I am attempting to design a planet that would have the same gravity as earth, but would be as large as possible (so its mantle would be of a less dense element).

Now, my initial thought is for silicon, but I'm wondering if anyone has any better ideas for a lighter mantle and how much bigger than earth this could be made

  • $\begingroup$ Make deeper oceans, less rocks and more water=less gravity, Then add moons that affect the gravity of your planet. $\endgroup$
    – Charon
    Aug 9, 2016 at 14:55

1 Answer 1


Having less dense element works perfectly for example 1g on earth weighs 1,064 g on the surface of saturn (of course it will sink in the planet). Someone will probably show up soon with all the formula you need to find what element it should be.

But you will have just the same gravity, not the same magnetic field and not the same atmosphere. The magnetic field keeps the atmosphere from being destroyed by solar wind. The strength of the magnetic field is bound to the heavy metal in the core so if they are too rare you might lose the magnetic field.


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