* Astronomy

Konstantin Eduardovich Tsiolkovsky (17 September 1857 - 19 September 1935) was an Imperial Russian and Soviet rocket scientist and pioneer of the astronautic theory.
His most important work, published in 1903, was The Exploration of Cosmic Space by Means of Reaction Devices, Tsiolkovsky calculated, with the Tsiolkovsky equation, that the horizontal speed required for a minimal orbit around the Earth is 8,000 m/s (5 miles per second) and that this could be achieved by means of a multistage rocket fuelled by liquid oxygen and liquid hydrogen.
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