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

works?”
    A dark-haired girl, lounging against her seat back, dressed in a rumpled tee shirt, spoke up without raising her hand. “You use old things as a source for sights and sounds and smells. When you put them in the box, they act like they’ve been little recorders all along, but you don’t get their stuff until years and years later.”
    “Yes, exactly. So we can use them to find out what happened when no recorders were present. And then we can save the recordings for other people to analyze and interpret. If historians disagree about how something happened, they can go back to the same source that the first researchers used and draw their own conclusions. Does anyone know what we call that kind of research?”
    A boy in the middle with bright blue hair leaned forward in his seat. She invited him to speak with an open hand held out in his direction. “That’s original research, right? Not based on anyone else’s research? And that’s supposed to be more reliable.”
    Dani nodded. “It’s very important to our view of the past to be able to establish things as true or false, or as simply someone’s opinion of what’s true. What are some things that you can’t learn from a recording?”
    More of the students were getting drawn into the discussion. Maybe they were realizing that this wasn’t going to be the propaganda talk they had expected. Answers started coming more quickly.
    “People’s motives.” “People’s thoughts.” “Anything that happened out of the room, or out of the line of sight,” which gave rise to, “anything hidden in any way.”
    Dani smiled. There were some sharp minds in this group. “You’ve thought this through already, haven’t you? Let me tell you what we find when we analyze a typical object.”
    She showed them the plastic and leather samples and told them the former wasn’t helpful and the latter yielded only still photographs, which could be useful for establishing dates and times.
    The girl in the white shirt asked, “How can you learn when something happened? If I look at a photograph, I can’t tell when it was taken.”
    “One of the most important developments in the science of chronography was when we first learned how to calibrate for dates and times. Today, when we examine an object, we can zero in on a specific minute—even second—in time.”
    “How do you know what time to zero in on?” blurted a girl in a dark hooded sweatshirt who, until this moment, hadn’t spoken.
    Dani was impressed. It was a question she rarely heard, but it was so much a part of her job. She was starting to like this talk-only-about-the-science stuff. It got her into topics that she didn’t usually get to address. “We don’t. Not at first, anyway.”
    She reached over and picked up a ceramic vase from a nearby bookshelf. “Let’s say someone donated this vase, or that we found it in an old house or museum. We have a vague idea that it might be useful because of where it was found, but we don’t really know if it was always in that house, or museum, or anywhere, really. Let’s say it spent most of its existence in a school like this one, but we don’t know that.”
    She had their attention. “Ceramic is a good material to use as a source. We can get complete visual and audio recordings from it, with moving images, for as long as we want. If we pick a random time, and we happen to end up in the summer, what will we see and hear?”
    There they were, on the cusp of summer. They didn’t have to think long at all. “Nothing.” “We’re all gone in the summer.”
    “That’s right, and we could have assumed that if we knew this vase was from a school. But we didn’t. So we see nothing except this room, with nobody in it. Once we see that, we might be able to guess that it’s in a school, and our second try at a recording will be more useful. What day and time would you pick?”
    Hands went up. “You—when would you pick?”
    “Well, I know that class meetings