Blaise Pascal was the French mathematician and religious philosopher who is remembered in science mainly for his work on pressure. A child prodigy, at the age of 16 he published an essay on conics which describes his first great discovery, Pascal's Mystic Hexagram. In 1647 he constructed the first arithmetical calculating machine to help his father with his accounts. Pascal arranged for this machine to be manufactured and it became the first 'calculator' available for sale (only seven now remain). He repeated Evangelista Torricelli's experiment (1647), which demonstrates that air pressure supports a column of mercury of about 76 cm high, and suggested that the height of the column would be less at a higher altitude. This was verified when Pascal's brother-in-law took a column of mercury up the mountain of Puy de Dôme (1648). These results led to the development of the mercury barometer and its subsequent use in weather forecasting. Pascal later explained that the pressure of a fluid at rest was transmitted equally in all directions (Pascal's principle, 1654). In the same year he experienced a religious vision that eventually led him to cease his experimental work. He became more reclusive in his later life, retreating to the convent of Port-Royal in 1655. His last project was to design a new transport system for Paris and this was introduced a year after his death. The SI unit of pressure and a computer language are named after him.
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