We live at the bottom of an ocean of air that’s held close to Earth by gravity. This layer of air is more than 60 miles deep, and the weight of the air above us is always pushing down on us. We don’t feel the pressure because we have always lived under it, but we can see its effects. When you drink from a straw, you create a little space of low pressure inside your mouth and in the top of the straw. Then the air outside the straw pushes down on the surface of the drink and forces the liquid up through the straw and into your mouth.
Photo by: Bon Appetit/Alamy