Atmosphere Atmosphere An atmosphere (from Modern Greek ἀτμός "(atmos)", meaning 'vapour', and σφαῖρα "(sphaira)", meaning 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low. The atmosphere of Earth is composed of nitrogen (about 78%), oxygen (about 21%), argon (about 0.9%) , carbon dioxide (0.03%) and other gases in trace amounts. Oxygen is used by most organisms
Gas-operated reloading piston has traveled a short distance. Most systems, however, vent excess gas into the atmosphere through slots, holes, or ports. A gas trap system involves 'trapping' combustion gas as it leaves the muzzle. This gas impinges on a surface that converts the energy to motion that, in turn cycles the action of the firearm. Hiram Maxim patented a muzzle-cup system in 1884 described in though it is unknown if this firearm was ever prototyped. John Browning used gas trapped at the muzzle to operate a 'flapper' in the earliest prototype gas-operated firearm described in . The Danish Bang rifle used