When the circumference of a planet, say Jupiter, is measured, is the gaseous atmosphere included in the measurement? If so, why do we not measure the Earth in a similar fashion?

woodardr

I would guess it depends on teh planet. There are rocky planets (Mercury, Venus, Earth, Mars, Pluto) who either have no atmosphere, or it's very thin (On Earth space is defined to start 50 miles up, but as a substantial part of the planet it's much thinner, and the earth is 8000 miles in diameter. Venus also has a earth-sized atmosphere). The other planets are called gaseous planets, and in fact there's doubt that Jupiter even has a rocky center. Since the atmosphere is actually what makes those planets up, that's how they're measured. Rob Aug 04 06, 9:49 AM