September 08, 2006

From John Beckman:

Re: Protest over new planet definition (Sept. 5): The mistake by the IAU was to attempt to define a planet at all. Although the IAU’s role in naming astronomical objects is fully accepted and non controversial, we should not assume that naming and defining are in any way the same type of process. One can give an example which has been used in trying to define “a definition”. Consider the case of a craftsman who starts work on a large cube of wood and eventually carves it into a chair. At the end of the process we can see the chair clearly. The question can then arise: “At what point in the process should we say that the object has become a chair?”

Obviously put like this we can see that this exercise is futile. Nobody can claim that they can draw a line between chair and non-chair with greater authority than anyone else. The attempt is meaningless. The argument about when an object of a certain mass is or is not a planet has many aspects of this kind of futility about it. The definition is sufficiently difficult to make that two groups of “experts” can, and in this case did, come to opposite definitions of Pluto and several other objects in a similar mass range. The definitions were made in such a way as to satisfy the previous requirements of each group, i. e. whether or not they wanted Pluto to remain a planet, so that the criteria adopted were in a very important sense arbitrary. Both groups attempted to put physical parameters to their definitions, but these were not clear cut, in the same sense that one can say that an object which is able to turn hydrogen to helium in its centre is a star, and if it is not massive enough to do this it is not a star. The final name adopted to distinguish objects of around Pluto’s mass from “planets” is also silly. The term “dwarf planet” has a strong sense of ambiguity about it. Dwarf galaxies are galaxies and dwarf stars are stars (the Sun is one of them) so why should dwarf planets not be planets?

The IAU should not have wasted its time on this matter. The scientists who make up the IAU (I am one) have far more relevant contributions to make to the advancement of human knowledge and understanding without getting bogged down in a debate which was sure to be widely publicized, but which has contributed nothing to the science of astronomy.

John Beckman
Research Professor of Astrophysics
Instituto de Astrofisica de Canarias


Blogger VM said...

A notable post

September 13, 2006 4:49 AM  

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