I am currently visiting Colgate University, giving a physics colloquium about dark energy. I'm hosted by my friend Jeff Bary (who's a first year professor there). Yesterday evening, his class gave presentations about discoveries that they'd researched. A few of the talks touched on the Big Bang. Afterwards, I was sitting around musing with Jeff and the departmental chair, Thomas Balonek. Thom was saying that it's disingenuous for us to claim that we're still talking about the Big Bang as it being the same theory that we had all those decades ago. What with the introduction of inflation, cold dark matter, dark energy, it's changed so much that really it's not entirely the same theory any more. I argued that the basic picture is the same-- the Universe expanded from a very hot, very dense state to its current form-- that it warrants having the same name.
I then asked the question: which theory has evolved more, the Big Bang or Biological Evolution? To point a finer point on it, let's go back to the (say) 1950's or early 1960's, when people were arguing about Big Bang vs. Steady State cosmology, before the discovery of the Cosmic Microwave Background, well before the introduction of inflation to solve the flatness and horizon problems. Take what people were talking about then as the Big Bang, and compare to what we talk about today. Has that changed more or less than the Theory of Evolution has changed from what Darwin originally envisaged when he wrote the Origin of the Species?
To be sure, the theory of Evolution is better understood and understood in better detail than the Big Bang theory. They both share the feature that they are theories describing the evolution of a system, not it's origin (although both the name of the cosmological theory, and the title of the work that started Evolution, both would seem to indicate that they do). We know a whole lot more about both today than we did then. Both have features today that people in the early days couldn't have anticipated. (I understand the cosmology better, of course, but know, for instance, that DNA and the genetics gives us an actual mechanism for Darwin's Evolution.)
So, what do you think? Which one has changed more? And is either theory similar enough to what was originally proposed that it deserves the same name, or should we have changed the name by now?