torsdag 30 juli 2009

Science or PseudoScience?

According to Karl Popper, astrology definitely represents pseudoscience, faked science, while marxism and psychoanalysis belong to the risk-zone.  The basic principle of astrology is:
The relative position of celestial bodies influences your life.

What makes astrology into pseudoscience is that a cause-effect description of the influence of the positions of celestial bodies on your fortune or misfortune, is lacking. It could be that there is such an influence, but what is required is a mechanism for the action and as long as this mechanism is lacking, astrology will remain pseudoscience.

Let us compare with the Boundary Layer Theory BLT by Ludwig Prandtl, the father of modern fluid mechanics. BLT states that the drag and lift of a body moving through a fluid with very small viscosity, such as air and water, is influenced by a very thin boundary layer close to the surface of the body, where the flow velocity changes quickly from zero on the boundary to the free stream value just outside. In short BLT states:
  • A very thin boundary layer influences drag and lift in a fluid with very small viscosity.
Is BLT science or pseudoscience? What is the mechanism of how the boundary layer influences drag/lift?  BLT claims that the mechanism is generation of vorticity from strong shear in the boundary layer, which somehow is transported into the fluid and then causes drag/lift. The basic argument is that even if the boundary layer gets thinner with decreasing viscosity, the total vorticity from shear does not decrease to zero and thus possibly can influence drag/lift. 

But BLT does not describe a mechanism of how the boundary layer vorticity can get into the fluid and influence drag/lift. 

Similarly, astrology does not describe a mechanism of how a far away celestial object can influence your life.

BLT and astrology both involve a large effect from a small cause, but a corresponding mechanism is unstable and thus delicate to work with. It is like saying that anything can happen from nothing, which is not science; science requires stable mechanisms with substantial effects from substantial causes.

If you claim that you have a theory which allows you to predict the outcome of a roulette
or single throw of a dice, possibly based on the position of Pluto or state of a very thin boundary layer, then you have a problematic probably pseudoscientific theory. Compare with the following confession by K. Stewartson in his survey article on D'Alembert's paradox:
  • ...great efforts have been made during the last hundred or so years to explain how a vanishingly small frictional force can have a significant effect on the flow properties.
We conclude that BLT seems to be more pseudoscience than science, a conclusion supported by the survey article Laminar Boundary Layer Theory: A 20th Century Paradox?

Let's subject some other theories to a quick test as concerns the presence of a stable cause-effect mechanism:
  • planetary system: mechanism: gravitational force: science
  • acoustics: mechanism: wave propagation in material medium: science
  • light: mechanism: electromagnetic wave propagation in vacuum: science
  • evolution: mechanism: genetic variation + selection: science, possibly incorrect
  • gravitation: mechanism: unknown: pseudoscience
  • quantum mechanics: mechanism: electrostatic repulsion/attraction: science
  • string theory: mechanism: unknown: pseudoscience
  • special relativity: mechanism for spacetime dilation: unknown; pseudoscience
  • general relativity: mechanism for spacetime warp: unknown: pseudoscience
  • circulation theory of lift: mechanism for circulation: unknown: pseudoscience
where we consider a theory without stable cause-effect mechanism as pseudoscience.

The purpose of a scientific theory is to make predictions of effects of certain causes through certain mechanisms, while the mechanisms behind the causes can be left without explanation.
Thus the motion of a planetary system or a space rocket, can be predicted in a scientific theory based on Newton's law of gravitation, which itself is left without explanation.

The correctness of a scientific theory including a stable cause-effect mechanism, like Darwin's evolution theory, depends on the correctness of the mechanism. It may be that genetic variation + selection, is not the mechanism of evolution. But intelligent design is pseudoscience as long as no design mechanism is presented.

In the hierarchy of sciences, theoretical physics/mathematics is viewed to be the foundation carrying the different levels of science and engineering: physics-mechanics-chemistry-biology-....cosmology. Each level above the foundation contributes a specific cause-effect mechanism
starting from the previous level, while it seems that the foundation has to come out of the blue, so to speak.

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