Why we cannot calculate the future, even when taking every single variable into account
In: Physics
The computer you’d need to calculate the future is the actual current universe. Anything you build inside the universe would by definition not include every variable.
On top of what u/Moskau50 said, the quantum realm is made up of fluctuations that (to our best knowledge) appear completely random.
Since these events are random and don’t seem to correlate with any known physical process, they are by definition unpredictable
Because we cannot actually take every single variable into account, with the proper degree of accuracy/precision, in order to model the present. Without fully understanding the present, we can’t hope to fully predict the future.
Several problems:
First Heisenbergs Uncertainty states we can’t know exact data, it’s simply not defined to infinite precision. Quantum effects are naturally propabilistic.
Second even if we could we can’t store infinite precision numbers. Lets start with just a single variable, the temperature at the exact northpole at midnight today. Okay lets take a billion digits after the decimal point. It’s still not perfectly exact. And what about the temperature exactly 1 atomic radius to the left?
There aren’t enough atoms in the universe to store the information of all physical properties of all atoms in the universe.
So we need to make concessions about precision. And small deviations often grow exponentially so that even with very precise data the prediction becomes imprecise after a very short time.
Only by knowing the grand universal theory (GUT) or possibly by building a Jupiter brain (a computer the size of a planet) could we possibly predict the future by considering every variable, otherwise we simply dont understand enough about how the universe actually works.
The grand universal theory would (theoretically) allow you to calculate anything with just 1 formula. At the moment we can calculate a lot of natural phenomena but we have to use many different equations and formulas some of which contradict each other.
A Jupiter brain is straight out of science fiction but is theoretically possible to build( in the same way a Dyson sphere is, easy right) A computer the size of a planet that would make any of our current super computers look like an abacus
Because *randomness* is a thing. The quantum world does not follow the mechanical mechanisms of the „big“ world. Even if the randomness of the quantum world smoothed out, it does not do so in a precise way. E.g. if you flip a coin 1.000 times you *expect* 500 times head and 500 times tails.
– macroscopic you get a probability curve with 500/500 as the most likely outcome and 0/1000 as a very, very unlikely outcome (roughly 1:2^1000)
– on a quantum („per coin toss level“) you have chaos: the 999 coin tosses before the last will not tell you a single bit about the result of the 1000th toss
So: we can predict macroscopic events to a certain degree. But each random micro event will make the predictions more and more foggy.
1. We lack the accuracy to measure everything (every atom to perfect precision) – it’s a rule baked into quantum mechanics.
2. Some processes are genuinely random – there’s no internal clock saying whether an unstable atom will decay in any one moment, just a probability.
3. Complex systems (where small parts can make big differences) are very difficult to model more than a few cycles in advance. You’d literally need a computer bigger than the universe to model the universe for any length of time.
4. Because in complex systems small parts can make a big difference, we can’t even make some approximations and then hope the simulation will still be accurate.
5. We also don’t have a perfect model of how the universe works. Current models of physics don’t work in a lot of cases (e.g. Black Holes). We also don’t know a lot of what’s going on in the wider universe (Dark Matter). So we’d need a complete model of physics, which we are nowhere near yet.
Reasons 3-5 mean we definitely can’t do it with current technology. Reasons 1 and 2 are why it is literally impossible, no matter what technology.
Depends what you mean by “calculate the future”. We can predict things on large scales like the movement of stars and planets with pretty good accuracy.
The more accurately we want to predict something, the harder it gets. I think it will only ever be something that we can do on very small scales. Perfectly simulating even a small number of particles is very hard. And simulating every possible quantum state of a system is currently intractable.
Which variables would those be, and how do you know?
In order to make accurate predictions, we need a model that includes all of the important variables. For something like a prediction regarding what will happen when we mix this amount of calcium chloride with that amount of sodium carbonate under these conditions, the model is pretty simple, easy to reproduce, and even if we don’t truly know all the variables, the ones we don’t know we don’t know don’t seem to be important…
Other issues are far more complex, and time is an important variable. We cannot accurately predict the temperature in my back yard tomorrow morning, nor can we accurately predict whether or not it will be raining at 7 a.m. in my back yard. Presumably that’s because we don’t know enough of the variables, even though we can build a model, make a prediction, test that prediction, and then adjust the model every single day. Add in more than 24 hours, and more variables (presumably many of which we don’t know we don’t know), and predicting the future becomes orders of magnitude more difficult.
Which of course is my issue with anthropomorphic climate change… we can build a model to predict where the moon will be 30 days from now relative to where we are, then test and adjust that model every month, and we seem to be getting pretty good, as we hit the moon with spacecraft. (But how precise is the prediction? Do I need to be able to predict where it will be to the closest foot, or is 5,000 kilometers close enough?). But if I build a model for climate 50 years from now, how am I testing and adjusting my model? Especially if I am concerned about small fluctuations in temperature? If I can’t get my backyard temperature correct tomorrow morning, why do I think I can get the planet correct in 50 years?
As a counter point to all the other answers, we “calculate the future, taking variables into account” all the time.
For example, weather prediction is generally accurate for the next 6 hours up to the next day. Looking a week ahead, maybe not as accurate, but short term it pretty much is.
And as another example, you have a pretty good idea what you’re going to be doing for the next 6 hours, and probably tomorrow too. Most people have schedules, jobs, household chores when they get home, planned evenings perhaps, etc.
You can’t function without “calculating the future”, as humans we don’t just react to the present situation, we always plan ahead. That’s calculating the future.
You’re going to argue that it’s not mathematical, but it is. The ACCURACY of it is not down to what every atom is going to be doing in the future, but you don’t NEED to know that in order to function.
And it’s impossible to know that, mostly because we have to use atoms (in the measuring device) in order to measure what other atoms are doing, and inserting atoms into what other atoms are doing disrupts what the other atoms are doing.
As an analogy, think of a sports game, but your measuring device is “as big as” the game, so basically you have to have 25 referees in the field (same number of referees as the two teams of players), dispersed among the players; the game will be affected, it won’t be the same game as with a single referee.
Latest Answers