Causality and Fixing the Past in A.G. Riddle's Lost in Time

The Thematic Claim

The central claim of A.G. Riddle's Lost in Time is that the past is not a scene you can revisit and edit; it is the load-bearing structure of the present. The novel articulates a precise rule through its scientists: changing one's own timeline risks collapsing reality, while the past of a different timeline remains open to intervention. From that tension the book builds its drama. Characters want to undo grief, prevent murder, and rescue loved ones, but every attempt collides with the same warning: the past must happen as it happened, or the universe will cease to exist. The desire to "fix" the past is therefore both the most human impulse in the novel and the most dangerous one.

How Causality Works in the World of Absolom

The rules of time travel in the novel are established through the physics of the Absolom machine. Nora Thomas explains that Absolom always transmits to the past because matter and time cannot be separated; displacing an object in the present without displacing it in time is physically impossible. The consequence is strict self-consistency: you can only send something to the past that was already there. If an event happened, it will happen, and it must happen for the present to continue existing. Sending something new into a past that did not contain it would break the causal sequence and risk what Nora calls a causality collapse, the instant erasure of reality.

Daniele Danneros reinforces the idea when Adeline asks whether Absolom Two could prevent Nora's murder. Daniele answers that the past cannot be changed and must not be changed. She describes the present as the eventuality of a series of causal events: thin slices of time stacked like building blocks with no end and no beginning. Modify one of the blocks and the present ceases to exist at the moment causality is ruptured. Her comparison to a black hole's event horizon is deliberate: nothing that crosses it ever comes back, and likewise nothing that has become part of the causal chain can be removed from it.

Absolom Two introduces a variation on the rule. Elliott Lucas reveals that his breakthrough allows the machine to target specific universes, provided those universes were created from the original one. Entanglement acts as a bridge between timelines, a string that can guide a payload to another universe. This means Absolom Two can transport matter to any timeline, including the characters' own, but the older warning still applies. The book resolves the apparent contradiction through branching: when Absolom transports a payload, it creates an alternate timeline in which the payload is deposited. A person sent to a different timeline's past can act and even change events there, because that past is not the causal foundation of the universe the characters inhabit.

The tuning bar experiment is the clearest demonstration of the novel's causal logic. The team plans an experiment, makes a pact to carry it out no matter what, acquires a small dated tuning bar, and locks it away. Only then do they go to Death Valley to try to find it. If they find it, they send it; if they never find it, they never sent it. The order is deliberately strange. Discovery precedes sending, because the object's presence in the past is proof that the future has already acted. The past contains the consequences of decisions that have not yet been made, and the universe stays consistent only because someone eventually makes them.

Tracing the Theme Across the Plot

First Movement: Sam Anderson's Arrest

The novel opens at Sam Anderson's annual visit to his wife Sarah's grave, a scene of private grief interrupted by police drones and officers. Sam is arrested for Nora Thomas's murder, and surveillance footage places him and Adeline at Nora's home during the probable time of death. The causal chain here is already fixed. Sam cannot argue his way free because the events have already happened and been recorded; the footage is not evidence of a crime so much as a confirmation that the sequence unfolded as it had to. His arrest, his classification as an Absolom offender, and his eventual transport all become links in a chain that reaches back before the story begins.

Second Movement: The Dig in Death Valley

The middle of the novel follows Elliott Lucas and Hiro Sato as they dig holes in Death Valley and fill them back in, searching for tuning bars that have not yet been sent. Adeline watches them work and understands what they are doing: testing Absolom Two's ability to target times and locations. The experiment inverts ordinary cause and effect. The team cannot send the bar first and then look for it; they must find the evidence of the future sending before they perform the sending. This is the novel's purest portrait of time as a closed loop, and Adeline's reaction, that the logic is breaking her brain, is the reader's own disorientation made explicit.

Third Movement: Adeline and the Murder She Cannot Prevent

Adeline's investigation ultimately confronts her with a horrifying possibility: that she is the person who must go back and kill Nora. The older Adeline realizes that the past has to occur as it had, or the universe would break, and that someone has to be sent back to commit the act. Her greatest fear is that she is that someone. The theme here stops being abstract and becomes moral. To preserve reality, Adeline might have to perform the very murder she has spent the novel trying to prevent. The epilogue offers a version of resolution: Adeline appears in photos with Nathan performing Absolom rescues just before natural disasters, and she later reunites with him at a startup event, inviting him to join a project centered on saving innocent lives. The ending does not undo the past; it shows a future built around the acceptance that time moves forward only when its earlier moments are honored.

Characters Who Carry the Theme

• Sam Anderson is the living illustration of the novel's rule. His mistakes and his grief place him inside a causal sequence that ends with his exile to a different timeline's past, where his presence can change events precisely because that timeline is not his own.

• Adeline Anderson is the character most torn by the theme. She wants to prevent Nora's murder, yet she learns that doing so would destroy the present; her arc is the slow acceptance that fixing the past is impossible within her own timeline and that her role may instead be to ensure the past happens exactly as it did.

• Nora Thomas is the novel's theorist of causality. She formulates the rule that a past event must happen for the present to exist, and she takes the danger a step further by suggesting that Absolom Two is the answer to the Fermi Paradox: all sufficiently advanced civilizations eventually destroy themselves through causality failure.

• Elliott Lucas embodies the temptation to break the rule. His grief over Charlie drives him to want to use Absolom Two to change the past, and he is open with Adeline about his willingness to risk it, making him the cautionary example of how love can become a threat to reality.

• Daniele Danneros serves as the guardian of the causal order. She refuses to discuss Absolom Two, insists the past must not be changed, and believes the machine has already been used, a suspicion that keeps the theme uncertain until the end.

• Hiro Sato and Constance Niven support the practical side of the theme: Hiro in the digging and testing, Constance in the private rooms where images of the past are studied like clues to a crime, both connected to the loop the Absolom Six have entered.

Symbols of the Causal Loop

The Absolom machine is the novel's central symbol of irreversible commitment. It began as an idea for instant shipping, a plan to do for physical matter what the internet did for data, but the discovery that displacement in space always carries displacement in time turned it into a device that branches universes. Every use of the machine is a causal act with consequences no one fully controls.

The tuning bars are the theme made physical. They are small enough to transport, dated by their radioactive decay, and designed to emit a locating signal so the team can dig them up. Their existence collapses the distance between intention and evidence: the bars prove that a future decision has already shaped the past.

The diamond earrings and the disappearing-ink driver's license carry the same idea in a more personal form. Adeline prints a fake license and watches the present cover the past and the future, wondering where the object originally came from. The license and the earrings exist in the past only because a future Adeline will send them, and their origin is a loop that resists explanation. They are the universe itself in miniature: something whose past before it existed is a mystery.

Complexity and Contradiction

The novel intentionally leaves its own rule in tension. Characters say the past cannot be changed, yet the plot depends on Sam being sent into the past of another timeline, where change is possible. The resolution is that the timeline Sam enters is a branch created by the machine, not the timeline the other characters inhabit. The universe survives because the alteration happens somewhere else.

Nora's Fermi Paradox theory deepens the contradiction. If every advanced civilization eventually invents a machine like Absolom Two and destroys itself trying to fix the past, then the rule is not a law of physics alone but a kind of cosmic trap. The novel does not confirm that all universes end this way; it leaves the idea as a frightening possibility, one that makes the characters' restraint look heroic rather than merely cautious.

Elliott's ongoing desire to use Absolom Two for Charlie represents the emotional pull against the rule. The novel sympathizes with his grief even as it shows why his plan cannot be allowed to succeed. The contradiction between what the characters want and what the universe demands is the source of the book's tension, and the ending suggests that the only healthy response is to stop trying to alter the past and instead build a future around the lives that remain.

Study Questions and Answers

1. Why does Nora say Absolom cannot be used to send anything you want to the past?

Nora explains that Absolom transmits to the past by the nature of its physics, but a payload can only be sent if it was already there. If an event happened, it will happen, and it must happen for the present to exist. Sending something new would alter the causal sequence that produced reality and could trigger a causality collapse in which the universe ceases to exist.

2. What is the order of the tuning bar experiment, and why does that order matter?

The team first makes a plan and a pact, then acquires a tuning bar and locks it in a secure box. They go to Death Valley and search for it; if they find it, they send it, and if they never find it, they never sent it. The order matters because discovery must precede sending: the object's presence in the past proves the future has already acted, keeping the timeline self-consistent.

3. Why does Daniele tell Adeline that the past must not be changed?

Daniele says the past is the causal sequence of events that created the present. She compares the present to building blocks of time and warns that modifying even one block would make reality cease to exist at the moment causality is ruptured, much as matter cannot escape a black hole once it crosses the event horizon.

4. How does the novel distinguish between changing your own timeline and changing another timeline?

Changing your own timeline risks destroying reality because that timeline is the causal foundation of the present. Transporting a payload with Absolom branches the universe and creates an alternate timeline, so a person sent to another timeline's past can act and change events there. The original causal chain remains intact because the change happens outside it.

5. What is Adeline's greatest fear, and what does it reveal about the theme?

Adeline fears that she is the person who must go back and kill Nora, because the past has to occur as it had or the universe will break. The fear reveals that causality is not only physics in the novel; preserving reality may require a moral cost that feels identical to the crime the characters want to undo.