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Imagine an Earth sized planet consisting of only ferrous metals. The creatures living on the planet move around like a maglev trains, interacting with the world and each other electromagnetically.

The planet generates a powerful magnetic field of at least 10 tesla!

Let us suppose this interstellar planet is alone in a super void drifting through the emptiness of space and the inhabitants managed to develop calculus.

I'm wondering, since electromagnetic force is much much greater than gravitational force, would these creatures ever know gravity exists?

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  • $\begingroup$ They will, the same way we did...Why does the apple fall downwards in the first place? $\endgroup$ – Shadowzee Mar 17 '20 at 3:37
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    $\begingroup$ Electromagnetism is stronger than gravity, yes, but because you have positive and negative particles mixed all over the place mutually canceling out and gravity emerges as the most evident force on a larger scale. Conditions to electromagnetism overcome gravity need a very ionized environment like in a neutron star. Need lots of fantasy to imagine any kind of lifeforms in this kind of place. How you would make molecules? $\endgroup$ – Rodolfo Penteado Mar 17 '20 at 4:18
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    $\begingroup$ This world is only ferrous metals? No carbon or silicon? Iron-based life? I think you may have broader chemistry and biology challenges. $\endgroup$ – JamesFaix Oct 27 '20 at 0:53
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    $\begingroup$ @JamesFaix -- No worries. It's not our job, really, to complain how things can't be done, but rather to take the OP's query, and the world it depicts, as factual. It's our job to imagineer ways to describe the reality the OP posits! $\endgroup$ – elemtilas Dec 14 '20 at 1:07
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Two possibilities spring to mind... I'm not sure if they are certainties, but:

  • The shape of their world will be strongly determined by gravity, not magnetism. In the absense of a sun it will be difficult for them to determine the shape of their world (that might be an interesting question in itself) but there will always be a horizon and they could conceivably circumnavigate their world giving them an idea of its extent and a rough idea of its curvature.
  • Ferrous does not imply ferromagnetic. Nonmagnetic allotropes of iron such as asutenite exist, and if they were fabricated by your aliens or occurred naturally on their world they'd clearly show that some other force was present when dropped, etc.
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the planet generate a powerful magnetic field of at least 10 tesla!

That world will become dry in a very short time at cosmic scale.

Reason: water is diamagnetic - so indeed any creature containing lots of water may levitate (if not heavy enough). But this also applies to water vapors; those will be repulsed into space - hence, no water based life will develop.

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    $\begingroup$ Water isn't a ferrous metal, so the planet doesn't have any to begin with. $\endgroup$ – Christopher James Huff Dec 14 '20 at 1:26

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