Science fiction is a genre rich with wonderful stories, action-packed adventures, and worlds beyond our own. Everyone can agree that sci-fi stories are fictional, but they aren’t necessarily impossible. Their use of theoretical physics to explain tropes like time travel and hyperspace goes to show that attention is paid to real science while constructing these fantastical stories. The question is, how much of the science in sci-fi is real, and how much of it is the result of creative liberty?

Conquering time

The physics underlying time travel isn’t always explicitly stated in the books, shows, or even novels that portray it; many of them just assume time travel is possible and get on with the story. 

Take Doctor Who, where time travel is made possible through the TARDIS. The TARDIS, the infamous bigger-on-the-inside blue police box, is powered by what’s called the ‘Eye of Harmony,’ a star that is forever collapsing into a black hole and can travel anywhere in time and space. It navigates an extradimensional tunnel known as the ‘Time Vortex,’ travelling between different points in time and space in much the same way that hyperspace in Star Wars allows for travel between different points in the Galactic Empire.

Despite being fictional, Doctor Who has had an impact on actual physicists’ time travel theories. Physicists Benjamin K. Tippet and David Tsang have written a paper explaining how a mechanism like the TARDIS might be able to travel through time. 

Their paper calls upon Einstein’s theory of general relativity, which states that time and space are combined to make up a four-dimensional spacetime. Tippet and Tsang propose the creation of a ‘bubble’ of spacetime that could travel freely backwards and forwards through time. Although such a bubble would violate certain universal laws of physics, Tippet and Tsang helpfully suggest a hypothetical kind of matter that the bubble could be built from that just doesn’t follow these rules. 

Splice and combine enough of those bubbles together, and you could create a tunnel removed from the regular flow of time like the one found in most of Doctor Who’s opening credits. It’s not a theory we’ll ever see tested, but it does demonstrate how theoretical physics can be mapped onto fictional scenarios.

Jumping through the multiverse

The show Loki employs the unique version of time travel found in the Marvel Cinematic Universe. Rather than employing the butterfly effect, where the time traveller’s actions in the past affect the present, or the loop effect, where the time traveller is already part of past events, time travel in Loki creates a branching timeline: the actions of time travellers in the past have no effect on their original timeline.

Loki’s version of time travel does hold merit in the scientific community. A physics professor from the California Institute of Technology provided a similar explanation of time travel to the one Loki established, where a branching timeline is actually a branching universe. This concept of branching timelines ties into the ‘many worlds theory’ of quantum mechanics.

While Loki and Doctor Who both employ a degree of actual science, they are also both based on the assumption that time travel is possible. They use time travel as a plot device, taking creative liberties to make it possible — but when it comes to showing how it works, they try their hand at creating an explanation that’s more scientific than magical.

Taking speed to the limit — literally

Spaceships are a staple of science-fiction stories, and none more so than the ships in Star Wars and Star Trek. Almost everyone recognizes the names Millenium Falcon and USS Enterprise. 

They each take their own approach to traversing galaxies. Star Trek’s warp speed precedes Star Wars’ hyperspace. It creates an engine known as the warp drive, which uses a reaction between matter and antimatter to reach and exceed the speed of light. Each speed increase is called a ‘warp factor,’ and the engines go from warp factor one — the speed of light — to warp factor 10 — infinite speed. Everything in between is a multiple of the speed of light.

The warp drive operates by pushing spaceships through a wormhole — a part of space that has curved in on itself, connecting two different parts of the universe.