Comment Re:Pluto is a planet (Score 1) 46
Thank god for that. It was hard enough to learn 9 (now 8) planets at school. Can you imagine having to learn all the names if the hydrostatic equilibrium definition held?
Since when does science work by a standard of "what is easy for children to memorize lists of"? Do we say "There are 8 rivers in the world, and all others are dwarf rivers, which really aren't rivers" to make it easier on kids? Do we say "There are 8 bones in the human body, and all others are dwarf bones, which don't really count as bones"?
That's not how science works. Science is focused on practical distinctions about how things developed and their physical properties relative to each other. Hydrostatic equilibrium is a very practical definition. The process of undergoing relaxation induces metamorphism and releases heat, altering bodies. You go to non-equilibrium bodies if you want to study the primordial makeup of our solar system. You go to equilibrium bodies if you want to study tectonics, volcanism, non-primordial chemistry, and search for past or present life. The boundary could not be more meaningful. Yes, there is a bit of fuzz between equilibrium and non-equilibrium, but the same applies to pretty much all scientific fields.