Thursday, January 2, 2025

Physics, Mathematics and Mathematical Physics

Eugene Wigner

Eugene Paul Wigner was a Hungarian physicist who received the Nobel Prize in Physics in 1963 for his contribution to the theory of the atomic nucleus and elementary particles. In a famous article published in 1960, Wigner said:

It is important to point out that the mathematical formulation of the physicist's often crude experience leads in an uncanny number of cases to an amazingly accurate description of a large class of phenomena. (“The unreasonable effectiveness of mathematics in the natural sciences”. Communications on Pure and Applied Mathematics 13: 1-14).

He later notes that scientific advances based on mathematics are often applied to previously unsuspected fields. For example, Maxwell’s equations, proposed to unify electricity and magnetism, also apply to radio waves, whose existence was not suspected when Maxwell formulated his laws. Newton’s laws of Universal Gravitation predicted the existence of the planet Neptune. Wigner sums up his argument in the article mentioned above:

[T]he enormous usefulness of mathematics in the natural sciences is something bordering on the mysterious, and… there is no rational explanation for it.

And in the conclusion, he adds:

The miracle of the appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve. We should be grateful for it and hope that it will remain valid in future research and that it will extend, for better or for worse, to our pleasure, even though perhaps also to our bafflement, to wide branches of learning.

However, Bertrand Russell, although he fundamentally agrees with Wigner, said in this quote something that seems to weaken this conclusion:

Physics is not mathematical because we know much about the physical world, but because we know very little; we can only discover its mathematical properties. (An Outline of Philosophy. George Allen and Unwin, 1927).

In an article on the history of science published in this book in 2011, entitled Creation and Inertia: The Scientific Revolution and Discourse on Science-and-Religion, William E. Carroll notes that mathematics and physics have been distinct sciences since ancient times. It is true that mathematical principles can be applied to physics, but what is practiced in this way is neither physics nor mathematics, but a different science, mathematical physics. This distinction is also very old: In his second book on Physics, Aristotle recognizes the existence of mixed sciences, which he considers branches of mathematics, including optics and astronomy. And St. Thomas Aquinas, in his Commentary on Boethius, writes this:

It does not belong to the mathematician to treat of motion, although mathematical principles can be applied to motion… The measurements of motions are studies in the intermediate sciences between mathematics and natural science (i.e., Physics). So there are three levels of sciences… Some treat of the properties of natural things, like physics… Others are purely mathematical and treat of quantities absolutely… Still others are intermediate, and these apply mathematical principles to natural things, [like] music and astronomy. These sciences… have a closer affinity to mathematics, because in their thinking what is physical is… material, whereas that which is mathematical is… formal. (Material and formal are understood here in the Aristotelian sense.)

Isaac Newton

Isaac Newton was very clear about the difference between physics and mathematical physics. It can be seen in the title he gave to his most famous work: Philosophiae Naturalis Principia Mathematica, (Mathematical Principles of Natural Philosophy). Natural Philosophy was the name given to Physics at that time. He says it more clearly in an article that was not published until 1978: De Gravitatione et Aquipondio Fluidorum (On Gravitation and the Aquipondium of Fluids):

Moreover, since body is here proposed here for investigation not in so far as it is a physical substance endowed with sensible qualities but only in so far as it is extended, mobile and impenetrable, I have not defined it in a philosophical manner, but abstracting from the sensible qualities… I have postulated only the properties required for local motion.

Unfortunately, today this distinction has been partly lost. Many mathematical physicists act as if their elucubrations were immediately and undoubtedly applicable to the real world. Hence all those dead ends of current physics that I have denounced in other posts in this blog, which make one think that physics is losing touch with reality. The extreme case of this tendency is provided by Tegmark’s mathematical multiverse, which states that every coherent mathematical construction is a universe that must exist somewhere. It is not entirely clear what the phrases exist and somewhere may mean in this context.

Mathematical physicists should be aware of the limitations of their science. In his article, Carroll agrees with this diagnosis: Principles of mathematics, although applicable to the study of natural phenomena, cannot explain the causes and true nature of natural phenomena.

The same post in Spanish

Thematic Thread on Science and History: Previous Next

Manuel Alfonseca

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