ABSTRACT
A balloon is a sack filled with gas.Large balloons filled with gascan rise and stay in flight because of the gas inside the balloon.
How Balloons Stay Up Archimedes (AR-key-MEE-dees), a Greek scientist of the third century B.C.E., realized that an object will float when its weight equals, or is less than, the weight of the fluid (gas or liquid) it displaces, or pushes away. His discovery explains why a ship floats. It also provides an explanation of why a balloon flies, because air displaces in the same way as water. This force is called buoyancy.
