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A meta-theory of physics could explain life, the universe, computation, & more

#1
C C Offline
https://www.gizmodo.co.uk/2020/08/a-meta...-and-more/

EXCERPTS: You may think of physics as a way to explain the behaviours of things like black holes, colliding particles, falling apples, and quantum computers. But a small group of physicists today is working on a theory that doesn’t just study individual phenomena; it’s an entirely new way to describe the universe itself. This theory might solve wide-ranging problems such as why biological evolution is possible and how abstract things like ideas and information seem to possess properties that are independent of any physical system. It’s called constructor theory, but as fascinating as it is, there’s one glaring problem: how to test it.

[...] While many theories are concerned with what does happen, constructor theory is about what can possibly happen. In the current paradigm of physics, one seeks to predict the trajectory of, say, a wandering comet, given its initial state and general relativity’s equations of motion. Constructor theory, meanwhile, is more general and seeks to explain which trajectories of said comet are possible in principle. For instance, no trajectory in which the comet’s velocity exceeds the speed of light is possible, but trajectories in which its velocity remains below this limit are possible, provided that they are also consistent with the laws of relativity.

The prevailing theories of physics today can explain things as titanically violent as the collision of two black holes, but they struggle to explain how and why a tree exists. Because constructor theory is concerned with what can possibly happen, it can explain regularities – any patterns that warrant explanation – in domains that are inherently unpredictable, such as evolution.

Constructor theory can also capture properties of information, which do not depend on the physical system in which they exist: The same song lyrics can be sent over radio waves, conjured in one’s mind, or written on a piece of paper, for example. The constructor theory of information also proposes new principles that explain which transformations of information are possible and impossible, and why.

The laws of thermodynamics, too, have been expressed exactly in constructor theory; previously, they’d only been stated as approximations that would only apply at certain scales. [...] By recasting the laws of thermodynamics in terms of possible and impossible transformations, rather than in terms of the time evolution of a physical system, constructor theory has expressed these laws in exact, scale-independent statements...

[...] The basic ingredients of constructor theory are the constructor, the input substrate, and the output substrate. The constructor is any object that is capable of causing a particular physical transformation and retains its ability to do so again. The input substrate is the physical system that is presented to the constructor, and the output substrate is the physical system that results from the constructor’s transformation of the input.

For a simple example of how constructor theory might describe a system, consider a smoothie blender. This device takes in ingredients such as milk, fruits, and sugar and outputs a drink in completed, homogenised form. The blender is a constructor, as it is capable of repeating this transformation again and again. The input substrate is the set of ingredients, and the output substrate is the smoothie.

A more cosmic example is our Sun. The Sun acts as a nuclear fusion reactor that takes hydrogen as its input substrate and converts it into helium and light as its output substrate. The Sun itself is the constructor, as it retains its ability to cause another such conversion. In the prevailing conception, one might take the Sun’s initial state and run it through the appropriate algorithm, which would yield a prediction of the Sun’s ending once it has run out of fuel. In constructor theory, one instead expresses that the transformation of hydrogen into helium and light is possible. Once it’s known that the transformation from hydrogen to helium and light is possible, it follows that a constructor that can cause such a transformation is also possible.

Constructor theory’s fundamental principle implies that all laws of physics – those of general relativity, thermodynamics, quantum mechanics, and even information – can be expressed as which physical transformations are possible in principle and which are not. This setup is, perhaps counterintuitively, extremely general. [...] Because explaining which transformations are possible and which are impossible never relies on the particular form that a constructor takes, it can be abstracted away, leaving statements about transformations as the main focus of constructor theory. This is already extremely advantageous, since, for instance, one could express which computer programs or simulations are realisable and which are not in principle, without having to worry about the details of the computer itself.

[...] Samuel Kuypers, a physics graduate student at the University of Oxford who works in the field of quantum information, said that constructor theory “has unequivocally achieved great successes already, such as grounding concepts of information in exact physical terms and rigorously explaining the difference between heat and work in thermodynamics, but it should be judged as an ongoing project with a set of aims and problems.” Thinking of potential future achievements, Kuypers hopes that “general relativity can be reformulated in constructor theoretic terms, which I think would be extremely fruitful for trying to unify general relativity and quantum mechanics.”

Time will tell whether or not constructor theory is a revolution in the making. In the few years since its inception, only a handful of physicists, primarily at Oxford University, have been working on it. Constructor theory is of a different character than other speculative theories, like string theory. It is an entirely different way of thinking about the nature of reality, and its ambitions are perhaps even bolder than those of the more mainstream speculations. If constructor theory continues to solve problems, then physicists may come to adopt a revolutionary new worldview. They will think of reality not as a machine that behaves predictably according to laws of motion, but as a cosmic ocean full of resources capable of being transformed by an appropriate constructor. It would be a reality defined by possibility rather than destiny... (MORE - details)

RELATED: Using constructor theory to explain free will
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#2
Zinjanthropos Offline
How’s this tie in with the universe starting from nothing? Suppose starting from something might also make one ask where did the something come from. So I think it appears this theory might not be able to explain origins other than a constructor did it with the material at hand, even if there wasn’t any.

When I try to make sense of the universe I can’t help but wonder why there are so many subatomic particles, some arranged into larger particles/objects, but there‘s only so many ways they can come together. Is there a limit to amount of construction material available in the universe? Would all the elements in the Periodic Table be possible without the first element and whatever was available before that? Seems endless. It’s like being a kid supplied with a box full of Legos who starts building something.
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#3
Syne Offline
(Aug 26, 2020 08:22 AM)C C Wrote: It’s called constructor theory, but as fascinating as it is, there’s one glaring problem: how to test it.
If it can't be tested, it's not science, much less physics.
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#4
C C Offline
(Aug 26, 2020 06:12 PM)Syne Wrote:
(Aug 26, 2020 08:22 AM)C C Wrote: It’s called constructor theory, but as fascinating as it is, there’s one glaring problem: how to test it.
If it can't be tested, it's not science, much less physics.

That's the sensationalism or drama of the writer addressing it in the beginning like it's an "object-level" theory (as he puts it further down), but then clarifying (as in title) that CT is a "is a theory about theories ... its statements are laws about laws."

Elsewhere: Constructor Theory is a new approach to formulating fundamental laws in physics. Instead of describing the world in terms of trajectories, initial conditions and dynamical laws, in constructor theory laws are about which physical transformations are possible and which are impossible, and why. This powerful switch has the potential to bring all sorts of interesting fields, currently regarded as inherently approximative, into fundamental physics. These include the theories of information, knowledge, thermodynamics, and life.

Deutsch: "... this is going to provide a new mode of description of physical systems and laws of physics."

As Chipkin says in that article: "Constructor theory’s fundamental principle implies that all laws of physics – those of general relativity, thermodynamics, quantum mechanics, and even information – can be expressed as which physical transformations are possible in principle and which are not."

So right there is a test or challenge with regard to its type of claims, and far from being one that can't be conducted. We'll see over time whether it can indeed do that. Samuel Kuypers asserts that constructor theory has "already unequivocally achieved great successes already". I have no idea if that's the case or not -- again, time will tell more clearly.

A statement like "If a theory doesn’t make a testable prediction, it isn’t science" is itself prescriptive rather than predictive of specific empirical events via experiment. It's not testable in that context, either (like a horde of other presuppositional, philosophical, and guideline baggage and formal standards in physics). "Oughts" apparently rely upon the consequent general results or the feelings of practitioners that science has been "bettered" by following them. 

Constructive theory arguably has a prescriptive aspect from the standpoint of "we should use this new descriptive system and its concepts for understanding and organizing things, and representing laws". And would similarly rely upon the desires and projects of scientists being improved/overcoming problems or not after adopting it. Or making no significant difference whatever.
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#5
Syne Offline
You know what is a theory about theories and statements about laws? Philosophy of science. That already tells us what is possible, utilizing the known standards of evidence. Recasting that as something in between philosophy and physics would only seem an attempt to bolster the reputation of the former while harming the precision of the latter. It sounds much more like people desperate to make some pretense at progress than any tangible result, of which there don't seem to be any.

And arguing differing philosophy of science views, e.g. what's prescriptive, has no bearing on the pragmatic question of whether something can be demonstrated.
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