Final answer:
An aneroid barometer measures atmospheric pressure without fluids by the mechanical movement of a spring in a metal capsule, translating changes in air pressure into a dial reading.
Step-by-step explanation:
The barometer used now that contains no fluid is known as an aneroid barometer. Unlike the traditional mercury barometer, which uses a column of mercury to measure pressure, the aneroid barometer does so through the expansion and contraction of a spring within an evacuated (airless) metal capsule. When atmospheric pressure changes, it causes the metal capsule to alter its shape, hence shifting the spring. This movement is then translated into a pressure reading via a mechanical linkage to a needle on a dial, providing meteorologists with valuable information for predicting weather without the need for mercury or any other fluid.