Why Theories Don’t Go Into Hospitals

I’m always amused at how very reasonable remarks so often generate attacks from unreasonable people.  I wrote a perfectly ordinary post about what one does and doesn’t learn from LHCb’s important new measurement at the Large Hadron Collider [LHC] (and in fact I overstated the significance of the result — more on that later), and somehow I touched off a mini-firestorm.  Well, that just indicates how essential it is to have calm people expressing sensible points of view.  When people become so politicized that they can’t distinguish propaganda from science, that’s not good.

Forget supersymmetry — because none of my remarks have anything to do with this theory in particular, and the theory doesn’t deserve the excessive attention it’s getting.  Take any theory: call it Theory X.  Extra dimensions; compositeness of quarks and leptons; non-commutative spacetime; grand unification; your-theory-here.  The idea behind theory X may be very clever, but as always, there are many variants of theory X, because an idea is almost never precise enough to permit a unique realization.  Each variant makes definite predictions, but keep in mind that detailed experimental predictions may very well differ greatly from variant to variant.

Now, here is a logical fact:  one of two options is true.

  • Option A: One variant of theory X is “correct” (its predictions agree with nature) while all other variants are “wrong” (disagree with nature)
  • Option B: All variants of theory X are wrong.

Nature is what it is; there are no other options (and this is not the place for a discussion about this basic scientific assumption, so pace, please, philosophers.). [More precisely about option A: the space of variants is continuous, so the correct statement is that an arbitrary small region in this space is correct; you can put in the correct calculus vocabulary as you like.  I’ll stick with the imprecise language for brevity.]

For either option, as more and more data is collected, more and more variants of theory X will become “dead” — excluded because of a disagreement with data.  Therefore — obviously! — a reduction in the number of live (i.e. unexcluded) models always takes place over time.  And this has absolutely no bearing on whether, at the end, all variants of X will be dead, or one (or perhaps several very similar ones) are still alive.

And thus it makes absolutely no sense to describe, as a “blow to theory X” — in particular, to the idea behind theory X — a measurement that excludes (“kills”) even a big fraction, but not virtually all, of the variants of theory X.  It’s certainly a blow to those variants; in fact, it is a fatal blow for them.  But it does nothing to distinguish between Option A and Option B.  It only tells us that if Option A is true, the variant of X that will be alive at the end is not among the ones that have just been killed.

This isn’t rocket science, folks.  It’s logic.  [Well – As a commenter points out, it’s  not “logic” in the strictest sense; but it is basic scientific reasoning.] And if we take theory X to be the Standard Model itself, I’ve just described its history.

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Shock, Foreshock and Aftershock in Italy

It’s hard to know quite what to say about the verdict in Italy convicting scientists — experts on earthquakes — for having… for having… well, what, exactly did they do?  That’s the whole question.  They made pronouncements that tried to state that risks of a big quake, following a swarm of smaller earthquakes in the L’Aquila area of Central Italy, were low, although of course not zero.  But their wording and their calls for calm led to some people staying in their homes instead of remaining outdoors, and consequently losing their lives when, in fact, the big quake did take place soon after.   The issue is not whether they failed to predict the quake — no one is arguing they could have done that.  The issues are whether they did enough to make clear that there was a small risk of a big quake, and also, who is ultimately responsible — the experts, the government, or the public — for making the final cost-benefit analysis about the risks to individuals’ lives?

And of course, following the conviction, and a sentence of six years in prison for manslaughter, the next question is: even if this sentence is overturned on appeal, what scientist, or expert of any type, will dare to give advice to the Italian public in future, knowing that if the advice proves incomplete or unwise in retrospect, the result may be incarceration? Has Italy lost its wisest advisors?  (Four members of the “Great Risks Commission” have already resigned, including one of Italy’s greatest theoretical particle physicists, and I doubt they’ll return without new legal protections.) Will other countries lose theirs?

The issue at stake is clearly not Italian earthquakes; it is expert advice.  Sometimes I feel that we in modern society are forgetting how to be grown-ups and take responsibility for our own actions, and how to accept that bad things do just happen sometimes and it isn’t always someone’s fault.  When we go and get advice from anyone — whether it be medical advice,  financial advice,  advice about the weather or advice about the risks from earthquakes — we need to remember it’s provided by a human being.  Ideally that human being has access to the best information available and understands the odds, and will give us a recommendation based on the odds — on the probabilities for various things to happen.  But even when it is the best available advice, it’s based on odds… on statistics.  It’s an educated guess — yes, it’s educated, but also yes, it’s a guess.

And one thing that is dead certain, given that it is a guess based on odds, is that occasionally — rarely, perhaps, but not never — that guess will be wrong.   It’s inevitable, even if the expert is making the best possible recommendation, based on the best available information and the most accurate possible assessment of the odds.  When that bad guess happens, property may be lost, and people may die.  It’s sad, but it is inherent in the nature of odds and probabilities.

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