> Might this be a misunderstanding of color? Light has a spectrum, and thus a color, regardless of where the light came from. And can be so bright as to appear to the eye white, or so dim as to appear dark gray (rods vs cones), also regardless.

“Color” is by definition a perceptual response, something that happens inside the brain. It depends on the observer, their eyes’ current level of adaptation, other stimuli which provide context, etc. If you move an object from a light background to a dark background, the color it evokes changes. If you take an object into a dim room and allow the eyes to adapt, the color it evokes changes.

Objects don’t inherently have a color. Light sources don’t inherently have a color. Light rays don’t inherently have a color. The same spectral power distribution can evoke (sometimes quite dramatically) different colors in different circumstances.

Of course, if you talk to philosophers or physicists instead of color scientists, you might get alternative definitions.

> bright as to appear to the eye white, or so dim as to appear dark gray (rods vs cones)

This is a bit confusing/confused. The retina has two types of detectors, rods and cones. In bright conditions, the rods are overstimulated and so provide no useful signal (and are therefore ignored in favor of the signal from the cones). When the eye is adapted to very dim conditions (e.g. starlight) and looking at a dim stimulus, the cones don’t respond vigorously enough to get much signal from them (and are therefore ignored in favor of the signal from the rods). In some dim-but-not-too-dim situations, signals from both rods and cones are integrated.

You can have both light gray and dark gray colors in any kind of context, but which specific stimuli will look light or dark depends on context.

* * *

> I've come to think of "you can't explain <subject> to <age>" as analogous to a code smell.

I have a 2.5 year old, and there are many topics which have too many prerequisites to adequately explain to him, or which are not relevant enough to keep his interest.

But he is learning a lot every day. Ask me again in a few years what he can learn at age 5.

> often seems like the teacher is coaching students on how to pretend to understand the material

Trying to teach a classroom with >10 students is extremely difficult in my opinion. I find that lecturing can’t truly teach most ideas; students have to grapple with them independently while working problems or projects or doing their own introspection. A lot of 1:1 attention from an expert mentor/tutor who can suggest problems or projects, ask a lot of questions, provide patient guidance, gently nudge a student back on track, stop the process from time to time and prompt some introspection, etc. is generally the most efficient way to learn. But this doesn’t easily scale to a classroom setting, and 1:1 tutorial isn’t considered economical for widespread adoption.

> goal of "learn science"

I think to “learn science” students need to be spending at least some time on all stages of the process: coming up with research questions, proposing hypotheses, designing experiments to test them, evaluating the experiments, etc.

(And it helps if they have some context for that scientific investigation, e.g. a bunch of experience observing bugs in the forest or trying to make mechanical devices out of meccano or learning to cook or ....)

In a similar way, to “learn journalism” students would need to go out and do a whole bunch of interviews and then write stories and publish them.

But this kind of learning is hard to achieve in a classroom setting.

Of course, “learn how to solve exercises in a typical introductory physics textbook” (or whatever) also has some value, so long as everyone is clear on how it relates to the world.