Light is a funny thing--we see what's reflected, not what's absorbed, of course, but the reflected light becomes the object, at least in our minds. That's how we survived through millennia.
That berries change color is obvious. The how, less so, but we got fancy words and molecular structures to dazzle any child who dares ask. Answering the why is the tough one.
If a child asks "why are blueberries blue?"--not an unusual kind of question in a science class--how do you answer it?
This is not a trivial point. We live in a culture that defines knowledge as bits of information, and how I approach a child's questions helps shape how she sees the world.
Some possible answers follow, along with my issues with each.
Blueberries are blue because they have anthocyanins....
Unless you are teaching a post-doctoral botany student in grad school, this is like saying blueberries are blue, because they're, well, blue; saying anthocyanin adds nothing to the child's grasp of the universe. If she is satisfied by this answer (and she may well be given the way we teach "science"), she learns that what matters in the classroom are the words that signify the universe, not the universe itself.
The answer isn't wrong, it's just inane. It goes from inane to insane when we promote this as science. It may be cute to hear little ones parrot big sciency words, in the same perverse way it's cute to promote beauty via pageants for 5 year old children, but it's a dangerous pedagogical practice.
Blueberries are blue so we know they're ripe...
No doubt blue blueberries taste a lot better than the less mature green ones, and yes, there's a complicated relationship between seeds ready to germinate and the sweet juices surrounding them tempting animals to eat them. Raccoon scat around here can be loaded with seeds, and some gardeners will swear that blueberry seeds grow best after traveling through a mammal's gut.
If you have the time in class (days or weeks) to
digressdigest this, to pursue the bioenergetics of sugars and scat, to explore evolution, then this answer can go a long way. If you shorten it to "so we know they're ripe," you've just placed the child in the center of the natural universe, and set back her chances of grasping descent with modification later.
(Language matters--yes, we know they're ripe because the berries are blue, but that is not why the berries are blue, at least from the point of view of science. )
Blueberries are blue because God made them so...
The problems with this answer should be obvious, but these days some folks need it spelled out. Science does not dabble with the supernatural. It has no truck with miracles, either, for a variety of reasons.
Despite the noise from some corners, not all science teachers are godless atheists trying to subvert your child's mind. Atheism requires more faith than I have.
So how do we answer seemingly simple questions in class? Very carefully. Sometimes no answer is better than any answer. If I'm stuck, I'll often probe a bit to grasp what the child is really asking--and many time the child does not know either.
Uncertainty is fine with me--far more damage has been done by folks who know the truth than those of us plodding along the nooks and crannies of the natural world.
I have faith that my blueberries will ripen, and enough biochemistry background to grasp how they will ripen. I'll save pondering the why until the day's end, as I sit on the patio watching the nearly full moon inch up over the maple tree in back, sipping melomel made from last year's blueberry bounty.
The blueberries in the photo now sit in my gut. Yum!