Beauty is truth, truth beauty,"--that is all
Ye know on earth, and all ye need to know.
John Keats, Ode on a Grecian Urn
Most people would not associate the dry pursuit of objective scientific knowledge with a powerful sense of aesthetics. But in many areas of science there has always been a strong belief in the correspondence between truth and beauty--to the point where today some theories almost seem to be competing in a beauty contest.
Three of the main aesthetic properties in science are the classical ideals of elegance, unity, and symmetry. Perhaps the archetypal example of a beautiful theory is Newton's law of gravity, which is the scientific equivalent of the Parthenon, or maybe Grace Kelly. Its design is deceptively simple and elegant. It unifies a broad range of phenomena--everything from the motion of a planet around the Earth, to an apple falling to the ground--just as an artwork or beautiful face brings an inherent unity and consistency. And it is highly symmetric, in the sense that the force produced by a body acts the same in every direction.
People seek out partners with symmetric facial features because they are considered attractive. Physicists seek out symmetries in nature because these allow them to produce simplified mathematical representations (and because they are considered attractive).
Another famous example of a beautiful theory is Einstein's E=mc2, which unifies the concept of energy (E), mass (m), and the speed of light (c). The equation grew out of Einstein's theory of relativity, which his colleague Max Born called "a great work of art, to be enjoyed and admired from a distance."
The success of these elegant theories meant that beauty has become a kind of a goal in itself. But, with due respect to John Keats, is it possible that beauty is not truth? And could the quest for beauty be leading science down the wrong path?
An obsession with beauty has in the past certainly motivated generations of scientists, but at times has also led them astray. The problem usually occurs when a fascination with theory loses touch with the reality check of observations. It's like falling in love with a pretty face, while ignoring obvious failings and incompatibilities, such as the person's inability to tolerate your friends or personality.
The ancient Greeks initially believed that the stars and planets moved in perfect circles around the Earth, on the basis that circles are the most symmetric and beautiful of forms. When the results didn't quite match reality, instead of ditching the circles, they just added more of them, by incorporating epicycles (which are circles around circles).
Some three centuries ago, Johannes Kepler spent years trying to prove that the radii of the planetary orbits were determined by a nested set of highly symmetric geometric figures known as the Platonic solids. It was only with the greatest reluctance that he realised that the data showed the shapes of the orbits had little to do with classical geometry or perfect symmetry, and were eliptical rather than circular.
The ultimate aim of physics has long been to produce a Theory of Everything, which will explain all the laws of physics in just a few lines of beautiful mathematics. Einstein spent much of the latter part of his life pursuing such a theory, without success. And despite enormous effort on the part of many scientists, the passionate pursuit of the elusive Theory of Everything has remained unrequited.
The closest thing we have to a complete model of subatomic particles is something known by the unexciting name of the Standard Model, which has been around for over 40 years. It does an extremely good job of simulating the behaviour of the electrons, protons, neutrons, and other bits and pieces which make up matter. It has been extensively tested in decades of experiments--most recently at the Large Hadron Collider, where the last part of the puzzle, the Higgs boson, was recently discovered. Despite its considerable successes, the theory has two main disadvantages.
One is that it doesn't include gravity, so isn't a true Theory of Everything. The other is that, from an aesthetic point of view, it is downright homely. As Steven Weinberg, who gave the theory its name, puts it, "we know that the Standard Model is not the final answer, because of its obvious imperfections--and those imperfections, I have to say, are aesthetic."
Newton's law of gravity is considered simple and elegant because it requires only one number, known as the gravitational constant, to be adjusted by hand in order to give the right answers. In contrast, the Standard Model involves some 20 such arbitrary numbers, which include things like the masses and charges of particles. Physicists would love to trade it in for a better-looking theory which will resolve these aesthetic difficulties.
One such sexier alternative is "supersymmetric string theory", which sees subatomic particles as being just the detectable part of tiny strings oscillating in a nine-dimensional space. To its many fans, supersymmetric string theory is an exceedingly gorgeous theory--the supermodel of physics--which can encompass all particles and forces in a single adorable package. It has been described as "too beautiful" to be wrong. It isn't just symmetric, it's supersymmetric. However, while the theory may be based on an attractive idea--little vibrating strings--the actual implementation is a mess (imagine a supermodel with mental issues). The theory has also failed to make any predictions that could actually be used to validate (or invalidate) it. Theory has again become detached from reality.
As I argue in Truth or Beauty, our obsession with a certain kind of beauty may again be leading science down the wrong path - and not just in physics, but in everything from medicine to finance.
It might even turn out that the structure of the universe is uglier (at least by conventional standards) than we thought. After all, as in life, looks don't count for everything.