TLDR: A barometer is a scientific instrument used to measure air pressure. It can help predict short-term changes in the weather. Barometers and pressure altimeters are similar instruments, but used for different purposes. Barometers measure subtle pressure changes caused by weather, while altimeters measure atmospheric pressure to determine altitude. The word "barometer" comes from the Greek words for "weight" and "measure". The invention of the barometer is credited to Evangelista Torricelli in 1643, although there is evidence that others may have unintentionally built similar devices before him. Barometers have been used for centuries to study atmospheric pressure and its relationship to weather patterns. There are different types of barometers, including mercury barometers, aneroid barometers, and digital barometers. Barometric pressure is an important factor in weather forecasting and is used to create weather maps and predict changes in the weather.