We at the Foundational Questions Institute have often been asked what exactly “foundational” means, and what relation it holds to “fundamental” as a term describing some branches of physics. Today we’re happy to turn the tables.They appear to be asking for a definition. It is not clear why one definition is better than any other.
It is time for the next FQXi essay contest, and so we ask, What Is “Fundamental”?
We have many different ways to talk about the things in the physical universe. Some of those ways we think of as more fundamental, and some as “emergent” or “effective”. But what does it mean to be more or less “fundamental”? Are fundamental things smaller, simpler, more elegant, more economical? Are less-fundamental things always made from more-fundamental? How do less-fundamental descriptions relate to more-fundamental ones? ...
We are open for entries from now until January 22, 2018.
I sometimes see physicists and philosophers of science act as if "fundamental" were some well-agreed concept. They will say, for example, that the Schroedinger equation (for the time evolution of the wave function of quantum mechanics) is fundamental, while the collapse associated with an observation is not. Or that particle physics is fundamental, and solid state physics is not. Or they say that reversible physics is fundamental, while irreversible physics is not.
They further explain:
Interesting physical systems can be described in a variety of languages. A cell, for example, might be understood in terms for example of quantum or classical mechanics, of computation, or information processing, of biochemistry, of evolution and genetics, or of behavior and function. We often consider some of these descriptions “more fundamental” than other more “emergent” ones, and many physicists pride themselves on pursuing the most fundamental sets of rules. But what exactly does it mean?The string theorists over-hype their field with claims that they are the only ones studying what is truly fundamental. Otherwise, no one would pay attention to them.
Are “more fundamental” constituents physically smaller? Not always: if inflation is correct, quanta of the inflaton field are as large as the observable universe.
Are “less fundamental” things made out of “more fundamental” ones? Perhaps – but while a cell is indeed "made of" atoms, it is perhaps more so “made of" structural and genetic information that is part of a long historical and evolutionary process. Is that process more fundamental than the cell?
Does a “more fundamental” description uniquely specify a “less fundamental” one? Not in many cases: consider string theory, with its landscape of 10500 or more low-energy limits. And the same laws of statistical mechanics can apply to many types of statistically described constituents.
Is “more fundamental” more economical or elegant in terms of concepts or entities? Only sometimes: a computational description of a circuit may be much more elegant than a wavefunction one. And there are hints that even gravity, a paragon of elegance, may be revealed as a statistical description of something else.
This contest does not ask for new proposals about what some “fundamental” constituents of the universe are. Rather, it addresses what “fundamental” means, and invites interesting and compelling explorations, from detailed worked examples through thoughtful rumination, of the different levels at which nature can be described, and the relations between them.
I have submitted essays to FQXi in the past, and some were favorably review by the online community, but last year my essay was censored.