Monday, June 11, 2018

Physics is the Simplest Science

Physics is the simplest science, a hard won truth that Eli has reached after many years in many fields. A bunny can do a lot of physics with pencil and paper, maybe even without those if enough homework has been passed in and marked.

This may seem, perhaps, a bit simplistic to some and mistaken to your average physicist, but consider, science is done through a mix of observation and computation. Physicists in the 17th century didn’t have to observe very much before they could start generating computational theories using pen and paper and testing them against observation. Physics is simple enough that one only need observe a few things before starting to build theories and compute results that could be compared to observations.

Other areas, not so simple. Lavoisier put it well, you cannot have a science without an agreed nomenclature because without you cannot talk about anything.

“The impossibility of separating the nomenclature of a science from the science itself, is owing to this, that every branch of physical science must consist of three things; the series of facts which are the objects of the science, the ideas which represent these facts, and the words by which these ideas are expressed. Like three impressions of the same seal, the word ought to produce the idea, and the idea to be a picture of the fact. And, as ideas are preserved and communicated by means of words, it necessarily follows that we cannot improve the language of any science without at the same time improving the science itself; neither can we, on the other hand, improve a science, without improving the language or nomenclature which belongs to it. However certain the facts of any science may be, and, however just the ideas we may have formed of these facts, we can only communicate false impressions to others, while we want words by which these may be properly expressed”
A useful working definition of science, a well liquored and tasty combination of observation, ideas and discussion.

Just to pick the next simplest science chemistry, the nomenclature is voluminous, systematic though it might be, to occupy a huge database and committees of learned souls called together by the International Union of Pure and Applied Chemistry to deal with new discoveries. Biology is worse. A lagomorph might argue that biology began with Linnaeus’ nomenclature for living organisms and for quite some time stayed there. And then we have geology and the rest of the alphabet soup of the geosciences each with their own dictionary that has to be mastered.

Eli conceptualizes this as the cladistic dimension. The physics dictionary is pretty thin by comparison except where physics meets materials and the other sciences bring their descriptive overload in.

Computationally a lot of physics can indeed be done with pen(cil) or paper depending on how many mistakes are to be made. You can do damn near no chemistry with pencil and paper beyond simple physics applications such as thermo or stat mech.

When Eli moved over to chemistry in the 1970s, theory was an object of derision and, as general chemistry today, required a series of rules, sequentially setting forth any number of simple models for chemical bonding and reaction following the historical development of the science. As each model was stacked on the next to extend them and handle myriad exceptions to each, students struggle. Why each of these simplifications works and their limits of applicability was not obvious, or at least not so until reaching the quantum basis of atomic and molecular structure. At that point, perhaps, when it became obvious how each of the historical models is an expression of quantum mechanics everyone, hopefully nods their heads and says "Oh yeah".

By the 1970s computational chemistry was a hungry beast posed to devour computer cycles. The formalism was prepared and a few brave souls had seen the future, working out relatively simple cases on several reams of paper, or with mainframe heat pumps filled with vacuum tubes.

The driving force is interesting. About twenty years ago it became clear that observation could never be complete enough to describe all the chemistry that was wanted. One could never measure any chemical process for all of the conditions possible and even if one could and could do a statistical parameterization of the results it would be flying blind because there would be no understanding of the underlying chemistry. It would all be handwaving, perhaps statistically valid handwaving but handwaving none the less, and worse, it would not be clear under what conditions the handwaving would fail.

Computational chemistry, validated against observational chemistry is today’s gold standard.

Eli would posit that atmospheric science has passed through this same progression enabled by computational forcing, but more so. Not only can we not make all the observations that would be needed to fully describe the Earth’s atmosphere, but absent a time machine and a large ensemble of Earth, or at least Earth like planets, we could never do so.

Thus Earth System Models, if you like Global Climate Models grown up.

Part II will add a few dimensions to the Kuhn Cycle and Part III will use all of this to illuminate the crisis in fundamental physics


David B. Benson said...

Geology is much easier than biology.

Fernando Leanme said...

The crisis in physics cant be iluminated until you figure out if the cat is well fed.

FixedCarbon said...

Geological nomenclature is gawdawful, especially when you get to the names of rocks.


It can only get worse if we let their parents name them.

CapitalistImperialistPig said...

Physics, or at least known physics, is simple, but the math is hard.

Fernando Leanme said...

CIP, I don't see how you can find physics simple when there's no way to assemble a puzzle which includes general relativity and quantum physics. The problem is so screwy I think they'll have to go toss out the idea that spacetime folds and define an (energy-momentum) field associated with quantized space. Or something like that.


The zero-order problem with Leanmechanical bafflegab is that there is at most one kind of physics.

EliRabett said...

CIP, Eli's point is that the math is not only possible, but was possible 300 years ago.

EliRabett said...

And David, have you ever see a geological phase diagram?

David B. Benson said...

Not only seen, but worked with.

My geology professor, sophomore year,was Robert P. Sharp. An unforgettable experience and I remain a top notch amateur geologist to this day.

I'm just now seriously studying biology. Much harder. I understand now why Richard Feynman told me he was going back to theoretical physics after a sabbatical year doing biology.

Hank Roberts said...

> Thus Earth System Models, if you like Global Climate Models grown up.

So, I understand it's not feasible to make a great many runs of a climate model -- time cost, computer cost.

But what if? Suppose that there's a 1-in-10,000 outcome with some peculiar combination of variables that would give us a clue about making some change that could help us out here? We need an outlier.

Some form of plankton that emulates our financial system, accumulating every bit of CO2 that it can grab out of the environment, locking it up, and sinking into stable form in the sediment

Some interaction/combination of the many organic chemicals we're dumping into the environment that promotes microbes that form soil, stopping erosion.

Some microorganism that promotes cloud formation at a useful level ....

EliRabett said...

Hank, a better strategy is a lower resolution model quick to run that points in the right direction. Think of it as a search function, first you explore a wide set of parameters, then you refine the search. If the point is so narrow that you need the ultimate resolution it is almost certainly unstable and any kind of variation would cause the system to move away.