Both explosions and implosions create heat to some degree, and when things get really hot vaporization can occur, but only in the right circumstances. The phenomenon sees liquids transition to a gaseous state as enough energy is released to break the intermolecular forces keeping them together.

Vaporization is a dramatic phase change that requires a lot of power, but it has its limits. From boiling kettles to the heart of atomic bombs, vaporization can achieve things big and small, but is it theoretically possible to vaporize a human? Does it occur in implosions as well as explosions? And what have some of the most devastating events in history taught us about its power?

Explosions vs implosions

Explosions and implosions are effectively opposites, and we’ll start with the former first. There are different types of catalysis for explosions, such as certain chemicals mixing to the point of superheating, or the collision of particles. Nuclear explosions can happen through fission (atomic bomb), or a combination of fission and fusion (hydrogen bomb), creating temperatures of around 100 million degrees Celsius (180 million degrees Fahrenheit), seven times hotter than the center of the Sun.

An implosion occurs when there’s a sudden collapse due to an imbalance of pressure, something that deep-sea submersibles such as the recent Titan disaster are vulnerable to. This is because submersibles are highly pressurized vessels that need to be incredibly strong to withstand the crushing pressure of diving deep in the ocean, but an implosion is not the same as rapid decompression, which can also be deadly.   

“An implosion is essentially a very rapid crushing event, but it is not caused by the release of energy in the same way an explosion is: the energy (pressure) is there surrounding the object already, it's just that the object’s ability to resist this pressure suddenly changes (its strength is exceeded in some way, it buckles, etc.),” Dr Sam Rigby told IFLScience. Rigby is an expert in blast and impact engineering, and senior lecturer in Civil and Structural Engineering at the University of Sheffield.

“Think of it like a fault line on the earth’s surface; it will be able to resist pressure and movement up to a certain point, then will suddenly and violently jerk (causing an earthquake). Now imagine this all around the outside of an obstacle, with the jerking movement being inwards. That’s an implosion.”

“For comparison, the deepest point on earth, the Mariana Trench, is beneath nearly 11 kilometers [6.8 miles] of water. The pressure acting immediately after an explosion is equivalent to around 2,500 kilometers [1,553 miles] of water! So, you can see how the energies involved in implosions and explosions (at least on earth) are different by orders of magnitude.”

Can implosions and explosions coincide?

Sometimes implosions and explosions can be connected, such as in the case of collapsing stars. The pressure within stars is maintained by nuclear burning that generates heat and pressure. The super-heated core is pushing outwards while the surrounding gravity is pushing inwards, forcing all that energy into the smallest ball possible.

When the fuel runs out and a massive star starts to fail, the pressure drops low enough that it succumbs to gravity, which is capable of taking over and collapsing it in seconds. The collapse happens so quickly that it creates enormous shock waves, causing the outer part of the star to explode in what’s known as a supernova – the biggest explosion that humans have ever seen.

Implosions and explosions also come together in atomic bombs, which kick off with a core of fissionable material collapsing. This increases the density and therefore the likelihood of a neutron striking a nucleus of a heavy unstable isotope, which splits in what’s known as fission.

The split releases fragments and enormous amounts of energy, and the fragments feed a nuclear chain reaction. It sounds slow, but that chain reaction takes around a millisecond before an atomic explosion occurs releasing a massive amount of heat and gamma radiation.

What is vaporization?

Vaporization is caused by flash heating hot enough to break the bonds that ordain whether a substance is solid, liquid, or gas. Known as intermolecular forces, their destruction at speed results in a phase change that can turn a puddle of water into a puff of vapor instantly.

“For a physical explosion, the temperature of a liquid in a closed container is increased. The increase in temperature will cause the pressure of the liquid to rise,” explained Professor Jackie Akhavan, who specializes in explosive chemistry and is Head of the Centre for Defence Chemistry at Cranfield University, to IFLScience. “If the pressure inside the container becomes so high that the container bursts, then you get a change in state from a liquid to a gas. This is vaporisation.”

It sounds like the stuff of Bond villains, but evaporation is a type of vaporization and something that anyone who has ever boiled a kettle has seen. For water, the heat of vaporization at 100°C is about 2,230 joules (533 calories) per gram, and the resulting steam carries a lot of thermal energy, which is why it’s a great working fluid for engines.

Vaporization in explosions

The flash heating needed to achieve vaporization is the bread and butter of thermal explosions.

“Explosions are violent chemical or nuclear reactions that release a tremendous amount of energy in a very small volume,” said Rigby. “As that energy violently expands outwards, it leads to the formation of a blast wave, which is the main cause of the damage (seen in events such as the Beirut explosion in 2020).”

“Explosions, particularly nuclear bombs, also release a large amount of thermal and visible light radiation (about one-third of the energy from a nuke is released as thermal radiation). This can cause objects in the immediate vicinity to undergo flash heating and vaporise, essentially getting so hot that they go from a solid to a vapour almost instantly.”

Can objects be vaporized?

Vaporizing a physical object like a bicycle isn’t technically possible because vaporization involves taking a liquid and turning it into a gas. The phase change that sees a solid object skip the liquid phase and go straight to gas is known as sublimation, but heated objects can melt and then vaporize, as in the “Rope Trick Effect” (seen in the above video).

“High-speed imaging of the early nuclear tests showed a strange mottling of the fireball surface. This was found to be caused by the vaporisation of steel guy ropes holding the bombs in place,” explained Rigby. “So significant is the thermal radiation from a nuke that US citizens during the Cold War were encouraged to keep their houses clean and freshly painted to reduce the risk of them catching fire!”

Can a human be vaporized?

Humans and animals can be partially vaporized theoretically because they contain a lot of liquid. According to the US Geological Survey, up to 60 percent of the human adult body is water, but following a blast you would expect at least some remains of the remaining 40.

You may have seen the Human Shadow Of Death imprinted onto a stone step that was in Hiroshima the day the atomic bomb was dropped. It’s thought a person was sitting there waiting for the bank to open when the aerial bombing carried out by the United States took place, and many believe it to be the shadow left behind by a vaporized human. However, this isn’t the case.

When the explosion of extreme heat and gamma radiation we covered earlier was released from the atomic bomb dropped on Hiroshima, that energy was absorbed by objects – living or inanimate – in its path, but the force bleached the environment around them. The shadows left behind mark the spots where people died, which would’ve been instant, but their bodies were not turned to vapor from the explosion.

Theoretically, what temperature would vaporize a human?

It goes without saying that trying to vaporize people isn’t good or clever, but a study in the Journal of Interdisciplinary Science Topics did explore the idea. Building on previous research by the same authors that calculated the energy needed to vaporize a skeleton, it found the total dissociation energy for the water constituent of the body and the remaining tissues (which were represented by dry pork).

“From analysing the individual dissociation energy of each of the main human body constituent we described, we have been able to determine the total amount of energy required to completely vaporise an adult person of 78kg,” concluded the authors. “This was calculated to be 2.99×10⁶ kJ.”

That’s the equivalent of around 710 kilograms (1,565 pounds) of TNT, but before you add that to your shopping cart, it’s important to remember that it really isn’t so simple.

“It is however important to realise that to achieve a complete instantaneous vaporisation of a person would require that the calculated energy of vaporisation is applied evenly in a short amount of time. Thus, vaporising a human completely would require a very high power input in practice.”

Can implosions trigger vaporization?

An “explainer” video recently went viral claiming to portray the most likely scenario for the implosion of the Titan, but it falsely claimed that the implosion would “heat the air in the sub to around the surface of the sun’s temperature”. Implosions do produce heat, but temperatures inside the sub would not reach 5,500 degrees Celsius (10,000 degrees Fahrenheit), as seen on the solar surface. The comparatively small amount of heat generated by an implosion in this context would also quickly be eliminated by the mass of cold water surrounding the vessel.

Vaporization and implosions do come together in the case of pistol shrimp that can snap their claws shut at speeds of around 100 kilometers per hour (62 miles per hour). It’s so rapid that it causes vaporization creating a cavitation bubble which then collapses in an implosion, producing sound and light in a phenomenon known as sonoluminescence.  

For all of the sci-fi surrounding vaporization and explosions and implosions, vast and miniature, it seems a lot of misconceptions remain at the core of these powerful events.

“Real life explosions are very different to typical “Hollywood” explosions (although I’m hoping Mr Nolan bucks the trend with the new Oppenheimer movie!),” said Rigby. “We’re led to believe that explosions are big flashes of fire that we can see with our own eyes, but in reality, they are much quicker and much, much more violent. Reading about the Rope Trick Effect really revealed to me how much of an alien world it is in the first few instants after an explosion.”