Over at Cosmic Variance Sean Carroll is fighting an interesting battle. In a series of recent blogs that started under the title "The Laws Underlying The Physics of Everyday Life Are Completely Understood" he is making the claim that physicists have fully figured out whatever we may encounter in our day-to-day lives. Everything. No exception. Sean wonders why this several decades old achievement never got the attention it deserves.

The reactions to these blogs are interesting. There are hundreds of them. Not entirely surprisingly, a considerable number of commenters implicitly or explicitly call Sean smug. They observe a smugness not in any way different from the infamous Von Jolly, the German physics professor who is remembered not because of his achievements, but because of a piece of advise he gave. Back in 1878, Von Jolly advised a student of his not to go into physics, because 

"in this field, almost everything is already discovered, and all that remains is to fill a few unimportant holes".

The student name? Max. Max Planck. Luckily, this young fellow ignored Von Jolly's advise and years later managed to initiate a complete overhaul of physics.   


Sean Carroll, The New Von Jolly?

Sean, well aware he has to walk a thin line in making his opinion public, does his very best to explain his position is entirely different from the Von Jolly's who lived at the end of the nineteenth century: 

A hundred years ago it would have been easy to ask a basic question to which physics couldn’t provide a satisfying answer. “What keeps this table from collapsing?” “Why are there different elements?” “What kind of signal travels from the brain to your muscles?” But now we understand all that stuff. (Again, not the detailed way in which everything plays out, but the underlying principles.) Fifty years ago we more or less had it figured out, depending on how picky you want to be about the nuclear forces. But there’s no question that the human goal of figuring out the basic rules by which the easily observable world works was one that was achieved once and for all in the twentieth century.

In his most recent post on this subject he further elaborates:

What there won’t be is some dramatic paradigm shift that says “Oops, sorry about those electrons and protons and neutrons, we found that they don’t really exist. Now it’s zylbots all the way down.” Nor will we have discovered new fundamental particles and forces that are crucial to telling the story of everyday phenomena. If those existed, we would have found them by now. The view of electrons and protons and neutrons interacting through the Standard Model and gravity will stay with us forever — added to and better understood, but never replaced or drastically modified.

I think I understand what Sean tries to convey here, but in the way it is phrased I simply can not agree.



Sean Carroll: the modern Von Jolly?


Unification Versus Prediction

Although, in contrast to Von Jolly, Sean does allow for future new physics to be discovered, just like Von Jolly he is making claims that ignore the potential size of the unexplored future territories of knowledge. Nothing prevents these unexplored territories to have consequences that overlap with day-to-day phenomena. 

We can't blame a nineteenth century physicist who does not see any problem with tables and other objects being stable. For him matter just is. His laws of physics are not violated by the phenomenon of stable matter. It requires the knowledge of atomic substructure and their interactions to recognize there is a problem. And subsequently it requires the discovery of quantum physics to solve the 'stable matter problem'. Thus one progresses from a consistent view in which matter is defined to be stable, to one in which matter is understood to be stable as a consequence of the laws of physics. This type of progress is not going to stop.      

Imagine a mid nineteenth century physicist making the claim:

What there won’t be is some dramatic paradigm shift that says “Oops, sorry about Newton's law of gravity, we found that such a gravity force doesn't really exist. Forget about Newtonian gravity, now it’s zylbodynamics.” The view of planets and apples interacting through an inverse-square-distance law of gravity will stay with us forever — added to and better understood, but never replaced or drastically modified.

Half a century later Einstein comes along and dramatically modifies our view on how apples and planets interact: gone is gravity as a force, it's space-time curvature that rules. And yes, let's make no mistake about it: this has impact on our day-to-day experiences. You don't need a laboratory or expensive equipment to experience the equivalence between inertia and gravitational mass.  

Now Sean would likely object and say something like: "right, but this paradigm shift although profound does not change the applicability of Newtonian gravity to day-to-day phenomena, it rather elucidated some key aspects of gravity".  

And this is where Sean's claims are misleading. 

Obviously it is true that Newton's laws of gravity are sufficient to describe and predict everyday phenomena. You don't need general relativity when aiming a cannon. We have send men to the moon using just Newton's laws. But physics is not about making successful predictions. It's about unifying our predictive systems. Ptolemy could predict the positions of the stars and planets. We could have sticked with his theory and refined it by adding more epicycles. However, although not giving more accurate predictions, we went for Copernicus' conceptually simpler approach. And building on this approach, Newton made a giant step in unifying celestial and earthly dynamics. 

This journey of unification is continuing and there is no question that we still have some way to go. A remark like "Never replaced or dramatically modified" rules out future unifications and paradigm shifts akin to the transition from Newtonian to Einsteinian gravity.    


The Arrow Of Time

Let's face it: current physics has not even begun tackling some of our profound everyday experiences. Several of the reactions to Sean's recent blogs highlight the enigmatic issues of consciousness and free will. I don't want to open up these Pandora's boxes, so let us focus instead on a less controversial issue. An issue Sean has commented on extensively: the arrow of time. His recent book "From Eternity To Here", promises its readers:

By the end of this book, we will have defined time very precisely, in ways applicable to all fields. Less clear, unfortunately, will be why time has the properties that it does—although we’ll examine some intriguing ideas.

Wait a second. Is Sean saying here that one of our most profound day-to-day experiences, the passing of time, is not understood? Yes he is. He elucidates in the preface to his book:

The mystery of the arrow of time comes down to this: Why were conditions in the early universe set up in a very particular way, in a configuration of low entropy that enabled all of the interesting and irreversible processes to come? That’s the question this book sets out to address. Unfortunately, no one yet knows the right answer. [..]
The arrow of time connects the early universe to something we experience literally every moment of our lives. It’s not just breaking eggs, or other irreversible processes like mixing milk into coffee or how an untended room tends to get messier over time. The arrow of time is the reason why time seems to flow around us, or why (if you prefer) we seem to move through time. It’s why we remember the past, but not the future. It’s why we evolve and metabolize and eventually die. It’s why we believe in cause and effect, and is crucial to our notions of free will. And it’s all because of the Big Bang.

Here, Sean's own words shine a different light on his "The Laws Underlying The Physics of Everyday Life Are Completely Understood" claims. He refers to the big bang, the moment the entropy was low, as key to the solution of why we perceive in our everyday life the arrow of time. Few physicists, if any, would maintain that the big bang can be understood based on general relativity and the standard model alone.  

Understanding the big bang requires new physics, and as implied by Sean's recent book, more than likely the same new physics is what is missing to understand everyday phenomena like the passage of time. There is no reason to assume that a current physicist who just accepts the arrow of time is in any way different from a mid nineteenth century physicist who just accepts matter is stable. For the latter, a rise to a next level of understanding required new insights at subatomic scales. Similarly, current physicists will probably require new insights at cosmological scales, to rise to a next level of understanding of time. 

Why Physicists Are Smug

Let me finish by saying that I really like Sean's blog, including his latest. And as I said, I agree to what I think he meant to express. And that is to give expression to the fact that physics has come a long way in the last century. A less controversial way of stating this would be: 

To stand a reasonable chance to observe phenomena not predicted by the standard model plus general relativity you need deep pockets. You need expensive equipment like the Large Hadron Collider or the Hubble Space Telescope. Both required an eleven digit funding. 

Why are physicists smug? You need ten billion or more to prove them wrong.