gravity Gravity is a kind of force that a object pull on others. When you throw a ball off in the air, it will definitely fall down toward th ground. The reason is that the gravity of earth pulls on it. Gravity is based on mass which everything has and won't change in wherever the object is. So gravities of objects are really relavent with which planet they are because planets' masses are differient. The gravity in Jupiter which has the most volume of mass is largest and in Pluto which has the leastest mass is smallest in Solar system. Gravity is really important for people who will float off the surface of earth if earth does offer gravity. Gravity is really interest sometimes. For example you can feel flying in the air if you fall down in a container which is falling down freely.