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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