In Scientific American, John Horgan has published a fascinating interview with Lee Smolin, author and theoretical physicist, who describes why he was initially attracted to the field, as well as his work today on a theory that would finally unite quantum physics, or the world of the vanishingly small, with Einstein's relativity, or the physics of time and gravity and colossal, universe-sized matter.
Quantum mechanics and relativity are well tested theories supported by empirical evidence. Sadly, the project to harmonize both descriptions of nature is no closer to completion than it was 60 years ago.
In his exchange with Horgan, Smolin makes an intriguing argument for why this is so: the laws of physics themselves may evolve, a process he refers to as "cosmological natural selection." Scientific American:
Horgan: Why hasn’t the acceleration of universe—arguably the most important discovery in physics of the past 30 years–led to more theoretical advancement?
Smolin: At one level there is no problem, in that the acceleration of the universe’s expansion is easily described by adding a cosmological constant to Einstein’s equations, just as Einstein proposed in 1917. The problem is just with the value of that constant—it’s ridiculously tiny. This is an extreme example of the basic problem that plagues the standard model of particle physics, which is that we don’t understand the reason for the value of any of the roughly 30 parameterize we need to write the laws of physics.
I am convinced that the answer to all these puzzles must be that these constants evolve, so the explanation for their values must be historical. Indeed cosmological natural selection gives a plausible explanation for the observed value of the cosmological constant.
Horgan is a skeptic about whether a unified theory can be had.
He briefly pursues this line of thinking. Does saying that laws evolve, he asks Smolin, also mean throwing out notions of falsifiability? Smolin counters by noting that the time scales involved should increase the chances that any theory could also make falsifiable predictions. It is after all what natural selection does. Smolin:
As Roberto Mangabeira Unger and I argue in our new book The Singular Universe, the most important discovery cosmologists have made is that the universe has a history. We argue this has to be extended to the laws themselves. Biology became science when the question switched from listing the species to the dynamical question of how species evolve. Fundamental physics and cosmology have to transform themselves from a search for timeless laws and symmetries to the investigation of hypotheses about how laws evolve (emphasis supplied).
The physicist, however, acknowledges "bedeviling metaphysical baggage" haunts these kinds of questions. We are, after all, metaphorical machines. Interested in things as they are, we live as creaturely poets in a beglamored space between, describing ever-always what things are like. Our analogies hold us back.
For fans of popular physics and the humanities majors among us, the lengthy email exchange between science journalist and scientist will reward.
While reading it, I was reminded of a favorite video of mine, in which Mars scientist Nathalie Cabrol argues passionately that we must "explore or die." The parallel is certainly far from exact, but change, whether in the inanimate or animate worlds, is inescapable. I've posted it here for you to watch.