Book 3, Question 10
Why Do Hot Air Balloons Go Up?
Heat makes the air molecules spread out. So the same bag of hot air weighs less than the cool air around it. Cool air pushes the lighter bag up, and the balloon rises!
From the book
Page from A Million Whys Book 3
More fun facts
- A balloon rises when the balloon and what is inside it weigh less than the same amount of the air around it.
- Most hot air balloons heat their air with propane burners.
- The first hot air balloon was invented in France by the Montgolfier brothers in 1783.
- Instead of hot air, some balloons use a very light gas, such as helium.
- NASA flies science balloons above 100,000 feet so experiments get a clear view of space.
- NASA's balloon program launches about 10 to 15 flights a year from sites around the world.
- Today hot air balloons are used less for travel and more for tourism, events and sport.
Sources: Smithsonian, BBC, NASA
Questions kids ask
Who flew the first hot air balloon?
The Montgolfier brothers invented the first hot air balloon in France in 1783.