Toy balloon in "Swiss Family Robinson" (1813) and in "Moby Dick" (1851). The first rubber balloons were made by Professor Michael Faraday in 1824 for use in his experiments with hydrogen at the Royal Institution in London. "The caoutchouc is exceedingly elastic", he wrote in the Quarterly Journal of Science the same year. "Bags made of it...have been expanded by having air forced into them, until the caoutchouc was quite transparent, and when expanded by hydrogen they were so light as to form balloons with considerable ascending power..." Faraday made his balloons by cutting round two sheets of rubber laid together and
Two-balloon experiment a similar way as the balloon expands. Because rubber strongly resists volume changes, the volume "V" can be considered constant. This allows the stress-strain relation to be written where λ=L/L is the relative extension. In the case of a thin-walled spherical shell, all the force which acts to stretch the rubber is directed tangentially to the surface. The radial force (i.e., the force acting to compress the shell wall) can therefore be set equal to zero, so that where "t" and "t" refer to the initial and final thicknesses, respectively. For a balloon of radius formula_4, a fixed volume of