9.8 meters per second per second

Thank God I remembered his name: Ortho. I wouldn't have been able to sleep tonight if I had lost that little bit. It only took a call to my mother and a quick rehash:
"Lothar?"
"No."
"Ragnar?"
"No."
"Amir?"
"No - it had something to do with bug spray."
"Ortho?"
"That's it!"
Ortho was a young man - probably in his early twenties - who decided to do a free climb up the face of the big pile of granite that stood at one side of our mountain property. Three of us kids (I was about nine at the time) watched him make slow progress, stretching for holds, straining to reach the next step. Then he fell. It was a very matter of fact thing - not a dramatic, clinging with one hand - clawing the air with the other kind of moment. Gravity just caught up with him all of a sudden.
He landed with a thud in a small grove of aspen trees. A couple of Ortho's friends came running as well as my dad. There was some brief discussion about what to do with him, but since we were miles from the nearest hospital or fire station, we rigged up a stretcher and dragged him over to the porch of our cabin. This is where the brain trust went into high gear, trying to determine the next steps. For his part, Ortho was quite lucid, but still not quite ready to move on his own. One of his friends claimed knowledge of spinal injuries (why wouldn't the hippie guy from across the road know about spinal cord injuries?) and we fashioned a combination sling/traction device out of cardboard boxes to transport him down the mountain to an emergency room.
It was some time before we heard back (we had no phone at the cabin) that Ortho had cracked a vertebra but was going to be all right - eventually.
I learned to respect gravity that day - though I still chose to flaunt it for some time after that (jumping from swings, etc.), but watching Ortho taught me just how quick up can be down.