Sometimes non-physicists accuse physicists of ad hockery with regard to dark matter and dark energy, and chameleon models are very useful in that case because t

Sometimes non-physicists accuse physicists of ad hockery with regard to dark matter and dark energy, and chameleon models are very useful in that case because they show what ad hockery really looks like: "Chameleon models are not especially well motivated from the standpoint of fundamental physics, admits Burrage, who began studying them in graduate school, but since dark energy presents such a profound mystery, physicists are willing to consider just about anything." They are also something to bring up when your New Age [1] friends claim that some weird effect "can't be tested by science" because it only happens when no one is paying attention, or something. Chameleon models are specifically designed to be "not there when there is a detection apparatus present", and yet to be useful as an explanation at all they have to have some interaction with the rest of the world, so it turns out we can test them regardless. This is a general property of things that are useful in explanation: if they can explain something, they can cause something, and if they can cause something, they can be investigated by systematic observation, controlled experiment, and/or Bayesian inference. [1] I just realized how dated the term "New Age" sounds. It turns out it went out of fashion in the '90's: https://en.wikipedia.org/wiki/New_Age#Social_and_political_movement https://en.wikipedia.org/wiki/New_Age#Social_and_political_m.... We really need an inclusive term for the whole swath of people from across the political spectrum who reject science.