subjext http://www.subjext.com Sun, 07 Sep 2008 07:05:27 +0700 FeedCreator 1.7.2 http://www.subjext.com The weight of air resting on a given area of the Earth's surface is known as air pressure. Air pressure (or atmospheric pressure) is always greatest at sea level, where the air is at its most dense. Therefore at the top of a mountain the air is less dense and therefore the pressure is lower.The air is composed of billions of tiny particles that are constantly moving in all directions, Thu, 24 Apr 2008 00:00:00 +0700