Traveling Through Space-Time: Physics VS Fantasy

Have you ever looked up at the stars and imagined flying through the cosmos to reach some distant planet in a faraway galaxy? Maybe you imagine having a close call with an asteroid or comet, or fear missing your destination point, even winding up at an event horizon with a belly in knots, or stumbling into an alien nest and waking a sleeping nightmare. You know, all the fun stuff.

Perhaps it’s because my partner and I recently watched The Martian (movie adapted from Andy Weir’s gripping novel) but I’ve been on a space travel kick recently, even dusted off my copy of Hawking’s A Brief History of Time to remind myself of the awesome science it takes to actually leave Earth’s atmosphere and go to another place, even just to see Earth from an alien-eye view.

As fun as it is to conceptualize, philosophize, and ‘what if’ oneself through astrophysics, it’s important to know what the scientific and literary rules are for space travel so you can either use them to your story’s advantage (and please your readers with your knowledge) or disregard them intentionally in pursuit of imaginative creative expression.

So, let’s talk about travel.

What is space-time travel?

In the aforementioned book, A Brief History of Time, Stephen Hawking wrote: “We must accept that time is not completely separate from and independent of space, but is combined with it to form an object called space-time.”

Traveling through space means traveling through time. You simply cannot have one without the other. As Hawking said only a few pages later in the book, “When we look at the universe, we are seeing it as it was in the past.”It is with this acknowledgement in mind that I’m choosing to refer to “space-time travel” in this article; they are one and the same.

Why does your story need space-time travel?

Whether the space-time travel is a focal point of the story or whether it’s naught but background explanation for certain plot events, if a character must travel through space-time, there must be a specific reason for such travel; the travel must be important to the larger story to avoid poking out like a crooked finger and jabbing your reader in their believability zone.

There are several reasons why you may choose to use space-time travel in your story:

• Explore rifts or challenges in noncontinuous space-time
• Show a developing society, perhaps one several millennia in the past or future
• Leverage a new or radically different landscape, something you can’t find on planet Earth
• Conceptualize a thoroughly developed alien society to explore differences between it and Earth’s societies
• Spotlight a faraway frontier where there’s no help available (or available quickly) and your characters are on their own

Some of these reasons work well for literary works. Novels like Audrey Niffenegger’s The Time Traveler’s Wife and Octavia Butler’s Kindred come to mind where the space-time travel is  prominent but the scientific basis of the travel is not the focal point to the story. Then there are stories in which the science behind the space-time travel is focal to the larger story. Like H.G. Wells’ The Time Machine or Cixin Liu’s The Three Body Problem.

No matter which kind of space-time travel story you’re writing, know why and how traveling is important to your characters, your world, your plot, and your overall arc, as well as your story message. Without some level of import, the space-time travel may come off as unnecessary, superfluous, even distracting from the larger work.

What do you need to know about space-time physics?

Using space-time travel in your story means keeping a few rules in mind so readers can suspend their disbelief and immerse themselves in your story. Here is a general list for your use:

For an alien-centric stories without space-time travel, there can be no humans.

Because humans come from planet Earth, and because — according to photos captured by Voyager II — aliens must be in another star system, without using some kind of space-time travel, you will not be able to use any human experiential processing to inform your reader of the differences between alien life and human life. In fact, by not using space-time travel in a story about aliens, there are some details about those aliens or their world you may not be able to provide to your reader without “As you know, Bob,” interjectory disruptions.

For example, if all your aliens have seven eyeballs, then having seven eyeballs would be considered normal. Your alien characters would not have reason to talk about the number of eyeballs they have unless there’s an express reason for calling attention to those eyes.

Think about what you want your reader to know about the aliens and how you will deliver that information without disrupting the reading flow. This analysis may help you determine whether human comparison would be helpful, or even necessary, for reader understanding.

Space-time is infinite but has no boundary.

If you read Nietzsche’s “Doctrine of Eternal Recurrence” or watched season one of True Detective, you may be familiar with the saying, “Time is a flat circle.” In astrophysics and space-time travel, you can almost take this literally. Hawking shared, “[W]hen one combines general relativity with the uncertainty principle of quantum mechanics, it is possible for space-time to be finite without any edges or boundaries.” Flat circle, indeed!

Because the night sky is dark, we know the universe is finite, which is Olber’s paradox. This doesn’t mean, though, that we have to accept a flat universe the way some folks long ago (and still a few today) accept a flat earth. While the universe itself is finite, it doesn’t need to have edges or boundaries due to the curvature of space-time and the possibility of the multiverse theory involving the cosmic foam. To wit, your spaceship need not bump into an invisible barrier or some other “end of the universe” Truman-Show-esque explanation for the far reaches.

If your story does include some end of the universe, think about why there needs to be an end and how to handle space-time if such an end, or boundary, exists because, given the laws of gravity and the centripetal force at play, the modern spaceship would likely travel along such a flat circle and would never encounter something as mundane as a limit, especially since we know the universe is still expanding. Readers may need to know what is happening to the ship or to space-time to keep invested if they encounter a limit.

If your vessel moves at the speed of light, it must become light-energy, which means space-time travel is, then, not only possible but available.

You read that right.

If any ship or vessel traveling through space-time reaches the speed of light, or lightspeed, that vessel must become — at least temporarily — light itself; pure energy. Hawking wrote that, “[A]ny normal object is forever confined by relativity to move at speeds slower than the speed of light. Only light, or other waves that have no intrinsic mass, can move at the speed of light.”

The second your vessel reaches lightspeed is the same second at which it basically blips out of tangible or observable existence. Now, when writing science fiction, there are some clever ways to handle this in stories, such as a temporary blipping out, which ceases the moment your traveling speed dips below lightspeed. Think about what happens to your vessel at the moment it reaches lightspeed so that your readers stay with your travelers as they race toward their destination.

Traveling faster than the speed of light (Trekkian “warp speed”) is not allowed within physics rules.

Sorry to be a bummer, y’all, but no vessel can travel faster than lightspeed.

Hawking wrote: “The idea that one could go right round the universe and end up where one started makes good science fiction, but it doesn’t have much practical significance, because it can be shown that the universe would recollapse to zero before one could get round. You would need to travel faster than light in order to end up where you started before the universe came to an end — and that is not allowed!”

While Hawking does give a nod to science fiction writers who have skirted this rule, know that skirting this rule should be done with caution, as the terms “warp speed” and “warp drive” are most often associated with Star Trek and may cause the more science-minded readers to discredit your story.

There are several other physics rules that may be important for your story.

Here is a brief list of physics rules you should know if your story includes any of these elements:

“The present evidence therefore suggests that the universe will probably expand forever, but all we can really be sure of is that even if the universe is going to recollapse, it won’t do so for at least another ten thousand million years.” (Hawking) If your story sits at the edge of universal collapse, know that you’re writing a story set at least ten thousand million years in the future, and even humans on planet Earth (assuming there still are humans) will be radically different from the friends and neighbors you know today.

“There could be whole antiworlds and antipeople made out of antiparticles. However, if you meet your antiself, don’t shake hands! You would both vanish in a great flash of light.” (Hawking) I’m not sure I need to say much more about this, except I already imagine several story premises in which people meet their antiparticle dopplegangers with varying degrees of curiosity, awe, understanding, even rage.

And since black holes offer worlds of possibility in themselves, here are a few Hawking-sourced rules about black holes and their event horizons of which you should be aware:

“[A]fter gravitational collapse a black hole must settle down into a state in which it could be rotating but not pulsating. Moreover, its size and shape would depend only on its mass and rate of rotation, and not on the nature of the body that has collapsed to form it.”

“Gravity gets weaker the farther you are from the star, so the gravitational forceon our intrepid astronaut’s feet would always be greater than the force on his head. This difference in the forces (when approaching the event horizon of a black hole) would stretch our astronaut like spaghetti or tear him apart before the star had contracted to the critical radius at which the event horizon formed.”

“Anything or anyone who falls through the event horizon will soon reach the region of infinite density and the end of time.”

More about space-time travel and story world building . . .

When planning or revising your space-time travel story, consider why travel is important, where your travelers are headed, and the nature of the travel itself.

For stories set on generation ships, for example, where the character may neither reach their destination nor even remember the original destination, you may be writing a story driven by place, or milieu. So be sure to answer the question posed at the beginning of the story for reader-promise fulfillment.

And generation ships are but one way to get your characters from point A to point B. Hyperspace is also an option, as is cryopreservation, and other methods. But as with any technological advance, if the tech exists for one purpose, it likely can (and will) be used for other purposes.

• Generation ships may be lost or hijacked by space pirates.
• Hyperspace travelers will experience delays of varying lengths, from weeks to decades, and may miss events.
• Cryopreservation for space travel would also likely lead to cryopreservation for medical and other interventions and would likely be used by bad actors for ill-gotten gains.

So think about why a bad guy, for example, would want to use your space-time travel tech for the worst, and see how many risks you can come up with for your character to handle. And if you’re writing a story that has anything at all to do with space-time travel, I highly recommend two nonfiction books to fill out your understanding of the science and the craft of writing that science:

• A Brief History of Time (there’s a reason I mentioned Hawking so many times in this piece)
• Writing Fantasy & Science Fiction: How to Create Out-of-This-World Novels and Short Stories

Happy writing (and reading)!

♥ Fal

P.S. Want me to cover a specific topic? Tell me about it in the comments. When I write the article, I’ll credit you for the subject matter.

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Fallon Clark

Fallon Clark is the book pal who helps you tell your story in your words and voice using editorial, coaching, writing, and project management expertise for revision assistance, one-on-one guidance, and ghostwriting for development. Her writing has been published in Flash Fiction Magazine. Check out her website, FallonClark.com, or connect with her on LinkedIn or Substack.