Torricelli and his Hypothesis

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Evangelista Torricelli (16081647) created the first mercury barometer by filling a 0.9 meter (3 foot) glass tube with mercury and inverting the open end into a dish of mercury. The level of mercury in the tube dropped to 71.8 centimeters (28 inches). He demonstrated that air pressure raises a liquid to a height relative to the weight of the liquid. Torricelli hypothesized that the space above the mercury in the tube was a vacuum.