Museo Galileo - Museum of the History of Science in Florence
Galileo invented many mechanical devices besides the telescope, such as the hydrostatic balance, a pendulum clock and a high power water pump powered by one horse. Of course, his most famous invention was the telescope. Galileo made his first telescope in 1609, modeled after telescopes produced in other parts of Europe that could magnify objects three times. He created a telescope later that same year that could magnify objects twenty times. You might argue that although he didn't invent the first telescope, he obviously improved upon it.
With this telescope, he was able to look at the moon, discover the four satellites of Jupiter, observe a supernova, verify the phases of Venus, and discover sunspots. His discoveries proved the Copernican system which states that the earth and other planets revolve around the sun. Prior to the Copernican system, it was held that the universe was geocentric, meaning the sun revolved around the earth
Evangelista Torricelli was born Oct. 15, 1608 in Faenza, Romagna. He was an Italian physicist and mathematician who invented the barometer, a device that measures atmospheric pressure, commonly used in forecasting changes in the weather. The catalyst for inventing the barometer was spurred on my a suggestion by Galileo that Torricelli use mercury in place of water for his vacuum experiments.
After reading his papers in 1641, Galileo invited Torricelli to Florence, where he became the aging astronomer's secretary and assistant during the last three months of Galileo’s life. After Galileo's death, Torricelli was appointed as his successor as professor of mathematics at the Florentine Academy.
Two years later, pursuing the suggestion by Galileo, he filled a glass tube 4 feet (1.2 m) long with mercury and inverted the tube into a dish. He observed that some of the mercury did not flow out and that the space above the mercury in the tube was a vacuum. Torricelli became the first man to create a sustained vacuum. His observations proved that the variation of the height of the mercury from day to day was caused by changes in atmospheric pressure. He never published his findings, however, because he was too deeply involved in the study of pure mathematics. Since atmospheric pressure also changes with altitude, Torricelli's barometer also could be used as an altimeter.
Torricelli died Oct. 25, 1647 in Florence at a mere 39 years old.
As a further honor, Torricelli had both a crater on the moon and a submarine named after him...
Play the video to see how Torricelli's experiment worked.