Why? Because of the many factors which affect atmospheric pressure. Pioneering scientists discovered atmospheric pressure (also known as barometric or air pressure) in the 17th century ...

Air molecules colliding with a surface cause atmospheric pressure. Atmospheric pressure at sea level is about 101,000 Pa (101 kPa) but just 27,000 Pa (27 kPa) at the cruising altitude of a ...

Normal air pressure is 1000 millibars (mb ... Isobars are lines that are drawn to join places that have the same atmospheric pressure. These are usually drawn for every 4 millibars (eg 996 ...