Physiologia Kircheriana Experimentalis

PARADOX V.

If the entire earthly globe were to be cut horizontally through the center of the earth—that is, diametrically—no one could stand in a straight and natural position on this cut plane by mathematical positioning, though by physical positioning many could.

Let the surface of the earthly globe, cut horizontally or in any other way, be A B C D; I say that on said surface, no one can consist in a straight and natural position by mathematical positioning, namely at the center E. For since

A circular diagram representing a cross-section of the Earth labeled A, B, C, D with a central point E. A human figure stands upright at the center point E, aligned with the vertical axis B-D.

all lines of the said surface converge downward toward the center, it is impossible for anyone to fix himself at any point other than the center. For let someone support himself on the line A E or C E; truly, since those lines are lines of direction, he could fix himself on them and could not fix himself, which is absurd and impossible. Therefore, he will consist in a natural position only at the center of the said surface, yet with this condition: that if he attains a perpendicular position on said surface, he could stand upon his feet; if, however, he obtains a position parallel to the vertical plane, he will not adhere by his feet, but by his navel to the center of the earth in a natural position. The reason is that one standing perpendicularly to the plane has something beneath him by which he may be supported; if, however, he has a position parallel to the vertical plane, he can no longer stand upon his feet, but his body will be fixed near its center of gravity at the center, as appears in the following figure, where the plane L M N O is displayed in a perpendicular position, in which it clearly appears that a man can stand upright nowhere on the line L N,

nor can he stand upon his feet even at the center S, but his body will be fixed only where the center of gravity of the heavy body corresponds to the center of the earth; all of which is evident from the figure.

A circular diagram labeled L, M, N, O showing a human figure positioned horizontally at the center point S, with the center of gravity (the navel) aligned with the Earth's center.

It follows from this also that in whatever way the globe of the earth is cut—whether normally, horizontally, or in a slanting position—the same result always follows; for a plane of this kind cannot properly be called horizontal, but however it is situated, it will always obtain a position perpendicular to the center. Hence we have called the plane A B C D horizontal only insofar as it appears as such to our imagination, even though it is not horizontal in the least, but a perfectly perpendicular surface. For just as no one can naturally and freely stand upon some wall or flat partition, so neither can one upon said surface, which acts like some vast wall that is perpendicular on every side, whose midpoint is the center of the earth, the point of rest.

PARADOX VI.

A wheel rotated in the center of the earth will be carried neither upward nor downward.

On the surface of the earth, a wheel cannot be rolled unless one of its halves is always ascending and the other is descending. But in the center of the earth, said wheel, once rotated, will be carried neither upward nor downward, and it will always maintain the same position relative to the center of the earth, to which it is equidistant and of equal weight on every side, nor [will it have] any