Comments about the article in Nature: Does quantum theory imply the entire Universe is preordained?

Following is a discussion about this article in Nature Vol 624 28 December 2023, by Eddy Keming Chen
To study the full text select this link: https://www.nature.com/articles/d41586-023-04024-z In the last paragraph I explain my own opinion.

Contents

Reflection

Introduction

The article starts with the following sentence:
Was there ever any choice in the Universe being as it is?
That is a strange question, because no one knows what the present state of the universe, in its entirity, is.
Albert Einstein etc. : “What I’m really interested in is whether God could have made the world in a different way; that is, whether the necessity of logical simplicity leaves any freedom at all.”
This remark is not clear: What means logical simplicity?
US physicist James Hartle, made seminal contributions to this continuing debate.
This debate will never come to any conclusion.
Early in the twentieth century, the advent of quantum theory seemed to have blown out of the water ideas from classical physics that the evolution of the Universe is ‘deterministic’.
What means ' deterministic'? The two '' are important, because they indicate that the Universe is both deterministic and not exactly deterministic.
Hartle contributed to a remarkable proposal that, if correct, completely reverses a conventional story about determinism’s rise with classical physics, and its subsequent fall with quantum theory.
The central problem with this sentence is a clear defintion of the concepts: determinism, classical physics and quantum theory.
One could claim that Newton's Law is good description of the movement of the planets around the Sun. At the same time one can also claim that GR gives a better description.
A different question are these Law's accurate. For Newton's Law the answer is no, because Newton's Law assumes that the planets are round. This allows to replace each planet as a point source, which is incorrect. The consequence is that Newton's Law gives an approximation of the future trajectory of the movements.
A different issue is to what these laws involved with (a part of) the physics of the trajectories with movement of the planets. The answer is: nothing at all. The explanation lies in the forces between all the objects involved. Newton's Law gives a mathematical description of these forces, and allows the user based on observations to calculate the future trajectories of the planets.
As mentioned the actual trajectories of the planets are caused by the forces between the planets and the Sun and because the trajectory of the Sun is also influenced by all the stars in our Galaxy, the actual trajectories of all the planets are also influenced by all of these stars. It is important to realize that the trajectories of the planets are influenzed by all the planets but also by all particles in 'empty' space.
My understanding is that determinisme involves the assumption that the laws of physics are the physical cause that the planets follow the path around the Sun in the way they do. That is not correct.
A quantum Universe might, in fact, be more deterministic than a classical one — and for all its apparent uncertainties, quantum theory might better explain why the Universe is the one it is, and not some other version.
The question why "the Universe is the way it is" and "not different" is an impossible to answer. Understanding the Universe involves the concepts objects, forces and masses and is relevant at almost all levels of detail, including the elementary particles.
In physics, determinism means that the state of the Universe at any given time and the basic laws of physics fully determine the Universe’s backward history and forward evolution.
Newton's Law can be used to predict the future of the solar system based on observations in the past, assuming that nothing is done to influence the normal evolution. This means that the evolution is not disturbed. The path of a bullet is also described Newton's Law in the future when the bullet is not disturbed. This also means the backward history is always based on observations in the past and the forward evolution on observations in the future.
If someone knew the present positions and momenta of all particles, they could in theory use Newton’s laws to deduce all facts about the Universe, past and future. It’s only a lack of knowledge (or computational power) that prevents scientists from doing so.
It is not a lack of knowledge. The mathematics of Newton's law require what is called an initial state. This requires that the position (and velocity) of all the objects in the universe, also the objects outside the visible universe at one specific moment.These measurements are physical impossible. Not only that. All these observations (measurements) will influence the positions of all the other objects large and small. That invalidates this whole exercise.
Along with this distinctive predictive power, determinism underwrites scientific explanations that come close to the ‘principle of sufficient reason’ most famously articulated by German polymath Gottfried Leibniz: that everything has an explanation.
The meaning of the remark: "that everything has an explanation" is not clear. To improve the remark I would write: "that everything has a specific explanation" to amplify "that everything does not have the same explanation".
If the Universe is a train, determinism says that it’s running on a track, with no option to switch to any other path because different tracks never cross.
The problem is that Universe is no train, nor resembles in any way a train. That means any comparison does not make sense.
Physicists have conventionally liked determinism’s predictive and explanatory power.
More detail is required, to understand the importance of this sentence.
Others, including some philosophers, have generally been more divided, not least because of how determinism might seem to preclude human free will: if the laws of physics are deterministic, and our actions are just the summation of particle interactions, there seems to be no room for us to freely choose A instead of B, because the earlier states of the Universe will already have determined the outcome of our choice.
Understanding the Universe have nothing to do with what people do or feel. Specific it has nothing to do with our free will.
In any physical experiment, except if specific mentioned, like in medical experiments, humans have nothing to do with the outcome of the experiment.
It should be mentioned that the laws of physics are mathematical descriptions, based on measurements of the results of certain reactions. See for more detail: Reflection 1 - Deterministic versus inderterministic

1. Space Invaders

The strange behaviours of quantum particles that began to emerge in the twentieth century fundamentally shifted the debate surrounding determinism in physics.
The behaviour of elementary particles can never be strange. The outcome of any experiment can never be strange.
The laws of quantum mechanics give only the probabilities of outcomes,
Generally speaking the same experiment can never exactly be repeated. What that means the outcome is always different. This is true at all levels of detail.
See also: Reflection 2 - Understanding Physics - Kale with sausage the Dutch way.
A cat is trapped in a box with a vial of poison that might or might not have been broken by a random event — because of radioactive decay, for example.
Also this experiment in general can never exactly be repeated. That means the outcome can not be predicted. What is important to know how this experiment is performed, specific it is important what is known about the half-life of the radio active element used.
If quantum mechanics applied to the cat, it would be described by a ‘wavefunction’ in a superposition of ‘alive’ and ‘dead’.
What is the exact meaning of wavefunction and superposition? In the physical world a cat can never be both 'alive' and 'dead'. The state of a cat always involves four states: born, alive, dying and dead. It is always one or one other. The same for any human being.
The important point is that the evolution of these four states, in principle, don't require any human intervention, but the details are wrapped with uncertainty.
The wavefunction, when measured, randomly jumps to one of the two states, and quantum mechanics specifies only the probability of either possibility occurring.
Generally speaking the wave function can not be measured.
The probability of the outcome depents on half-life of the radio-active element used and the details of how the experiment is performed. IMO this has nothing to do with the wave function.
One consequence of the arrival of quantum mechanics was that it seemed to throw determinism out of the window.
Both the concepts determinism and wavefunction are not clear.
The quantum Universe could actually be more deterministic than a classical one, for two reasons.
The Universe can neither be called: deterministic or classical or both.
Newton’s laws allow situations in which the past does not determine how things will move in the future.
Newton's law does not do anything of that.
Newton's law are a set of mathematical equations relevant for the objects considered, a set of initial conditions and a set of parameters.
The initial conditions and the parameters are calculated based on observations in the past of the relevant objects considered and can be used to calculate the future positions of these objects or the path of these objects.
Newton's Law is in no way involved with changes in the physical universe.
For example, the laws do not provide an upper bound on how much an object can be accelerated, so in theory a classical object can reach spatial infinity in finite time. Reverse this process, and you get what have been called ‘space invaders’ — objects that come from spatial infinity with no causal connection to anything else in the Universe, and which can’t be predicted from any of the Universe’s past states.
In the previous comment I wrote: "Newton's law are a set of mathematical equations relevant for the objects considered". I should have written fixed object. You cannot just write "Reverse this process". Most probably in the past there were many more small objects involved in a cloud around the Sun. Many of these small objects disappeared because they were captured by the larger ones. This makes 'going back in time' speculative.
The equations of general relativity lead to ‘singularities’ of infinite curvature, most notoriously in black holes and at the Big Bang at the beginning of the Universe. Singularities are like gaps in space-time where the theory no longer applies; in some cases, anything can come out of them (or disappear into them), threatening determinism.
Infinities can also happen using Newton's Law. Basically this are errors in the description of the program, with can happen when you divide by zero, assuming that the distance between two objects is zero, which is physical impossible.

2. Into the Quantum Cosmos

With Stephen Hawking, Hartle went on to become one of the founders of quantum cosmology, which applies quantum theory to the entire Universe. In a classical Universe, there is freedom in choosing how it all started.
If you want to understand the evolution of the universe, you must try to understand the entier universe, vissible and invisible for all human beings.
We can go back to earlier states to explain the current state, and do that all the way back to the initial state — but this initial state is not explained by anything that precedes it. Ultimately, standard determinism fails to fully satisfy Leibniz’s principle of sufficient reason: when it comes to the initial state, something remains without an explanation.
This failure is not just philosophical.
This failure is not just philosophical, but also realistic because the evolution of all process go in the forward direction.
A typical case is the inflation theory which involves a rather dramatic epoch in which the size of the universe in creased drastically. The two important events to explain are the period that this inflation started everywhere in the unverse simultaneously and the second event that it stopped everywhere simultaneously.
Which phenomena show up in our observations depend sensitively on the initial conditions.
We must look at what we see in the Universe around us, and use this information to determine the initial condition that might have given rise to such observations.

3. A universal wave function

4. The ultimate theory

Density matrices can be thought of as ‘superpositions of superpositions’, and they provide extra options for the initial condition of the Universe.
Such a sentence must be crystal, clear but they are not.
What should be know is the initial state of the universe at t0 with t0 very small and accurate. That is impossible. The result is that the state of tn with tn very large can only be calculated inaccurate.

Reflection 1 Deterministic versus inderterministic in the physical sense.

Understanding the Universe starts by observing that many processes or reactions are the same. That means the details of how these reactions evolve are the same.
At the same time that also implies that there are other reactions which are different. That means the evolution of these processes are different. They are composed of different elements. The descriptions are different and the laws involved could be different.
However, if you want to understand all what is happening in the universe, you should study as many different processes as possible. Two of the most important concepts are, related to understanding the Universe, that there are different elements and the force of gravity. Other important factors are temperature, pressure, electricity and magnetism.
With these concepts we can understand many of the processes that take place in the universe or in many experiments. That means how the different parts, in any mechanical experiment or the different sub processes in any chemical process work together and influence each other.

In order to understand a process the first step is often to start with one specific process and measure the amounts that go into the process and, as a result of a reaction, measure the amounts of the unkown products produced by the process.
In a second step you modify one of the amounts that go into the process and again mesure the amounts of the products produced by the process.
By doing that and if you know the chemical composition of the products that go into the process you slowly unravel the composition of the produced products.
What I want to emphasize in this text is the importance of experiments

If you want to understand the secrets about why do the planets move approximate in circles around the sun you should also start with simple experiments. Select this link: https://catalogue.museogalileo.it/indepth/GravitationalAcceleration.html When you read the text you see That means that the two most important concept to understand why planets move around the Sun is Gravitational atraction and the masses involved. I will leave it about that, as of this moment.

Now we come to the title of tis reflection: what has the concept of determinism to do with this. To be more specific: what has determinism to add, on top op what Galileo and Newton tell us ?

Reflection 2 - Understanding Physics - Kale with sausage the Dutch way.

Curley Kale, in dutch boerenkool, in french Chou frise, in german Grünkohl is a very interesting ingredient which allows you to prepare a dish in a kitchen which resembles like the Yellowstone geyser. https://www.yellowstonepark.com/things-to-do/geysers-hot-springs/about-old-faithful/. To do this experiment you need Curley Kale, potatoes, one smoked sausage and some milk. For the sausage it is important that is has the shape as shown in this document: https://www.lekkerensimpel.com/boerenkool-stamppot-met-worst/

The recipe:

What will happen next is that the dish will become hotter, specific the bottom part. The top part services as a type of lid. Specific the sausage services as an extra weight. The pressure will build up. The water within the kale will be removed and collected at the bottom of the pan. That moisture will start to boil. The pressure will build up and all of a sudden there is a small erruption and steam will be released. This happens almost at the center with in the 'round' sausage. Next the same will happen again and again. It resembles the framework of a Cuckoo clock, which repeats it self.

What is the most important lesson of this experiment?
The most important lesson is that the whole process is a physical and chemical process. That what is happening has nothing to do with any physical law and specific not with determinism, nor with the cook, nor with human free will, nor with the strugle between classical mechanics versus quantum mechanics. What is more important, it can not be described accurately by simple mathematics and if you could every time when you repeat the same experiment the physical parameters involved are different. The reason is that the cycle time is not constant.

Reflection 3 - Deterministic versus inderterministic in the mathematical sense.

Any computer program on a DC is deterministic. That means when you execute the program again, assuming the program does not require any human interventions, the outcome is the same.
The same is the case when your computer program is a simulation of planets around the sun, or all the stars in our Galaxy. It is also the case for a simulation of the universe.
An analog computer is not deterministic. When you execute the same program again all outputs seem identical but they are not. For analog computers accuracy is a real issue.
For quantum computers accuracy and repeatability are serious issues.

The main problem with a DC is in sofar the simulation gives an accurate description of the reality. This is not the case.
The analog computer is an implementation of a model of what is called a differential equation. A differential equation is a description of a process continuous in time. If want to simulate a car which has a constant speed, the solution, which is the distance travelled is a straight line.
An digital computer is an implementation of a model of what is called a difference equation. A differential equation is a description of a process where time is considered discrete, that means the time increases in steps. If you want to simulate a car which has a constant speed, the solution, which is the distance travelled increases in steps. The accuracy of the solution depends in this case on the value v.
Suppose that the speed is 100.000000 km/sec. An AC requires an potentiometer to implement a constant. The accuracy is roughly 0.2%.
The accuracy in case of a DC is very high.

However there exist a complete different problem, which is much more important.
The question is how accurate do we know the speed? And more specific: How is the speed measured?
In general to calculate a speed, you need the coordinates of two points and the time when these two points are reached.
When the position of point n is defined x(n) and the time of arrival as t(n) then the velocity v(n) = (x(n)- x(n-1)) / (t(n) - t(n-1)).
This equation is a good model when you drive a car in a straight line from point n-1 to point n on the surface of the earth and when there are two clocks available at both points n-1 and n
However this becomes a problem if you want to know the speed of the planets around the Sun. In that case you must know the position of all the planets at t(n-1) and t(n). And that is a very difficult excercise. To calculate these positions you must monitor the position of each planet seperately over a periode before t(n-1) and after t(n), and use these observations to calculate the actual positions at t(n-1) and t(n).
The idee behind all of this that in a DC a simulation runs at a very synchronised way. That means in a simulation all the positions must know at a certain moment and the program calculates all the positions for the next moment 1 sec later. And this again and again.

Now we can again discus the issue: deterministic
My understanding is that a computer program is deterministic and this is the same for a computer program simulating the movement of the planets around the sun or for a program simulating all the stars in the Milky Way. But that does not mean that the movement of the stars in the Milky Way are deterministic.
But that does not mean that the trajectories of the planets are deterministic. That means the trajectories are described by forces and these forces by the masses of the objects, and these masses inturn are influenced by other masses and colissions between masses and supernova's

Reflection 4 - Deterministic versus inderterministic in the Universe.

If you want to understand the Universe you must select this link: https://nicvroom.be/friedmann's equation L=0.01155.htm
The next 4 figures show the same information.
Excel parameters
Figure 1
c = 60 Lambda = 0,01155 v0 = 3
Figure 1 A
c = 60 Lambda = 0,01155 v0 = 3
Figure 1 B
Figure 1 C Detail
Figure 1 C shows the detail of Figure 1 B in the range of 0 to 1 billion years.
  • The black line represents the 100% distance line.
  • The blue line shows the light ray starting from the Big Bang which reaches the Observer now.
The most important picture to study is Figure 1B which shows the expansion of the Universe using the Friedmann equation.
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Created: 20 December 2022

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