The grandfather paradox and time-travel paradoxes

The grandfather paradox and time-travel paradoxes give Natasha Kingsley and Daniel Jae Ho Bae a shared intellectual subject, turning a hypothetical question into an exploration of causality, alternate lives, and the uncertain boundary between chance and destiny. The paradox is not presented as an actual journey through time. It is a thought experiment that lets the characters test what it would mean to alter the past—and lets the novel ask how many unlikely events seem necessary for a life, or a love, to take shape.

The Hypothetical and Its Causal Loop

Daniel raises the possibility of a time machine while trying to keep Natasha engaged in conversation. The question changes the mood: Natasha, who had seemed bored or irritated, leans forward and begins pressing him on what kind of time travel the machine allows. Her interest is not simply in the machine as a fantasy device. She immediately attends to the logical trouble that follows if the past can be changed.

To explain the grandfather paradox, Natasha asks Daniel to imagine an evil grandfather and a time traveler who goes back to kill him. If the killing happens before the grandfather meets the grandmother, one of the time traveler’s parents is never born, and the time traveler is never born either. Without existing, the traveler cannot make the journey or carry out the killing. The proposed action therefore removes the conditions that made it possible.

Changing the timing does not straightforwardly dissolve the problem. If the grandfather is killed after meeting the grandmother, the traveler is born and can later invent the time machine and return to kill him. The sequence then loops: the traveler’s existence permits the action that, in the past, threatens that existence. Natasha describes this not as a simple contradiction to dismiss but as a causal circle whose two directions depend on each other. The puzzle asks whether an event can both occur and erase the preconditions for its occurrence.

Daniel’s contribution makes the imagined example more personal without resolving it. He contrasts Natasha’s invented evil ancestor with his own grandfather, whom he says is dead and whom he met only once; his memory of the man is benign. The difference between the actual family recollection and the hypothetical villain makes clear that the paradox depends on a constructed case, not on a revelation about Daniel’s family.

Self-Consistency and the Prevention of Paradox

Natasha next invokes the Novikov self-consistency principle, another way of thinking about travel to the past. In the explanation she gives, the traveler may be unable to perform an action that would make the past inconsistent with the history that produced the traveler. Rather than allowing a contradiction, events prevent the impossible outcome.

She illustrates the idea through improbable interruptions: the gun might misfire at exactly the necessary moment, or the traveler might suffer a heart attack. Daniel responds playfully by imagining that a girl could walk into the room and bowl him over. Natasha accepts the structure of the joke while restating the principle: something strange and unlikely would happen so that the impossible could not. The exchange makes self-consistency feel less like a mechanical rule than a pressure exerted by the entire chain of events. A small contingency can become the means by which a larger history remains intact.

The scene also marks a shift in the interaction between the two characters. Natasha’s knowledge and animation draw Daniel’s attention; his attempt at flirtation takes the form of joining her speculative example. The paradox thus works on two levels: it is an argument about whether the past can be changed, and a conversational opening through which Daniel and Natasha begin to connect. Neither of them demonstrates that time travel is possible. Their interest lies in what the hypothetical exposes about causes, consequences, and the fragile routes by which people meet.

Multiverses and Lives Not Lived

The novel introduces multiverse theory as a distinct possible solution to the grandfather paradox. Associated in the narration with Hugh Everett, the theory proposes that versions of past and future histories exist in alternate universes. At the quantum level, events divide the current universe into multiple universes; each choice is accompanied by other versions in which a different choice was made. If every possible outcome exists in a separate universe, the outcomes need not cancel one another in a single history, and the paradox is avoided.

The idea expands from a theoretical account of time travel into a vocabulary for Natasha’s uncertainty about her own life. The narration imagines different universes in which Samuel Kingsley does not derail his daughter’s life, in which he does but Natasha manages to repair the damage, and in which she cannot. Natasha is unsure which of these possible histories most resembles the universe she inhabits. The alternatives do not establish that she can move between worlds; they give form to the unresolved question of what her choices can still change.

That speculation becomes concrete in Natasha’s attention to the damaged phone screen and the headphones that might have remained intact in another version of the day. In one imagined universe, she stays home and packs as her mother wanted, preserving both objects but never meeting Daniel. In another, she goes to school and sits safely in English class rather than nearly being hit by a car; again, Daniel remains a stranger. These alternatives connect a large-scale theory to ordinary consequences. Avoiding one bad event would also erase the encounter that has become important to her, so the imagined branches offer no simple distinction between a fortunate history and an unfortunate one.

Chance, Causality, and the Shape of Love

The paradoxes belong to a wider disagreement in the novel over how events acquire meaning. Natasha’s mother believes that things happen for a reason and that a larger plan can bring comfort. Natasha instead believes in determinism: one action leads to another, and actions help determine fate. Daniel occupies a less settled position between those views. He wonders whether meeting Natasha was chance, but once they have met, he experiences the love between them as inevitable. The multiverse makes the alternatives visible without deciding which interpretation of their meeting is true.

Years later, after Natasha and Daniel have found each other again following an argument, the book returns to the image of a universe assembling from a vast number of events. Natasha had argued that falling in love could not rival the number of things that had to go right for their universe to form; Daniel had always thought she was wrong. He understands apparent chaos as a matter of scale: viewed closely, events seem disordered, but order may emerge if one pulls back far enough and waits long enough. Their universe, he thinks, may simply be taking longer to form. This reflection does not solve the grandfather paradox or confirm a single theory of fate. Instead, it carries the paradox’s central tension into their relationship: the same chain of causes can look accidental from one vantage and coherent from another. The alternate histories remain imaginable, but the story’s emotional emphasis falls on the fragile sequence of events that brought the two characters together.