A sling psychrometer works when the scientist spins two thermometers through the air, one plain and one with a wet cloth around it. The dry thermometer measures the air temperature. The wet thermometer measures the dew point, because the wet cloth is cooled as the thermometer spins. Since the water on the cloth evaporates, due to latent heat, which is the loss of heat energy when matter goes through a phase change, the cloth cools. Then, the thermometer measures the temperature of the cloth. Eventually the cloth will match the amount of water absorbed in it with the amount of water absorbed in the air, or the humidity. When the matching happens, the temperature will stabilize. Then, the scientist looks on a table to find the dew point according to the air temperature and humidity measured by the wet bulb. 