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| | balloon. The Columbia Encyclopedia, Sixth Edition. 2001-05 |
 | | In 1932 the Swiss physicist Auguste Piccard, one of the major figures in 20th-century ballooning, ascended in a balloon with a sealed spherical gondola to a height of 55,500 ft (17,000 m); since then manned balloons have reached heights of 100,000 ft (30,500 m) and unmanned balloons have exceeded 140,000 ft (42,500 m). |
 | | In contemporary sporting balloons, which use air heated by a small gas-fired burner, altitude is controlled by varying the temperature of the heated air. |
 | | Gas bags made with space-age materials are more durable and weigh far less than the traditional silk; heaters have similarly become more efficient. |
| www.bartleby.com /65/ba/balloon.html (536 words) |
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