Sapphire has an index of refraction of 1.77. The critical angle for sapphire in air with an index of refraction of 1.0 is degrees.

the only real purpose of sputnik 1 was to beat the us into space. we were getting close to launching a useful satellite, explorer 1 - which launched on january 31, 1958. the ussr had to beat that, so they launched sputnik 1 on october 4, 19

e/c, where e is its total energy