When I bent to remove the leaf, my foot squished into the wet material. I struggled for a bit to catch my balance, but I stumbled and sailed right off that roof. I didn't fall far -- only about 11 feet, like jumping off a standard basketball hoop. I even landed feet-first. My head hit the ground, but I didn't fracture my skull or anything else. If you were an adventurous kid, you've probably jumped from that height dozens of times.
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But the brain is fragile -- that's why you evolved that fancy skull you're wearing around it. So when the left side of my head met the ground, my brain hit the interior of the other side of my skull in exactly the wrong way. That gave me a subdural hematoma and subarachnoid hemorrhage, thanks to something called a contra coup head injury. That name makes it sound like Nicaraguan rebels took over my brain, and that's actually pretty much what happened.