A tiny bit of physics

Back in high school physics, I remember, I had been part of a classroom discussion regarding friction. A scenario had been proposed that without friction, someone who started walking down the street would have nothing to oppose their forward inertia and would just slide forward uncontrollably. What if the person grabbed a tree to stop himself? Without friction, he would keep going. One of my classmates, Nick, opposed this view, saying there was something else that would keep the person bound to the tree and the tree stuck into the ground. The teacher semi-mockingly called this new fifth force "grab." I knew what Nick was talking about, and he was right.
I couldn't quite explain it at the time, but I can now. I don't know exactly why, but this is something I find important and interesting.
If friction is the force that resists the motion of one surface sliding against another, a fairly accurate and common definition, then we can imagine a frictionless world by imagining every object in it as having been greased with a perfectly effective lubricant. The person slides down the street with nothing to slow his inertia. Ordinarily, millions of tiny impacts with the air and between the bumps and grooves of your shoes (knees? face?) and those in the ground, absorb some of that momentum. You slow, shoe rubber streaks the ground, which is likewise worn smooth, and heat is generated. Not so here. But there are still the larger impacts: slamming into the tree. It's the same kind of force at work, only on a macro scale, so we don't normally think of it as "friction." It's just an impact.
To keep going, either you or the tree would have to break, or you'd have to go right through the tree, or it would have to pop out of the ground, its entire root system and a ton of earth either bending, breaking, or interpenetrating.
None of these options are possible, because there are forces that hold the tree together, hold you together, and hold the ground together, and also keep solid objects from passing through one another. In high school physics, you spend a lot of time ignoring these forces because you take it for granted in so much of mechanics that you are dealing with solid objects. Solid here means they hold together and don't occupy the same space as other solid objects. But those forces are necessary. They are the reason gravity  doesn't pull you through the solid ground, or that the ground itself doesn't fall, shrinking the earth until the nuclei of atoms are pressed together.
Electromagnetic forces. Good to have. Time is cool because it keeps everything from happening at once. Space is cool because it keeps everything from happening in the same place. But that space would be a lot smaller without good old EM.
Don't know why, just wanted to post that.