Science FACT-ion #3: Time Travel

By Riley Hughes

Time travel! Popularised in H.G. Well’s story The Time Machine (1895), time travel has not only become a staple in sci-fi, but in pop culture as a whole. Dramatic movies and TV shows such as About Time (2013) and Outlander (since 2014) use time travel as a framing device to explore human choices, while comedic films and shows such as Bill and Ted’s Excellent Adventure (1989) and Dr Who (1963–89; 2005-) take audiences on whimsical adventures.

So, what can movies tell us about time travel? Well, despite the method of time travel, be it magically, mechanically or genetically, there seem to be two overarching types of time travel, multi-branch and single-branch. Multi-branch time travel essentially follows Back to the Future (1985) rules of time travel. This means that as time travellers affect the past, they may also affect the future. This creates a branching of alternate futures. In this way Marty is able to create a ‘cooler’ version of his parents by the films end, changing everyone’s lives.  Other films that use this model include About Time (2013), Groundhog Day (1993) and Looper (2012).

Single-branch time travel on the other hand prevents time travellers from changing history as they are locked to a single branch of history. In this version, time is self-consistent, with any efforts to change the past by the time traveller instead resulting in its maintenance. The best example of this is in Harry Potter and the Prisoner of Azkaban (2004) when Harry and Hermione save Buckbeak, Sirius and past Harry. The events play out the same, with the mysteries surrounding the broken window, the wolf call and the stag Patronus being revealed to have been future versions of the two the whole time. Other films that use this model include Predestination (2014) and The Time Travellers Wife (2009).

But of the more recent time travel films, Avengers: Endgame (2019), breaks from these two moulds and sort of combines them. As the Avengers travel through time to gather the infinity stones, they create alternate realities, similar to the multi-branch model, yet are stuck on their own timeline. It is in this way that Loki is able to escape New York with the Tesseract and not affect the main MCU timeline in the slightest.

So, with all this thought behind fictional time travel, is it actually possible to travel through time? Time travel to the past is impossible, at best hypothetical. There are a lot of theories to do with wormholes, quantum physics and timey-whimey nonsense by people much smarter than me but frankly it’s all still too hypothetical. This said, time travel into future is very, very real.

If you have ever seen Christopher Nolan’s Interstellar (2014), then you already know what I am talking about. In the film (spoiler alert!), when Mathew McConaughey returns from his space mission, he discovers that he was actually gone for more than one hundred years, his child now an old woman about to die. This is all thanks to a phenomenon called time dilation. Essentially time dilation is a variance in the time passed between two clocks, either due to a difference of gravity or of their relative velocity. Essentially, the higher the gravity a clock is experiencing and/or the faster it is travelling the less frequent the clock will tick.

William A. Hiscock, a physics professor at Montana State University explains that if a ship were to travel at speed close to the speed of light, “a round trip to the centre of our galaxy…could be completed in only a little more than 40 years of ship time. Upon arriving back at the earth, the astronaut would be only 40 years older, while 60,000 years would have passed on the earth”.

So, we may not be able to meet past humans but, given enough energy and engineering, we may be able to meet future ones. And one day, if we do figure out time travel to the past, it’ll be interesting to see which movie got time travel right.