How could someone measure air? Or how to get air on a scale? Seems easy.
As we go deep down from the sea level, for example in water, the pressure increases. In deep water we get more hoops as compared to at the top because the pressure down there increases. In other words the lower you are in the atmosphere, the heavier the pressure is.
At sea level the Air Pressure is 14.7 pounds per square inch. Lets assume that value to be 15 pounds. For instance, assume taking a column of air from the sea level and lift it until it reaches the outer atmosphere. Now vacuum all the air beside that column. Now that column will weigh 15 pounds.
If Air weighs 15 pounds why don't we feel the weight of air?
The pressure in a fluid is manifested in all directions at that location. So if the air is applying a downward force or is pushing down, it is simultaneously pushing upward with the same force, and in every direction. Therefore all the forces are neutralized and you don’t feel any force or burden of the air.
What makes us believe that air weighs 15 pounds?
Here is a quick experiment. > Take a suction cup and plunge it onto a flat surface like a table. > Now try to remove it.
You may need to apply some force to pull that cup out.
Imbalanced Air Pressure
When the cup was plunged onto the table, the air from the other side of the cup which helped to maintain that balance was disturbed. This removed all the air from that side of the cup. Therefore now more force is required to lift that cup.
If the cup covered 10 square inches the total atmospheric weight pushing on that cup would be 150 pounds. Pulling that cup would be equivalent to lift 150 pounds of weight. If there’s any hole for the air to pass through the cup, this wont work because now the air has a way to apply pressure.
To conclude, the weight of the air is NOT nothing, but something.