The technical problems of space travel in scifi

10 min readMar 12, 2024

The Ideas for Writers Series #1

The need for (predictive) possibility

Science fiction (all fiction) works best when it’s got a clear link to our reality. When it credibly could happen. Some of the science in the best classic scifi has happened.

Credibility has other advantages to writers. It is plot-interactive. The precise nature of the proposed science can shape, drive, expand and limit possible events. Authors are pressured to consider the social impacts of the postulated science, not just add it to current reality with no broader interactive impacts. They have to conceive more complete universes.

Imagine a writer before the age of air travel needing to move characters around faster-then-sound. He could have them just say car-zoom, followed by a rush of wind to the face — and arrival. That would enable the plot. But imagine instead he postulated airplanes. Now the plot can engage with the design of aircraft, fatal accidents, sabotage, military use, the need to regulate the skies, business competition, lost flights, social interaction on planes, costs and airplanes as status symbols, jumping out of airplanes, cargo transport, jurisdiction outside national borders. war… The implications of the postulated science will shape the story and open up a wealth of new plot possibilities. The possibilities of the science will also open up the imaginations of readers, an essential to the best scifi.

But modern science fiction, focused as it largely is on contact with other intelligent life forms, has a real credibility problem.

Inter galactic (even inter-solar system) space travel is impossible within human time frames and our understanding of the universe. Not technically impossible, just impossible. We can’t even communicate over those distances, unless the conversation spans generations between question and answer.

In our understanding of the universe, nothing can travel faster than the speed of light and nothing ever has. Of course, science has been wrong before, but this one is fundamental not just to theories but to all observable facts. The probability of being wrong is small enough to squeeze credibility. Actually being wrong would be such a big thing it would utterly change human thinking and lives, not merely enable a few spaceships. Science fiction in which 80% of the present remains in the future would not be viable.

Stories with travel beyond our solar system look like science fantasy, not science fiction.

Early sci-fi writers had it easy, they could have their invaders come from Mars or living on Jupiter, within practically traversable distances from Earth, but we’ve probed these places and we know they do not harbour civilisations.

The imagination of modern readers hungers for galaxies far, far away. Writers need a way to get them there.

Simply postulating faster-then-light travel without credible explanation is a plot enabler with no plot impact, that puts no creative pressure on the writer. “Hyperdrive” is just a kind of engine super-charger, it doesn’t change anything. It’s lame and lazy.

Quantum space travel

Quantum theory offers two pathways that might underpin credible intergalactic travel, that could in the future become practical science: entanglement and superposition. As well as adding credibility, they suggest plot twists resulting from the way the science in scifi should work, that make it more interesting.

One of mankind’s most impressive achievements, and still in its infancy, quantum theory is a perfectly self-contained but imaginary mathematical universe that makes anti-intuitive predictions that sometimes turn out to be true in the real world, making it a little less imaginary. It’s like AI and it’s a little bit like God. It annoyed Einstein, which I imagine God might find rather amusing, especially after the over-endowed brain tried to tell God whether He might or might not enjoy the occasional game of chance.

Superposition

Quantum superposition predicted that an object could be in two places (or even many places) at once, which clearly violates “classical” understanding of the universe but was later proven to be literally true, at last for tiny, sub-atomic particles. A counter-intuitive prediction that moved from imaginary maths to real word fact.

Every particle (atom, person, planet) is also a wave and waves can occupy multiple spaces at once. When we observe it, it is physical and in only one of the places it was in as a wave. Arguments continue as to whether it is the act of measurement that causes all the potentials to settle on one location, or something else, and this is not critical here.

From this generally accepted fact, that particles can be induced to be in two or more places at once, as waves, and then to become matter in one of those places, comes the core theory we need for plausible space travel.

Initially, bound by the needs of complex equipment, scientists performed quantum superposition demonstrations in small spaces and with particles containing just a few atoms. More recently this has been expanded to 2,000 or so atoms, almost big enough to see with the human eye if clumped together.

We can imagine a very much larger scale experiment where the space between multiple locations is measured in kilometres. Or is, potentially, infinite.

Scaling up the classic experiment then, we have an object (a spaceship) in one place as matter, we induce it to be in multiple spaces as waves, then we observe one of those spaces and immediately the spaceship is physically present in that space.

Perhaps that distance could be light years.

Obviously, this is far from current practicality (there’s the scale and also that the technique happens in a vacuum, which is not good for humans), but there is theoretical possibility.

Not practical now, but not theoretically impossible, is the stuff of credible, interesting science fiction.

Plot twists from superposition

This theoretical under-pinning has implications for plot development.

Exactly where the spaces are, that are multiply occupied, may not be controllable. Random. There could be a large number of them but apparently not infinite.

So, you press the quantum superposition button on your star cruiser’s control panel and there are a large number of places available for you to be at.

How will you know where they are? Well, as it takes no time to become physical in one of them, you could set your quantum computer to flit around testing them. But the number is finite and the universe is infinite. If none of the smorgasbord of travel destinations suits you, you could press the button again to get a new random selection.

This would be great for exploration and space tourism (any place will be amazing), but often you will really need to get to a particular place.

To get to a specific place could sample lots of random options but you’ll have to get lucky. Your quantum computer is fast but space is vast., so searching will take time. Maybe big time. Rather than demand specific coordinates you might set an acceptability parameter of the distance your craft could actually travel in a day or a year, post quantum superposition leap. Anywhere within that range would be good.

Then you have a time-accuracy trade off. Where you set the balance might vary. With enough time, you could keep rolling the dice for something nearer to what you want. If a death ray battleship is about to blast you to space dust, anywhere you can be right now might be better. Random destinations means anything interesting might happen.

If you have time to be pickier, still your arrival won’t be exact. What will lie between you and there? A wide open plot twist.

We might also ask, can your superposition leap be tracked? Does it leave space crumbs? How long will you have before that death ray battleship can manage its own superposition leap (also a time-accuracy trade-off which might put them near soon but nearer later.)

The quantum universe is very different from our “classical” universe and those differences will shape plot and require a much more completely imagined world.

Superposition star travel won’t be ordinary travel with a supercharger, it will be far more than that.

Entanglement

Quantum entanglement is an older concept still clouded in uncertainty, but with the appeal of being mind-blowingly counter-intuitive and having successfully made the leap from imaginary theory to real -world fact, albeit at a micro scale.

While superposition says a thing can be in two places at once, entanglement says two things can be the same thing, in different places, so what happens to one instantly affects the other. Even over a large distance. Again, measuring the thing in a location makes it real in that location.

Einstein hated this one too, he declared it impossible, but science proved him wrong. Labs have created entanglement at distances over 1,000 kilometres.

The theoretical possibility is that your spacecraft object could be entangled with another object which you can then measure and presto that object is your spaceship, instantly in a new location.

A review of the science suggests that for technical reasons entanglement may be a less promising candidate for instant travel than superposition, but from a writers point of view this doesn’t much matter, the potential plot twists could be similar.

Non-quantum ways of inter-galactic travel

A thousand year journey is long relative to a 100 year lifespan — but it might be trivial for a being that lives a million years, or perhaps has no age limit. Such a being could be about to arrive on earth, having started the journey before sapiens existed.

A writer could postulate intergalactic travel over long time frames, focusing on them reaching us.

Interesting plot speculations arise as to the operational activity speed of longer-lived beings. Will they take a minute to move a finger, perhaps processing the same lifetime amount of data as us, but taking longer to do it? Or will they operate at the same speed and process much more data? What would that mean for memory and learning?

If our meeting these creatures led to conflict, would they view a 100 year war as a short test skirmish?

A more complex speculation is communication, which has the same speed-of-light limit as travel. When you are a light year into your journey, “Hello base?” “Hi explorer” takes two years.

If our long/slow lived arrivals sent for reinforcements, we might expect them in a million years.

We could postulate long-lived human travellers by putting them into suspended animation. This is science that does not exist but conceivably might. Instead of launching adult humans we could launch frozen embryos (science which does exist) with robotic parents waiting to be fired up. From a writer’s point of view, there will be problems building tension, when conversations with Earth span lifetimes. Everything will have to happen within the capsule or on another planet, a bit of a limitation and irrelevant to a current Earth where everyone alive will die without hearing about what happened.

Also a consideration is direction of travel. If you are going with the expansion of the universe, your destination is getting further and further away from your start point. There might not be enough time for you to ever reach the ends (the oldest parts) of the universe. By the time you give up, they might be further away than when you started.

If you travelled towards the point of big bang origin, you would get to places faster (as they are travelling towards you). In theory, you could get to the middle of the universe (the beginning), which would be as empty as the end you can’t get to, because everything left billions of years ago. Although the end doesn’t remain the end, it continues outwards, while the middle will always be the start.

Another consideration, if you travel outwards, you will encounter older and older planets and so potentially more evolved life forms. Travel inwards and the space you enter will be younger.

We might launch a mission to another star, but we wouldn’t be getting any feedback from the destination in our lifetimes. Nations might come and go, Homo sapiens might be gone, extinct or perhaps replaced by Homo next.

People have explored (and funded exploration) because they wanted to know; exploration without personally getting to know will require a major shift in our attitudes.

From a plot perspective, we could do credible long distance space travel, as long as we were prepared to wait (and fund) a dinosaur time frame view of species survival. This, unfortunately, falls outside the realms of credibility. Humans are such a volatile and dangerous species it’s not likely they will be around for any number of thousands of years more, let alone millions.

From a writer’s point of view, quantum remains the more interesting option.

Time travel

The other great theme of science fiction, time travel, is as impossible as travelling faster than the speed of light, but time relativity is proven. If you travel at the speed of light over years, your time frame can be slightly different from that of someone who did not. You can’t go back in time, but you could go from being after some situation chronologically to being before where it is in the future. Not go backwards, but go forwards more slowly until you are passed. The possibilities for a cat-and-mouse, death ray and explorer chase are much expanded.

Maybe quantum superposition counts as travelling at the speed of light, for large scale time.

If two space battleships simultaneously employed this tactic they might jump all across the universe looking for advantage. One wins. But by then, after lots of urgent near random jumps, where is it? And what is it’s time frame? Can it get back and what will it get back to?

It’s not time travel in the normal sense, but it does include travelling across time (and space).

Notes

I have no doubt that this article contains glaring errors as to both quantum and classical physics, but my ignorance saves me from embarrassment and I can only apologise.

In this and all my writings I use “man” (and its compound terms, like chairman), “him” and “he” as non-gender specific terms, inclusive of all the varieties of gender identity now recognised and yet to be recognised, unless specifically stated. I derive “man” from “human”, referring to the entire species.