# So the air is so good

Maybe you didn’t realize that, from getting up to studying in the classroom, from running on the sports field to going home listening to music, in essence, all are actually swimming. Why do you say that? Because the air is flowing. It flows like water, with waves and swirls. When you ride the wind and waves in the air, countless air molecules hit you head-on and form a vortex behind you. Then why do we not feel the presence of air in most cases?
Air is not “empty”
an empty bottle, not as “empty” as we seem. In 1 liter of air, there are approximately 3×10 22 molecules. Maybe you have no idea about this quantity, which is roughly equivalent to the sum of all sand grains on the earth. When these molecules collide with each other, they will exert pressure on the surroundings, just as the water molecules in the bottle exert pressure on the bottle wall, the air molecules in the bottle will also exert pressure on the bottle wall, which is atmospheric pressure.
Although air is much lighter than water, these molecules still have a considerable weight. Can you calculate the weight of air in a classroom? The volume of a classroom is about 150 cubic meters, and the density of air is about 1.29 kg/m3. By multiplying the air density by the volume, we can get that the air in a classroom weighs about 193.5 kg, which is about the same as the weight of an adult African lion. . Then when you are in the classroom, why don’t you feel pressured to breathe?
In the huge “pressure” Life is what feelings
go outside our heads actually suffer from hair start to the gravity of the Earth’s atmosphere edge all the air, this pressure be? A standard atmospheric pressure is 1.013×10 5 Pa. Assuming the area of ​​our head is about 0.1 square meters, each of us receives a force of about 10,000 Newtons, which is equivalent to the weight of two lions pressing on top of our heads. But our mouth and nose can breathe, the body is not vacuum, there is atmospheric pressure in the body to apply in all directions, so we will not be crushed.
Because we have lived under such atmospheric pressure for a long time, we have adapted to the existence of air pressure and hardly feel the pressure. Although strictly speaking, there are different numbers of air molecules hitting you at different times, but because the numbers are too large, this small difference cannot be reflected.
If the air pressure is inconsistent
inconsistent with what would happen if the local air pressure? In this study we discuss only a few existing:
Teenage heating and / or bad mood
atmospheric pressure air inconsistent description of a region strong pressure, air pressure and other small areas, which can cause air to flow from the high pressure area Areas with low pressure. Our most direct feeling is the wind. The “high air pressure” and “low air pressure” mentioned by the weather forecast host are the main reasons for various weather changes. For example, the area controlled by high air pressure is not conducive to the formation of clouds and rain, and it is often sunny. People often say that the “high” in autumn is also the air pressure in autumn, which is higher than other seasons. Then why do you feel “fresh” in autumn?
Air pressure changes not only affect the quality of the weather, but also the conditions on which we live. We control the air pressure in the lungs through the expansion and contraction of the chest muscles. When the chest muscles expand, the air pressure in the lungs decreases, allowing oxygen-rich air to enter; when the chest muscles contract, the lung pressure increases and the air in the body is exhaled. In the autumn of high-pressure control, the oxygen content in the air is more sufficient, and people can reduce the frequency of breathing, so they feel more comfortable. On the contrary, people will feel bored on rainy days controlled by low air pressure, because the oxygen content in the air is low and the breathing rate needs to be increased. In plateau areas, where the air contains low oxygen, people will experience altitude sickness due to similar reasons.
Sailing with wind
pressure of the air flow rate related changes, this is the famous Bernoulli principle: in the water or air, the large flow of small places pressure: Small flow rate places strong pressure. Therefore, scientists have mastered the secret of flight by controlling the flow rate.
When an airplane is flying, the air around the wing has a streamline distribution. Due to the asymmetrical shape of the cross section of the wing, the streamline above the wing is dense and the flow velocity is high, and the streamline below the wing is sparse and the flow velocity is small. Therefore, the atmospheric pressure below the wing surface is stronger than the atmospheric pressure above the wing surface, producing upward lifting force; and the faster the speed, the greater the lifting force. In a real aircraft design, many factors need to be considered, such as frictional resistance, differential pressure resistance, and air viscosity. In order to optimize the shape of the aircraft and obtain an efficient moving aircraft, scientists artificially generate and control the air flow in the wind tunnel laboratory to simulate the flow of air around the aircraft and measure the effect of the air flow on the entity. In addition, indoor skydiving, which is popular in the world in recent years, also uses this principle-without using parachutes, hang gliders and other aircraft, it can float in the air by means of vertical air currents.
The air surrounds us, and its quality, density, pressure and other properties have been gradually studied by scientists and gradually become familiar to humans. Now, we know that air can transmit sound; it can help us resist electromagnetic radiation from the universe; it can also help the earth maintain a stable surface temperature… But there are many characteristics of air that are not fully understood by humans. Studying the characteristics of air is of great significance to our lives and national security. For example, aerodynamics research will promote our research and development of aerospace aircraft, supersonic vehicles, supersonic missiles, etc.; and the research of atmospheric physics can help us prevent and reduce disasters and guide our production and life. At present, our research on air is far from enough. I believe that in the future, with our in-depth research on air, future life will be more convenient!