Archimedes of Syracuse was a Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily. In terms of rocketry he was meant to have had a lightbulb moment in the bath understanding what “displacement” was.

As he lowered himself into the bath, he saw the level of the water rise. Then he had a sudden flash of inspiration! When an object is dropped into water, the level of the water rises. He realised that objects made of the same material and with the same weight must displace the same amount of water.

The word displacement implies that an object has moved, or has been displaced. Displacement is defined to be the change in position of an object. This is what happens when the rocket moves through the atmosphere.

Have a look at this video: How taking a bath led to Archimedes’ principle