This article is part of the Fantasy Science & Coffee column on Film Inquiry
Faster Than Light Travel in Science Fiction
Faster than light (FTL) travel is one of the coolest hallmarks of science fiction. It’s practically essential for stories involving space travel, because of the mind-blowingly vast distances between stars. The closest stellar system to our Sun, for instance, is Alpha Centauri which is about 4.3 light-years away, which means if we traveled at the speed of light, it’d take us over four years to reach. I’m pretty sure you’d agree that Star Wars would be incredibly boring if travel took years rather than hours.
Interestingly enough, different fiction realms utilize different story tools to explain the science behind their FTL technologies, but most appear to share a single seed: hyperspace. This isn’t a fictional word; hyperspace refers to space with more than our regular three dimensions. In science fiction stories, if the technology can utilize extra dimensions, then what appears to be FTL travel is possible. Dr. Daniel Jackson from Stargate SG-1 describes it rather well in a fun instructional video:
Hyperspace, also called subspace is another dimension, in which certain laws of physics like the speed of light or the effects of relativity don’t apply. Now by entering hyperspace, a ship can travel vast distances at many times the speed of light, and return to normal space once it reaches its destination. The actual math of how it all works is still highly classified, and I’m not completely sure I understand it myself, but it’s how most advanced races get around the galaxy when they’re not using a stargate.
Note that different story universes have their own rules and terminologies for hyperspace travel and how it can be achieved. For instance, the terms ‘hyperspace’ and ‘subspace’ aren’t always used interchangeably the way they are in Stargate.
In Star Wars, the hyperdrive allows one to traverse through hyperspace between two points in a finite amount of time up to a few days. Two distant points in normal space are connected in hyperspace, so whenever Han Solo uses the hyperdrive, he appears to travel between the two points at a speed faster than light.
Star Trek, on the other hand, makes use of a warp drive that creates a subspace bubble with the help of warp fields, distorting the space-time continuum. Interestingly, ‘subspace’ in the Trek universe appears to refer to a space fabric that’s coexistent with normal space. Travel in the Trek universe can sometimes take up to weeks, or even years if you’re stranded in the Delta quadrant the way the USS Voyager was.
Some fictional technologies allow instantaneous travel such as the jump drives in Battlestar Galactica, and the wormholes in Stargate (which we talked about in Part 1 of this series).
When time travel is involved, the way it is in Doctor Who, then your travel can appear to be instantaneous if you want it to, even though the Doctor spends a finite amount of time traveling in the Time Vortex. This Time Vortex appears to be descriptively different from hyperspace given in the earlier examples, yet still involves alternate dimensions. The Time Lords in the Doctor Who universe described the Time Vortex as existing outside of time and space, yet as an established environment of its own with residents, such as the Reapers from Series 1 Episode 8 of the new series.
There’s a reason I love all of these fictional explanations: they give solutions to the FTL conundrum without just saying, “the spaceships go super fast!”. There are countless other examples among sci-fi stories, of course, but instead of listing more, let’s address the pressing question of the hour: what’s so special about the speed of light? And what would happen if you tried to hit it?
Moving Faster Than Light in Real Life
It all comes down to relativity. Einstein discovered in 1905 that nothing could move faster than the speed of light, through a series of very long and laborious calculations. It might seem a little funny that the universe appears to have a speed limit, but it does. No matter how fast you move, you’ll never cross it.
Imagine you’re riding on a technologically advanced train traveling at nearly the speed of light. You get up from your seat and you decide to challenge Einstein by jogging to the front of your car. If you did this on a normal train, you’d effectively be moving at a speed faster than the train. Theoretically, this sounds like a fun little trick to cross the speed of light threshold.
What would actually happen is that you would be prevented from moving faster than the train. You’d face resistance, unable to move your limbs because your mass would increase. You’d need more and more energy to move ahead, and this energy requirement will become infinite when you hit the speed of light. That’s actually why nothing with mass can attain light speed. Photons can travel at this speed because they don’t have mass! So you can diet all you want, but you’ll never hit that limit. Sorry.
Apparent FTL Phenomena in Real Life
While you can’t physically move faster than light, there are real examples of seemingly faster than light phenomena in physics. One such example is quantum entanglement across large distances.
Entangled particles are basically particles that share a history and are linked with one another in such a way that something that happens to one will affect the other as well. Now, suppose we separate two quantum entangled particles across vast stellar distances. If we manipulate one, the other one would instantaneously be manipulated as well. It therefore appears that there’s some sort of FTL communication between the two, but that’s not the case. In fact, even though the second particle is instantaneously affected, a person next to it wouldn’t get to know that anything has happened unless someone from the first particle’s lab gives her a call to let her know!
Potential theories have arisen to not cross this limit, but to work around it so that things can be achieved that would otherwise require FTL properties — which is exactly what these science fiction examples do. So they aren’t actually very far-fetched. Things like multiple dimensions, wormholes, and warp drives have been theorised, but I’ll save that discussion for a follow-up article and a second cup of coffee with you.
Till then, tell me what your favourite science fiction FTL technologies are!
More to Explore
Interesting StackEx question: Why don’t Star Trek vessels experience time dilation while travelling at impulse speeds
Arxiv: How superluminal motion can lead to backward time travel, Robert J. Nemiroff and David M. Russell, 2015
Arxiv: On the impossibility of superluminal travel: the warp drive lesson, Carlos Barceló, Stefano Finazzi, Stefano Liberati, 2010
On the Electrodynamics of Moving Bodies, Albert Einstein, 1905
Interesting old Angelfire site: Star Wars Hyperspace Travel Times
Disclaimer: I haven’t read the book and papers completely, they appear to be interesting. I don’t necessarily endorse what they say. I’m also unsure of the accuracy of the Star Wars resources, but they are fun!