For the uninitiated, Quicksilver is the resident “fast guy” from Marvel Comics, an angsty, destructive knock-off of DC Comic’s The Flash. Depending on what version of Quicksilver you’re reading about or watching on screen, he’s capable of running and moving anywhere between Mach 1 and Mach 10. That’s a big range, sure, but from a scientific perspective it doesn’t really makes much of a difference. Human physiology hits its limits way before the sound barrier. So Quicksilver’s super power implies other, hidden powers at play.

If the ability for a human to move at supersonic speeds was possible, what would Quicksilver need to be like to keep from vaporizing away?

To answer this, we’ll need to back up for a moment. The human body, as it runs, is not designed to move at ultra high speeds. Human’s don’t move smoothly like a car on wheels or have the aerodynamic shape of a plane — each step creates an impact on the body and all of its bones and muscles. When an athlete runs at a constant speed and hits the ground, 90 percent of his/her force goes towards vertically pushing the body up again. Only five percent of that force is used to move forward, horizontally.

If you’re moving at even just Mach 1, every step you take is also hitting the ground with such a force as to propel you past the sound barrier. That’s an incredible amount of force, and your bones, without some superhuman mutant reinforcement, would be instantly crushed and shattered. To make matters worse, the rest of your frame would experience something similar. Even if accelerating to those speeds wasn’t an issue, stopping would be. Hitting the breaks would be the physiological equivalent of running into a wall.

Okay, so let’s assume part of Quicksilver’s powers mean he has superhuman bones and muscles and can withstand this kind of force (that also means Quicksilver would essentially be the strongest living thing ever). And let’s also assume that, given the amounts of force exerted, the ground/buildings miraculously didn’t turn into dust.

Supersonic speeds mean intense pressure and frictional forces caused simply by the atmosphere. A supersonic jet aircraft is encased in a metal exterior that is explicitly designed to be both lightweight and durable enough to withstand ambient forces acting upon it — not to mention it’s shaped in such a way as to maximize aerodynamic efficiency and reduce drag. Quicksilver, as he’s portrayed so far, doesn’t have any of those things. He’s usually just wearing a tight-fitting shirt and pants, both of which would get shredded Hulk-fast.

A supersonic jet breaking the sound barrier.

In addition, it’s also worth emphasizing that the way humans run is actually highly inefficient with regards to reaching maximum speeds. Running upright forces you to move your body through the air in its entirety — there’s no reduction in drag. You’d be hitting the full brunt force of the air even if you had the necessary armor to keep yourself from being melted apart.

The last limitation for why Quicksilver would die in real life is that he simply would not be able to breathe in a normal way to keep up the pace. With such a high pressure on the front and such a low pressure on his back, he’d have an insane amount of trouble trying to expel air from his lungs and out through his mouth and nose. It wouldn’t go anywhere.

Perhaps Quicksilver could be genetically engineered to have a body capable of withstanding the forces of running at Mach speeds. Perhaps he could invent some miracle clothing that protects himself from the friction caused by the air. Perhaps he even found a way to breathe properly during his run, or at least held his breath long enough. There are still other issues to deal with: motion sickness, blacking out a G-forces, the devastating effect any small object that hits him would have, the noise (especially caused by the sonic boom), and much more. Quicksilver would have to be some kind of mad scientist to find solutions to all of these problems. All superheroes are fiction, but Quicksilver in particular is something that stretches the imagination in more than just scientific ways.

Hope that helps — particularly for the next time you and your nerdy buddies are spending your hours debating if the Flash or Quicksilver is the faster superhero.