So you think you know what causality means?
Let me guess… You’ve watched a bunch of movies, read some books or manga, played a lot of video games… And you think you know what causality means.
Sorry, but most likely, you don’t.
Causality is a scientific (physics, if we want to be precise) principle that is quite specific, easy to define and which has a lot of consequences that are somewhat easy to derive from.
But that has little to do with what is portrayed in fiction.
Chances are, when you hear “causality”, the first things that come to your mind are “causes lead to consequences”. Which means next to nothing, really, if you think hard about it for a while. I mean, sure, you drop a ball, it will go all the way down until it hits the guy that was right under your hand. Is there any meaning to couching such obvious trivialities into scientific principles?
Some extremists will say “causality” goes farther and means that “there is no consequence without cause”. If you take it at face value, it is a tautology. Consequence is indeed a word that induces the need for a cause. Taken a little more seriously, it is a likely an attempt at proving that some kind of fate is weaving itself into daily happenstance. “You see some passersby getting run over by a car and think it’s only random, but see, it is a consequence and must have a cause!!”
Anyway, those “definitions” have next to nothing to do with the actual scientific definition of causality.
Causality is directly linked to the speed of light. The principle is that nothing, no information, no interference can be transmitted between two points in space-time, without an information-broker, some particle or wave that will carry information from the “cause” point to the “consequence” point if you will.
If you also accept, and I am not saying you should, that NOTHING can go over the speed of light in our universe, then it follows that no information can go from a point to any other faster than the speed of light.
And that’s what causality really is. It’s the principle that when you observe an event A, say “I just clapped my hands”, and an event B, why not “the sun just had a flare”, you can dismiss the idea that A caused B if A is outside B’s causality cone, aka light cone.
For instance, it takes roughly 8 minutes for light to cross the distance between Earth and Sun and I just clapped my hands, so anything that happens on the Sun in the next 8 minutes cannot have anything to do with me clapping my hands, because “causality” means I can only hope to affect events that are reachable from me while staying under the speed of light.
Of course, that does not mean that everything that stands in my causality (or light) cone is affected by me. I’m not that far gone yet. It only means that anything too far away in space, or not far away enough in the future, can never be a consequence of what I did, because nothing goes faster than the speed of light in the universe.
Sounds constraining, and it might be, but it still has more consequences than the boring layman interpretation of “causes lead to consequences” that every science-impaired writer has latched unto in the past few decades.
For one thing, it means time travel and teleportation are almost impossible. If you believe causality to be a real thing, then the only time travel you can dream of is one where you are shuttled off to a distant future. Anything going to the past or even to a present that is away in space, is forbidden by the principle.
Next time you hear someone say they are in direct communication with an alien on a distant planet, obviously one that is a few light-years away, please ask them what they think of causality. Chances are they will throw you a puzzled look, not seeing what is conflicting between their outrageous claim and whatever they think causality means (which it does not). Feel free to feel and act smug at that point, you’ve earned it.
Cheers.
Attributions
- Causal structure of a space-time with two time dimensions and one space dimension by M. Velev [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
- Causality Manipulation http://fictional-battle-omniverse.wikia.com/wiki/Causality_Manipulation?file=Causality_Manipulation.jpg
- Speed of Light — Space Star Universe https://pixabay.com/en/speed-of-light-space-star-universe-726251/
- smug by various brennemans https://www.flickr.com/photos/brenneman/5498845759
