Contemplating the End of Physics

Whenever this topic comes up I think of Philip Anderson's[0] paper "More is Different": https://cse-robotics.engr.tamu.edu/dshell/cs689/papers/ander...

It looks like most of the big ideas have been discovered (although physicists were saying this in the 1890s as well), but there are still many things whose collective behavior is not well understood.

[0]: https://en.wikipedia.org/wiki/Philip_W._Anderson

> While it is never safe to affirm that the future of Physical Science has no marvels in store even more astonishing than those of the past, it seems probable that most of the grand underlying principles have been firmly established and that further advances are to be sought chiefly in the rigorous application of these principles to all the phenomena which come under our notice.

That's Albert Michelson, famous by the Michelson-Morley interferometer, that you know, helped destroing some of those "grand underlying principles" of physics and lead the way to the modern relativity theories.

By the way, he said that after the experiment, when he already had the result. But before the most interesting consequences of it were explored. If you search for him on the web, there's another famous phrase with him impressed, saying that it only took one extra decimal to change everything.

We seem to hear the argument about the "end of physics" every so often, on multiple time scales. This argument usually arises in the context of high energy/particle physics. Unfortunately for those saying things like this particle/high energy physics is not equivalent to "physics". Its not the entirety, nor the majority of physics.

Yet we keep seeing this discussed as if it is. This isn't an HN issue. This is an contextual issue in the broader physics community.

I've raised this point here, and other places, before. It is important to understand that people claiming an end to physics, are usually being hyperbolic about one specific subfield that seems to have run into a set of dead ends for the moment. Not the entirety of physics.

As I've noted, this is a recurring theme throughout physics. Max Planck was apparently told that there was "nothing new to be discovered in physics"[1]. There are other examples of this throughout history. Some of these theories had the weight of government or religious institutions behind them (earth-centric view of the universe, etc.). To question them was to be labeled a heretic, a blasphemer, or worse.

Physics isn't over. Not by a long shot. If someone wants to argue semantics over "fundamental" vs "non-fundamental", they are welcome to, though their argument will only contribute to hastening the heat death of the universe[2]. That is, energy will be expended for no useful work.

There are existing deep, profound questions, which are ultimately fundamental in nature, that we have not answered yet. And our asking of these questions, has exposed other concerns over our understanding of "fundamental" ... really ... foundational ... physics.

Some of these questions are opening profound links between seemingly disparate fields. That is, physics is getting broader and more intricate. Just because one small (yes, really) subfield nears its end (really due to economic and time constraints, you can't spend infinite amounts of money to build the next generations of colliders), doesn't mean the rest of the subfields are.

[1] http://www.pbs.org/wgbh/aso/databank/entries/bpplan.html

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

The fact that we already know an awful lot of Physics doesn't mean we're any closer to even think about it. A few broad examples not in Applied Physics next:

We don't have a working and then fully boring computationally detailed theory of quantum gravity. We have candidates for BSM physics and BSM facts such as neutrino masses but we don't have a BSM SM. We have a 120 orders of magnitude problem with the cosmological constant. We don't know what this stuff that we call dark matter which shows up pretty much everywhere is. We don't have an actual mechanism for inflation. We don't even have hope for maths department rigorous QFT any time soon.

And then there's stuff like nuclear physics which is dark and full of models even when you know it's all somehow QCD, whose confinement problem isn't solved yet.

But then apparently people preach on the Internets that philosophical interpretations of QM are the real problems and some other people preach to their choir that spending money on actual experiments by actual particle physicists asking to do them for getting data that would help is a scientific waste unless you afterwards match somebody else's theory paper published beforehand.

I would happily contemplate the end of musing about the future of fundamental Physics so we all could focus on the meat and potatoes of Physics, which is maybe a less fun and a bit more technical endeavour but also surely a more productive one.

As a complete non-physicist (whatever that means), I feel uncomfortable about this quote in general (or the thinking related to it) for some reason:

"Instead of studying a natural phenomenon, and subsequently discovering a law of nature, one could first design a new law and then reverse engineer a system that actually displays the phenomena described by the law."

I throw that in the bucket of virtual particles, massless things, string theory and all that other untestable mess (which again, I admit to knowing little about)

But it all looks so...backwards

Another (albeit restrictive) way to consider the progress of science is asking what practical advances it has made that people value. Obviously the understanding that allowed us to create semiconductors and lasers has been put to good use, but, outside of biology, have there been many discoveries from science in the past 50 years, say?

I'm not saying that the only research worth doing is that which leads to an institution or company making a profit from the discoveries, but understanding the economic factors behind scientific research is helpful if we want to think about its future trajectory.

To go some way towards answering my question above, though, I will give the examples of graphene (isolated and characterized in 2004) and arguably the understanding from climate science about how the Earth's climate can vary with specific changes in atmospheric CO2 concentration (which has important policy implications).

Others can probably think of a few more, although there is much scope for debate about what counts as a "discovery" and "science". For example, public-key cryptography was invented in 1970s, but this could be said to be "merely doing engineering" or "merely inventing mathematical processes" rather than learning about the natural world.

It's interesting to consider what disciplines it makes sense to imagine being "completed" one day. Physics definitely yes. But imagining a "complete chemistry" one day is harder (revealing chemistry is as much an art as a science, as much about building as about discovering)

And imagining a "complete mathematics" seems even harder.

“ Nature’s agonizingly slow process of discovery, driven by cosmological and biological evolution on time scales of millions and billions of years, is accelerated to breakneck speeds in the laboratory.”

The slow process is not quite true.

For example, humans have about a half a million polypeptide machines (proteins, etc.) that make up the human body.

They are made of 20 amino acids in sequence and can be 10s to 100000s units in length.

If you calculate amount of polypeptides ribosomes could make given the base 4 DNA string and the choice of 20 amino acids, you will find there are not enough planck voxels in the observable universe to digitally represent them. I.e. the fact that nature found 500k to use for humans to be constructed in only a handful of billion years is profound.

It would have made more sense had the universe just been existing forever with no beginning.

Plenty of big problems and small problems in physics to be solved. My father was a research physicist who sat on the international committee for defining temperature, his little contribution to the world was to improve the low temperature model of measurement to make it 50000 times more accurate... and still had a lot of room for improvement. An area still under active research. At the broad scale we need to understand the mysteries of dark energy/matter, develop a quantum understanding of gravity, etc..... One problem that's happened is a lot of the physics in the early 20th century didn't have any experimental proof till late 20th century, physics pushes at our technological limits and has to wait patiently :)

Are we going to simply give up when it comes to understanding the fundamental nature of complexity? Why do multi-component systems undergo phase changes, why does it occur at the points at which they do, how could we design simple systems which, in sufficient quantity, exhibit useful properties upon phase shift? What techniques can be used to predict or derive macro-scale emergent phenomenon from micro-scale complex interactions? Why, exactly and with the same precision as quantum mechanics achieves, is more different?

For solving our problems as a species/society/individual we should assume physics is basically over. We should assume either there is not much more to find, or even if there is a lot more there isn't a way to make new technology leverage it.

We don't make this assumption because it is true. I honestly don't think it is true but we should make this assumption because we must ignore the attractive hazard of seeing simply waiting for new physics and new technology to be the solution to our problems.

I bet theoretical physics will play a crucial role in cultural shifts over the next century.

You can find a strong parallel between the emerging "metamodernism" era and Hawking's "model-dependent realism": the acceptance of contradicting realities.

We potentially face a future cultural enlightenment in which theoretical physics plays both a philosophical and expository role­— a future which acknowledges the importance of the observer in the "actual" nature of reality.

You could know everything there is to know about python or javascript and still not even begin realizing what can be made with them.

I suspect that meaningful progress in physics is going to face two hurdles for a couple of decades:

* Society has to catch up with what we have discovered over the past century. The physics that most people learn is primarily classical mechanics plus a bit of electricity and magnetism. There is some discussion of other aspects of physics, but it tends to be limited to discussion. You need some degree of mathematical understanding in order for physics to have a meaningful impact. The mathematical basis is important since it gives the ability to test the validity of physical models. This ability to verify or falsify a model is fundamental to science. High level discussions of a topic usually ignore the mathematics, which means they are asking students to accept something based upon authority. That is problematic since it is far too easy to choose an authority based upon criteria other than verifiable truths when one doesn't have the tools to verify what is being said.

* Technology also has to play catch-up. Physics has always been an expensive field since it pushes the boundaries of engineering. The precision instruments of past centuries may appear as quaint as a (quality) modern ruler, but they were pushing the limits of the times. That being said, there is a difference in scale. Pushing the boundaries of physics may have taken the resources of a nation in the recent past and wealthy benefactors in the more distant past. Some of the more recent experiments, though admittedly exceptional, take an international effort.

I don't really think that physics is coming to an end. I do think that some areas of physics will stagnate until humanity catches up with it.

The Yang Conjecture: http://chaosbook.org/extras/CNYang.html (last para)

> I believe that what we currently know is an absolutely negligible fraction of the physics that’s out there, waiting to be investigated.

Blessed is one who believeth...

I know they built that big collider in Europe but already they are saying they need a bigger one. I guess things are getting harder to discover.

Even if physics is now at an end, what a run it has had since Galileo, Kepler and Descartes!

This is exactly what we thought before Einstein came along and disrupted the whole scene.

Is there way to filter out quantamagazine from one's ycombinator feed?

“Nobody understands quantum mechanics.” This being as true as when it was first said, it is philosophy of physics that is still severely lacking, and that is where we hope to see some progress, eventually.

Figure out how to make quantum mechanics make sense to people. That’s my challenge for physicists. Find an interpretation that’s intuitive or comprehensible or something.

"The End of <Thing>" Articles are so cliche.

I have two main problems with the idea of the end of physics:

1. Physics has an obfuscation problem - the terminology is too thick so we can't see meta connections between concepts or form new insights at other levels of abstraction.

2. Tragically, the more advanced physics gets (as in the more money is directed at things like high-energy particle colliders), the fewer real-world applications are found for new discoveries.

The problem with (1) is that, the deeper we look into the edge cases, the less we are sure we know what we are doing. For example, I looked up "nucleon self-wave" because I couldn't remember the terminology around self-interaction, and stumbled onto this article:

https://www.osti.gov/biblio/6862283-imaginary-part-nucleon-s...

Not to pick on it too much, but even if it wasn't behind a paywall, it would probably take 10 years of study to even begin to read it.

Why is this important? Because when we're thinking about the very large or small, second-order effects usually overwhelm any first-order effects that we're used to. So we don't have the abstractions to properly think about what happens in, say, the nucleus of an atom. The vast majority of weekend warriors brainstorming about physics will never get anywhere, because their initial assumptions have little bearing on reality. In other words, today we're unlikely to stumble onto a new idea along the lines of relativity or quantum mechanics, because we can't see the forest for the trees and simply map the evidence to formulas which describe it.

A simple example of this is the recent hubbub about black hole information escape. As a layman, I can totally understand how a particle could teleport across the event horizon. But as a layman, I also look at different edge cases. If we imagine space as flowing into a black hole at faster than the speed of light past the event horizon, then I find it extremely unlikely that matter will ever teleport out. It's probably all packed into the center, squeezed smaller than a neutron (since pressure there is higher than neutron degeneracy pressure) and maybe even traveling backwards through time, while the event horizon is miles away:

https://jila.colorado.edu/~ajsh/insidebh/rn.html

Can someone prove to me that the new equations account for all that, and more importantly, fit the explanation on a napkin? Probably not. I have to take their "proof" on faith. Not good.

The problem with (2) has more to do with attention than failures of execution. We spend $10 billion here on a particle accelerator, $10 billion there on a fusion reactor, but absolutely nothing on grants to hackers. The next Einstein is likely working for a startup somewhere optimizing ad revenue. He or she will simply never have the time to daydream and see the forest for the trees.

My prediction for the 21st century is that this problem will become so widespread that capitalism will reach maximum underemployment. Nearly everyone will spend the entirety of their lives paying the fruits of their labor to wealthy individuals and organizations to innovate in areas that are profitable but aren't material to human progress.

A specific example of this is an organization like Google (again, not to pick on them) sinking vast sums into proprietary/niche machine learning hardware and software, rather than providing general-purpose parallelized computing to the masses. We should be able to buy 1000+ core chips for around $100 and program them with something open source like GNU Octave or run a Docker swarm utilizing every core so we can run our Python programs 1000+ times faster. Instead we have to adapt our experiments to subsets of computer science like DSP and SIMD. So we focus on neural nets or genetic algorithms and completely miss the abstract portions of machine learning that don't care about implementation details.

And why that's important is that stuff with seemingly emergent behavior (like fluid dynamics) can become tractable when we're not compute-limited. But we can't build simple simulations from first principles and scale them, because we're forced to rely on cookie cutter tools for NVIDIA video cards that others have put together because most languages and frameworks aren't up to the challenge of modeling whatever we're trying to do.

Put all this together, and the real innovation is either hopelessly out of reach (who has a compute cluster?) or is happening on a shoestring on YouTube instead of at CERN. I don't know whether to laugh or cry about that.

Sorry this got long, but I've been discussing physics like crazy during the first vacation the world's had in half a century, courtesy of COVID-19. Happy Thanksgiving everyone.

With the discovery of bronze, we have reached the end of metallurgy. Our ancestors struggled with inferior iron, often unalloyed and scooped out of riverbanks and swamps. But our technology has now progressed to the point of creating the perfect metal. It is very likely we have achieved the pinnacle of science. There is nothing more to learn!

Maybe it's time for a revival of idealism (in the philosophical sense of the term). Its rejection would account for a lot of the current frontiers in physics.

Close your eyes.

Twist the physics plan around, enter the new dimension.

You will see yourself watching the physics plane.

Twist the plane around to watch yourself watching the physics plane.

Do it until you see just a dot.

At this point nothing would make any sense other than your breath.

Amusing. It's like a cavemen saying "Yep, we are done. We made fire ourselves, what else could there possibly be?"

I mean we did a whole 200 years of scientific research. Of course, there is little else to discover. Humans are smart after all.

There are only a "few" obvious questions left:

* Can we generate a black-hole? If so how? If not, where is the proof?

* Can we move faster than light? If so how? If not, where is the proof?

* Are wormholes real? If so how? If not, where is the proof?

* Can we travel backwards in time and if so, how do we do it?

* Where did the universe come from?

* What is outside of the universe? I.e. where does it expand into?

* Are there other universes? Where is the evidence? Can we build a machine to go there? How do we build this machine?

* Can we prevent the sun from dying?

* Or let's start with the basics. How can we predict the weather of tomorrow reliably? How can we prevent our earth from becoming uninhabitable?

* Is the silicon really the best we can do for computers?

But sure, we are done with physics. Let's just bathe in our glory and praise ourselves as gods lol.

Humans are experts at forgetting that "Mathematics does not proof anything outside of mathematics". All we have are models. Are we at the end of our models? Perhaps? But all that means is that we need better models and perhaps even different mathematics.