version-control

He pulled out his wallet and extracted a twenty-dollar bill, fastidiously folding it in half so that the crease cut across the face of Theodore Roosevelt, with its shining spectacles and its Chesire Cat grin.

What we are proposing,' Alicia said, 'is that the laws of physics are such that causality violation is subject to a form of version control, one that prevents a forking of history. That instead of causality violation creating an alternate universe, one version of history is outright overwritten by another. One past is replaced with another future. Which means that the memories of the past of the people in that future are replaced with memories of a different past.'Carson interrupted. 'Including the memories of any_''Purely hypothetical_''__ime travelers.''So take our time traveler from the traditional story,' Carson continued. 'He leaves his utopian future for the past. He kills the butterfly. The Magna Carta is never written. He returns to the dystopian future that his misstep created. But he doesn't see it as a dystopia: he sees it as home, the world he grew up in, the world he left to go back in time. Because he doesn't remember that first future, and has no other world to which he can compare this one. Maybe he even sees it as a utopia. Maybe everyone does. Maybe everyone in this dark place believes that they live in the best of all possible worlds.

Later__ow much later? Hard to tell. In times of tragedy clocks will trick you__hilip stood in the kitchen doorway.

I can__ comprehend why any black man with even a lick of sense would have the slightest bit of interest in time travel. Going backward in time? A black man? You have got to be out of your mind.

But who, in these modern times, slept well?

Rebecca approached the causality violation chamber (too grand a name for such a faulty thing), placed her hand against its door, and closed her eyes, much as Philip had during its christening years ago. There was no response from the machine; no prophecy; no apology; no advice. It did not relay the news from other, brighter timelines. It did not tell her what would have transpired had she returned from yesterday's shopping trip a few hours later, or had she turned the steering wheel left instead of right two years ago, or had she not taken that first drink, or had she turned down any one of the thousands of drinks that had followed, or had she chosen not to respond to Philip's insistent and perhaps deliberately oblivious messages during the early days of their online courtship, or had her parents or her grandparents, or her great-grandparents never met. The machine's obstinate silence was all it had to offer; the message of that silence was that she had made her choices in life, and her choices had made her in return.

He felt that race was not a characteristic that was a part of his identity, but one that was projected upon him by the gaze of others who looked on him; as such it was ephemeral, there and gone as soon as the gaze was broken.

And yet Rebecca felt that it was hard to tell whether the secret algorithms of Big Data did not so much reveal you to yourself as they tried to dictate to you what you were to be. To accept that the machines knew you better than you knew yourself involved a kind of silent assent: you liked the things Big Data told you you were likely to like, and you loved the people it said you were likely to love. To believe entirely in the data entailed a slight diminishment of the self, small but crucial and, perhaps, irreversible.

And as Sean climbs into bed and closes his eyes, Mother comes, riding astride a lion the size of a house, blowing a clarion from a horn made out of a hollowed-out elephant's tusk. Her eyes have a faint crimson glow from the lasers that are mounted behind her irises, ready to fire at will.'I touched a prince's chest today and made his heart stop,' she says. 'I'll do it again if I have to: they'll see what happens if anyone gets in my way. Good night, my son. Remember that I will always keep you safe; that I am always everywhere and always here.''Good night, Mom,' Sean says, and falls asleep.And Mother recedes, wise and beautiful and strong, a genius and a hero, a punisher of thieves and a slayer of wicked men, to watch over her son in all her different versions.

That's one of our speculations, by the way. That the prior version of history that this one overwrote was horrible. Complete geopolitical mayhem; half of New York City is underwater. The United States is headed toward civil war, or ruled by an artificial-intelligence construct, or some such other thing. Real end-of-days stuff. That the instances of ourselves who existed in that history figured out what we have: that the invention of the causality violation device was the cause. That in that prior version of history, Rebecca did not die in a car accident. That she went back to the past on a mission, as a volunteer, well aware of her sacrifice.