# What is Atmospheric Pressure?

What is Atmospheric Pressure?
Atmospheric pressure is a force of a weight of air applied to a surface below it. In simple terms, atmospheric pressure is also the same as air pressure. To imagine clearly, what atmospheric pressure is, simply think of a force in the atmosphere that is applied to a specific area. A barometer is an instrument that measures atmospheric pressure.

Atmospheric pressure can be calculated. In 1641, Evangelista Torricelli made an experiment on measuring the atmospheric pressure. On his experiment, he used a tube sealed at one end. Torricelli immersed the tube in a container of mercury. He noticed that when the tube was immersed, the mercury was pushed up to the tube. He concluded that the atmospheric pressure is pushing the mercury up the tube because the level of the mercury is higher than its level in the container. One thing more noticeable is that the height of the mercury in the tube differs with variation of the outside weather condition.

There are several types of barometer. However, the most commonly used is the aneroid barometer, which used in homes. Aneroid barometer is a tiny, flexible capsule made of metal. This capsule is called the aneroid cell. Inside the capsule is a vacuum, which is intended to make the capsule contract and expand at a slight change in the atmospheric pressure. The aneroid cell’s size is calibrated. As the cell expands and contracts, springs and levers transmit the volume change to an arm, which indicates the equivalent atmospheric pressure.

In weather reports, the atmospheric pressure given is the mean seal level pressure of the MSLP. Barometers at home that read atmospheric pressure might tell a different reading from the actual atmospheric pressure at your locality. However, this is only true when your barometer at home is set to match the local weather reports. This will mean any rise and fall in pressure will be the same for each everybody.

Atmospheric pressure is not only affecting the environment. It actually has a direct effect on human beings, most especially to their blood pressure. Air pressure is continuously changing and it is different underwater and up high in the sky. A diver in the deep sea experiences a different atmospheric pressure than a pilot flying up in the sky. Depending on how deep the diver is and how high the altitude of the pilot is traveling, atmospheric pressure varies.

As a diver goes deeper, the atmospheric pressure increases. This can have direct effect on the blood pressure of a diver. The water presses hard on the diver and it can raise blood pressure. People with high blood pressure are not recommended to go on diving for their life might be at a higher risk.

On the other hand, pilots and astronauts experience a different atmospheric pressure. As the altitude gets higher, atmospheric pressure decreases. On the part of the astronauts, when they reached outer space, there is no gravity. When they go back to earth, they are susceptible in fainting. Gravity has great effect on air molecules and so is the mass air density. Atmospheric pressure is not just something that has effect on people. It is also a vital element for living things to survive on Earth.