I think you mean "relative density". This is the ratio of the densities of two materials. Specific gravity is just the density of an object in relation to the density of water.



Do you mean the relative level of gravitational pull on different planets?

I know the gravitational pull on different planets and celestial bodies is different depending on their mass. The larger the body, the stronger the gravitational pull.



For example, the sun is the star that all the planets in our solar system orbit around. It has the largest mass and the strongest gravitational pull.


Earth orbits the sun and the moon orbits earth so the earth's mass and therefore, its gravitational pull is stronger than the moon's.


This is why astronauts can jump so high on the moon. Imagine Dwight Howard on the moon! Superman!