A deterministic universe and what to do about it

Throwing a ball

Imagine you are throwing a tennis ball and you want to work out exactly where it will land. In order to achieve this, you need 3 pieces of information:

The initial conditions.

“Initial conditions” being at the time the ball leaves your hand. This includes conditions like the ball’s initial angle of trajectory, momentum and angular momentum. You might also want information on the environment such as the density of the air, the speed and direction of the wind and the force of gravity at that particular point on Earth. There are other initial conditions you might want depending on how accurate you want to be, but this is a good starting point.
Equations to model behaviour.

Once all of the initial conditions are retrieved, you need some way of modelling how the ball will behave in its environment. Mathematical equations are typically how people achieve this. You could use Newton’s equations from his model of gravity, combined with Galileo’s model of projectile motion and some equations for air resistance to predict the ball’s behaviour with reasonable accuracy. Note that Einstein has since proved flaws in Newton’s model of gravity (and today’s physicists have since proved flaws in Einstein’s model of gravity) but Newtonian equations were accurate enough to launch people to the moon, so you conclude that they are good enough for your ball calculations.
Resources to calculate.

Now that you know all the information about the initial conditions of the ball and its environment, and you have the equations to accurately predict how the ball will move over time, all that’s left is the resources for calculating where the ball will be at t = x seconds. For a projectile motion question like this, you could probably do all of this manually with a pen and some paper.

What’s fun to note is that if you know the conditions of the ball at one point in time, then you can derive its conditions at any point in time.

A calculable universe?

If we can accurately derive the trajectory of a tennis ball at any point in time of its trajectory, can we scale this calculation up and do the same for the entire universe?

Let’s look at our 3 requirements again.

The initial conditions.

We of course do not know the exact initial conditions of the universe, or even the exact conditions of the universe right now. It would take a long time to capture the state of the entire universe at any point in time however this is theoretically obtainable.
Equations to model behaviour.

We have plenty of equations to model the behaviour of particles. Even though these are constantly being updated and it’s very unlikely that the current equations are exact models of the behaviour of particles, maybe one day we will land on some final, correct equations.
Resources to calculate.

Computers in 2021 are unable to process a model of a human brain on a cellular level, let alone the entire universe on a quantum particle level. There are however constant innovations being made on the computer processor so who knows how long until we can run computations as large as this.

Even though satisfying the requirements for 1, 2 and 3 is completely infeasible in 2021, it is not impossible. Just because it can’t be done now, doesn’t mean it can’t be done ever. So is the universe just as deterministic as the tennis ball that you have thrown through the air?

There are some bleak consequences that arise from a deterministic universe. Can the position of every particle in the universe at every point in time, future and past, be known? Is free will an illusion that can only manifest from our ignorance? Could someone have calculated that the spicy wings from Red Rooster would not taste that great and leave me with a night of gastro?

The mathematician Pierre-Simon Laplace theorised about a deterministic universe. After Newtonian physics was grounded amongst the scientific community, Laplace said that if an intellect could know all the conditions of the universe at a point in time and put the data to analysis, then “nothing could be uncertain and the future just like the past would be present before its eyes”.

Except we don’t observe a universe where nothing is uncertain. There are some systems where knowing every single initial condition doesn’t allow you to know the outcomes at every single point in time. To understand this, we need to talk about the 2nd Law of Thermodynamics.

The 2nd law of thermodynamics

The 2nd law of thermodynamics states that any isolated system will trend towards maximum entropy.

Entropy and disorder and information and randomness

What is entropy? Entropy can be thought of as the amount of disorder in a system. When you pour your milk into your English breakfast tea, it starts in a very ordered state with all the milk and tea molecules grouped separately. Over time, even without stirring, your tea will become disordered as the milk and tea molecules mix together until it is all a homogenous milk and tea solution.

In mathematics, entropy and information are fundamentally the same. The amount of information contained in a string of digits can be thought of how much entropy, or how much disorder, it contains. The string 010101010101010101 doesn’t contain as much information as 001110010101011001 since the second string is more disordered. This makes intuitive sense as well since the first string contains repeated patterns which could probably be compressed into a smaller string. For example, we could represent the first string as 019 where 01 is the pattern and 9 is the amount of times it is repeated. The same compression would not be as effective in the second string since the occurrence of its digits don’t follow an obvious pattern; it’s essentially random.

This was a quick explanation of the link between entropy and randomness. If you would like a more in-depth explanation, Veritasium has an excellent video of here.

So entropy is essentially the amount of randomness in a system. A fixed amount of entropy implies a fixed amount of randomness meaning a predictable pattern will emerge over time.

A non-calculable universe

Let’s look back at what Laplace thought about an intelligence that learns the entire state of the universe: “nothing could be uncertain and the future just like the past would be present before its eyes”.

If the universe is entirely calculable and nothing is uncertain, then a pattern has emerged in the universe that can be used to deduce its entire trajectory, future and past. In other words, the amount of entropy in the universe would be a fixed amount; it would be constant. But this is not the universe we observe! This is in direct contradiction to the 2nd law of thermodynamics which entails an increasing amount of entropy and randomness and uncertainty. So Laplace’s envisioned intelligence (under our current understanding of the universe) cannot exist.

If you are someone who doesn’t want to live in a totally predictable and certain universe, you have the 2nd law of thermodynamics to thank.

So where is this information coming from?

Quantum physics

The answer to where the universe’s ever increasing entropy comes from is not known, however a good place to look might be quantum physics.

As I mentioned previously, there are some systems in the universe in which knowing every single initial condition does not allow you to know the outcomes at every single point in time. Knowing the initial conditions of a fundamental quantum particle, say an electron, does not let you predict exactly where the electron will be at t = x seconds in the same way that you can for a tennis ball, but you can predict probably where it’s going to be.

The Schrödinger Equation is used in quantum physics to derive a probability density function from a particle’s initial conditions. As opposed to in classical physics where a function will tell you where an object will be at any point in time, the probability density function will tell you the probability that a particle will be in a certain location at any point in time. It is not until a measurement is taken that the particle’s properties become known, however a calculation and prediction on the future value of these properties is entirely probabilistic. It is uncertain beforehand; it is (within constraints) random.

Every time quantum particles interact, the universe gains a small amount of entropy. Randomness is baked into our universe.

Why it’s probably not free will

So what can we make of this randomness? Some people (including Muller in his video which this article was largely inspired by) hypothesise that human free will could come from the quantum events in our brains.

If you take one message away from this article, it should be to not share this opinion.

To clarify, I am not saying that this statement is wrong. It is entirely possible that human free will exists and its source is in our 2021 understanding of quantum physics. Nobody knows the answer to those questions and therefore it could be true. But here is why I think this is probably not the case.

My argument

When I say “free will” I mean the idea that people have control over their decisions and given the exact same circumstances, can produce different outcomes for themselves. The more we learn about the human body, the more we realise that there is a lot we don’t have control over. Do you consciously regulate red blood cells in your body? Do you consciously tell the 100 trillion bacteria in your stomach to break down the Red Rooster you ate? Do you consciously produce hormones like cortisol and adrenaline when placed under stress?

It can be tricky to effectively convey the argument that we don’t have control over our thoughts and decisions, so if I haven’t done that successfully in one paragraph and you aren’t convinced, let’s assume that free will does exist.

If free will is real and its source is from quantum events in our brains, that would imply that we as people have control over the fundamental behaviour of the universe. Ok fine, but think about all the things that currently exist in the universe and that have existed that aren’t humans. We have only been around for the latest 0.0000145% of the universe’s lifetime and only occupy a sliver of our solar system, let alone the entire universe. If we can control these quantum events, what was controlling the quantum particles before we were around and in the rest of the universe that we don’t occupy?

Yes the universe is inherently random and non-deterministic, but it feels almost narcissistic to suggest that the fundamental behaviour of the universe can be willed by free will - a phenomenon that occurs in one species, on one planet, in one solar system, in one galaxy, in one supercluster.

Why?

I think it makes sense that people make suggestions like this when they are confronted with something we don’t know. There is a sort of repetition in societies where people assert humanity as special in the universe. We want to feel important so we cling to what is unknown and use it to differentiate ourselves from the other animals, plants, rocks and things that exist in the universe. But really, we are just another thing existing in the universe.

I think the “free will arising from quantum physics” argument is another attempt to assert ourselves as special in the universe. We aren’t like trees and rocks and particles because we can alter the path that we take in the cosmos through free will and therefore are special! That would be pretty special, but I’d be fooling myself if I believed it.

What to do now

Luckily, I think we have the knowledge today so that we don’t need to assert ourselves as special through the possible existence of something like free will or God or Scientology, but rather we can recognise it right now.

To me, the fact that we can understand so much about the universe and deem ourselves cosmically un-special, is special. What other thing on Earth (or the universe for that matter) has this level of self-awareness? What else can trip over in public and feel embarrassed, can tell their mate they have no gum left (when really they are saving the last piece to themself) and feel guilty or can spend a day with friends and feel content? These experiences are all unique to being human and nothing else. And even though, when confronted by the vastness of the cosmos and its ever-increasing entropy none of these experiences matter, does that even matter?

I think we can all be humbled in our little corner of the galaxy, embrace our insignificance in the cosmos and smile at the fact that we can even know that we are here.

In the words of Carl Sagan:

“The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself.”