My dad’s opening gambit is to explain why most time-travel models in popular culture don’t work: because the Earth moves.
I already summed this up in chapter 4, but if you skipped that part, okay, the Earth spins on its axis—we call that a day—while also rotating around the Sun—we call that a year—which is also moving through the solar system, which is also moving through the galaxy, which is also moving through the universe, which may well be moving through the multiverse. We have no words for those movements because the patterns are too vast to calculate with our current tools. It’s immanently probable there’s a clockwork charm to the whole mess but all we can see is the lonely tip of the smallest hand on the infinite watch face of reality.
The Earth travels through space, really fast, nonstop, every day. In the three and a half seconds it takes you to read this sentence, the planet spun a mile on its axis. Time travel isn’t just going back in time—it’s also leaping vast distances of space and landing in a hyperspecific location so you don’t materialize inside something. Either the time traveler must be immaterial or the location must be empty at a molecular level, because one stray particle in your brain could kill you.
Penny delights my dad by knowing way more about this stuff than anyone could reasonably expect. They spend dessert discussing the merits of creating a vacuum-sealable pod, powered by a nuclear engine that emits a trackable half-life frequency, so if time travel is ever mastered in the future there would be a safe place for time travelers to arrive and a direct path for them to follow. Theoretically, it could prove time travel is possible because if such a pod were built presumably someone from the future would immediately appear as soon as it’s activated—the ultimate if you build it, they will come according to my dad.
Feeling festive, my dad digs out a dusty bottle of small-batch bourbon from a kitchen cupboard and pours glasses for everyone. My mom looks oddly jealous, like she assumed that after dinner she’d get to drag Penny away to show off more gems from her book collection, but somehow my dad got his hooks in and won’t let go. She makes a few attempts to steer the conversation back to nineteenth-century literature via H. G. Wells’s The Time Machine, but my dad keeps a firm hand on the conversational wheel. It’s a character trait my mom’s not used to over here, but I recognize it as the softest possible iteration of the man he’s supposed to be. I feel an uncomfortable pang of homesickness.
Greta’s had a few too many glasses of wine and she lies down on the couch, while Penny and my dad discuss Novikov’s self-consistency principle—that there’s only one causally rigid reality and anything a time traveler might do in the past has always already happened, so there’s no way to change the present timeline. I snort into my second glass of bourbon, because clearly Novikov didn’t know what the hell he was talking about.
Penny and my dad work their way through branching universes and timeline corruption, causal loops and the self-healing reality hypothesis. Greta naps. My mom does the dishes. I drink too much bourbon. I feel like I haven’t spoken in hours, although it’s probably more like twenty minutes. But when they segue into temporal merging, I make the catastrophic decision to pipe up.
“What about temporal drag?” I say.
“Sorry, what?” my dad says, squinting at me.
“I go back in time to before I was born,” I say, “and, I don’t know, accidentally change the past. What if I’m never conceived? What if I’m born but I’m not the same person, even at the most minute genetic level? Wouldn’t I have to exist in the altered reality in order to have gone back in time to cause the change?”
Penny looks unsure, like maybe she should be tense or maybe she should be glad I’m engaging with my dad on the thorny topic that hangs over my life, and now hers.
“Well, yes,” my dad says, “that’s sort of what temporal merging suggests. There aren’t multiple simultaneous dimensions, just one coherent reality, so causal changes in the past ripple through the timeline to resolve paradoxes. But the mechanisms that might make such a thing possible are hazy. Is there a kind of chronal energy that accumulates and releases in the event of a paradox, like a nuclear reaction? And, if so, why would it be oriented to resolving temporal paradoxes here on Earth, when we exist in a cosmic metasystem far grander than the inconsequential life of one particular human being? This kind of thing quickly descends into some vast intelligence guiding events and unknotting conflicts, which gets a bit theological for my taste.”
“I’m not talking about god,” I say. “I’m talking about what actually happens.”
“I didn’t know you were interested in this stuff,” he says. “When did you even read my book?”
“This has been such a lovely night,” Penny says. “But it’s getting late. Thank you so much for inviting me . . .”
Penny presses her foot onto mine, hard. My mom looks out from the kitchen, wiping her hands on a dish towel.
“I’ll be right there,” my mom says. “I need to moisturize as soon as I finish the dishes or my hands get dry.”
“Fundamentally, there’s no way for us to know,” my dad says.
“No,” I say, “this is what happens. When a time traveler changes the past before they’re alive, they become a temporal anchor. Subsequent events fall into place to make sure that they’re born.”
“Isn’t that just a causal loop?” he says.
“No, because when they return to the present,” I say, “everything could be radically different. You could be a disgraced genius, mom could be dead, Greta could’ve never been born, I could be an embarrassing screw-up . . .”
“John,” Penny says.
“My name could be different,” I say. “I could be Tom instead of John but still be the exact same person, I mean, genetically. If I traveled back and then returned to a changed present, the fact of my existence swimming up the time stream would require events to line up in a way that ensures I’m alive to receive my consciousness in the present. I’m the temporal anchor and the ripple effect through time is temporal drag.”
I fill a glass with the resiny bourbon. Then, to demonstrate, I pour it into another glass. My dad leans back, engaged but skeptical.
“So, what,” he says, “the liquid is supposed to be your mind and the glasses are different realities? It sounds too New Agey for me. Consciousness moving between timelines. Would the version of you in the changed present have your memories from the original reality?”
“Yes,” I say, “but he’d think of them as dreams. Or an overactive childhood imagination. He’d have a vague sense of unease, that he doesn’t belong here, that this isn’t the way things are supposed to be. It would be chalked up as just his personality. Maybe the few people he allows himself to get close to secretly worry he suffers from some social disorder or an undiagnosed coordinate on the autism spectrum. But he seems otherwise functional, even capable in certain ways, so they tamp down those worries and do their best to keep him emotionally connected to them. And it would continue like that until the two timelines sync up at the moment the original version of him, the real him, returns from the past. In that moment, the other consciousness would overwhelm his mind and take control. He’d be flooded with memories of another life in a very different world. His brain would feel like it’s constantly at war, twin versions of himself wrestling for dominance, each seeing the other as an existential threat. Because it is.”
Everyone has gotten quiet. My mom stands in the kitchen doorway, chewing a fingernail. My dad stays very still. Penny stares at the intricate pattern on the tablecloth. Greta sits up on the couch. I finish my bourbon and the empty glass smacks against the table a bit too hard.
“Dude,” Greta says, “are you going completely fucking crazy? You can tell us. We love you and we’re here to help.”