Influence of aesthetic ideas in physics

The Birth of Venus by Botticelli

In a previous post I reviewed the new book in Spanish by Francisco José Soler Gil, entitled The enigma of the natural order. Its third chapter, whose title is Aesthetic ideas in physics, which reproduces a lecture given by the author at the Faculty of Chemistry of the University of Seville, has provided me with matter for this post in my blog.

The influence on physics of aesthetic ideas is very old, perhaps as old as physics. One of its oldest precursors is Pythagoras, who proposed the concept of the harmony of the celestial spheres, according to which the distances between the planets would reproduce harmonious musical intervals.

Two of the most influential aesthetic concepts in physical theories are symmetry and simplicity. It is curious that the first was used by Copernicus as a justification for his heliocentric system compared to Ptolemy's geocentric system, with these words, taken from an English translation of De Revolutionibus Orbium Coelestium:

Nor could [the astronomers who built the Ptolemaic system] elicit or deduce from the eccentrics the principal consideration, that is, the structure of the universe and the true symmetry of its parts. On the contrary, their experience was just like some one taking from various places hands, feet, a head, and other pieces, very well depicted, it may be, but not for the representation of a single person; since these fragments would not belong to one another at all, a monster rather than a man would be put together from them.

This paragraph is very curious, as Copernicus was here several centuries ahead of Mary Shelley on the idea of ​​the Frankenstein monster.

The concept of simplicity is also implicit in the work of Copernicus, since his heliocentric system is much simpler than that of Ptolemy, although later Kepler made it a bit more simple, by replacing circles with ellipses as the shape of the orbits of celestial bodies. It is also implicit in the work of Newton, who unified earthly and celestial mechanics, thus considerably simplifying physics. And in that of Maxwell, who unified electricity and magnetism. And in that of Weinberg, Salam and Glashow, who unified electromagnetism and the weak interaction. There are many more examples.

Soler Gil points out, however, that the idea that theories (or equations) must be beautiful, which is usually understood to mean that they must be simple or exhibit symmetry, can be carried too far, in which case, rather than helping physics to advance, it could become a drag, pushing researchers into dead ends. And he quotes several examples, many of which have taken place quite recently, at the end of the 20th century and the beginning of the 21st:

• 

  The cosmic microwave
  background radiation

  The perfect cosmological principle, proposed by Fred Hoyle in support of the steady state cosmological theory, which asserts that the universe is homogeneous and isotropic in both space and time. This theory was preferred by many cosmologists to the Big Bang, until the perfect cosmological principle was disproved by the discovery of the cosmic background radiation, which showed that the universe has changed its appearance over time.



• The fact that the weak interaction breaks several symmetries much loved by physicists, such as the P symmetry (parity symmetry, or symmetry between right and left) and the CP symmetry (the joint symmetry of parity and charge), which implies that time is irreversible, against the wishes of many physicists, who at all costs would maintain the reversibility to time exhibited by the Einstein and Schrödinger equations.


• The concept of supersymmetry, a hypothetical symmetry that would relate the properties of bosons and fermions (two different types of elementary particles), and predicts the existence of many new particles, beyond the standard model of particle physics. Supersymmetry is an important component of superstring theory, which generalizes string theory, but neither has achieved experimental confirmation in the more than four decades since these theories were proposed.

Soler Gil points out that striving to impose an excess of symmetry on the cosmos can lead to unpredictable and undesirable consequences. For example, the cosmic background radiation exhibits great spatial symmetry (its temperature is practically the same in any direction in space), but not perfect symmetry: between any two points there are usually differences of the order of the fifth decimal place (I discussed this in another post in this blog). Well, if its symmetry were perfect, we wouldn't be here, because there would be no stars or galaxies in the universe. Would the cosmos be more beautiful in that case? I doubt it. Our existence and that of many beings surrounding us are beautiful precisely because we are different, unique and irreplaceable.

Or as the Japanese aesthetic specialist Kuki Shūzō put it: beauty depends on the existence of some difference between the beautiful object and the ideal order. If there is no such difference, there can be no beauty; and beauty cannot exist when the difference is large. To illustrate this concept, Soler Gil uses Botticelli's painting The Birth of Venus and asks the following question: Would the painting be more beautiful if Aphrodite's face were perfectly symmetrical, or do the slight asymmetries contribute positively to her beauty? And he ends with the following words: Nature is no less an artist than Botticelli.

The same post in Spanish

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Manuel Alfonseca