Dear David,
To celebrate your 70th Birthday, here are my musings on one of constructor theory’s key ideas. I first stumbled upon it while reading your early writings on that topic (during the first year of my DPhil), and it has fascinated me ever since.
The idea is that all the various branches of fundamental physics are expressible as theories explaining the limitations of programmable machines (constructors).
For instance, studying the repertoire of universal quantum computers is equivalent to studying the foundations of quantum theory. Likewise, all physical laws are expressible as constraints on what the universal constructor can or cannot do. Hence the whole of physics coincides with an explanatory theory stating the limitations of the universal constructor's repertoire. That theory we call 'constructor theory': it provides the ultimate unification of thermodynamics, information theory and the theory of living entities. Surprisingly, we can express it by referring only to what transformations are possible or impossible, without ever mentioning particular constructors.
This idea is striking because it implies that some regularities displayed by emergent and macroscopic entities like constructors (traditionally considered non-fundamental) are the basis of fundamental physics. This fact is surprising and counterintuitive, and it's the heart of constructor theory as a new approach to formulating the laws of physics.
It also has unexpected implications for seemingly unrelated issues. For example, it may come to the rescue to address the so-called 'fine-tuning' problem. In the traditional conception of physics, this problem has this formulation: a slight variation in the dynamical laws of the universe (according to some appropriately chosen metric) results in radically different physics, which, e.g., does not allow for phenomena such as ordinary chemistry, replication, and life. But in constructor theory, a 'slight variation' of the laws may not result in such a radical change. That's because a slight variation in constructor-theoretic terms would consist of slightly changing the repertoire of the universal constructor. What this means in exact terms is an open problem, but it will be very different from the notion of a 'slight variation' in a dynamical law. This line of thought could offer an exciting way out of the fine-tuning problem –something that perhaps you will find amusing.
I wish you the happiest 70th Birthday that the laws of physics can permit. May it be yet another beginning of infinity!
Chiara
To celebrate your 70th Birthday, here are my musings on one of constructor theory’s key ideas. I first stumbled upon it while reading your early writings on that topic (during the first year of my DPhil), and it has fascinated me ever since.
The idea is that all the various branches of fundamental physics are expressible as theories explaining the limitations of programmable machines (constructors).
For instance, studying the repertoire of universal quantum computers is equivalent to studying the foundations of quantum theory. Likewise, all physical laws are expressible as constraints on what the universal constructor can or cannot do. Hence the whole of physics coincides with an explanatory theory stating the limitations of the universal constructor's repertoire. That theory we call 'constructor theory': it provides the ultimate unification of thermodynamics, information theory and the theory of living entities. Surprisingly, we can express it by referring only to what transformations are possible or impossible, without ever mentioning particular constructors.
This idea is striking because it implies that some regularities displayed by emergent and macroscopic entities like constructors (traditionally considered non-fundamental) are the basis of fundamental physics. This fact is surprising and counterintuitive, and it's the heart of constructor theory as a new approach to formulating the laws of physics.
It also has unexpected implications for seemingly unrelated issues. For example, it may come to the rescue to address the so-called 'fine-tuning' problem. In the traditional conception of physics, this problem has this formulation: a slight variation in the dynamical laws of the universe (according to some appropriately chosen metric) results in radically different physics, which, e.g., does not allow for phenomena such as ordinary chemistry, replication, and life. But in constructor theory, a 'slight variation' of the laws may not result in such a radical change. That's because a slight variation in constructor-theoretic terms would consist of slightly changing the repertoire of the universal constructor. What this means in exact terms is an open problem, but it will be very different from the notion of a 'slight variation' in a dynamical law. This line of thought could offer an exciting way out of the fine-tuning problem –something that perhaps you will find amusing.
I wish you the happiest 70th Birthday that the laws of physics can permit. May it be yet another beginning of infinity!
Chiara