed to move. This is just as impossible as these vortices.

1. A single ray of light, which does not weigh, by a great deal, a hundred-thousandth part of a grain, would have to dislodge the whole universe if it had to open a path for itself to us through an immense space, of which each point would resist by itself, and by the whole line by which it would be pressed.

2. Let these two hard bodies A B (figure 47) be; they touch by a surface, and are supposed to be surrounded by a fluid which presses them from all sides; now, when they are separated, it is clear that the so-called subtle matter arrives sooner at point A, where they are separated, than at point B: therefore there is a moment when B will be empty; therefore, even in the system of subtle matter, there is emptiness, that is to say space.

3. If there were no emptiness and no space, there would be no movement, even in the system of Descartes.

He supposes that God created the universe full and consisting of small cubes: let there therefore be a given number of cubes representing the universe, without there being the slightest interval between them: it is obvious that one of them must leave the place it occupied, for if each one remains in its place there is no movement, since movement consists in leaving one’s place, in passing from one point of space to another point of space.

One of these cubes cannot leave its place without leaving it empty the instant it leaves it? for it is clear that this cube, by turning on itself, must present its corner to the cube that touches it, before the corner is broken.

Therefore then there is space between these two cubes; therefore, even in Descartes’ system, there can be no movement without a vacuum.

4. If everything were a plenum, we would experience an infinite resistance when walking like how we experience the resistance of fluids.

For example, that of water, which resists us 860 times more than that of air; that of mercury, which resists about 14,000 times more than air.

The resistances of fluids are as the squares of the speeds, that is to say if a man travels in a third of a second a foot of space of mercury, which resists him 14,000 times more than air; if this man, in the second third of a second, has double this speed, this mercury, which is 14,000 times denser than air, will resist as the square of two, the resistance will soon be infinite: therefore, if everything were a plenum, it would be absolutely impossible to take a step, to breathe, etc.

5. People have tried to evade the force of this demonstration, but one can only answer a demonstration with an error.

It is claimed that this infinite torrent of subtle matter, penetrating all the pores of bodies, cannot stop their movement.

They do not reflect that any moving object that moves in a fluid experiences all the more resistance the more surface it opposes to this fluid; now, the more holes a body has, the more surface it has: thus the so-called subtle matter, by striking all the interior of a body, would oppose the movement of this body much more than by only touching its exterior surface; and this is again strictly demonstrated.

6. In the plenum, all bodies would be equally heavy; it is impossible to conceive that a body weighs on me, presses me; that by its mass a pound of gold powder weighs as much on my hand as a piece of gold of a pound.

In vain do the Cartesians answer that the subtle matter penetrating the interstices of bodies does not weigh, and that only what is not subtle matter should be counted as heavy: this opinion of Descartes is only a pure contradiction in him, for, according to him, this so-called subtle matter alone causes the gravity of bodies, by pushing them towards the earth.

Therefore it itself weighs on these bodies; therefore, if it weighs, there is no more reason why one body will be heavier than another, since everything being a plenum, everything will have equally a mass, whether solid or fluid; therefore the plenum is a chimera; therefore there is a vacuum; therefore nothing can be done in nature without a vacuum; therefore gravity is not the effect of a so-called vortex imagined in the plenum[2].

We have just noticed, by the experiment in the pneumatic machine, that there must be a force that makes bodies descend towards the center of the earth, that is to say that gives them gravity, and that this force must act in proportion to the mass of bodies: we must now see what the effects of this force are, for if we discover its effects it is obvious that it exists.

So let us not first imagine causes and make hypotheses: that is the sure way to go astray; let us follow step by step what is really happening in nature. We are travelers who have arrived at the mouth of a river: we must go up it before we can imagine where its source is.