Five Sci-Fi Movies With Scientifically Plausible Time Travel

Most time travel movies ignore the quantum physics of how time travel might actually work. Writers and directors include concepts that help their story and ignore the ones that do not. For example, when Doc Brown takes Marty and Jennifer to the future in Back to the Future Part II, they cannot meet their kids because Marty and Jennifer would have been absent from the timeline for the past 30 years.

That is just one example of how beloved time-travel franchises ignore theoretical rules. The moment you apply basic real-life science into the equation, the narrative falls apart.

However, a select few movies actually make scientific sense. In these cases, the writers either meticulously researched the laws of quantum physics for their story or started with the laws of quantum physics and built a story from there.

Interstellar

Christopher Nolan’s 2014 science-fiction epic Interstellar explores the laws of quantum physics thoroughly. Alongside producer Lynda Obst, the concept was developed by theoretical physicist Kip Thorne, who also served as a scientific consultant.

The movie explores black holes and time dilation, alongside time travel in its final act. The astronaut Cooper, played by Matthew McConaughey, goes into a black hole and arrives in a tesseract. This device was constructed by future humans and represents time as physical space, allowing Cooper to communicate with his daughter in the past.

The tesseract is explained by the fact that future humans built it. The story device explores how time travel might come about and utilizes the fact that black holes remain largely a mystery.

Planet of the Apes

Any depiction of time travel where someone goes forward in time without going back has a scientific advantage over other stories. Forward time travel is entirely possible if you travel close to the speed of light.

Time moves slower the faster you go. The effects are imperceptible on Earth but become noticeable at extremely high speeds in space. Satellites orbiting Earth experience time differently than people on the ground. If an astronaut travels very fast in space, time moves slowly for them while passing normally on Earth. This is called time dilation, and Interstellar explains the concept well.

In Planet of the Apes, astronaut George Taylor, played by Charlton Heston, is on a space mission traveling near light speed before crash-landing on a mysterious planet. He discovers at the end of the movie that the planet is actually Earth far into the future.

This kind of time travel is possible, whereas backward time travel is generally considered impossible by top scientific minds. While backward time travel appears in some Planet of the Apes sequels, the science in the original 1968 film checks out.

Avengers: Endgame

Avengers: Endgame features a green, irradiated monster and a talking raccoon, but the movie deserves credit for rejecting the most flawed trope of time travel stories. Typically, characters go into the past to fix the future by rewriting events.

Avengers: Endgame does not do that. The Avengers venture back in time to steal items and return to the present to use them. While Ant-Man, played by Paul Rudd, thinks this alters history, Hulk, played by Mark Ruffalo, explains that this is impossible. Time branches off instead, creating new timelines where the objects go missing.

British physicist David Deutsch proposed that time travel altering the past creates a brand new timeline rather than changing the existing one. This utilizes the Many Worlds Interpretation embraced by Endgame, which is a scientifically recognized understanding of quantum mechanics.

While Avengers: Endgame takes creative liberties with how Tony Stark, played by Robert Downey Jr., creates his Time-Space GPS, accessing time travel via the quantum realm aligns with real-life physics, where time operates differently and may not exist at all.

Primer

While Avengers: Endgame can be enjoyed casually, the low-budget 2004 film Primer requires complete attention. Written and directed by Shane Carruth, who also stars as a main character, the film utilizes Carruth’s undergraduate degree in mathematics and background as a software engineer to tell a time travel story often considered the most scientifically thought-out time travel movie ever made.

Primer follows two engineers who conduct scientific experiments in a garage. During a gravity experiment, they accidentally discover a method for traveling backward through time and build a box large enough to hold both of them.

The characters use the box to check the stock market, travel back, and purchase stocks before prices rise. They create doubles of themselves, lie to each other, and break the rules established by typical time-travel stories.

The movie enforces strict time travel parameters. No one can travel back to a point before the creation of the box. To go back an hour, a person must turn on the box, wait an hour, get inside, and wait another hour before emerging. This returns them to the moment the box was turned on. For example, turning the box on at 1:00 PM, entering at 2:00 PM, and waiting another hour brings the traveler back to 1:00 PM. Time travels backward for the person inside the box without a portal, meaning they must experience that duration in reverse.

Carruth based this version of time travel on a Feynman diagram, which describes subatomic particles moving forward and backward in time simultaneously. Carruth also used complex scientific language to portray realistic conversations between engineers. The result is a precise movie that follows its own rules.

Predestination

In 1978, astronomer Carl Sagan wrote an article for The New York Times about science-fiction stories helping viewers glimpse real truths of the universe by fictionalizing scientific principles. Among the stories he praised was “—All You Zombies—,” a 1959 short story by Robert A. Heinlein. The story follows an intersex individual who uses time travel to go back and impregnate their younger female self. The resulting child is a female brought back in time, who is revealed to be both the mother and the man who impregnated her. The story maintains that no original timeline exists where the baby is the product of anyone other than the two older versions of themself, making their life an unaltering loop.

The story explores a causal loop, which is the paradox time travelers warn about in movies. If someone goes back in time to fix something and succeeds, they lose the reason to travel back, causing the problem to reappear and restarting the cycle.

This concept is explored in Heinlein’s story and adapted into the 2014 film Predestination, which stars Ethan Hawke as the older male self and Sarah Snook as the younger female version of the character.

The story functions less as a scientifically accurate depiction of time travel and more as a rigorous demonstration of why time travel stories ultimately defy logic.

Source: Polygon