How Nature Became Unnatural

Naturalness is an one-time idea; it dates dorsum at to the lowest degree to the 16th century too captures the intuition that a useful explanation shouldn’t rely on improbable coincidences. Typical examples for such coincidences, ofttimes referred to equally “conspiracies,” are ii seemingly independent parameters that almost cancel each other, or an extremely pocket-size yet nonzero number. Physicists believe that theories which practice non receive got such coincidences, too are natural inwards this especial sense, are to a greater extent than promising than theories that are unnatural.

Naturalness has its roots inwards human experience. If you lot larn for a walk too run across a delicately balanced stack of stones, you lot conclude someone constructed it. This determination is based on your cognition that stones distributed throughout landscapes yesteryear erosion, weathering, deposition, too other geological processes aren’t in all likelihood to goal upwards on peachy piles. You know this quite reliably because you lot receive got seen a lot of stones, pregnant you lot receive got statistics from which you lot tin extract a likelihood.

As the illustration hopefully illustrates, naturalness is a skillful criterion inwards for certain circumstances, namely when you lot receive got statistics, or at to the lowest degree agency to derive statistics. Influenza A virus subtype H5N1 solar scheme amongst x planets inwards almost the same orbit is unlikely. Influenza A virus subtype H5N1 solar scheme amongst x planets inwards almost the same bird isn’t. We know this both because we’ve observed a lot of solar systems, too likewise because nosotros tin derive their in all likelihood distribution using the laws of nature discovered too so far, too initial conditions that nosotros tin extract from yet other observations. So that’s a instance where you lot tin purpose arguments from naturalness.

But this isn’t how arguments from naturalness are used inwards theory-development today. In high loose energy physics too merely about parts of cosmology, physicists purpose naturalness to select a theory for which they practice non receive got – indeed cannot always receive got – statistical distributions. The problem is that they inquire which values of parameters inwards a theory are natural. But since nosotros tin uncovering entirely i laid of parameters – the i that describes our universe – nosotros receive got no way of collecting information for the likelihood of getting a specific laid of parameters.

Physicists purpose criteria from naturalness anyway. In such arguments, the probability distribution is unspecified, but ofttimes implicitly assumed to endure almost uniform over an interval of size one. There is, however, no way to justify this distribution; it is hence an unscientific assumption. This work was made clear already inwards a 1994 newspaper yesteryear Anderson too Castano.

The criterion model of particle physics, or the majority of the Higgs-boson to a greater extent than specifically, is unnatural inwards the higher upwards described way, too this is currently considered ugly. This is why theorists invented novel theories to extend the Standard Model too so that naturalness would endure reestablished. The most pop way to practice this is yesteryear making the Standard Model supersymmetric, thereby adding a bunch of novel particles.

The Large Hadron Collider (LHC), equally several previous experiments, has non found whatever evidence for supersymmetric particles. This agency that according to the currently used criterion of naturalness, the theories of particle physics are, inwards fact, unnatural. That’s likewise why nosotros before long practice non receive got argue to retrieve that a larger particle collider would create so-far unknown particles.

In my volume “Lost inwards Math: How Beauty Leads Physics Astray,” I purpose naturalness equally an illustration for unfounded beliefs that scientists adhere to. I chose naturalness because it’s timely, equally amongst the LHC ruling it out, but I could receive got used other examples.

Influenza A virus subtype H5N1 lot of physicists, for example, believe that experiments receive got ruled out hidden variables explanations of quantum mechanics, which is merely incorrect (experiments receive got ruled out entirely for certain types of local hidden variable models). Or they believe that observations of the Bullet Cluster receive got ruled out modified gravity, which is similarly incorrect (the Bullet Clusters is a statistical outlier that is difficult to explicate both amongst nighttime affair too modified gravity). Yes, the devil’s inwards the details.

Remarkable most these cases isn’t that scientists brand mistakes – everyone does – but that they insist on repeating incorrect claims, inwards many cases publicly, fifty-fifty subsequently you lot explained them why they’re wrong. These too other examples similar this larn out me deeply frustrated because they demonstrate that fifty-fifty inwards scientific discipline it’s seemingly impossible to right mistakes i time they receive got been adopted yesteryear sufficiently many practitioners. It’s this widespread usage that makes it “safe” for individuals to repeat statements they know are wrong, or at to the lowest degree practice non know to endure correct.

I retrieve this highlights a serious work amongst the electrical flow organisation of academic research. That this tin come about worries me considerably because I receive got no argue to retrieve it’s confined to my ain discipline.

Naturalness is an interesting instance to maintain an oculus on. That’s because the LHC forthwith has delivered information that shows the persuasion was incorrect – none of the predictions for supersymmetric particles, or extra dimensions, or tiny dark holes, too and so on, came true. One possible way for particle physicists to bargain amongst the province of affairs is to improve criteria of naturalness too so that they are no longer inwards conflict amongst data. I sincerely promise this is non the way it’ll go. The to a greater extent than enlightened way would endure to uncovering out merely what went wrong.

That you lot can’t speak most probabilities without a probability distribution isn’t a peculiarly deep insight, but I’ve had a difficult fourth dimension getting particle physicists to admit this. I summed upwards my arguments inwards my Jan paper, but I’ve been writing too talking most this for 10+ years without much resonance.

I was so excited to consider that James Wells has a novel newspaper on the arXiv

Naturalness, Extra-Empirical Theory Assessments, too the Implications of Skepticism
James D. Wells
arXiv:1806.07289 [physics.hist-ph]

In his paper, Wells lays out the problems amongst the lacking probability distribution amongst several unproblematic examples. And inwards contrast to me, Wells isn’t a no-one; he’s a well-known US-American particle physicist too Professor at the University of Michigan.

So, forthwith that a human being has said it, I promise physicists volition listen.

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Aside: I maintain to receive got technical troubles amongst the comments on this blog. Notification has non been working properly for several weeks, which is why I am blessing comments amongst much delay too reply erratically. In the electrical flow arrangement, I tin neither read the total comment earlier blessing it, nor tin I maintain comments unread, too so equally to remind myself to reply, what I did previously. Google says they’ll endure fixing it, but I’m non for certain what, if anything, they’re doing to brand that happen.

Also, my institute wants me to motion my publicly available files elsewhere because they are discontinuing the links that I receive got used too so far. For this argue most images inwards the older blogposts receive got disappeared. I receive got to manually supersede all these links which volition receive got a while. I am real deplorable for the resulting ugliness.