A Chronetic Memory (The Chronography Records Book 1) by Kim K. O'Hara Page A

are here on some Wednesdays at 2:00 P.M., and those are usually pretty active, so that would be a good time.” This, from a boy with short dark curly hair.
    “Okay, but what if you didn’t have that inside knowledge? What would you do?”
    “I’d look at the room at regular intervals until I found something interesting.”
    “That’s exactly what we do. Our initial scans are for a few seconds every fifteen minutes or so over an interval of a month or more at a time. I can set the scanner to automatically jump ahead and take these samples, but we restrict those to just visual recordings. Do you think that would be enough to tell when something interesting was going on?”
    They were nodding, except the girl in the hooded sweatshirt. Now she spoke. “Not always, I think. What if someone stole something or got shot or something else that takes less than a minute from start to end? You wouldn’t see anything.”
    “You’re right. You wouldn’t see anything at all. We’d look right over the top of that little incident, unless we knew right where—and when—to look. If we are trying to solve a crime, we can fine tune our calibrations a little better, to catch things like that, but the likelihood of our stumbling onto it randomly is really small. Anyone want to do the math?”
    “I already have.” The boy with bright blue hair looked up from scribbling on his worktablet. “If you assume five-second scans every fifteen minutes, and an event that takes about one minute from start to finish, you will see five seconds of it only about six and two-thirds percent of the time. If you only looked at one month a year, that percentage goes down to a little over a half percent chance of seeing anything at all. I assume you’d need all five seconds to get anything useful.”
    “That was quick, and you’re exactly right. Would you like a job?” The students laughed, but the boy sat up a little straighter. Dani was impressed again. She hadn’t expected anyone to actually take up her challenge. Not only had he done the math, he had taken it beyond the original question. She realized that she was beginning to really like these kids and starting to look forward to the political part of the discussion coming later.
    “If we do happen to find something interesting, then we narrow down our time window and go back and take a second look. With this second look, we usually include the audio portion and the olfactory portion, if the material permits, but we narrow down the viewing angle for the visual to just the part we’re interested in. With this vase, for instance, we don’t really care about what the wall behind it looks like, and we’d probably have a general idea in which direction the action was taking place.”
    “What do you mean when you say, ‘if the material permits’?” asked the boy who had done the figuring.
    “We can’t get scents from anything but metal. We could turn on the scent scanner, but it wouldn’t give us anything. We didn’t find that out until we’d been doing recordings for several years. We’re a little more efficient now.”
    A girl in a bright yellow shirt was waving her hand. Dani nodded at her. “How do you set the viewing angle? I mean, I know there’s a number you type in or scroll to or something, but what if someone turned the vase? Would you have to adjust for that?”
    “You know, no one has ever asked me that before. We don’t have to adjust, and the reason is simple: The angles are absolute angles, related to the earth’s magnetic field. So ‘north five degrees east’ is always the same direction, regardless of whether someone has turned the vase or even upended it.”
    She looked at the clock on the viewwall to her left. It was already 1:45, and she hadn’t even gotten out her equipment. “Would you like to try out the holographic projector before we get to the political questions?” Several students did, and she invited several of them to come up and learn how. Once