Leibnitz replied to Bernoulli: “I am not afraid of advancing the opinion that there are in the universe animals that are as much our superiors in size as we are above the animalculæ which we only discover by means of a microscope, for nature knows no limits. On the other hand, it may be and it must be that there are in the small grains of dust and in the smallest atoms worlds which are not inferior to ours in beauty and variety.”
The exceedingly small microscopic organisms discovered and studied by Ehrenberg at the beginning of the nineteenth century seemed to place this population in evidence.
Pascal had written, as early as 1660, or perhaps even in 1654, in his Pensées:
“What is man in the infinite? Let a flesh-worm offer him in the smallness of its body parts which are yet smaller. Legs with joints, veins in those legs, blood in those veins, humours in that blood, drops in those humours, vapours in those drops. Suppose that in dividing up these last things he should spend his forces of imagination and that the last object at which he could arrive be the subject of our present discussion. He will perhaps think that that is the extreme of smallness in Nature. But I shall open for him a new abyss. I shall not only paint for him the visible universe but the immensity of nature which one can conceive within the range of this small atom. Let him see in it an infinity of worlds, every one with its firmament, its planets, its earths, in the same proportion as the visible world, on that earth animals and finally flesh-worms in which he will find again what the first flesh-worms presented to him. Let him go on finding the same thing without end and without rest. Let him lose himself in those marvels as astonishing in their smallness as the others are in their size, for who would not be astonished that our body, hardly perceptible in the universe which itself would be imperceptible in the grand totality, should now be a colossus, a world or rather a universe in comparison with the nothingness which we can never arrive at.
“Whoever follows these thoughts will be afraid of himself and, considering himself sustained by the weight which nature has given him, between those two abysses of the infinite and nothing, he will tremble in face of those marvels, and I believe that as his curiosity changes to admiration, he will be more disposed to contemplate them in silence than to seek them with presumption.
“For indeed what is man in nature? A nothing in comparison with the infinite, a universe in comparison with nothing, a mean between nothing and all. Infinitely removed as he is from comprehending the extremes, the goal and principle of things are invincibly concealed from him in an impenetrable secret; he is equally incapable of seeing that nothingness whence he sprang or that infinite which swallows him up.”
More than one of our contemporary savants has republished this conception of “the atom as a world system,” imagining that it is new and without appearing to recollect either Bernoulli or Pascal.
* * * * *
As we have seen before, the invisible world is the basis of creation and the visible universe is composed of invisible bodies. What we see is made up of things which we do not see.
In the sky every star of the Milky Way being below the seventh magnitude is quite invisible to our eye. Yet we see the Milky Way.