Parallel

eyes dart to Caitlin for help. “A concrete example would be useful,” she tells Dr. Mann.
    “Of course,” Dr. Mann says kindly. “I’ll use the illustration I give my students.” Caitlin pulls out a notebook to take notes.
    “Unlike many of my colleagues,” Dr. Mann begins, returning to his whiteboard, “I believe that every world that presently exists was divinely created at a unique moment in history. If this is true, then the ‘now’ of our world must occur at a different moment in time than the ‘now’ of any other world.” He uncaps a marker and draws two parallel lines. “In our world, ‘now’ is September 9, 2009. But in a parallel world, ‘now’ could be December 31, 2020, or April 9, 1981. Or—”
    “September 9, 2008,” Caitlin interjects.
    “Ah.” Dr. Mann looks impressed. “The date of the tremor. Of course.” He writes the date beneath the top line and circles it. “That,” he says, pointing, “is the parallel world. And this”— he taps the bottom line—“is our world.” As he scribbles today’s date in shorthand beneath it, my eyes lock on the repeating numbers. 09/09/09. Does the repetition mean something?
    “So what would happen—specifically—if these two worlds were to collide?” asks Caitlin. Eager, as always, to get to the point.
    “At the precise moment of impact, the reality of the parallel world would replace the reality of our world,” declares Dr. Mann, popping the cap on his marker with a snap.
    Beads of sweat prickle on my upper lip. “Replace?”
    Dr. Mann mistakes my panic for fascination and prattles on. “I had the same reaction, when I realized the implication. To think that in a single instant, the reality of a parallel world could completely overtake the reality of our world, wiping out and replacing everything we know and believe to be true.” He smiles broadly. “It’s an exhilarating notion, yes?”
    Roller coasters are exhilarating. This, dear man, is terrifying.
    “Why can’t it go the other way?” I demand. “Why does the parallel world get to win?”
    “Because time only moves in one direction,” Caitlin says before the professor can answer. “The present can’t change the past. The past creates the present.”
    “The past of some other world ?” I stare at them incredulously. “Come on. We’re talking about the physical world here. Everything can’t just change overnight.” My voice has taken on an I gotcha tone, as if I’ve somehow bested the man with a Nobel.
    The professor’s lips curl into an amused half smile. “Are you familiar with Seurat’s Un dimanche après-midi à l’Île de la Grande Jatte ?” he asks.
    I blink. La Grande Jatte was the centerpiece of my mom’s pointillism exhibit. It was reproduced in miniature on the banner I saw this morning. “Uh, yeah,” I reply, rattled by the synchronicity. “I know the painting pretty well, actually.”
    “Is that the big one with all the little dots?” Caitlin asks. I swallow a smile. As soon as Dr. Mann starts speaking my language, he stops speaking hers.
    “Hundreds of thousands of them,” Dr. Mann replies. “Arranged in a very particular way to create a very particular image. But if one were to rearrange those dots, that image would become unrecognizable and a new one would take shape. Same dots, same canvas, different picture.” The old man looks at me. “Reality is the same way, I think.”
    Somehow, this metaphor strikes me as more concrete than all the science-speak. Maybe because I’m accustomed to this vocabulary—it’s the one my parents spoke at the dinner table every night when I was growing up. Reality as a pointillist painting. That I can wrap my brain around.
    “But how could it happen without anyone noticing it?” I ask. “You said this entanglement thing affects everyone. So why does no one but me—” I stop short as the professor’s eyebrows shoot up. “Why does no one realize it?” As much as I like this man, I’m not about to become the lab specimen for his wacky theories, even if they happen to be true.
    “Shared reality,” Caitlin says before Dr. Mann can respond. “We’re getting our parallel selves’ memories, and our brains are processing them as our own.” She looks to Dr. Mann for confirmation. “Right?”
    “Exactly right,” he replies. “If our world has indeed collided with a parallel world, then as your parallel self moves forward in time, your memories are continuously being erased and