> What happens as you pile mass into a planet is that the planet becomes dense, not large, and this is because of gravity. It's more complexe than this. Yes Ju

> What happens as you pile mass into a planet is that the planet becomes dense, not large, and this is because of gravity. It's more complexe than this. Yes Jupiter is twice as dense as Saturn, but so is Uranus, which is much smaller. Also the main reason for why Jupiter is just moderately larger than Saturn is that, at equal density, mass goes as the cube of diameter. If Jupiter had a density as low as Saturn, its diameter would only be 26% higher than it is today, and just 50% bigger than Saturn despite being 3.3 times as heavy.