# Is there a way to provide evidence that causality runs in both directions?

Suppose in our own world, it turns out that an event in the future is extremely likely to happen, despite it being extremely to happen were the universe purely random.

Some may call it "fate", but I prefer the term "bi-causality", in that the event's occurrence in the future causes events in its past to occur (in addition to the usual forward causality). It's not that every step towards this conclusion is pre-ordained, but this particular event, up to some wiggle room, is extremely likely to happen.

My question is, as human beings, would there some plausible way that we could determine that this was the case? Is there some kind of experiment that would properly falsify this hypothesis?

• Welcome to worldbuilding. Take the tour and visit the help center to get familiar with this community. Your question is a bit unclear to me, especially the first sentence. Can you try to phrase it in more understandable terms?
– L.Dutch
Commented Jul 24, 2018 at 5:15
• @L.Dutch I don't really want to go into the details of the event(s), but as an illustrative example, maybe a mountain on Earth was going to whittle down to become a perfect sphere, 20km in diameter, within maybe 1mm tolerance. Such an event would be extremely unlikely to happen in our world as a lot of random things would have to line up. Maybe the path of least resistance would be the universe producing a madly wealthy and ambitious sculptor? it's extremely unlikely. In this universe, I want something similarly unlikely to be pre-ordained. What consequences would there be to measure? Commented Jul 24, 2018 at 5:29
• @TheoBendit so basically something unnatural is going to happen, one way or another? Commented Jul 24, 2018 at 5:38
• @Starpilot Yes, exactly! Commented Jul 24, 2018 at 5:40
• Actually, this would be something cool. Have you read Asimov's Foundation books? Hari Seldon's mathematical phsychohistory is 50% what you're looking for. The other 50% would be the mathematical self-validation looking into the past, making causality utterly deterministic. Staggering.
– JBH
Commented Jul 24, 2018 at 5:46

Statistics are funny.

It turns out the probability of any future event that is going to happen actually occurs is 1.0. Boring, but accurate. Things that will happen will happen.

Now the tricky part is with the idea of a "random" universe. There is actually no empirical evidence whatsoever that the universe is "random" in any way shape or form. None whatsoever. There's also no empirical evidence that the universe has a plan. Statements like that are simply outside of the domain of the concept of empiricism.

Now what could be interesting would be some exploration a. la. Norton's Dome. Norton's Dome is a curiosity of Newtonian physics. It's a construct which suggests there's some inconsistency in the laws of Newtonian physics because Newton's laws are time symmetric (they work the same in both directions), but when you abuse that symmetry thoroughly, you can get some strange inconsistent results. They might be akin to what you are looking for, though obviously it is known that Newtonian physics is merely an approximation for reality.

• That's a good point about randomness. The crux is that there has to be a comparison with a "random" universe, so that we can tell the universe is not "random". Without a well-defined concept of randomness, the concept is dead in the water. Commented Jul 24, 2018 at 6:19

In a way, we have already have determined this to be the case via a concept in physics called symmetry. What symmetry dictates (in essence) is that if something occurs under one set of conditions, then it will occur under different conditions that match the original conditions apart from a key set of attributes.

This may sound confusing, but let me illustrate. If I have two snooker tables set up side by side, and the balls are placed perfectly identically on each table, and I hit one of those balls with a cue on each table in perfectly the same direction and power then the end state of the balls on teach table will be identical.

This is called translation symmetry, and there are many different kinds; angular symmetry temporal symmetry (hitting the same ball at a different time), and of course reverse symmetry, or the fact that if you put the same amount of energy into the balls in the reverse direction, your balls will all end up at the starting position. In other words, most of the laws of physics work in both directions of time already.

So; why do we think of causation as only going in one direction? It all comes down to the second law of thermodynamics, often referred to as the law of entropy. When you get right down to it, the reason why we perceive time as linear and why we can only remember in one 'direction' of time is because the brain relies on entropy to create higher localised order by reducing universal order. Put another way, our brains release a lot of heat as they work to put down memories and process what we know, and that heat adds to the entropy of the universe. Incidentally, this is why wearing a beaning in the snow actually helps preserve body heat. We actually lose a lot of body heat through our heads as a result of this process.

Let's look at this in terms of relativity, and spacetime. We now think of time as just another dimension of space, meaning that it's entirely possible that linear time is just an illusion. If that's the case, then it's further possible that the universe is a static four-dimensional construct. If that's the case, then there is no causality, either forwards or backwards in time. But, this is drifting into almost philosophical realms and out of scope of your original question. My reason for raising relativity and spacetime in general is that it's entirely possible (albeit unlikely) that causality DOES work backwards and that we just perceive it the other way. What's more likely (though hotly contested) is that both the past and the future exist and always have and that the pattern between them is a feature of the design of the universe, not a causal chain.

So, that's rather heavy and I've dropped a lot on this topic, but to summarise; causality is in and of itself a concept that relies heavily on a deterministic or close-to-deterministic universe. Such a universe could have a reversed causality model, but to the average human it would look no different to one that goes in the same direction as us through time. As for non-determinism; well, it's possible even in our world, but it can't be TOO non-deterministic, otherwise our laws of physics just couldn't work as consistently as they do.

For the Quantum Folks:

I'm not arguing for or against quantum theory in any way; I'm deliberately trying to stay out of the small scale determinism argument and just focus on the ability to predict an end state from a starting state. No attacks on quantum theory are intended and any resemblance thereto is entirely coincidental.

• +1 Thanks for the informative answer. Incidentally, in this world, temporal symmetry will actually not quite be true. Commented Jul 24, 2018 at 6:46

Things that happen in the future can already be seen to increase the probability of things that occur before them. As mentioned in a previous post, take a step back from a linear perspective of time, and imagine you're viewing this post of me responding to a question asking about the possibility of causality running in both directions of time. Now if you had no way of scrolling back up to see the original question, you'd still be able to tell it's pretty probable that there was a post asking about this topic and not something completely related like whether the Silence from Dr Who actually exist.

If you want to run an experiment, just roll a weighted die 100 times, have a computer record them, but then do calculations on the probability of the first few rolls based off of the last ones without looking at the first few rolls first. Your math will be exactly the same regardless of the order you look at the rolls as long as you performed this experiment with proper scientific integrity.

However, bi-casualty is normally not relevant and not thought of because we perceive time to be moving forward and it's just more useful to predict a future that hasn't happened and will affect us, than a past which we don't know and don't particularly care about.

Another example that could help illustrate what I'm trying to say is the field of Paleontology. The theories about how dinosaurs went extinct, and how they behaved aren't set in stone or anything. (haha) They're only theories based off of what we believe to be the most likely scenario that could have led up to the fossils that we have today. Sure, it's widely believed now that it was a meteor or a volcano erupting that did them in, but those beliefs are based off the logic that those versions of the past are the most likely given the present.

The only way would be to enter a state outside of time. That we be the only way to discover the phenomenon at all. To an observer in the linear flow of time it would appear as if the past impacted the future (because that would be the order in wich he experiences it) not the otherway around.

• Is there no way to detect, possibly with some statistics, the implausibility of the chain of events so far? Since nothing happens genuinely out of the blue (i.e. every event has an event that "causes" it), I can definitely see how people would not tend to interpret the phenomenon for what it is, but with the right (crackpot) perspective, couldn't there be a way to falsify this intrinsically? Commented Jul 24, 2018 at 5:53
• We could generate some electricity now from Einstein's spinning corpse. Commented Jul 24, 2018 at 5:53
• @TheoBendit Unfortunately, when you really try to pin down the implausability of things, you find the plausability is "Perfectly plausable." In fact, philosophically speaking, it is impossible that things could have taken any path they did not take. It makes such calculations really buggered. Commented Jul 24, 2018 at 5:56
• @Theo Bendit yes but the conclusion they would assume that past events effect future events not the other way around Commented Jul 24, 2018 at 6:58