Non-linear System

'''Nonlinear systems''' are those mathematical systems and natural 
phenomena that are not linear. The study of nonlinear dynamical 
systems is sometimes called nonlinear science.
Strange attractors and limit cycles can only appear in
nonlinear systems. Non-Linearity is sometimes used as
a [[buzzword]].

== Non-Linear, Non-Equilibrium and Non-Elephant ==

Stanislaw Ulam apparently once remarked: 
"Using a term like nonlinear science is like referring to the 
bulk of zoology as the study of non-elephant animals.”
(the quote can be found in James Gleick "Chaos: Making a new science",
Viking Penguin, 1987 and on page 374 in Campbell et al., 
"Experimental mathematics: the role of computation in nonlinear science",
Commun. Assoc. Comput. Mach. 28 (1985) 374–84)

The study of non-linear systems in physics is in fact like the 
study of non-elephant systems in biology or zoology. Nearly 
everything interesting is non-linear. The vast majority of 
interesting mathematical equations and natural phenomena 
are nonlinear, with linearity being the exceptional, but 
important, case. Nonlinear systems are ubiquitous,
linear systems are the exception.
Linear systems are simple, nonlinear systems are complex. 
There are many forms of [[Complexity|complexity]], but only a 
few forms of simplicity: all linear systems are similar,
but nonlinear systems can be quite different from each
other.

"Nonlinear system" is a word similar to "Non-Equilibrium System", 
an ambiguous word for a vague concept. Next to "Non-Equilibrium Systems" 
comes "Dissipative Structures". The worst phrase of all is 
"systems far from equilibrium". It does not says how from equilibrium
the system is really, or in which direction.

[[Category:Systems]]