What is Explosion?
[[Image:Explosions.jpg|thumb|Three explosions happening as the photograph is taken]] [[Image:NTS - BEEF - WATUSI.jpg|thumb|Large experimental explosion]] An '''explosion''' is a fast increase in [[volume]] and increase in [[energy]] made available. It normally makes high [[temperature]]s and makes [[gas]]es. Many natural events can make explosions, such as [[lightning]], [[volcanic eruption]]s, [[meteor]]s, and [[supernova]]e. People make explosions mostly by using chemical [[explosive material]]s. A chemical explosion starts pressure waves in the [[Media|medium]] where it happens. Explosions are categorized as deflagrations if the pressure waves are [[subsonic]] and [[detonation]]s if they are [[supersonic]]. When a detonation happens, the resulting pressure waves are named [[shock wave]]s. == Unintentional explosions == '''Unintentional explosions''' can be caused when chemicals are mixed together, or when pressurized containers or flammable materials are heated or exposed to flames. To cause an explosion, pressure does not have to be present but is always a result of an explosion. Several safety measures are used to prevent unintentional explosions. Many countries require that chemicals, fuels, and pressurized containers that may explode be labelled with warning labels. As well, many countries have regulations restricting the possession and use of potentially [[explosive material]]s so they will only go to appropriate industrial and research uses. Transportation regulations require potentially explosive chemicals, fuels, and pressurized containers to be transported safely. == Intentional explosions == '''Intentional explosions''' are caused when armies fire [[artillery]] or when [[air force]]s drop [[bomb]]s on enemies. [[Military engineer]]s handle explosives and arrange intentional explosions during wartime. Intentional explosions are also used by civilians in ''demolition''. They break up old and obsolete [[building]]s and [[bridge]]s, and break rock and stone for construction. Explosions are