Le 15-12-16 17:59, Sven Littkowski a écrit :
> Thanks to both of you, Thomas and Clipka. Yes, I assumed it is the
> amount of matter, like mountains or valley which have the one or another
> influence. But I wonder, if also the TYPE OF MATTER has influence, too.
> Example: I wonder, if a iron sphere of 10,000 km diameter produces the
> same gravity as a styrofoam sphere of 10,000 km diameter. I believe, not
> only the amount of matter matters, but the type of matter matters, too.
> Am I right?
>

As the sphere of iron is probably about 5 times as dense as your 
styrofoam, even after it have collapsed from it's own mass a few Km 
down, the iron sphere will have a much greater gravity than the styrene 
one. It all depends on the average density of the planete, whitch 
dictate it's total mass, whitch, with the radius, determine the surface 
gravity.

A planet made entirely from water would be about 5 times larger than the 
Earth to have about the same surface gravity, and an escape velocity 
about 5 times higher.

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