Markers and Erasers 2019-10-07 When I was in the fifth grade, we were sometimes given dry-erase markers and small whiteboards to draw on. Occasionally, we'd use them for lessons, but mostly they came out when it was raining and we couldn't go outside to play. For a time, my friends and I would play a "video game" with these unlikely implements. One person would draw a target, another would slowly move the marker up and down a vertical edge of the board, and a third---the player---would choose the precise moment when they wanted the marker-bearer to "shoot". The marker-bearer would then "simulate" a "shot" with "realistic gravity" at the target, and we would all judge damage incurred on the target as well as the veracity of the simulation. Curiously, the player would only call the simulation unfair if he didn't hit the target, and the target-drawer would always take the opposite position. In remembering that little game, I also remembered a strange assumption---an extrapolation, really---about markers and erasers. I knew, of course, that markers could leave ink on the board and that erasers could wipe it away. That was obvious. I further knew that the ink left by the markers was a physical substance, since the erasers got dirty, and accumulated ink would form a sort of dust that could be pushed around. To me, it seemed that markers and erasers were opposites; one created, one erased. It was as if the Expo corporation had at their disposal the immense power to instantiate two equally-powerful forces in the universe, intended to work together, but never to meet. Somewhere along the way, nine-year-old me formed a question with frightening implications: what would happen if you touched a marker *directly* to an eraser? My little mind raced. Well, I thought, since the marker marks and the eraser erases, the only possibility is that touching the marker directly to the eraser would result in *all* of the ink in the marker getting sucked out of it and into the eraser *instantly*. I recall being afraid for some time after that to ever touch the two halves of this reaction together, lest I ruin both. (I may have also inserted that memory after repeated rememberings over the years, but I can't say.) Obviously, this is an incorrect conclusion. Touching a marker to an eraser, while counter-productive and a little silly, doesn't result in some matter-antimatter annihilation phenomenon. At some point, I gathered up the courage to try it, and I remember being both relieved and a little disappointed at the uninteresting result. Every time I've remembered that story since, I've idly searched for some meaning in it. It sounds like it could be profound, at least to me. Perhaps this is the core of some commentary on creation and deletion, sources and sinks, good and evil. Or maybe it's the hook in a cautionary tale about blind extrapolation without evidence. It could even start a discussion about childhood curiosity and learning. I've yet to come up with anything satisfying to say about it. Maybe the whole thing is nothing more than a story about a child who thought a thing was true and turned out to be wrong. I don't know, but I know for sure that I like remembering it.