Air pressure- molecules of air up in the atmosphere creates pressure through their size and number. These factors play a part in the density of the air. ^taken about 10 meters from the ground for accuracy, taken in knots. Galileo"s pupil evangelista torricelli is the first guy who developed a barometer while trying to sold a mine drainage issue. Winds are named for the direction from which they originate. Example: a wind from the west is a westerly wind. (it is blowing eastward) Named after admiral beaufort of the british navy in 1806. These forces determine both speed and direction of wind. High and low pressure areas exist in the atmosphere principally because earth"s surface is unequally heated. Poles- cold, dense air exerts greater pressure. Equator- warm, less dense air exerts less pressure: temperature is the reason for change in pressure. Spacing of isobars indicates intensity of pressure difference (or gradient) Isobar- line of constant pressure value on weather maps.