Borrowed Time by Jack Campbell Page B

still-unsolved mysteries of the universe; why we had access to all of human history but always seemed not to have any time to spare. “Okay. Put him on.”
    An image of Bill Farrow appeared before me, his usually cheerful face looking worried. I started talking before he could. “Look, I’m sure this is really important, but I just got back from dodging homicidal priests through the City of the Dead so I could stop someone from looting a tomb a few millennia before it was supposed to be looted. In other words, I had a really long night last night a long time ago. Can’t this wait?”
    Bill frowned. “You guys always talk funny.”
    “T.I.’s, you mean? It comes from living in circles. Can this wait?”
    “No.”
    I smothered another exasperated expression and tried to look halfway accommodating. “What’s up?”
    “Tom, we’ve been friends since college, right?”
    “Right.”
    “Have I ever remembered stuff that wasn’t true?”
    I started to give a flippant reply, then thought better of it. “No.” Not more so than anyone else, that is. But I didn’t want to get into Quantum Memory Effect at the moment.
    “Then why . . . ” He looked bewildered now. “I was preparing a lecture for my classes, and went to check some of the information, and, and . . . ”
    “Something didn’t match?”
    “Not at all! How could I have forgotten London, England was destroyed by an asteroid in 1908 Common Era?”
    “It was?”
    “Yes!”
    “Jeannie, please check Bill’s last statement for accuracy.”
    Her voice sounded as calm and confident as always. “Historical data bases all agree that London, England was destroyed in 1908 CE. I am unable to check the accuracy of Mr. Farrow’s alleged forgetfulness.”
    “Thanks.” I shook my head. “That’s not what I remember, either, Bill.”
    Bill spread his hands in a helpless gesture. “But that’s what happened! Every history I’ve consulted says so. How could we misremember something like that? How could I misremember it? Imperial England is my specialty.”
    I rubbed my forehead to fight off the first twinges of a headache. It looked like this conversation would take a while whether I wanted it to or not. “Have you ever heard of Quantum Memory Effect?”
    “Uh, no.”
    “Human brains work partly on a quantum level. That’s how we accomplish creative work, and it’s why our minds can accept apparent multiple realities simultaneously. You know, like fiction. But it also has an effect when there’s been a temporal intervention that causes changes to ripple up through history. Thanks to QME you remember something being a certain way, and it’s not, even though you’re positive you couldn’t be mistaken. That’s because part of you is still remembering a reality which has been altered, a reality which no longer actually happened. Usually, it’s just something small and insignificant. But if a really big change happens downtime it can cause really big changes uptime.”
    Bill didn’t look reassured. “But your assistant -.”
    “Jeannie, and every other artificial intelligence, doesn’t work the same way as our brains do. Not yet. They can only accept one reality at a time, even though they can shuffle through alternatives very quickly.”
    “You’re saying London wasn’t destroyed in Victorian times?”
    “Well, no. I mean, it obviously was. But it apparently wasn’t before. Maybe. Now it was.”
    “I don’t understand. You’re talking in circles again.”
    Despite everything, I laughed briefly. “Because that’s how I have to think. You can think in linear terms of before and after. But I have to deal with causality loops brought into existence when someone uptime goes downtime and changes something. The cause of the action takes place after the action, you see. It’s a causality loop through time, not a straight line.”
    Bill didn’t look reassured, then he looked puzzled. “What does that all mean? Look, what’re we arguing about,