The scientific instrument used to measure atmospheric pressure is called a barometer. Barometers typically work by detecting changes in air pressure, which can be used to predict weather patterns. There are two main types of barometers: mercury barometers, which use mercury to measure pressure, and aneroid barometers, which utilize a small, flexible metal box. Barometers have been essential tools in meteorology for centuries, helping people understand weather changes and patterns based on atmospheric pressure readings. They are still widely used today in both professional and recreational settings.