I have a suspicion that the 'variables' are actually pretty UNvariable....some things just make more sense than others.....and before you suggest that my idea of 'sense' is narrow & rigid, Amos..*grin*, I still would be willing to bet 25¢ that most theoretical varients will remain that way. Equations are fun, but we can always describe things we can't really conceive of or explain in any useful manner.