When I recovered, I began to wonder whether this could actually happen, and I spent part of Monday e-mailing back and forth with two researchers who have studied the strength of the human head.
The consensus: No way. Not a chance. Not even for The Mountain, whom George R.R. Martin, author of the novels that have been transformed into the hit series, describes as nearly eight feet tall and weighing about 420 pounds of solid muscle.
Tobias Mattei, who has looked at how well children's bike helmets protect their heads, was definitive in an e-mail to me. "It would be impossible for even the strongest human to break the skull through compressive forces exerted by any means (either with their hands bilaterally or by stepping [on] it) in any portion of the skull," he wrote.
Cynthia Bir, a biomedical engineer at the University of Southern California, said in an e-mail that her "knee jerk response is that there is no way to get the head to 'explode' by applying pressure from the eyes. You would need to create pressure inside the cranium. Even if you could generate pressure by squeezing the outside of the head, once the cranium is breached at the orifice where the eye nerves enter, this pressure would be greatly diminished."
Now let's look at the particulars.
Mattei, who noted helpfully that "fresh cadaver skulls are much more resistant to crushing/fracture than formaldehyde-preserved or desiccated skulls," said that the thinnest region of the skull bone is about two centimeters above and in front of the top of your ears. Sort of where your temples are.
To fracture the skull there would require 500 kgf, or the force that 500 kilograms (1,100 pounds) would exert in standard gravity. A man would have to weigh
235 500 kilograms ( 517 1,100 pounds) to do that by stepping on the head, and, Mattei said, it would be "impossible to break it with his hands even if 90 percent of the 235 500 kg were biceps muscles."
I asked Mattei, a neurosurgeon at the Brain & Spine Center of InvisionHealth in Buffalo, about the eye-socket strategy. "Extreme pressure on the eyes would lead to rupture of the globes with leaking of its content," he responded. "However, it would probably not be exciting for TV fans because it would only lead to a leakage of a clear fluid between the warrior’s fingers. Probably a small fracture of the inferior orbital wall – the thinnest portion of the orbital wall – would occur (this is a common fracture called "blowout fracture"). No explosion would be seen. The eyes of the victim would be pushed backward some few inches. That’s it."
For good measure, I asked Mattei about the strength of the human skull compared to other materials we know – wood, steel, etc. The standard for this kind of elasticity in solid materials is called "Young's Modulus" and it's measured in GigaPascals. (But you knew that already.) Turns out the human skull can withstand 6.5 GPa of pressure, while oak holds up under 11, concrete 30, aluminum 69 and steel 200. Atop the charts is graphene, which Mattei described as "a monolayer lattice form of carbon," at 1,000 GPa.
Finally, I just had to know whether any amount of pressure could cause a man's brains to blow out the top of his head. (Because I'm just wired that way, okay?) Again, Mattei showed why he'll never work in Hollywood:
"I would say that it would be almost impossible ... to 'blow up' the head's top from inside (even if you connect a firefighter's water pump in it) because the skull base as well as the squamous portion of the temporal bone ... would blow out (sideways) first."