Imagine a world whose sun is swinging like a pendulum above a flat surface. This is a sketch of the diagram.

Pendulum system

  1. A complete cycle lasts twenty-four (24) hours (from an end to the other and back again to the start point).
  2. The pendulum deviates one degree in each cycle, so after 360 days it would finish a full rotation (a year).
  3. There is no other celestial body in the sky to interfere with the motion of the pendulum.
  4. This world is flat and yet gravity attracts objects only from top to bottom, large bodies (like the pendulum sun) can affect this gravity.*

What would be like the gravitational pull over the oceans? I assume this Sun has enough mass to affect tides just as the Moon does in real life. I have made another diagram of what I think it could be like: enter image description here

Black arrows represent the direction of the pendular movement and blue arrows represent the gravitational pull.

Summing up, my question is: is this gravitational pull model plausible or am I missing something? Also, I'm not sure how would this affect winds, so if you have any idea about that feel free to comment.

I hope everything is clear, but please let me know if you need more details. Thank you.

EDIT: I haven't thought about the mass of the Sun and the distance between the pendulum and the surface, but I think these numbers may vary as long as human life on this "planet" is possible. Maybe the mass of the pendulum Sun is similar to real life Moon's, and the distance is approximately the same between Moon and Earth. But as I was saying, it's not important as long as life is possible.

*It might be that, since gravity works in an unidirectional way (from top to bottom), the pendular Sun does not affect tides at all...?

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    $\begingroup$ @JustSnilloc This question has nothing to do with real astronomy. This model would be impossible in real life. $\endgroup$
    – MoholyNagy
    Jan 28, 2018 at 22:49
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    $\begingroup$ Are you questioning how the sun could move in this way or just whether the gravity would act as you've described? $\endgroup$ Jan 28, 2018 at 22:50
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    $\begingroup$ @LioElbammalf Just if gravity would act as I've described. $\endgroup$
    – MoholyNagy
    Jan 28, 2018 at 22:53
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    $\begingroup$ Then yes but if you're asking people to accept the pendulum sun you've got free rein on this too $\endgroup$ Jan 28, 2018 at 23:18
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    $\begingroup$ First off, this is definitely not for astronomy. Second off, I need to know what motive force is keeping the sun in its pendulum-like 'orbit'. Then, how does gravity work? By the standard equation? Is the gravitational constant the same? Finally, what is the mass of your sun? Does your 'Earth' which appears to be larger than the sun exert any gravity on the sun? If not, why not? $\endgroup$
    – kingledion
    Jan 29, 2018 at 0:30

1 Answer 1


The question deals with an alternative cosmos: A flat Earth with a Sun that swings like a pendulum above the plane of the world.

First, there are some conceptual issues that need to be pondered. There must be 'something" that holds the Sun in place for it to swing like a pendulum. Also, for it not to fall on the flat earth or attract the flat earth to it. Holding the Sun in place may be easier. There may need to be a repulsive force keeping flat earth and Sun apart. Otherwise both bodies might be held in place by cosmic "anchors" embedded in the fabric of this reality.

The gravitational pull of the pendulum Sun will cause the oceans and seas on the flat earth to slosh forwards and backwards. This will resemble tides on the flat earth.

Winds are driven on our Earth by a combination of factors like Coriolis forces due to its rotation, but mainly due to thermal differences between parts of the planet's surface. Winds are mostly likely to be driven in a similar manner on this flat earth. Gravitation from the pendulum Sun will impart an aeolian tide to the atmosphere of the flat earth. The possibility of wind tides is most intriguing. However, to estimate this effect it would be necessary to factor the mass of the pendulum Sun and its distance from the surface of the flat earth. Without those details to do the necessary calculations this is guesswork. So please be clear about that.

  • $\begingroup$ Thanks for your answer. I haven't thought about the mass of the Sun and the distance from the surface of the earth. But the requisite is life to exist in this world, so the mass and the distance must be the needed to maintain a balance. Maybe the mass of the Moon and the distance of it from the Earth. $\endgroup$
    – MoholyNagy
    Jan 29, 2018 at 1:01
  • $\begingroup$ @MoholyNagy This is why asking questions helps test the elements of a created world. Certainly adjust the mass and the distance of the pendulum Sun to achieve the right balance. $\endgroup$
    – a4android
    Jan 29, 2018 at 1:11

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