“Our planet looks smooth to an observer from space, but this is because it is too small. If it were a bigger planet, then it would have mountains that would dwarf the Himalayas, and it would require observation from a greater distance to look smooth.”
source: The Black Swan: the impact of the highly improbable by Nassim Nicholas Taleb
Taleb makes this observation in a discussion of fractals. He follows to its logical conclusion the idea that organization is the same from the tiny to the gigantic. The rock is the mountain, more or less. But in following his logic Taleb makes one of those mistakes he often warns about – reality is not a logic game. Presumably a mountain on a Jupiter-sized planet would dwarf the largest mountain on earth the way Jupiter dwarfs earth, if not for gravity. Gravity is pulling at the Himalayas themselves.
Is a Jupiter-sized rocky planet even possible? If it did exist it would probably be quite smooth, as the planet’s gravity would be so great that the smallest nub would be squeezed down to nothingness.
The largest mountains are not on the largest planets. Olympus Mons is supposed to be the tallest mountain in the solar system (three times the height or Everest?), and it grew up on Mars, a planet much smaller than Earth. Venus, which has 90% of Earth’s gravity, also boasts mountains taller than any on Earth.