Confessions of a Theoretical Physicist

I am an ex-physist who stopped after his PhD in particle physics. I love physics but while money does not bring happiness, it is better to cry in a Mercedes than on a bike (this is not true, I just laughed when I first read it).

I went through the stages of OP (on a way smaller scale, I do not have his experience) and I think this is awesome. You continuously go from "oh yeah, now I get it" to "crap". This always have you on the bleeding edge between "this si physics, I know that" and "yes, but what if...". To me this is the essence of knowledge though curiosity.

I started my PhD on a specific topic and at some point I was a bit stuck (not panic mode stuck but pissed off stuck). I had dinner with a friend, we were discussing about my work (she is also a physicist) and she off-handly suggested something. And bam! my world changed. The direction of the thesis changed. I added an extra thesis director because what I was about to do was a world where the hands of men did not step on yet.

I thanked her profusely for her help in the thesis and suggested a joined publication (which she did not want to take because she was not interested and asked me to stop stalking her :))

And this is how science moves: because of eureka moments under the shower or at dinner or because someone thought "hmmm..." (looking at you Nikola Tesla).

So the fact that this guy doubts about what the world is, and that he is a theoretical physicist (so hopefully will not switch to some insanities) is awesome.

Humans are not “generally intelligent”; our intelligence is extremely well adapted to being a hominid family animal in a tribe or clan in a savannah habitat with large predators and hostile members of our own species lurking about.

Our senses and brains are well suited to reasoning about and making decisions in environments at “human” scales. By that, I mean that humans don’t receive relativistic, atomic or quantum phenomena directly with our unaided senses, and therefore our brains never developed intuition for these phenomena.

So it’s no surprise at all that our intuition completely fails us at those scales.

Again, our intelligence is not “general”; it’s hominid.

I could have been a theoretical physicist, but got out after my master’s. Subconsciously I think I had already come to this (the OP’s) conclusion then.

Since then I’ve worked a bit in statistics and machine learning. There’s a saying in this field that captures my subconscious conclusion well: “all models are wrong, but some models are useful”.

I’ve often said that I would have loved to do a PhD in physics in 1910, but less so in 2010. The models physicists found in the 20th century were extraordinarily useful. I have little hope that I will see anything comparable in my lifetime.

Don’t get me wrong: More models will undoubtedly be found, and there’s beauty and honor in that work. But they will most likely all be “wrong”, and far less useful than e.g. the models that let us harness nuclear reactions.

Do we care about "real" reality if we can, more or less, make sense of some of its manifestations through our senses?

That there is something deeper and unknowable and "informationally huge" seems obvious. We didn't bring quarks or quasars into existence, we "discovered" them as and when we extended our senses far enough using technologies (which are themselves a result of us becoming comfortable enough with our immediate reality, as a sort of positive feedback loop).

There is every reason to suspect that this deeper reality does not stop where our technologically extended abilities peter out. Our imperfect and tentative understanding when reaching the extremes of scales (of time, space, complexity, etc) is perfectly understandable. Why should a finite carbon brain be able to map out a coherent and finite model of something much, much bigger than itself.

On the other hand over millennia of brainstorming (literally) we have collected some interesting datapoints about this deeper reality: it is not "malicious", and somehow it agrees to be mapped by us (mathematically), even if in disconnected parts.

In fact this benevolent aspect of deeper reality has made us unusually cocky. Imagine the existential angst if the universe changed its laws at whim. We'd be back to praying. E.g., that gravity remains stable for a while so that we don't drift into space. This premature self-assuredness explains repeated scientific episodes of proclaiming "we have explained everything". This also feeds the sterile chase of "a theory of everything".

In fact the limits of our understanding are in front of our eyes, everywhere. We haven't really explained a single phenomenon in the so called "complexity science" domain. Deeper reality is all around us and the most dramatic and impactful scientific revolutions are still ahead of us.

I am a theoretical physicist, and I am very much in tune with the author. Take quantum mechanics (my field), it is clear that even though we have a working model of it, it doesn't explain how nature instantiates it. Entanglement is a prime example of this: I know exactly how to describe it, but nobody has a clue of how it works. In other words, physics is a mostly coherent and certainly useful story about reality, but it isn't grounded on "bedrock" reality, rather on our perception of it.

Sure, quarks and leptons are maybe a high-level concept that masks a more messy underlying reality, but surely quarks and leptons are less messy than dogs? There is an arrow of progress in the development of physical theories. I don't see a reason why a perfect description should not be possible.

It's refreshing to me to read articles like this. In the current climate of consensus science, and settled science. Here is someone well versed in Physics, and the Philosophy of it. Reminding people that we need to be humbled again.

Science is an open system. Everything is open to being "wrong"/"updated". There is nothing that grounds the system. You must be always open that your prediction of unobserved things will be wrong. To actually believe that science will one day solve the great mystery of the universe is scientism.

I'm not a physicist. An idea from physics that I recently learned and found very unnerving was that the solid objects we see and feel in the world are actually mostly empty space. We just see them as solid because of the way light interacts with the particles. So in a sense our visual and tactile perception of the world is just one representation of the underlying reality and you can imagine there being infinitely many other possible representations.

I'm just crudely saying the same thing as the author I think, but I wanted to emphasize how uncomfortable this makes me. In some sense it feels like being a prisoner in a perceptual cell you can't escape from surrounded by a reality you'll never know.

Having philosophy as a counterpoint (in my case dabbling in Buddhism) has been essential to keep me calm and relaxed.

Disclosure: I'm not a theoretician, but just an old industrial physicist who helps design measurement equipment.

What I've noticed is that most physicists are aware of the great epistemological puzzles, and may even have briefly dabbled in them, but also tend to ignore them if there's work to be done. There's a lot of pleasure and utility to be gained from just finding a hard problem and working on it, maybe even solving it, or inventing something.

When people find out that I'm a physicist, and ask me about those puzzles, I usually plead ignorance. I'm not dismissive of them, or anti-intellectual, but I think you shouldn't let them be an obstacle to the enjoyment of physics, either as a spectator or practitioner.

I'm in the final year of my PhD, and I feel very lucky to be working on the question of what it means for an explanation to be "good". The closest thing to a satisfactory resolution of the question of "reality" in theories, to me, is Dennet's Real Patterns [1]

It may well be that multiple explanations are consistent with the most basic phenomena. The criterion for the reality of the theory is whether it does better than random (its predictive power, equivalently how well it can compress the observational data). We can try to find the simplest explanation, but we can never know if we have it [2]. We can stop thinking of theories as being real or not in a binary sense, and merely ask how well they compress the data. Of course, different theories can achieve the same compression by compressing different aspects of the data! Your pattern can look like my noise :-)

Luckily and interestingly, the physics of the macroscopic world is in many cases effectively independent of the underlying microscopic rules [3], with the details of the microscopic physics being screened off as complexity emerges.

Personally, I like to think of abstraction as a kind of hierarchy of hardware + software: at each level, some useful ontology is picked out for stable patterns to emerge (e.g. the software of "fluids" emerging from the hardware of quantum "particles"). Layers of software at one level become the hardware substrate for the next rung up the abstraction ladder.

Luckily, we get to choose the software that runs on us, so don't forget to vote this fall ;)

[1]: https://ruccs.rutgers.edu/images/personal-zenon-pylyshyn/cla...

[2]: https://en.wikipedia.org/wiki/Kolmogorov_complexity

[3]: https://en.wikipedia.org/wiki/Effective_field_theory

There is some discussion below about evil, part of my study.

There could evil as judgement, as nature, as action, as consequences or as being.

One starting point is somehow someone can judge a being, a thought, an action and a consequence as evil. Is killing … it depends upon context so much … or should we just back to I or God or whoever think it is evil itbis evil?

Action if assume above seems easy. I or some beings know it is evil or not and act on it. It is an evil act.

It is when consequence are considered it is really complicated. It can change over time as an evil act can have good consequence in certain place and time.

Nature as evil or not is part of one major Buddha sect - Tien Tai claim Buddha has evil in its nature forever just not do it (if … )

Evil as a being like God?

The problem of evil in the religion context has a much wider issue one has to consider.

Physics is an empirical inquiry into the structure, composition and dynamics of the observable usensorium we inhabit. I find it just short of hybris to entertain any promise that the outcome can be more than a metaphor of the underlying reality. The whole quagmire of “the measurement problem” in quantum mechanics seems to largely come from misunderstanding Bohr’s philosophical objections on this difference between a theory of the measurable and the interpretation of the theory’s internal mechanics as evidence of the true reality it models.

Givens that twentieth century physics (apart from General Relativity) is based on Bohr’s foundation, no wonder people get confused.

The mathematization of physics hasn’t helped either. That Bell’s theorem “proves” something is language applicable to a mathematical structure, not to the physical world itself.

Yes, our models are never complete. As someone here already wrote: "all models are wrong, some are useful".

What makes me optimistic here is that since the enlightenment we have a good track record with arriving at better and better models. In the language of David Deutsch: We are arriving at better and better explanations, where the quality of an explanation is determined by rigidity ("how hard it is to vary") and reach ("in how many situations does it apply"). His books "The Fabric of Reality" is a great book by the way, he describes how the theories of evolution, quantum physics, epistemology and the theory of computation are connected with each other. The bit about good explanations is from "The Beginning of Infinity", also a very good read.

Near the end: "I believe that the quest to understand the reality of the universe must contend with the truncations imposed by the perceptual and cognitive limitations of the mind." Totally agree with him. Interestingly AGI will have different limitations. In fact different AGIs (transformers vs something not yet invented; or an AGI with an huge encyclopedic memory vs one without; or ones with different limitations of compute; etc. This touches on computability with limited or unlimited resources.) will have different limitations and be literally unable to understand each others' versions of reality.

There is little doubt left that materialistic reality (what people and even physicists usually mean when they say “reality”) is not the fundamental nature of reality.

This is the main philosophical, scientific and even cultural challenge today.

How can he be sure he's a theoretical physicist if he doesn't know reality exists at all?

The truth is, instead of reality, he would be better off questioning theoretical physics, which indeed does not exist outside the heads of academia.

His "questioning of reality" only happens philosophically (in other words, it is an academic farce), once he gets up to do some grocery shopping he sure knows what to buy so he can eat in order to survive. There is your objective reality.

Humans understand reality if they do not bury their heads in the sand. But academia can get in the way.

The Indian Philosopher that is gravely missing from the article is Nagarjuna. The kinds of questions the author raises, the path he is treading on, will benefit from the study of Shunyata Philosophy of Madhyamika school, especially Nagarjuna.

I am not alone in thinking this. I was surprised to see Carlo Rovelli talking about it in multiple occasions.

Heres one [0].

Nyaya and Madhyamika Philosophies still have many lessons that are not yet discussed in the spotlight.

[0]: https://m.youtube.com/watch?v=CgIfNuZs56w

I remember when I took my course of "Theoretical Physics" (so called, it was an Introduction to Quantum Field Theory in actuality) and I realized that particles do not exist. It was quite an enlightenment. Particles are a convenient description of Quantum Fields in the perturbative regime, but what Quantum Fields are is not known, not even at the mathematical level. When you live at frontier of knowledge, as a Theoretical Physicists, reality becomes fuzzy. But that's life.

The book Sublime Object of Ideology (Zizek) and a second volume due soon attempts an interdisciplinary reframing of the theory of everything - working with Quantum Physicists and Material Hegelian/Lacanian philosophy. I am a philosopher who works with theoretical physicists.

I mean, leptons are definitely real, not just concepts. An electron is a lepton, and an electron surely exists? You can spray individual electrons. If an electron is just a concept, it is in a sense that a tiger is just a concept, and in a sense it is, but that is not very useful thing to say.

We do not craft models of reality because reality and models have any kind of intrinsic connection. We craft models of reality because we value models.

That is arguably very funny.

“Yet these are concepts that reify a certain approximate sketch of the structure of the world. Physicists once thought that these categories were fundamental and real, but we now understand them as necessarily inexact because they ignore the finer details that our instruments have just not been able to measure.“

Thanks to Vijay for a thought provoking post. I like the juxtaposition of quantum gravity and neuroscience.

I think that it carries two messages, one trivial and one deep.

The trivial one is that physics builds on the human nature to build concepts. Both a jaguar and a quark are ideas that we extract from our perceptions, that we share with others and that help us to model and predict the world - quarks just need a more expensive microscope like the LHC. Sure eagles and prawns may have slightly different versions of concepts since they have different colour perception, but only marginally so.

A practical fellow like a physicist will be clear that when the concepts can make measurable predictions they are worthwhile (we call this meta concept "real"). It is not possible to store the full state of or compute the evolution of anything macroscopic to full precision - such as the positions and momenta of all the particles in a table. So concepts are the only things we can know about reality.

They argue that we may never be able to attain the deep underlying reality - either because it is theoretically unattainable or that we will continue to be resource limited. I contend that this dichotomy is false. It just may never be possible to attain deep underlying reality. The best we can do until we get there is to find some probabilistic rules that work in a pragmatic sense and to refine these tools over time.

[That's pretty much a restatement of the Copenhagen interpretation of 1922].

The deep one is that we are probably looking down the wrong end of the telescope. As far as I can tell (from popular neuroscience) is that our ability to model the perceptual / conceptual processes and how they compose into intelligence remains in the dark ages.

But, given that we each have 70 billion neurones or so, there is a lot of classical physics going on in our heads to make these concepts and we have practically no hard, proven theories about how this works. We are doing layers of pattern recognition and extraction and feedback that allows us to avoid being eaten by Jaguars.

So let's get a proper theory of intelligence. One that let's us work out which aspects of quantum mechanics are philosophically necessary to sustain our subjective experience of space and time. With a substrate with branching / collapsing features. Where time has an arrow with memory in the past and uncertainty in the future. Where cause and effect are loosely coupled. Where there is a notion of free will.

Some endnotes: - The quantum measurement problem is perhaps a limit of this theory - Perhaps the notion of computational reducibility is a stab in this direction [Wolfram] - Probably all you need is emergence for this and not a quantum brain [Penrose]

i can't read that due to the bobbing header. atrocious design.

So this is the new zeitgeist. Between AI, quantum fundamentals, disinformation, and a few other less obvious trends, "reality" is going to get less and less concrete and more and more contextual and non-binary.

Ultimately, we're all just living in an episode on Rick & Morty's galactic cable TV

Most likely, the nature of consciousness and reality are rigged in such a way that we cannot use our consciousness to decipher them. Any progress in that direction is useless and, at this point, almost ridiculous.

I didn’t know that Physics was about understanding reality (sure, from a romantic perspective yeah). I always thought it was about making our lives better (like any other branch of science).

I believe we will never find out what’s the real nature of reality. That doesn’t mean we should stop doing science, though: it makes human live better.

I believe that the “meaning of life” is not about the answer (science telling us what’s the actual meaning) but about the discovery process we embrace: knowing beforehand that we’ll never understand everything and nevertheless keep waking up every day to do the job.