(http://kids.earth.nasa.gov/archive/air_pressure/)
Air pressure is the force exerted on
you by the weight of tiny particles of air (air molecules). It is defined as the force
per unit area exerted against a surface by the weight of the air above that
surface. Although air molecules are invisible, they still have weight and take
up space.
Weather forecasters measure air pressure with a barometer. The Mercurial Barometer is an instrument used
for measuring the change in atmospheric pressure based on the principle
developed by Evangelista Torricelli in 1643.
Earth's atmosphere is pressing against each square
inch of you with a force of one kilogram per square centimetre (14.7 pounds per
square inch). The force on 1,000 square centimetres (a little larger than a
square foot) is about a ton!
Source: http://www-istp.gsfc.nasa.gov/Education/Iunivers.html
It was already noted here that matter conducts electricity only if
its ions or electrons (or both) are free to move. Molecules of air hold on to
their electrons rather tightly, so that air is an excellent electric insulator.
Only the high voltage of lightning can force a current through it! In 1912, to
test the electric leakage and radiation pressure, Victor Hess took his
instruments aboard a balloon, and noticed that the higher the balloon rose, the
greater was the leakage rate.
It is the well-known truth that the powerful radiation pressure, weight and the electric currents from the inner and outer activities of the earth and space surround the atmosphere. At the same time, every form of radiation pressure and electric current loses its fundamental quality after entering the atmosphere because air is an excellent electric insulator. Scientists who comprehend this activity can search for new method to generate electricity.
