UH OH! It turns out the classic red wire, blue wire trope...
… is utter nonsense,
and time’s almost up!
Get out of there!
With seconds to spare you’ll escape the immediate blast zone and be sent
flying into the air by the shockwave and thrown clear of a fiery death.
A little bruised and shaken, you’ll dust yourself off and thank your lucky stars
that movie physics are as accurate as you thought…
..or are they?
Given that much of the explosive content we consume is fictional,
…is it at all possible that we have a slightly unrealistic
idea of what explosions are actually like?
Do explosions actually throw things,
specifically people, into the air? If so, how powerful would it have to be…
…and could our protagonist survive such a fiery boom?
Let’s find out!
I’m Stu, this is Debunked, and we’re here to sort the truths from the myths,
and the facts from the misconceptions.
This video is made with the support of Brilliant. Annoyingly the short answer to the
question of whether explosions blow people up, away or to smithereens is a big fat ‘depends’,
because different types of explosions will treat your body very differently.
Let’s start at the absolute basics… What exactly is an explosion?
At the most fundamental level, an explosion is simply a very fast,
often nearly instantaneous expansion in the volume of something.
This can occur naturally, and at a variety of scales, ranging from relatively small
explosions of trees during extreme temperatures like heat waves, wildfires or a lightning
strikes due to sap boiling inside the trunk, to vastly more powerful explosions in the form
of erupting volcanoes, meteor impacts
or unfathomably gargantuan exploding supernovae out in space.
The type of explosions we’re talking about of course are usually artificial,
i.e. created by humans.
These explosions occur either in the form of accidents involving heavy machinery,
volatile chemicals etc, or actual explosives being used intentionally to blow things up.
In the movies and on television, explosions are frequently enormous,
fiery affairs that blow unfortunate baddies or heroes clear into the air.
And while those sort of explosions aren’t exactly fake,
they’re not entirely realistic either.
When it comes to chemical explosives, the aforementioned increase in volume
is achieved via a chemical reaction that results in the rapid production of gas,
which very quickly expands, et voila… you have an explosion.
Broadly speaking, explosives fall into one of
two groups based on how quickly the chemical reaction happens.
Low explosives explode at a rate slower than the speed of sound,
ranging from a few centimetres per second…
right up to the speed of sound at 343 metres per second.
High explosives, on the other hand, explode faster than the speed of sound, and usually much faster.
For instance, while the explosive known as ANFO explodes at around
3.2 kilometres per second, almost 10 times faster than the speed of sound,
it is still considered to have only a low to moderate velocity for a high explosive.
Trinitrotoluene [try-nigh-troh-TOL-yoo-een], also known as TNT, is at least twice as fast as ANFO,
exploding at a rate of 6.9 kilometres per second.
C-4, another well-known high explosive, explodes at roughly 8 kilometres
per second. So yeah… pretty fast.
You might not have heard of Octanitrocubane [OC-tuh-NIGH-troh-CYOO-bane], or ONC,
which explodes at a staggering 10.1 kilometres per second,
making it the fastest known explosive in existence. So yeah… pretty fast.
It’s worth noting that from a human perspective, the difference between
low and high explosives - i.e. explosions that move very fast vs. explosions that move very,
very, very, very fast - may not always be particularly noticeable or indeed relevant.
The blasts from low and high explosives can both move very quickly, produce a lot
of energy and heat, and are certainly dangerous enough to easily injure or kill a human being.
The key difference as it is relevant to our question - can explosions lift
a person into the air? - relates to how low and high explosives actually, well… explode.
Low explosives ‘deflagrate’ [deaf-LA-great],
which means that the explosion involves a flame front that moves rapidly, though subsonically.
While this is, of course, still extremely dangerous,
much of the energy produced in a deflagration… …takes the form of heat and light,
and the relatively lower pressures produced by deflagration generally dissipate more easily,
at least in open air conditions.
While low explosives certainly can cause incredible damage,
their characteristic deflagrations are ideal if you need an explosion that isn’t too powerful.
Gunpowder, for instance, burns at a rate that is able to lethally propel
a bullet out of a barrel without also blasting the gun apart.
Other low explosives are used in the mining
industry for precise extractions of rock that minimise damage and waste.
This is also why these sorts of explosions are favoured by Hollywood;
because they last longer, look cooler, and are far easier to safely control.
High explosives on the other hand are several orders of magnitude
more powerful than low explosives, because the chemical reaction that
takes place when they are activated happens so unbelievably quickly.
When huge amounts of gas are produced in a fraction of a second,
the almost instant expansion in volume displaces an equal volume of air,
creating a powerful supersonic wave of pressure, a.k.a a shock-wave.
And sufficiently powerful shock-waves can be very destructive indeed.
As a result, high explosives are pretty much exclusively designed to cause destruction,
…and as such are favoured in a range of areas; mining, for blowing up rock;
demolition, for blowing up old or damaged buildings,
and military, for blowing up people. It’s that last category that is pertinent to
our question. What happens to a human being when subjected to an explosive shock-wave?
Well, lucky for us, the medical implications of explosive weaponry is actually something
that militaries and governments around the world are unsurprisingly very interested in,
so there’s been a hefty amount of research into the subject.
Militarily-minded boffins have crunched the data, and sorted the human effects of explosions,
termed ‘blast injuries’ into four categories; primary, secondary, tertiary, and quaternary.
The category of injuries one will experience in an explosion depends on a number of factors,
but most immediately the type of explosive,
the amount of explosive, and your distance from it when it detonates.
Primary injuries occur as a direct result of the actual explosion;
the near instant spike in pressure, called an ‘overpressure’,
…that propagates outwardly in all directions…
…as a supersonic shockwave.
It is this shock-wave that imparts onto high explosives a distinguishing quality
known as ‘brisance’ [note - I believe this is pronounced something like ‘BREE-zunce’],
which refers to their ability to shatter into pieces anything caught in their blast radius.
Very brisant explosives tear apart the substantive bonds of physical matter
at very small scales, which can be extremely bad for your health.
Generally speaking, the higher the pressures produced by the explosion,
the more powerful the shock-wave, and the finer the fragments generated.
Thus, people standing sufficiently close to a sufficiently brisant high-explosive
when it goes off may experience something medical literature refers to as ‘total body disruption’,
which is the immediate and invariably non-survivable destruction of the body.
In other words, being blown to bits.
Whether you’ll end up as a pile of whole body parts
or a scattering of homogenised chunks depends on
the power and therefore the brisance of the explosive.
If you’re hit by something like RDX for instance, a particularly brisant high-explosive,
your physical remains may more resemble the proverbial ‘pink mist’ than anything actually
identifiable. One moment you’re there, and the next… you’re not.
If you’re standing far enough away from a detonation that you aren’t instantly
ripped to shreds by the initial blast,
your body may still suffer primary injuries as a result of the overpressure wave.
Because waves of pressure travel faster in denser mediums, they are forced to slow down
when they hit areas of lower density, and that energy has to go somewhere.
As a result, blast damage to internal organs are often most severe…
at the boundaries between bodily tissues of differing densities,
particularly bodily cavities like the lungs and the gut.
Indeed, ‘Blast Lung’, which refers to
bruising, bleeding or swelling of the lungs as a result of a blast,
is the most common cause of death amongst the initial survivors of an explosion.
Those positioned further away from a detonation may experience secondary or tertiary injuries.
Secondary injuries are very common and refer to the effects of shrapnel,
which can either be the blasted-apart fragments of one’s surroundings or small
chunks of metal deliberately included in the explosive device to maximise the carnage.
Tertiary injuries are those sustained by the blast wave of compressed air that follows a detonation.
This might not propel things through you, but they certainly might blow things into you
or you into things, causing serious blunt force injuries that vary in severity.
Quaternary blast injuries essentially constitute an “other” category,
and includes things like burns, radiation exposure,
or even psychiatric injuries like Post-Traumatic Stress Disorder.
But it is tertiary injuries that relate to our question,
as it is the blast of compressed air that can lift a person off their feet.
Under exactly the right conditions - i.e. with the right amount of the right explosives,
activated not too close but not too far away -
it absolutely is possible for a person to be shoved into the air,
up and away from the source of the explosion. Just like in the movies.
Well, not just like in movies.
Films vary in their adherence to realism when it comes to the physics of explosions,
and discrepancies are common.
If an explosion in a film involves a big, relatively slow-moving fireball,
that’s likely a deflagration and probably wouldn’t have the power to shunt a person into the air.
You also might see small explosive weapons like hand grenades throwing
baddies several metres off their feet despite them having been designed
to kill with the aforementioned lethal shockwave and deadly shrapnel methods.
This guy is in the air before the explosion has even gone off!
Grenades have nowhere near enough power to launch a person into the air.
Conversely, films that depict a hero picking themselves up after having
been launched into the air by a missile or bomb blast are also stretching the truth.
If a person is within range of an explosion that is powerful enough to throw them into
the air or substantially push them away from the epicentre of the blast,
they’ve almost certainly suffered serious damage to their innards, particularly the lungs and gut,
and may well have sustained fatal injuries before they even hit the ground.
“How do they walk away in movies when it explodes behind them with
out flinching?! NO WAY!” “I need an MRI!”
That’s of course if all the accompanying shrapnel hasn’t zipped through them as well,
or indeed that they’re still in one piece at all.
So… do explosions throw you in the air? Well… maybe.
They usually don’t, but they definitely can.
Depends on the explosion, how big it is, and how close you are to it.
But while it is possible for an explosion to throw a person into the air, as a general rule,
that person is not going to get right back up and
dust themselves off like all the best action movie stars.
They’d be dead.
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Thanks for watching and we’ll see you next time