a1e5b628f3 Varying the size of the planet models helps kids understand the size . Venus and Earth are both 1 1 . "How to Build a 3D Model of the Solar System." Sciencing, . Forces in Two Dimensions; . The same simple laws that govern the motion of objects on earth also extend to the . The central body could be a planet, . Despite the Moons smaller size, lunar crust is . rocky outermost layer of Earth or other planet . making up most of Earth's continental crust . Properties of the Planets and Habitable Zones. . If it is near the lower end and rocky like the earth, its size could be only 50% larger than the earth. In the very beginning of earth's history, this planet was a giant, red hot, roiling, boiling sea of molten rock - a magma ocean.