Air is all around us and wherever there is air, there is air pressure. This means that everything (including us!) has pressure being applied on it.
Most objects (and us!) stay in their original shape because of internal pressure being exerted from within it. This creates an equilibrium system where internal pressure equals that of the external pressure.
What’s awesome is that if you take away external pressure, internal pressure will do whatever it can to create an equilibrium!
In this gif, an explainer is using a vacuum to remove air (external pressure) from within the chamber. Shaving cream has many air bubbles in it, so the air in the shaving cream (internal pressure) pushes outward and expands to create an equilibrium!
Maker Faire 2014 was held this past weekend at the NY Hall of Science. This activity was one of many that explainers discussed during the weekend! You can check out some pictures here!