His calculations of the movement of a cycloid appear in his Geometric Works, and he was the first man to create a sustained vacuum.  
His calculations of the movement of a cycloid appear in his Geometric Works, and he was the first man to create a sustained vacuum.  He calculated the value of the gravitational constant by observing two weights connected by a string passing over a fixed pulley, and his namesake equation relates the velocity of a fluid in a tank to the square root of its height.  But he may be best known for his friendship with Galileo and his experiments with tubes containing various heights of mercury.  FTP, name this Italian scientist, the namesake of a unit of pressure and the inventor of the barometer.
His calculations of the movement of a cycloid appear in his Geometric Works, and he was the first man to create a sustained vacuum.  
Evangelista Torricelli