Special Relativity for Science-Fiction Authors

Albert Einstein is widely known for being the genius who first articulated our modern physical theories of space and time. For most people this has secured his status as an unparalleled mind, achieving more and seeing farther than most could hope to even imagine. There is one segment of society, however, for whom Einstein's notoriety comes not from his brilliant and uncanny mathematical and physical intuition, but for the havoc and despair which the fruits of that intuition have delivered.

I'm speaking, of course, of science fiction authors. The special and general theories of relativity have been, for as long as they've been articulated and understood, a thorn in the side of exciting, dashing, romantic, fantastical space adventures. Even those who know nothing about the details of special relativity (SR)* know the basics of the problem it poses: "Nothing can go faster than the speed of light." you might hear someone say. And while many are familiar with (some of) the limits SR imposes, I would guess that many fewer have a good grasp of (1) what the problems are which those limits impose, and (2) why the limits cause these problems.

In the absence of such an understanding, writers and readers are sometimes disposed to simply wave away the problems, or to gerrymander some special tool, substance, or circumstance which permits violation of the limits SR requires. And doing so is perfectly OK! "Science in service of story." is as good a motto as any. Plenty of lovely fiction rides roughshod over SR, either ignoring it or ignoring certain, fundamental, aspects of the theory. However, I think with a little time and effort invested, one can gain an understanding of the limitations which SR imposes, how they arise, and what they imply. Given such an understanding I strongly believe that one can better navigate their way around such limitations, in a way that is plausible and (mostly) consistent with the physical laws as we know them. Indeed, I think that understanding SR can give rise to interesting story and plot itself!

I plan, over the next several weeks, to begin to lay out a basic picture of special relativity. These posts will aim, by their end, to (1) offer up a clear explanation of what SR "is" and how it imposes limitations to how we travel through space; (2) show the variety of ways in which choices of how FTL works in science fiction can run afoul of SR; and finally (3) examine how we might "write around" the theory, doing as little violence as possible to SR, while still retaining a framework which would make for interesting stories.

The posts are planned as follows:

Aristotle, Galileo, and Einstein, a primer on space-time theories

[UPDATE: I lied! This will be broken up into two posts, one on Aristotelian space-time, and one on Galilean space-time.]

  • We'll begin by reviewing the basics of how Aristotle, and Galileo modeled space and time. We'll also see that all of our understanding can be represented in drawings.

Special Relativity via geometry

  • Using the drawing conventions we learned last time, we can set out the Special Theory of Relativity.

Consequences/Paradoxes of SR

  • We will use our space-time diagrams to explore some of the consequences of SR including some rather odd results.

FTL and SR

  • Finally, via space-time diagrams we can consider "Faster-than-light" travel and explore the variety of difficulties which arise.

"Writing Around" SR

  • To finish we think about different ways we can avoid or mitigate the difficulties, while exploring how and whether interesting stories can fit within these approaches.

My hope is that these will be edifying and entertaining. I really do believe that understanding these limitations can help in thinking of interesting, story-conducive ways of getting around them. Too often SR is held up as some sort of arbitrary stricture, with no real explanation or understanding as to why it limits what it does. Seeing it as arbitrary encourages authors to think they can just as arbitrarily ignore it. I hope these posts will help to dispel this idea.

That all said: IGNORE IT IF YOU LIKE! I love Star Wars and Star Trek. Good stories don't need to slavishly adhere to physics. I'm not here to police science fictional FTL---only to offer some tools to those who wish to do FTL slightly more realistically.


* As the title of this post suggests, I will be focusing the discussion exclusively on special relativity. This is for two reasons: First, the basic limitations that relativity imposes on space travel only require an understanding of the special theory (which is both conceptually and diagrammatically simpler). And second, I would be lying if I pretended to have anything like an authoritative grasp on GR---my understanding, as sketchy as it is, is best qualified to discuss SR. Perhaps a discussion about what GR adds, and my corresponding ignorance can be had in some future post...