Although we do not feel the air around him, the air is not nothing. Air is a mixture of gases: nitrogen, oxygen and others. And gases, and other substances consist of molecules, and therefore have weight, though small.
With experience you can prove that air has weight. In the middle of the stick length centimeters in sixty fasten the rope, and to the two ends will bind two identical balloons. Our stick the rope and you will see that it hangs horizontally. If you pierce with a needle one of the inflated balls, he'll make the air, and the end of the stick, to which he was tied, will rise up. If pierce and the second ball, the stick again will be in the horizontal position.
This occurs because the air in the pressurized ball is denserand therefore heavierthan the one that is around him.
What is the weight of the air, depends on when and where it is weighed. The weight of the air above the horizontal plane is at atmospheric pressure. As with all things around us, the air is also subject to gravity. It also gives the air a weight that is equal to 1 kg per square centimeter. The density of air is about 1.2 kg/m3, that is, a cube with sides of 1 m, filled with air, weighs 1,2 kg
Air column, vertically rising over the Earth, stretches for several hundred kilometers. Then standing straight man, his head and shoulders, the area of which is approximately 250 cm2, the pressure of the column of air weighs about 250 kg!
We would not be able to withstand such a heavy weight, if she were not opposed to the same pressure inside our body. The following experiment will help us understand it. If you stretch both hands a sheet of paper and someone with one hand, push on it with your finger, the result will be one hole in the paper. But if you press two index fingers at the same place but from different sides, nothing will happen. The pressure on both sides will be the same. The same thing happens with the pressure and counter pressure inside our body: they are equal.
Air has weight and on all sides of pressure on our body.
But he can't crush us, for the counter-pressure of the body is external.
Pictured above is a simple experience makes it obvious:
if on the one hand to press a finger on a sheet of paper, it will break;
but if you put pressure on him from both sides, this will not happen.
By the way...
In everyday life, when we weigh, we do it in the air, and so we neglect its weight, as the weight of the air in the air is equal to zero. For example, if we weigh the empty glass flask, we will consider the result in weight bulb, ignoring the fact that it is filled with air. But if the flask to close tightly and remove from it the air, we get a very different result...