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Could air pressure drop to zero? If so where?
Air pressure is caused by air so if there is no air, then there can be no air pressure. There is no air pressure in outer space because there is no air in space. However Earth’s atmosphere, which is made up of layers of air, doesn’t just end, the air gets thinner and thinner as you go up until it becomes so thin that it merges into space. There is not exact spot that Earth’s atmosphere and space meet but there is a commonly accepted boundary called the Kármán Line at 62 miles (100 kilometers) above sea level.