Hacker News Reader

Comment by monktastic1 | Hacker News Reader

I'm reminded of this beautiful quote from Chris Fuchs, regarding his advisor, the great John Archibald Wheeler:

> [Wheeler] would say things like, “In the end, the only law is that there is no law.” There’s no ultimate law of physics. All the laws of physics are mutable and that mutability itself is a principle of physics. He’d say, there’s no law of physics that hasn't been transcended. I saw this, and I remembered my joke about how the laws of physics must be wrong, and I was immensely attracted to this idea that maybe ultimately there actually are no laws of physics. What there is in place of laws, I didn't know. But if the laws weren't 100 percent trustworthy, maybe there was a back door to the stars.

View on HN

This sounds like semantic befuddlement (though, not on Wheeler's part; he was just engaging in wordplay).

Physical laws are not 'laws' in the sense that nature is required to abide by them. They are simply features of natural behavior that have been so overwhelmingly observed that we treat them as axioms.

An example of this is the 'law' of conservation of mass. Strictly speaking, nature does not follow this law. Nuclear reactions and subatomic interactions do not conserve mass. They conserve other quantities, but not mass in and of itself.

The idea that there is no ultimate law of physics is not novel or interesting. It's obvious on its face, unless you do not properly understand what 'law' means in the context of physics.

Law of physics implies a casual relationship in nature. Saying there are no laws of physics is saying nature is acausal. B always follows A for no reason other than it just happens to do so in our universe. This is the Humean view of causation, which is constant conjunction instead of there being a reason that A results in B.

The plus side is that you don't have to deal with causality, which is a tricky concept. Hume persuasively argued that causality is neither empirical nor a result of logic. The downside is that all necessity is totally arbitrary. It just so happens ... As such, there is no reason for anything we observe. Just descriptions.

Causality is separate. Laws of physics (conservation/symmetry) are constraints, not causality.

"a+b=7" implies that "a=3 implies b=4", and "b=4 implies a=3", without regard to what causes the other, or what caused the law to be true.

By implies, I mean that the laws of physics are approximating the actual laws of nature, which would be causal.

You are postulating here a priori that causality governs the movement of the universe. That is a philosophical position on how to interpret physical observation, but whereas archetypal temporal cause-and-effect phenomena is frequently observed, there are yet many physical phenomena that you and I regard as fact don't have obviously observed temporal causes. For example, we observe the Big Bang as well as the accelerating expansion of the universe, but don't have good explanations for their temporal cause. And everything in the universe is temporally caused by the Big Bang...

So what I'm trying to say here is that your claim here that causality governs the actual laws of nature is suspect, both because your comment has not been elaborate enough to specify what you mean by causality, and because one of the most popular notions of causality, i.e. temporal causality, seems, to a first approximation, not be a good model of the observable physics: it postulates a temporal cause for the big bang, but no time prior to the big bang is observable.

> Law of physics implies a casual relationship in nature

This is simply wrong. That is not what the term 'law' means in physics.

A law _implies_ a causal relationship because a law is thought to model a universal relationship (B always occurs when A). How you interpret the causality depends on your metaphysics. It can be descriptive based on constant conjunction, if you're so persuaded.

Scientists will state that B happens BECAUSE of A, when A is thought to be a necessary condition for B. That's the causal implication.

In what sense do Maxwell’s or Einstein’s field equations imply causality?

In that fields interact with particles, resulting in an electric current or acceleration, for example.

What, then, causes the phenomenon that fields interact with particles?

Historically, there has been a multitude of ideas and phenomena that have been labeled as causation. Aristotle, back then, identified four notions of causation, and the modern reader immediately will feel that some of these notions themselves are still too general. When you make a claim like "nature obeys causality", you need to be more precise in what you refer to by nature and causality, else your claim is far too ill-defined to mean much of anyting.

It's not obvious on its face, as it must be "properly understood" as you say. It takes years of education before people realize that the known laws of physics are just approximations or historically refined by discovering new details.

"conservation of mass" is either utterly trivial ("Nothing comes from nothing... except stuff that does") or has grown its asterisks over time.

https://en.wikipedia.org/wiki/Conservation_of_mass#History

> It takes years of education before people realize that the known laws of physics are just approximations or historically refined by discovering new details.

It's in high school chemistry textbooks. Typically in the first chapter or two. I'm assuming the audience of this site has taken at least one chemistry class in their life. Whether or not they paid attention is their own problem.

This is just sheer abject failure to distinguish between the description in one's head and the actual thing one is describing

Reply on news.ycombinator.com