I Just Don't Understand This About Physics

 Don't get me wrong, I do understand parts of it. Those things make perfect sense. But other parts are a puzzle. Today was a splendid example.

I tripped. It happens. I landed on one knee, in a paved parking lot next to my car. So far, no mystery yet. But once inside the building I had driven to, and sitting in a chair killing some time, I started feeling my knee complain. Nothing major, just a quiet whimper.

It wasn't serious. In fact, I'd checked the knee of my knit slacks once I got up, and there was not a thread mussed up, not a spot or stain, not a ravel. The pants bore testimony to it never having happened. I'd have expected some dirt, even though it had been raining much of two days but with minimal accumulation, like under 1/3 inch in the rain gauge. Hardly enough to clean a fairly level parking lot.

Of course, it wasn't true that nothing had happened. My memory works perfectly, recording the fall. Even my knee had started to send out little reminders that I hadn't just been bouncing on the bed or something. It was just a little tender. At a moment when there was no audience around I pulled the pant leg up to look at my knee. I expected a small bruise. Just a little thing, since it had been over a decade since I was on blood thinners and a tiny bump turned into an issue. By which I mean a huge bruise covering the front of that leg down to the foot. In the right light, the skin over that piece of me still shows a shadow. It's a souvenir just to remind me.

Today there was no bruise. My knee looked more like a grill had been scraped over the (nonexistant) kneecap, alternating parallel stripes of red and skin from top to bottom. It wasn't bleeding, just somehow scraped and raw. There was no indication of skin strips or blood or grit or anything on the inside of the pant leg either. No bits of gravel had forced their way through the weave, sticking to me. Absolutely no indication anywhere of an encounter with some asphalt.

Except the missing skin bits declared somehing had happened. So did a few nerve endings. And maybe a slightly pulled muscle on the back side of that knee, which has rapidly lessened with modest walking as the afternoon spent itself.

So the physics question I have is this: how does the force transfer itself into marking my skin, after going through a knit fabric, and leave no other evidence of its passage? Not one single broken fiber!

I just don't get it.

I bet crawling into bed tonight is going to be interesting however. I'm still off all painkillers these days, till the doc says otherwise. Maybe not even then.