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31.2 x 40.4 cm ⏐ 12.3 x 15.9 in (300dpi)
SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
1804 saw the first balloon ascent specifically for scientific purposes. The French Academy of Sciences sponsored an ascent to test a theory that the force of the earth's magnetic field declined with altitude, eventually to zero. In addition, measurements of density, humidity, and temperature of the upper atmosphere were to be made. The French physicist and chemist Joseph-Louis Gay-Lussac (1778-1850) and Jean-Baptiste Biot (1774-1862), also a physicist, made the ascent in August 1804. They attained a height of 4000 metres. No changes in the earth's magnetic field were observed but as the delicate instruments used were adversely affected by the balloon's instability, Gay-Lussac proposed to confirm these results by offloading all uneccessary items and ascending alone to 6000 metres. Unfortunately on landing they lost all the hydrogen due to lack of ground support preventing this.
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