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Physicists Explain Mortal Kombat's Gruesome Fatalities

by Hunter Wolfe on Mar 07, 2019 at 03:00 PM

Few games feel as bombastic as Mortal Kombat. Its roster of otherworldly fighters bash, choke, tackle, and torment each other across bombastic arenas; often while saying things like, “Your soul’s within reach!” and “Shut up and bleed!” In a landscape of games dominated by grounded, AAA blockbusters, Mortal Kombat stands as a reminder of video games’ earliest aspirations: It wasn’t about making things more real – it was about bringing the craziest ideas to life.

Perhaps Mortal Kombat isn’t as unrealistic as it seems. Is it possible to freeze someone’s head instantaneously, then shatter it with a quick jab? Could Scorpion’s fiery chain actually split someone in half? How hard is it to punch through someone’s rib cage and pull out their spine? We discussed some of Mortal Kombat’s most gruesome fatalities with two physicists to investigate the scientific plausibility of the series’ most infamous moves.

Fatality: Scorpion’s Classic Spine Rip

Punching through a character’s chest and ripping out their spine is an image that epitomizes a Mortal Kombat Fatality (to the horror of parents everywhere). But is it as easy as it seems? According to Jim Kakalios, a physics professor at the University of Minnesota and author of The Physics of Superheroes, it’s not.

Breaking a rib requires 800-1,000 lbs. of force, according to Kakalios. A study found that elite-level fighters can reach just under this range on average, but they can also top it. Performing this Fatality stops being realistic, though, when you consider the squishy, internal organs behind the ribs.

“Softer things are harder to punch through,” Kakalios says. “If you need to punch through a mattress behind drywall, [the mattress] dissipates a lot of the force. If you try to punch through a mattress, it’s a lot harder.”

That’s because of something Kakalios calls “rolling with the punch,” which is a term boxers use to describe moving one’s head in the direction of the jab, in order to stifle the blow. Rolling with the punch dissipates the force, spreading it out over a larger area instead of focusing it on one location. Thus, when someone tries to punch through drywall, the mattress is ostensibly rolling with the punch.

“This is why we have airbags in our automobiles,” Kakalios said. “An airbag spreads the force over a larger area so the pressure is reduced.”

What this means for Mortal Kombat contestants is that breaking through the ribs is the easy part. To punch even deeper through one’s internal organs would require a dramatically greater amount of force – one not attainable for humans in the real world.

“It’s hard for someone to break a rib. To rip someone’s spine out would require significantly more force,” Kakalios says.

Fatality: Jax’s Devastating Punches

Each character on Mortal Kombat’s roster can throw a good punch, but none can throw one quite so hard as Jax. His brutalities are devastating – in one move, he punches his opponent to the ground with his robotic arms so hard that their bodies explode before he can follow through with his swing.

According to Rhett Allain, an associate professor of physics at Southeastern Louisiana University and the mind behind Wired’s Dot Science blog, there are some interesting physics at play when Jax – or Mortal Kombat fighters in general – decide to go old-school and duke things out with their fists.

Punching does not just apply force to the victim. It also applies force to the person doing the punching, says Allain.

“A force is an interaction between two things. There are always two objects interacting. It’s like how you can’t have a rope with just one end,” Allain says.

In the case of Jax, when he throws a punch, the force of his punch returns to his body, too. But would Jax’s arms sustain any damage? Allain doesn’t think so, suggesting that he would, at most, be pushed backward if throwing a punch. There are interesting physics at play here, too.

“The thing that would save you from not getting pushed back is, one, having a very large mass,” Allain says. So, if Jax’s arms are incredibly dense, that would explain his ability to stay in one place while punching his enemies to a pulp. His mass is so much greater than his foes that the returning force is about as damaging as throwing a penny against a wall.

The second bit of physics keeping Jax grounded during his fist fights is frictional force. If Jax attacks someone from the ground, the frictional force between his feet and the floor would counter any returning force.

“One way that you can cheat and not get pushed back is if you punch up, like an uppercut,” Allain says. “When [Jax] pushes up on a person, the person pushes down. That pushes [Jax] into the ground more, and frictional force increases as the two objects are pushed together.”

Fatality: Sindel’s Exploding Screams

Sometimes Sindel uses her spear-like guandao to cut down her enemies. Sometimes she uses her hair as a whip in a way that puts Bayonetta to shame. But in Mortal Kombat IX, Sindel gets intimately close to her enemies, screaming at a lethal vocal range until their heads explode. (Imagine having that ability as a kid for those moments when your siblings annoyed you!)

Yes, Sindel is from a world with magic, but would our world’s physics allow her to rupture enemies’ heads with focused screams?

Consider soundwaves. According to Kakalios, soundwaves are really waves of pressure that can penetrate your body or pass through solid objects. With technology, one can produce soundwaves, focus them, and make them arrive at a certain location on an object at a specific time.

“The object is absorbing all this energy, and if the energy is delivered at a fast enough rate, the object can’t get rid of it fast enough and it starts breaking apart,” Kakalios says. 

Doctors use this technology in the form of ultrasound machines to eradicate gallstones, for example. But as for a character who screams to blow up her enemies, Kakalios wagers this isn’t achieved quite so easily.

“If the [soundwave] energy was focused at the head, it’s possible that it could break the chemical bonds that are holding parts of the head together,” Kakalios says. But that energy is far beyond a normal human’s capacity to produce. Thus, Sindel’s yells could only exist in a video game.

Fatality: Scorpion’s Melting Chain Attack

One of Scorpion’s fatalities in Mortal Kombat 11 is an attack where he lashes at his opponent with a flaming chain that melts through enemies on contact, splitting them in half. It’s one of those moves that’s so over-the-top, you just gawk – ignorant to the physics that are (or aren’t) occurring.

Could a chain really melt a body in half? How hot would the chain need to be? Could a normal steel chain even support such an incredible temperature?

“We’re all held together by chemical bonds,” Kakalios says. “If you provide enough energy in a short enough period of time, you can break those chemical bonds. Without those chemical bonds holding us together, then bad things happen.”

Bad things, like splitting in half.

That’s easier said than done, it seems. When a heated object touches another object, its heat doesn’t stay in one place; it diffuses across the entire object. The challenge of heating a chain, Kakalios explains, is that the chain would need to burn through a person faster than its heat diffuses. And heat diffuses at the speed of sound.

“It’s not about how much energy you have. It’s about the rate at which you can deliver that energy,” Kakalios said.

By that logic, for Scorpion’s chain to exist in the real world, it would need to be connected to a constant source of energy so that it wouldn’t lose its heat halfway through someone’s chest. Additionally, the chain would need to be crafted from specific materials. Steel and iron, Kakalios explained, would not be able to sustain the temperatures required to split chemical bonds.

“You couldn’t use metals,” Kakalios said. “But you could [create the chain] with a compound like boron nitride. High-temperature ceramics can go to even higher temperatures.” Silicon nitride, for example, is a fine ceramic that only begins to melt at 3,450 degrees Fahrenheit, as opposed to Aluminum, a metal, that begins to melt around 1,220 degrees Fahrenheit.

Scorpion’s chain may be the most realistic of Mortal Kombat’s fatalities, but like taking a knife to a gunfight, it’s not the most practical weapon, considering it technically requires constant connection to a high-energy generator.

Fatality: Sub-Zero Freezing And Shattering His Enemy’s Head

Sub-Zero is the M-rated version of Elsa from Frozen. His fatalities typically involve freezing his enemies with his ice powers, then shattering their bodies with a dismembered limb. As cool as these moves are (pun intended), they might be the most implausible of all the Fatalities on this list, like the one above from the upcoming Mortal Kombat 11.

Allain explains that it’s easier to heat things up than to cool things off. If you want to heat something up (say, a chain), you can attach it to a wire and add electricity. If you want to heat something up faster, you just need to add more electricity. Cooling things down, though, does not work the same way.

“Temperature is a measure of the motions of the atoms in a material,” Allain says. “If you stop the vibrational motion of the atoms, they’re not moving at all. You can’t go below absolute zero.”

Absolute zero is the coldest temperature an object can reach. It puts a cap on how fast something can freeze. Heat, on the other hand, does not have a cap. With enough energy, an object can always get hotter, faster. But because of absolute zero, at a certain temperature, you can’t speed up the rate at which an object freezes anymore.

One of Sub-Zero’s Fatalities shows the fighter grabbing an enemy’s head and freezing it, to which Allain scoffs. 

“If you put a head in liquid nitrogen – which isn’t absolute zero, but it’s close – it would take a good 10-20 minutes for it to freeze,” Allain says.

Sub-Zero’s (and Elsa’s) freeze powers might look cool, but sadly, their icy antics can only exist in a video game world. 

Fatality: Kenshi’s Sword Cutting Opponents In Half

Kenshi’s swords have more utility than most weapons in Mortal Kombat. Sometimes he uses them like lightning rods to call down electricity on his foes. And other times he uses them to slice his enemies in half in one swipe, a feat that – surprise – isn’t very probable in real life.

Swords aren’t sharp enough to cut something clean in half on an atomic level, according to Allain. What’s more, when you slice an enemy, you’re not actually cutting them. You’re squishing the sword through them. The sword must contend with surface area. The greater the surface area, the greater the force required to squish through an enemy.

“The material the sword would have to be made of would need to be magic,” says Allain. “You can’t get it that sharp and that strong.”

Allain uses kitchen knives as an analogy to explain: Sharper kitchen knives are more brittle than duller kitchen knives, and further, more susceptible to breaking. Swords work the same way. For Kenshi’s swords to be sharp enough to slice clean through his enemies (often multiple times!), they’d have to be extremely brittle. So brittle they would break on contact.

The only way Kenshi’s swords could exist, it seems, is if they were made of material that doesn’t exist in our world.

Enjoying video games often requires suspension of disbelief. Some worlds have dragons. Some worlds’ gravity works differently from our own. And even Mortal Kombat, a game series that tries to make its grit and gore look more realistic with every iteration, takes some creative liberties with its characters who, frankly, just don’t abide by our world’s physics. So don’t worry about someone punching through your chest and ripping out your spine – it’s just not possible in Earthrealm.

For more on Mortal Kombat, including the upcoming Mortal Kombat 11, here’s everything we learned from the game’s reveal event, our list of every character on the roster so far, and a deep dive on how Cassie Cage has changed.