Superphysics Superphysics
Chapter 12

The Ebb and Flow of the Sea

by Rene Descartes Icon
3 minutes  • 638 words

Weight on Earth is caused by the motion of the air-aether on the pores of bodies.

The Moon also affects this motion on the Earth.

Assume that the moon is stationary at B relative to the air-aether below it. This air-aether has less space to pass through between O and 6 than between B and 6 (if the moon does not occupy the space between O and B).

The Moon

Consequently, this air-aether has to move a bit faster between O and 6.

  • It pushes the whole Earth a little bit towards D, so that its center T moves away a little bit from the center of the planetary gravitational territory ABCD.

This is because:

  • only the air-aether keeps the Earth where it is.
  • the air 5678 and the water 1234 surrounding this earth are liquid* bodies.

This same force that presses the earth also make the Earth’s liquids sink toward T from the side 6, 2 and also from its opposite 8, 4

  • To compensate, they rise in 5, 1 and 7, 3.

The surface EFGH of the earth remains round because it is solid.

  • But the liquid water 1234 and air 5678 form an oval.

The earth is also rotating around its center.

The side F is now directly opposite the moon.

  • This makes the water there less high.
  • In 6 hours, it must be directly opposite the air-aether C.
    • There, this water will be higher.
  • In 12 hours, it will be directly opposite F at D.
    • There, the water will be lower.

Thus the sea, which is represented by this water 1234, should have its ebb and flow around this earth once every 6 hours.

While this earth turns from E through F to G (from West to East), the flood of the water and the air that remains at 1 and 5 and at 3 and 7 passes from its Eastern side towards the West.

  • It causes a flow without ebb very much like that which, according to the report of our pilots, makes navigation easier from the East to the West than from the West to the East.

The moon each month makes the same circuit as the Earth does each day.

Thus, it causes to advance little by little towards the East the points 1, 2, 3, 4 that mark high and low water.

Hence, these waters do not change precisely every 6 hours, but rather lag behind by approximately 1/5 of an hour each time, as do those of our seas also.

The planetary gravitational territory ABCD is not exactly round.

  • It extends a bit more freely at A and at C
  • There it moves proportionately more slowly than at B and D, where it cannot so easily break the course of the other air-aether containing it.

Thus, the moon always remains as if attached to its exterior surface.

  • It must move a bit faster and remove itself less from its path.

This is why the ebb and flow of the sea are much greater when the moon is at B (where it is full) and at D (where it is new) than when it is at A or at C (where it is only half full).

The effect of a full moon is different from a new moon because of its light.

The other special properties of the ebb and flow of the sea depend in part on:

  • the location of the seacoasts
  • the prevailing winds

The other general motions of the earth, moon, the stars, and heavens can be understood from what I have said.

  • Or they do not serve my purpose here, not falling under the same heading as those of which I have spoken. They would take me too long to describe.

Thus, I only have to explain this action of the heavens and the stars, as their light.

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