If you fill a balloon with helium, a substance lighter than the nitrogen, oxygen and other elements which compose the air around it, the balloon will immediately fly upwards. If you blow a dandelion seed out of your hands, a substance just barely heavier than the air, it will float away and slowly but eventually fall to the ground. And if you drop an anvil from your hands, something much heavier than the air, it will quickly and directly fall straight to the ground. Now, this has absolutely nothing to do with “gravity.” The fact that light things rise up and heavy things fall down is simply a natural property of weight. That is very different from “gravity.” Gravity is a hypothetical magnetic-like force possessed by large masses which Isaac Newton needed to help explain the heliocentric theory of the universe.