We know them today as "Hot-Air Balloons." They are these marvelous devices that were made to send mankind into the sky. In Book 7 of "The Years of Rice and Salt", this floating machine was considered a marvel to look at. In the beginning, Ismail the Anatomist was intrigied by the sight of the ascending devices droping bombs below onto their land. They were too high to be shot down, as well as too far to see clearly. Seeing a Hot-Air Balloon in action, during this time, was as if seeing a plane soar in the skies during World War I.

Hot-Air Balloons are, in a sense, giant balloons! They are tethered to a basket, which the proper term for is gondola, and consists of heating apparatus. Ussualy fuled by propaine, this heater warms the air that is in the balloon. In making this device fly, two principles of chemistry and physics are applied. 1.) Hot air expands. For instance, the tires on an automobile during the summer expand, therefore, one is told not to overinflate them. 2.) Hot air rises. Also in the summer time, you may notice that the upper levels of ones home is warmer than the lower portion. These two principles combined help the Hot-Air Balloon take flight.

References:

• http://travel.howstuffworks.com/hot-air-balloon.htm
• Lally, Vincent E. "Ballooning." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007.