Links for the Week of August 24, 2015


Live from Yellowstone Lake Lodge: WTF!?

Daniel Little: The Case for Realism in the Social Realm: "The case for scientific realism in the case of physics is a strong one...

...The theories... postulate unobservable entities, forces, and properties. These hypotheses... are not individually testable, because we cannot directly observe or measure the properties of the hypothetical entities. But the theories as wholes have a great deal of predictive and descriptive power, and they permit us to explain and predict a wide range of physical phenomena. And the best explanation of the success of these theories is that they are true: that the world consists of entities and forces approximately similar to those hypothesized in physical theory. So realism is an inference to the best explanation...

"WTF?!" is the only reaction I can have when I read Daniel Little.

Ptolemy's epicycles are a very good model of planetary motion--albeit not as good as General Relativity. Nobody believes that epicycles are real.

Consider General Relativity: a hundred years old and dead-on at every experimental and observational level we have been able to measure (if you accept the cosmological constant fudge, the "dark matter" galaxy-rotation fudge, and the "dark energy" cosmological expansion speed-up fudge). It says:

  1. Space-time is curved.
  2. Matter and energy moves along geodesics in space-time when not perturbed by strong- or electroweak-force interactions.
  3. The curvature of space-time is governed by the distribution of mass-energy-pressure in a way that is conceptually simple: a ball of test particles around a point in space-time at rest will start to lose volume at a rate proportional to the mass-energy-pressure density at that point, and this holds true for all local Lorentz reference frames.

But if you ask physicists whether the entities of Einstein's theory are really there, they will say: "Of course not: Those entities do not satisfy the quantum principle. We very strongly believe that what we see as particles moving along geodesics in a space-time curved by the mass-energy-pressure density is an approximate model--a very good approximate model--to emergent properties that are produced by some very different underlying set of real entities that are governed by the quantum principle."

There is something there. But just because your theory is good does not mean that the entities in your theory are "really there", whatever that might mean...