Why are the planets different sizes and what size are they?
The theory is the sun burned away matter from the inner planets, which is why these four are small rocky worlds. Mercury is very small but dense. Venus is almost as big as earth. Then comes earth, and Mars is quite a bit smaller than earth. Next is Jupiter, the first and king of the gas giants. Jupiter is bigger than all the other planets combined, over 300 times the mass of earth. Saturn is the next largest planet, followed by Neptune and Uranus.
