Despite some claims of radical postmodernism — which takes a rational idea and “runs with it” to silly extremes — nature operates in a particular way, and if some scientists describe it in another way their science is wrong. { This bold statement should be explained and clarified, to avoid misinterpretation, which is done in another page [the one you're now reading] — along with thoughts about short-term and long-term divergences in science & design — so it won't interrupt the flow of main ideas in this page. }
Convergence (common) and Divergence (rare) in Science
My statement that "their science is wrong" doesn't mean that every consensus-challenging theory is always wrong, and currently accepted theories are always correct. In fact, scientists often make small adjustments in minor theories. And occasionally, in some area of science, scientists discover that they were wrong in a major way, and their large adjustments produce a conceptual revolution in that area of science. During a time of transition between the old theory and new theory, there are two (or more) theories in a serious competition, which produces controversy in this area of science. But in current science, this is rare for the major theories in each area.
In many areas of science, more than one theory-based model co-exists because the models differ in their cognitive utility (for stimulating productive thinking) or research utility (for stimulating and guiding theoretical or experimental research). But the alternative models are variations on the same basic theme, because there is a limit to the possible divergence in scientific theories that are true and/or useful. Reality puts constraints on our search for truth, and thus on possibilities for divergence in theories; we see these constraints in Reality Checks.
In theory design, temporarily we may see a divergent generation of option-ideas that rewards a creative searching (for old) or inventing (of new), but eventually one theory usually emerges as the consensus choice of scientists.
Compared with a community of scientists in a mature area of science, students in a classroom often have a wider divergence in their own “alternative” theories; recognizing this variety is important when conceptual change (to revise a misconception) is an educational goal.
For more about the foolishness of radical postmodern relativism, see Eks-Rated Science and Reality 101.
Convergence (rare) and Divergence (common) in General Design
In general design, sometimes technology also converges, due to market choices by individuals (as with VHS vs Beta), or (with Blu-ray vs HD DVD) the collective benefits of standardization, or for other reasons. But more often we see divergence in the results of general design, as in the wide variety of vehicles, buildings, stores, video games, and songs.