Comments about the article in Nature: Cooperative AI: Thrill of the magnetic moment

Following is a discussion about the News & views article in Nature Vol 593 6 May 2021, by Harvey B. Meyer
To study the full text select this link: https://media.nature.com/original/magazine-assets/d41586-021-01172-y/d41586-021-01172-y.pdf

• The text in italics is copied from the article
  
• Immediate followed by some comments
  

In the last paragraph I explain my own opinion.

Contents

Reflection

• Reflection 1 - Theoretical prediction versus experimental results
• Reflection 2 -
• Reflection 3 -

Introduction

The established theory of particle physics is called the standard model, and has passed a vast number of experimental tests with flying colours.

The standard model is a description based on a certain number of experimental tests. All other tests thereafter are in agreement with this model.
The same with the periodic table of elements. The rules of periodic table were established based on a certain number of experimental tests. The first table was by Mendeleev in 1869. All other tests thereafter are in agreement with these rules.

Despite the many successes of the standard model of particle physics, it has patent shortcomings: it neither describes gravity nor contains a candidate particle that could account for the Universe’s vast amount of dark matter, which can be observed only indirectly.

This does not imply that the standard model has any shortcomings.
The concept of darkmatter is introduced as a solution to solve the discrepancy, that the observed galaxy rotation curve does not match the predicted galaxy rotation curve which uses Newton's' Law and all the visible mass.
In relation to gravity, the question should be raised to what extend the standard model 'solves' all the four forces of nature: gravity, electromagnetism, the weak nuclear force and the strong nuclear force.

Another well-established strategy is to precisely measure quantities that (*) can be calculated, using the standard model, to a degree of precision similar to that of the measurements; any differences in the measured and computed values would indicate the existence of physics not accounted for in the standard model.

(*) To add the word 'also' at the indicated position would make the sentence simpler to understand.
The problem in principle can have two causes: The possible calculations involved to calculate the measured quantities and the corresponding calculations based on the standard model.

The magnetic moments of elementary particles are prime examples of such quantities.

That means detail information is required how these magnetic moments are measured and how they are calculated.

They are proportional to the spin (intrinsic angular momentum) of the particle, and to the particle’s gyromagnetic factor (g, a proportionality constant that is characteristic of each particle type).

What that means there must exist a table which shows the g value for each particle type, created by means of an experiment. It is not know to what extend these values can be calculated by means of other parameters.

Reflection 1 - Theoretical prediction versus experimental results

Understanding physics starts with performing experiments and performing observations. The chalenge is to improve the experiments and the observations to improve our understanding.
A different line of attack is to use a mathematical model i.e. a set of equations, of the physical process involved and to match the results of the calculations with the observations of the experiments. In many cases the parameters of the mathematical model are not all known, that means in the first phase these parameters have to be calculted based on observations.

A different problem arises if all the parameters are known, but still the results of the observations don't match with the calculated results. In that case it makes sense to repeat the same observations at different location and observe is there is any discrepancy. If there is more study is required to explain these different observations, because specific observational errors can be involved. If by repeating the experiments and all the results are the same (within a certain margin) the only reason can be in the mathematical model which is a representation of a physical model. Both have to be adapted.

The major problem is the 'exact' definition of what is the difference between an experiment, a law, a model and a theory.

• In an experiment all the variables involved should be measured as part of the experiment. The result of the experiment is one of these variables, which should match the predicted value, defined as the result of calculation using all the other variables.
• In the case of Newtons law the result of the experiment is the observed forward movement of the angle of the planet Mercury. The calculated or predicted angle is based on Newton's Law and the observed positions of the planets. This predicted value is not in agreement with the observed value, that means Newton's Law is 'wrong', and has to be adapted.