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Explosion

physical science Maturity 7-9 Next article →

An explosion is a rapid expansion in the volume of a given amount of matter. This event is associated with an extreme outward release of energy. Usually, this process generates very high temperatures and releases high-pressure gases.

CastleBravo2
CastleBravo2

While many people think of explosions as sudden bursts, they can also be caused by a slower expansion. If matter tries to expand but is held back by a container, pressure builds up inside. When the container finally breaks from this pressure, the matter expands forcefully. This can be seen in volcanic eruptions when magma expands within a magma chamber.

Damages after 2020 Beirut explosions 1
Damages after 2020 Beirut explosions 1

Scientists distinguish between different types of explosive movements based on their speed. Supersonic explosions are created by high explosives and are known as detonations. These explosions travel through shock waves. On the other hand, subsonic explosions are created by low explosives. These move through a slower combustion process called deflagration. The speed of the reaction is the main factor that separates an explosion from ordinary combustion. For example, a wood fire in a fireplace releases heat and gas, but it does not happen fast enough to create a sudden pressure differential. This is similar to the difference between a battery discharging slowly and a camera flash capacitor releasing energy all at once.

Explosions can be categorized by their physical or chemical origins. Chemical explosions are very common and often involve a rapid oxidation reaction. This reaction produces large amounts of hot gas that expands quickly. These can be intentional or accidental, such as a fuel tank rupturing. Mechanical explosions are strictly physical processes. An example is a boiling liquid expanding vapor explosion. This happens when a vessel containing pressurized liquid ruptures, causing the liquid to evaporate and increase in volume rapidly.

Exploded Electrolytic Capacitor
Exploded Electrolytic Capacitor

Some explosions are also electrical. A high current fault can create an electrical arc that vaporizes metal and insulation. This is known as an arc flash hazard.

In the field of nuclear science, explosions work through different mechanisms. A nuclear weapon derives its destructive force from nuclear fission or from a combination of fission and fusion. Even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives. A single weapon can be capable of completely destroying an entire city.

CastleBravo2
CastleBravo2

These nuclear processes are also seen in space. Supernovae are among the largest known explosions in the universe. They occur after the end of the life of certain types of stars.

M1-67 & WR124
M1-67 & WR124

Astronomy provides many examples of massive energy releases. Solar flares are common, less energetic explosions on the Sun. This activity comes from the tangling of magnetic field lines in the Sun's conductive plasma. Another type of astronomical explosion occurs during impact events. This happens when a meteoroid or asteroid hits a planet or another object at very high speeds. The Tunguska event of 1908 is believed to have resulted from a meteor air burst.

M1-67 & WR124
M1-67 & WR124

Even more massive are black hole mergers. These can radiate many solar masses of energy in a fraction of a second via gravitational waves. For instance, the GW190521 signal in 2019 lasted about 100 milliseconds and radiated nine solar masses of energy.

Human history includes many important developments in explosive technology. Gunpowder was the first explosive to be invented and used. Later, Frederick Augustus Abel developed nitrocellulose in 1865. Shortly after, Alfred Nobel invented dynamite in 1866.

In modern aerospace engineering, engineers sometimes use the term "rapid unscheduled disassembly." This is a humorous way to describe the explosion of an aircraft or spacecraft. Elon Musk used this term in 2015 following a failure of a Falcon 9 landing mechanism.

Understanding the force and direction of an explosion is vital for safety and engineering. Explosive force is typically released perpendicular to the surface of the explosive. If a grenade explodes in mid-air, the blast direction is 360 degrees. However, military forces use shaped charges to focus these forces. These are used to breach doors or walls.

Defense.gov photo essay 090818-M-8752R-138
Defense.gov photo essay 090818-M-8752R-138

Explosions also cause fragmentation, which is the projection of particles. These fragments can come from the explosive casing, nearby structures, or even soil and rocks. High-velocity fragments can travel hundreds of meters and cause significant damage to vehicles or structures.

Defense.gov photo essay 090818-M-8752R-138
Defense.gov photo essay 090818-M-8752R-138
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🖼️ Images & Media (7)
File:A detonation erupts as U.S. Marines with the 1st Explosive Ordnance Disposal Company, Combat Logistics Regiment 2 conduct a demolition operation in Helmand province, Afghanistan, March 17, 2013 130317-M-KS710-206.jpg
A detonation erupts as U.S. Marines with...
File:CastleBravo2.gif
CastleBravo2.gif
File:M1-67 & WR124.png
M1-67 & WR124.png
2025 Shandong chemical explosion on CCTV.webm
File:Exploded Electrolytic Capacitor.jpg
Exploded Electrolytic Capacitor.jpg
File:Defense.gov photo essay 090818-M-8752R-138.jpg
Defense.gov photo essay 090818-M-8752R-138.jpg
File:Damages after 2020 Beirut explosions 1.jpg
Damages after 2020 Beirut explosions 1.jpg
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