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> Or am I just a lemur trying to figure out how an airplane works?

Unfortunately yes, all of us are.

This is not a problem with physics or abstractions. It's a problem with our intuition. Our intuition is based on evolution and life experience, which is all formed based on mostly solid objects from 1cm to 100m moving at 1m/s to 100m/s.

The universe however does not care what meatbags can experience with our senses. It doesn't mean that our complex math abstractions are necessarily correct - but they are more correct than casual intuition. You can train that intuition with enough work with the maths.

For example, you can map most of basic electricity to water flow and pressure, and some electromagnetic waves to waves in water - but you need to make a small jump to abstraction to combine both, and a large jump to get a gut feeling for special relativity to "feel right".

The crazy part is really that mathematical abstractions exist for all these things at all. There seems to be no natural reason that physics should be describable by small elegant formulas at all, let alone our experience of throwing rocks into a pond. Why isn't particle physics as messy as organic chemistry?

You are looking at it from the wrong way.

It is not nature that describes itself in math, it's people who describe in math what their current understanding is of how nature works. The more mathematical simplicity in the formula, the better we understand it.

Organic chemistry is harder because our powers to observe it are computationally and experimentally limited at this point.

Human intuition is based on limited sensors, boundaries which we have overcome with science and applied science over time. Our intuition had to be collectively replaced with rigorous mathematical methodology to incorporate these foreign sensors.

Yes. First, intuition depends on your experience. If you never studied physics, most things will be nonintuitive (heavy bodies don't fall faster than light ones? really?)

Second, modern 20th century physics education (courses, textbooks) suffered sustained corruption of methodology by scientific authorities, where the quest for understanding was renounced in favor of "modelling" and "prediction" (e.g. authors of orthodox quantum theory and their less bright pupils perpetuating that attitude) and later by institutionalized system of university research which propels tweaking and applying old ideas to detriment of trying new ones or questioning past ideas that are too ingrained.

This leads to a large portion of theoretical physics publications being more and more about complex calculations where most applicators do not even try to understand "what is going on", they just assume the same quantum methodology with some tweaks (i.e. different configuration spaces, more dimensions, different Lagrangians, new fields that fix problems of the previous ones, tricks with removing some ugly series terms etc).

Sometimes these tweaks get fancy names (superstrings, loops, dark matter) but they are really an additional concept that needs to be put in to save the edifice from those radicals who would like to try actually new and incompatible ideas.

When you study 20th century physics yourself from original sources, you'll find the stuff taught currently actually has highly varying degree of credibility. Some stuff is rock solid, such as relativity, molecular theory and chemistry, nuclear physics and solid state theory, and some stuff is ... well, more unfinished and less credible - such as standard model, force unification, quantum gravity, dark matter, etc.).

If you want to get some solid ground on which to build intuition, start with the rock-solid physics as known till 1905, then after that makes sense, learn about its problems (explanation of emission spectra, inconsistency of EM theory with Newtonian mechanics), then after that take a deep breath and read original papers on quantum theory and particle/nuclear physics.

This will take years to understand. The later theoretical stuff around Standard Model details (lepton generations, stability of particles, unification of gravity and QFT) is a decades old project that nobody knows how to finish. It is stuck for now, and has little relevance for understanding those previous things.

Yeah, if the author of the parent comment is willing to put in work to get the understanding they claim to want, this is the way to go

Hm. Comparing paradigm shifts with model based realism is not really valid criticism of either, yet understandable.

The folks who just added one more term to the old stuff to make it predict better - let's call them the old guard necessarily did it to point out that old models can become slightly new ones too. Even if in the long run they will be seen as the evil holdouts.

Yet at the same time we know that just whipping up a new fancy maths model won't solve anything in itself. New models need to make new testable predictions.

And then even new models require lengthy fine tuning, which requires costly experiments.

Alas textbooks are very often terrible, but not because they emphasize predictions and models over "understanding" - but usually because they omit to elaborate on how to select the better of two models, how paradigm shifts happen, how anomalies are ever present - and thus make practical model selection even harder. Plus they regularly fuck up the math explanation part, exactly because they use terrible language and models.

Finally, it's always data that cleans up the mess. Either practical usefulness - engineering, applied science. Quantum experiments, q-bits, and so on. And on the high-energy end cosmology and astronomy.

Anyone harking about how the crisis is about politics usually wants to allocate more money to theorists, so we will finally get breakthrough theories. Yeah, great, we already have a lot of those, but without data we don't know which one to take seriously.

Furthermore pouring money into theory is a nice idea, and comparatively cheap (compared to a new collider), but that won't solve the very pragmatic employment question for the collider builders. (Who are out of luck anyway, because the era of building bigger underground circles seems to be over. But they would gladly build anything, but they won't make good theorists, even if pundits' articles seem to imply there's a simple slider between theory and experimentation.)

As a layperson I recommend watching the PBS Spacetime channel on YouTube: https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g

Certainly the complexity of the experiments shows why theories are so complicated. The neutron wasn't even observed until 1930, with an experiment that fits on a tabletop. Even into the 1940s you could put together a cyclotron in a lab and discover a new particle. Or observations of the cosmic background radiation, which were made with a 6 meter radio dish in suburban New Jersey. Now most research requires a facility that only governments are willing to fund. If it were easy, it would have been discovered by now.

The casual observer hasn't been able to understand the forefront of physics for a very long time. Maxwell's equations have been known for 150 years[1], but the average high school physics student hasn't the foggiest idea of what a differential equation is. At best, they have a vague understanding that electricity and magnetism are more-or-less interchangeable.

Once you get into invisible forces acting across very small distances, nothing about how the world works is 'intuitive'. The most precise description of it is... A bunch of math, and not the kind of math that people learn in their K-12.

[1] As has entropy, and the laws of thermodynamics. Yet even educated people often have no idea of what the laws of thermodynamics actually imply! You'd figure that people would take a little bit of an interest in them, given that they live in a society powered by combustion engines...

Good point. I work on laser amplifiers, and I struggle to get clear on what Planck said in 1899. I'm definitely not caught up with where physics was in 1920.

Hearing casual observers talking about quarks or dark matter just makes me run the other way. I know I don't know.

A great deal of (19th century) thermodynamics has its roots in the desire to engineer better steam engines. Entropy as an example has been introduced as an abstract concept to get to engines with better efficiency. Even when statistical thermodynamics was suggested (which makes of a less abstract and more intuitive understanding of thermodynamics) it was strongly opposed by many of the pundits at that time.

> 2. What does it even mean to create more space? The universe is expanding. Ok, I can accept that. But what does it mean?

Consider several droplets of water on the surface of a latex-based birthday balloon. The balloon is inflated, and droplets spread further apart, yet each droplet retains its shape and size. If you measure the distance in droplets it appears that you have created space as more new droplets could now fit in between those placed earlier.

We only have two comprehension tools to help in grasping the universe - math and intuition. The above is intuition, and you know better than me where to find math. There isn't more "meaning" to it than that, just the tools.

Another way to think about it is just that if you had two solid particles, and measured the distance between them, you'd find it had increased over time.

Space everywhere is expanding, it's just all the other forces over short distances ensure that everything pulls itself back together. The Big Rip - if dark energy is increasing in strength - is what happens when at some point the rate of expansion exceeds the forces at various scales that are able to hold things together, till even the strong nuclear force can't sustain it.

Everything you touch on - except the Heisenberg uncertainty (which is due to fundamental property of any finite signal, shown through a Fourier transform) - is a big (really mind-boggling) anomaly of current contemporary physics/cosmology.

Just the other day right here on HN was a link posted about dark energy, and how maybe it's just measurement calibration error. Poof, solved. Or not, we shall see.

Reading about the statistics and epistemology behind the experiments (Andrew Gelman's blog) and models (eg why preferably hierarchical Bayesian models) will help a lot to cut through the problem of understanding and satisfaction. (Rarely we can have both for complex issues.)

Oh, and everything is a field. Fields are coupled (coupling constants, running couplings). Some fields' have non-null base energy state. (So vacuum energy is non-zero. Maybe. It depends how many and which fields your model deals with.)

Some kind of energy wiggle in some fields translates to one/two/a-lot of wiggles in other/the-same fields. (See the Feynman diagrams, how there are infinite number of possible but decreasingly probable interactions between "particles".)

What is a force? It's just one well separated aspect of the whole model. Ultimately we think all of them are coupled into one big interaction that involves every field. See the electro-weak unification.

Why gravity doesn't seem to be able to attract? Because maybe it's not a field, it's just the shape of spacetime warped by energy and we haven't found negative energy. (Einstein's General Relativity) Or it's just based on entropy and thus it's a very strange emergent property of our universe. ( https://en.m.wikipedia.org/wiki/Entropic_gravity - bonus, it explains dark matter too, so maybe it's simpler - but it's just the ugly MOND (modified Newtonian) in disguise, noooo!) Okay, so maybe back to higher dimensions and branes and loops and strings? But nobody understands that! So we wait.

Why three? Because so far we found three and thus our models reproduce exactly that many.

Re: "Does anyone else feel like the abstractions and models in physics have gone passed the point where the casual outsider (even a technically and scientifically minded one) can no longer intuitively understand it?"

That's how I feel when using Twitter Bootstrap compared to the WYSIWYG days of VB-classic and Delphi. Like Quantum Physics, getting Bootstrap right relies on probability and killing of cats, or at least hair follicles. (Our shop probably needs a dedicated UI coder, but office politics won't allow it.)

> 1. I originally thought the Heisenberg Uncertainty principle was a natural consequence of using particles (photos) for measurement. Instead however it seems to be a fundamental property of the universe, which I only learned after finding out most of the mass of hadrons comes from the relativistic motion of quarks and it explains why hadrons don't collapse to a point.

> 2. What does it even mean to create more space? The universe is expanding. Ok, I can accept that. But what does it mean?

IME both QM and Relativity are much more easily understood if you start from the actual equations and/or an undergrad textbook. I don't think physics is - yet - beyond the technical and scientific minded amateur who is willing to read and understand some equations. But it's probably gone beyond the ability of any science journalist to render into prose.

> 3. I find the models for dark matter and dark energy to be... unsatisfying. I realize there's experimental evidence for unobservable mass but it feels like a fudge.

I think working scientists would agree with you at least as far as dark energy goes. Dark matter is pretty indisputably just some kind of matter that we can't see (see e.g. the Bullet Cluster) - there's still something to be solved in terms of figuring out what it actually is, but I don't expect that to be major new physics. But as to dark energy: yeah, it's a fudge. Everyone knows it's a fudge. But it's still our best description of reality. Even if you knew there was something wrong with epicycles, they were still the best way to calculate planetary orbits at the time.

> I could go on. I don't for a second mean to suggest any of these notions are wrong. It's just that the models have gotten so complex (it seems?) that it just feels like something huge is missing, something that will eventually seem obvious in hindsight. Or am I just a lemur trying to figure out how an airplane works?

I think models aren't complex so much as unfamiliar. We're getting further and further away from everyday experience, and so more and more of the fundamentals of reality have to be understood from mathematical first principles rather than everyday intuition.

The models are actually really good though. Certainly once I understood QM it seemed so clear and simple that it couldn't possibly not be true.

> We're getting further and further away from everyday experience, and so more and more of the fundamentals of reality have to be understood from mathematical first principles rather than everyday intuition.

How much of that is an insistence on thinking of things in terms of fundamental particles and definitive properties instead of fields and packets of energy? I guess the question is that what the mathematical models are really about, and whether we're just having a hard time shrugging off Greek atomism and 19th century materialism when it comes to intuition?

Intuition could be built on top of a solid understanding of fields, backed by the math. The difficult part is connecting that to the classical world of our size that we experience.

> How much of that is an insistence on thinking of things in terms of fundamental particles and definitive properties instead of fields and packets of energy? I guess the question is that what the mathematical models are really about, and whether we're just having a hard time shrugging off Greek atomism and 19th century materialism when it comes to intuition?

I don't think it's "Greek atomism and 19th century materialism" to imagine a world made of persistent physical objects in well-defined positions. That's the entirety of everyday life.

Consider the competing ontological views: everything is made up of water, the five elements, everything is a sphere, the world is a simulation, everything is ideas being perceived by the mind, the world is matter formed by the ideal forms, etc.

Those views were prominent among certain intellectuals at different times which go against the grain of everyday experience. Since physicists are trying to understand the fundamental nature of the world, I take it they're used to not accepting appearance as a guide, and are rather operating under whatever philosophical intuition is dominant at the time. Since 19th century physics confirmed the existence of atoms, and the periodic able of ordinary matter is made up of atomic bonds, then it makes since that physicists have been influenced by that guiding intuition.

Regardless, fields are probably a better building block for intuition than particles.

I'll take a shot at trying to answer some of your questions:

1. I originally thought the Heisenberg Uncertainty principle was a natural consequence of using particles (photos) for measurement.

That's the observer effect. When quantum mechanics was first constructed, it was believed that the uncertainty principle could be explained that way. As you mentioned, today, it is considered a more fundamental feature of the theory. As an analogy, consider how a signal sharply located in the time domain gets smeared out in the frequency domain, and vice versa. It's kind of like that.

2. What does it even mean to create more space? The universe is expanding. Ok, I can accept that. But what does it mean?

Specific volume (the average volume occupied by a unit of mass) increases. If the universe was spatially finite, so would total volume.

3. I find the models for dark matter and dark energy to be... unsatisfying. I realize there's experimental evidence for unobservable mass but it feels like a fudge.

Shrugs. If dark matter turns out to in fact be just a bunch of yet to discovered particles, that wouldn't be too strange. Dark energy is more of an unknown.

4. Of course we still have no quantum model for gravity.

That's an issue.

5. I don't really understand what a fundamental force really is. Like why does electromagnetism have a repulsive opposite but gravity doesn't? When I tried to look into this I ended up down some rabbit hole of "gauge forces" and got completely lost.

For now, there's a certain amount of arbitrariness involved: We could easily construct universes that worked differently. Furthermore, gravity is special: At the classical level, it's not a regular force, but a pseudo-force (a consequence of Newton's first law). Also note that it can in fact manifest repulsively (eg via the cosmological constant). From the perspective of particle physics, it's also special because the hypothesized force carrier (the graviton) would have spin 2 instead of 1.

Why is the Higgs Field not a force?

To my knowledge, there should be an effect one could call Higgs force. It would be tiny.

6. Why are some predictions of the Standard Model so incredibly accurate (like the magnetic moment of an electron IIRC?) while others are so incredibly inaccurate (eg IIRC the QFT prediction of vacuum energy is off by 120 orders of magnitude).

Quantum Electrodynamics can be solved perturbatively. We know how to do that. Things that can't be handled that way tend to be hard.

Regarding vacuum energy, you'd have to account for every fundamental field there is to get it right, so no surprise we get it wrong. Also, given that we have no quantum theory of gravity, it's not even clear to me that it is even the right approach.

7. Why are there exactly three generations of particles (ignoring the Higgs)?

Figure that out, get a Nobel prize. It could even be arbitrary, like how it's futile to ask why a particular snowflake looks different than another snowflake created in similar conditions: Random chance.

Hope that helps a bit.

> It's just that the models have gotten so complex (it seems?) that it just feels like something huge is missing

Why shouldn't it be complex? The universe is complex. It's amazing that it's so simple, really.

1. Blame stupid pop-sci books. Anyone reading an actual QM book will know it's an intrinsic property.

2. again pop-sci books.

3. You and anyone not blinded by non-scientific factors...

6. The math we use for those calculations is adhoc bullshit and no one has been able to place it in a solid foundation.