A common problem with Sci-fi is how to deal with the speed of light.
Why is it interesting, who cares I hear you ask? I suspect some of the most interesting world building and storylines may happen when the corner cases are explored.
Please note, this isn’t real life. Real life is that you can’t go faster than the speed of light. Furthermore, an object with mass can’t even go at the speed of light. (Although I heard a PhD recently say photons may have a tiny mass but look, this isn’t a bleedin cutting edge paper!)
Now, back to the glorious world of sci-fi where we can pick and choose what we write!
There are a few options, and whichever is taken generally impacts the “world building”.
By far the most common way to deal with the speed of light is the ‘universal now’ that is, there is a ‘now’ that is true, whichever your perspective, distance or speed.
The interesting thing about this framework is that most people believe the real world is like this! It works pretty well for sci-fi because of this. It is the invisible way of dealing with light speed in fiction, and is, ahem, generally harmless.
The boat (Hyperspace); The time taken to travel from one part of the galaxy to the other is akin to a boat ride, very far away takes a long time, so that’s maybe like crossing the ocean. Going to a different galaxy is often ruled out due to this, going to a closer star system, is of course, quicker (culture series), like sailing up the coast perhaps.
The boat and wormhole; Other methods involve “worm holes”, like shortcuts, where your ship can travel slowly, and then go through a worm hole somewhere else instantly or very quickly (expeditionary force).
Sub-light; There is the hibernation options that are sub light speed. Unfortunately this generally means star systems are isolated from each-other in your world. Immortality can also fix this (savages from Galaxy’s Edge).
The set up
Planet ‘Alfalfa’, centre of your universe, Planet ‘Beetroot’ (you are a vegetable orientated species), a light year away. 1LY is not a measure of time, it means 10 trillion kilometres (ish).
The plague planet “Sprout” lies somewhere in the vast expanse between these two herbaceous planets. We don’t like them, they get up to ‘all sorts’.
Sprout likes no one, and has developed a… Hard to call it a weapon, maybe a overly developed sense of personal space? This “definitely not a weapon”, when triggered, can cause both Alfalfa and Beetroot to start moving away from eachother very quickly.
Initially concerned, the great kingdoms on Alfalfa and Beetroot no longer care, because they’ve managed to invent… Wormholes!
How it gets interesting
Here are a few things which I feel would be interesting to explore as a writer. I understand that many have been explored before, but thankfully, it doesn’t mean they can’t be looked at again!
If you were to travel to planet Beetroot at the speed of light; from your perspective, you would arrive instantly. To a photon, it’s journey is instantaneous. This kinda blows the boat analogy out of the water. As a passenger on a light speed ship, there is no delay to your destination once you get to light speed.
To the great vegetarian peoples of Planet Alfalfa however, it would have taken a year for you to get to Beetroot, and they, themselves, would be a year older.
Enders Game (the later ones) explored this problem. People who regularly travelled to other planets, gradually lost all their connections to “back home”. While the travellers stayed the same age, their friends and family left at home all aged and got older. Do this a bit too much and wham, you’re meeting your own grandkids, and they are older than you!
The universe in motion
The ‘universal now’ is great, and we need the universal now for worm holes to work (as the appear in most fiction). The Now is great… until we consider that everything is in motion. Here’s how it breaks causality, or allows ‘time travel’ backwards in time.
Forward in time
Forward in time is easy, as stated above, wormhole to somewhere moving very fast (Beetroot when Sprout is having an ‘off day’), and travel home again. Forwards in time is easy, you just need speed.
Backwards in time was much harder to figure out, until I realised it’s actually the same thing, you just bring the Universal Now with you!
The Great Race
“Every twelve hundred moons, our ancestors have taken part in our most honoured games. The origins of this ancient and noble tradition are lost in the mists of time. Once a century(ish), the greatest families on all Alfalfa supply a team, a team who must compete in the greatest of all races, a race which will decide who rules the great garden of Alfalfa, for the next twelve hundred moons. This race, as you all know, is called ‘Pass the Carrot’….. you back there, stop sniggering!”
“After consulting with the greatest minds and spookiest oracles on Alfalfa, it is decided that ‘Pass Th… I mean… The Great Race’ participants can indeed use our new ‘faster than light, instomatic wormholes’ to complete this holiest of all races. What could possibly go wrong?”
The Parsnip Partnership had a plan. Over the last year they had been coordinating with various succulents on planet Beetroot to make sure they would have success.
What could go wrong
The year is year 0 of the Tenth cycle. Patrick Parsnip takes a look at Planet Beetroot through the amazingly good telescope his Uncle Alfonso bought him for Harvest Day. He can see Beetroot are just beginning the last year of their Ninth cycle (Light takes a year to get to him). But he ‘knows’ Beetroot is really also in year 0 of it’s Tenth cycle (the universal now is with Patrick). That blasted planet Sprout can be seen too, but he tries to ignore them, their always up to something!
Patrick grabs the holy carrot, jumps in the wormhole, and appears on the surface of Beetroot, it is Year 0, he looks back at Alfafa, but something is wrong, something is very wrong.
Without anyone on Alfalfa knowing, half a year ago, Sprout had activated their ‘not a weapon’, and started moving Beetroot away at high speed.
That meant, Beetroot was only three quarters of the way through it’s final year! Not all the way through, as Patrick expected!
When the Parsnip Partnership were first hatching their plans, they had never considered this, they had arrived on Beetroot three months too early.
‘Pass the carrot’ was on; simply race to the top of mount molehill on Beetroot, and back to the vally of Lazy Bed on Alfalfa, and the crown would be his!
But… Was this cheating? When he wormholed back from Beetroot, he would arrive on Alfalfa, weeks before the race had even started!
A moving reference
If we pick a universal now, we have to choose a reference point. And that reference point needs to come with us on our story.
The short green ones had a plan… There was no rule against their entry… With their shorter legs, no way could they win the great race. Just as the other entrants, they wormholed to Beetroot, but were ready for the surprise, they saw Alfalfa was three months slower than expected, and jumped back straight away. They now had three months in which to sabotage Patrick of the Parsnip Partnership, before he even had a chance to race.
All hail our new green, pungent, king!
In a moving universe, Faster than Light travel and wormholes start to allow time travel backwards. Exploring the various corners of the implications of the ‘universal now’, and causality impacted by FTL, opens a nice space (ahem) for world building!