The Fundamental Plane of Early-Type Galaxies as a Confounding
  Correlation
  Early-type galaxies are characterized by many scaling relations. One of them,
the so-called fundamental plane is a relatively tight correlation between three
variables, and has resisted a clear physical understanding despite many years
of intensive research. Here, we show that the correlation between the three
variables of the fundamental plane can be the artifact of the effect of another
parameter influencing all, so that the fundamental plane may be understood as a
confounding correlation. Indeed, the complexity of the physics of galaxies and
of their evolution suggests that the main confounding parameter must be related
to the level of diversification reached by the galaxies. Consequently, many
scaling relations for galaxies are probably evolutionary correlations.
