When the air has many water vapor, we are talking about the air is humid. Scientists often use to describe the relative humidity of the air moisture levels. Simply say yes to imagine that the air is a towel. If you had spilled a cup of water, you can use a towel to absorb the water. But towels can absorb more than a cup of water. Perhaps he can absorb 5-10 cups of water. Some of the water quantity of water vapor in the air can only have the water vapor part, the relative humidity is a percentage. When the relative humidity is 100% when the air is saturated. Seem to do a wet towel, the air can no longer take water. When the relative humidity is 100% and the air is saturated, evaporation and deposition at a state of equilibrium. Reach equilibrium again shows the increase in the number of evaporation, as water sediments. Water vapor in the air Called to the humidity. Because water vapor molecules so small they can not be seen. Research humidity people have developed creative approaches to measuring the amount of water vapor. Perhaps Rianna degrees - one in the 15th century in Italy were born -- is the first one to find that one NG All measurements from the air by the water vapor content .. He will be a dry cotton on a day on the side of the slams. He then placement with a cotton is the same as the weight of the object slams days the other side. When dry cotton from the air to absorb water vapor, it becomes more important and slams the days of this side began to degenerate. In weight between the two is different humidity measurement standards. Scientists now use Taiwan as a "psychrometer," the relative humidity measurement equipment. "Psychrometer" tied together by the two caused the thermometer. A thermometer foam used water soaking material wrapped. Begin to measure relative humidity, psychrometer to brigade should be wrapped up the thermometer to maintain a stable temperature, This temperature certain that the thermometer of dry low. The actual air temperature was dry thermometer to measure that. In temperature between two different Called "wet-bulb depression" is material from the water Evaporation results. Scientists stem record low temperature of the thermometer and "wet-bulb depression" then made a chart to calculate relative humidity. Scientists also use Taiwan as a "hair hygrometer" moisture measurement equipment. Materials such as wood, cotton, epidermis, and hair to absorb moisture from the air. When a person's hair when the water absorption become long, it increased the length of about 21/2%. In a hair hygrometer, hair tied to the tail of a target, This winter the calibration targets to demonstrate the relative humidity. When the hair shortened or extended at pointer movement. If you need to bring a relative humidity of the record low, it can connect a hair hygrometer to a "humidity recorder" The device is a pen clockwise to the humidity in a continuous line records in the charts. Water vapor in the air to determine the number of days in which we would feel comfortable. The human body through sweating releases heat. Sweat evaporation can help us in the hot under cooling. We feel more cool, because during evaporation, water molecules need energy to change into vapor. This energy comes from our body heat. If air has covered many water vapor, we sweat it is difficult to evaporation, so we can not leave the body heat, We will continue to feel hot and uncomfortable.