Comment by breatheoften | Hacker News Reader

Comment by breatheoften | Hacker News Reader

I don't have any sense for how much the author is contributing to any discussions of worth -- but I do struggle with the phrase 'foundations of physics'. To me 'foundation of' invites comparison to similar uses in other domains -- in math where it tends to concern the nature of argument, or to computer science where it concerns mechanisms for accomplishing defined goals efficiently or reasoning about program performance/semantics, or to engineering where it concerns such things as stacking rocks and balancing forces so as to ensure that a given way of stacking is probably capable of lasting for a certain amount of time.

But why exactly should 'high energy physics' be considered more 'foundational' than other domains of physical observation? Particle physics pursues description of effects that can occur at very small sizes - but are there _really_ such tight linkages from the observational domain of particle physics to observable 'larger scale' physics such that one truly deserves to be labeled 'foundational' for the other?

Just to pick a domain out of a hat, when modeling things like electromagnetic potentials in material science, actively investigated theoretical models are coarse grained so far beyond the scale of the probing done in particle physics that I have wonder how much are the 'foundational' theories and the larger scale ones ever really expected/required to be consistent with each other ...?

If 'foundational' isn't a statement about the direction of the consistency requirements the components of argument - then what exactly is it a statement about?

As long as you hold onto the assumption that all physical phenomena on the macro scale can in a (perhaps not useful) sense be explained reductively by particle/field physics of some sort, it's clear that poking at the particle/field/whatever substrate is more foundational than studying high level emergent phenomena. That isn't to say that high-energy particle physics is the best or only avenue of fundamental exploration; obviously, much of the last century's advancements came from cosmology.

There's nothing wrong with studying condensed matter physics, and there is a huge amount to learn. But I don't see a conceivable way in which discoveries made by studying complex behavior closer to our scale will help solve quantum gravity or dark matter.

Then again, if humanity were one big game of Civilization, I'd be directing my tech tree towards engineering and applied physics research at the moment: we probably don't need any more fundamental physics to build sustainable fusion reactors.

> But I don't see a conceivable way in which discoveries made by studying complex behavior closer to our scale will help solve quantum gravity or dark matter.

In the main I only see reason and balanced in this post, but this particular statement is a bit risky. Historically, big breakthroughs in the sciences happen when new measurement techniques become available or existing measurement techniques are refined to produce a "significantly" greater level of accuracy.

A breakthrough in our understanding of reality could come from anywhere that anyone pushes the bounds of what we can measure; which admittedly is probably the folk with the budget for a big particle accelerator, but one could imagine a path for almost anybody to make a contribution. One of the take-aways of the whole quantum vs classical business is that just because the evidence seems to be converging on a well respected model doesn't mean that the evidence is actually going to converge.

I definitely agree with you and mathgenius that mathematical techniques and technological progress created while investigating macroscopic behavior may be useful for making breakthroughs in "fundamental" physics. There is certainly precedent for that sort of thing. Perhaps complexity theory will have some significant impact on physics this century, who knows. But it's unclear whether there's anything that pure mathematics or mathematical analogies to the macro world can tell us about how gravity and quantum mechanics are unified, or any of the other big open questions at the bottom.

There is a large overlap of mathematical techniques between cond-mat and high energy physics. This has led some to speculate that particles are just excitations in some deeper "condensed matter" substrate.

Overall I find Hossenfelder's attitude to be far too negative. I'm fine with canning the big particle accelerators, but apart from that, there is a huge amount of exciting research going on in physics, theoretical physics (not just high energy stuff!), and mathematics.

> There's nothing wrong with studying condensed matter physics, and there is a huge amount to learn. But I don't see a conceivable way in which discoveries made by studying complex behavior closer to our scale will help solve quantum gravity or dark matter.

Interestingly, this does actually work out. Excitations in solids are often described by quantum field theory, and many of the exotic ideas of field theorists in fundamental physics turned out to be things you can actually find in a sufficiently exotic material.

She is not claiming that high energy physics is foundational. The foundations of physics are the main theories on top of which the whole edifice is built. In physics, these foundations include the Theory of Relativity and the Standard Model of Particle Physics.

We know that the foundations are incomplete because the Standard Model cannot be combined with General Relativity, although there is overwhelming empirical evidence in favor of both. They also fail to predict Dark Energy and Dark Matter. So we know that there is something foundational we don't know. One of the hopes of finding out what this is is to gather more empirical data (also allowing one to put many hypothesis to the test along the way). On the side of the Standard Model, high particle physics provides the theoretical and experimental framework to gather more such empirical data, that being the purpose of the particle accelerators. The author is lamenting that these efforts did not produce the results we were hoping for, and that they did not lead to any breakthrough on the foundational mysteries.

I do not quite agree with your foundations of Computer Science. For me, these are the theoretical constructs that give sense to everything else, for example Turing Machines and the main results on Turing Machines. Perhaps also Lambda Calculus, or at least combinatory logic and so on.

Another example: in modern Biology, the concept of "imperfect replicator" is foundational. If you remove that piece, the whole edifice crumbles into stamp collecting.

> in modern Biology, the concept of "imperfect replicator" is foundational

Can you share some references to this concept? Google Scholar with "imperfect replicator" doesn't help me much. Thank you.

It's just a very succinct and abstract description of the modern synthesis of Darwinism and genetic theory.

All organisms are self-replicating mechanisms, in the sense that they can generate a new organism that is built from the same DNA program (replicator) with mutations and possibly recombinations in the program (imperfect). The fact that the replications are imperfect is what allows for evolution to emerge. Together with survival-of-the-fittest mechanisms, this explains why life is so complex, why this complexity tends to increase with time, why there are so many species and so on.

It is possible to understand many details of nature by building on this idea. Higher-order theories if you like: why do organisms from different species sometimes look so similar? Why do certain organisms, such as the peacocks, have features that seem so unpractical, etc. Without it, we would be left with just cataloging stuff, as we once were.

>Together with survival-of-the-fittest

There are actually many more mechanism in evolution, such as genetic drift or geographic separation. You're merely focusing on one special aspect of evolution here.

Biology in practice is a quite messy science.

Fitting quote:

Another curious aspect of the theory of evolution is that everybody thinks he understand it. I mean philosophers, social scientists, and so on. While in fact very few people understand it, actually as it stands, even as it stood when Darwin expressed it, and even less as we now may be able to understand it in biology (Jacques Monod)

> There are actually many more mechanism in evolution, such as genetic drift or geographic separation. You're merely focusing on one special aspect of evolution here.

No, it's not some ad-hoc aspect among many. Notice that I was trying to illustrate what it means to say that some theory is foundational in a field. It means that, if you remove it, the rest of the edifice falls apart.

Imperfect self-replication and survival-of-the-fittest are foundational in that sense. You cannot make sense of concepts such as speciation through geographical separation, neutral mutations, theories about why genders exist, kin selection, eusociality, etc etc etc without those foundational pieces.

What you say is a bit like saying that the Theory of Relativity is just one special aspect of theoretical physics: there's also planetary dynamics, for example.

> Fitting quote:

The danger with these types of quotes is that they tend to end up applying to oneself.

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