Most films that feature time travel prioritize storytelling over scientific accuracy, often disregarding the complex physics involved. However, a select few movies have managed to weave time travel concepts into their narratives with a notable degree of scientific plausibility, either through meticulous research or by building their stories around established scientific principles.
Christopher Nolan's 2014 science-fiction epic, Interstellar, stands out for its in-depth exploration of quantum physics. Developed in collaboration with theoretical physicist Kip Thorne, who also served as a scientific consultant, the film delves into concepts such as black holes and time dilation. In its final act, astronaut Cooper uses a "tesseract," a construct from future humans that visualizes time as a physical space, enabling communication with his daughter in the past. While the tesseract itself is a narrative device, it serves to explore potential mechanisms of time travel informed by the mysteries of black holes.
Planet of the Apes, the original 1968 film, presents a form of time travel that is scientifically plausible: forward time travel. This is achieved through relativistic speeds, where time slows down for an object moving close to the speed of light, a phenomenon known as time dilation, which is also depicted in Interstellar. In the film, astronaut George Taylor's journey on a ship traveling near light speed, followed by a crash landing, results in him arriving on a future version of Earth. This scenario aligns with the understanding that forward time travel is theoretically possible, unlike backward time travel, which is largely considered impossible by many scientists.
Avengers: Endgame offers a unique approach by avoiding the common trope of altering the past to fix the future. Instead, the film's characters retrieve objects from the past to use in the present, a concept explained by the Many Worlds Interpretation. According to this theory, any attempt to alter the past would result in the creation of new, branched timelines rather than changing the original one. The film also acknowledges the scientific basis of time travel by accessing it through the quantum realm, where time's behavior is significantly different and potentially non-existent.
The low-budget 2004 film Primer, written and directed by Shane Carruth, is renowned for its rigorous and complex depiction of time travel. Based on Carruth's background in mathematics and software engineering, the movie portrays two engineers who accidentally discover backward time travel. The film meticulously outlines strict parameters for its time travel mechanics, such as the requirement to experience time passing in reverse while in the time-traveling box. This mechanism is reportedly inspired by Feynman diagrams, which illustrate subatomic particles moving both forward and backward in time. The use of complex scientific language further enhances the film's commitment to a grounded portrayal.
Predestination, a 2014 film, adapts Robert A. Heinlein's short story "—All You Zombies—" to explore the concept of a causal loop. This phenomenon, often a source of paradox in time travel narratives, is presented as an unalterable sequence of events. The story details a protagonist who, through time travel, impregnates their younger self, leading to a closed loop of existence where there is no original timeline. While not strictly depicting the mechanics of time travel, the film offers a profound examination of its potential logical consequences, serving as an in-depth explanation of why certain time travel paradoxes are fundamental to the genre.