Gertrude Stein once asked Alice Toklas, "What is the answer?" When Toklas didn't respond, Stein asked, "In that case, what is the question?"
When my daughter and I discuss things such as the stars, sun, moon and sky, she incessantly asks "why?" Sometimes I have to take my answers to the subatomic level to satisfy her (or until I run out of explanations). In science, questions are as important as answers.
Recently, I served as a panelist for the National Assessment for Educational Progress achievement levels setting process. I was dismayed by how many students were unable to draw a map of the orbital relationship between the earth, moon and sun, or explain why we see one side of the moon. I wonder how few of them ever look up at night and ask "why?"
Perhaps, one unfortunate consequence of standardized testing is that students are deluded into thinking that the answer matters more than the question; and this can undermine learning.
So why do we only see one side of the moon?
My daughter would say it is "because the moon revolves on its axis with the same angular velocity that it rotates around the earth." So I turned the tables, and asked "Why, of every planet in the universe, do we live on the one where the two angular velocities are the same? Isn't that just a little too perfect?"
We see one side of the moon because its average mass center is not coincident with its geometric center — the bulk of the moon's mass is not at the center of its sphere. Thus, the gravitational pull of our planet keeps the moon's mass center, its geometric center and earth's center all one line. As a consequence (not a cause, then), the two angular velocities are made the same — and that is the answer.
We should teach our children to continue to question throughout their lives and remind them that science presents models; and models should always be questioned. Only through continuing questions of "why?" will they realize that that goal of science is not only the answer, but also the question.
(And if you know why the moon's mass is not evenly distributed, please post it below.)