Is Air Really There?

Activities you can do at home


Without air, balloons, birds and airplanes couldn't fly. But since you can't taste, see, or often even feel air, how can you prove to yourself that it's really there? Maybe you're convinced that air is stuff, but does it have weight? If so, how much?

Air is Stuff


How do these pictures show that air is stuff? Which one convinces you the most? Why?

Blow the Wad

Crumple a small piece of paper into a pea-sized ball. Hold an empty bottle on its side and place the wad just inside the rim. Now try to blow the wad into the bottle. It's harder than it sounds! Try different-sized bottles, too. If you find one that seems to spit out the paper, challenge your friends with the trick.

Weigh the Air

How much does the air in your room weigh? Choose an answer from the list below, before you read on.
  1. nothing
  2. hardly anything, like a bunch of fluff
  3. as much as something I could lift
  4. way more than I could lift
Now figure out the answer. First, measure the length, width, and height of your room; then, multiply these amounts together. This total equals the volume of your room. (Estimate the numbers if you can't measure the room.) Second, multiply the volume by 1.2, if you measured in meters; by 0.07, if you measured in feet. (A cubic meter of air weighs 1.2 kilograms; a cubic foot of air weighs 0.07 pounds.) Surprised?

Why Can't I Feel that Weight?

Hold a bag of sugar or heavy book in your hand. What does it feel like? Now have a partner support the weight by placing a hand under yours and pushing up. What does it feel like now?
Hint: If a friend isn't handy, rest your hand on a table and notice the difference.

Now try this: Hold your hand up to the end of a vacuum cleaner hose, then turn on the vacuum. The vacuum's pump removes some of the air under your hand while the air on top continues to push with its normal strength. How does your hand feel now? What is happening?

  • bag of sugar or heavy book
  • vacuum cleaner with attached hose

What's Going On?


Which glass is empty?
(It's not a simple question!)
 Since air is invisible, we easily forget that it's all around us. But air has substance, or mass. Because it has mass, it must have weight. As you found out in Weigh the Room, the air in one room weighs more than you might think. Even a fairly small room can hold close to 45 kilograms (100 pounds) of air.
Earth's gravity holds air to its surface, so we are all submerged in a "sea" of air. The weight of the air is constantly pushing against us, but it feels more like pressure than weight since it pushes from all sides. This all-around push is a force called air pressure. You're so used to it that you only notice it when its push increases or decreases.

Such a change occurred when you put your hand against a vacuum cleaner hose. It also happens when you travel in an airplane or drive up a mountain to a higher altitude where there is less air.
Air pressure also helps planes fly. When air moves around a plane, air pressure decreases above the wings. The air pressure below the wings remains almost normal and pushes the wings up. This push is called lift.
Produced by the National Air and Space Museum's Educational Services Department to accompany HOW THINGS FLY, an interactive gallery. HOW THINGS FLY is made possible through the generous funding of the Boeing Company and a grant from the National Aeronautics and Space Administration, with additional support from the National Science Foundation, The Smithsonian Institution Special Exhibition Fund, and the James Smithson Society. ©1996, National Air and Space Museum, Smithsonian Institution.

(Rev. 10/02/96)