We performed an experiment from Robert W. Wood's what? experiments for the young scientist, in preparation for staying up late with the stars on the 4th. I'm quite taken with the book, which is full of child friendly experiments, divided into six parts for engineering, astronomy, chemistry, meteorology, biology, and physics. Wood not only explains the science behind the experiments, but the scientists associated with them, too.
Some of the experiments are familiar to us already, like the pop bottle lung, or cloud in a jar, but others like this one from the astronomy section, meant to answer the question of why stars twinkle, are brand new to us.
The answer, in part at least, is that it is an optical illusion, caused by light passing through different densities of air in the atmosphere. This is only a partial answer, of course, or else the moon, and planets would also seem to twinkle, but it's a start.
To see the effect in action, we made some stars of our own, by poking holes, with a thumb tack, in a Pop Tart box (Wood calls for a cereal box, but we didn't have any empties).
Then, we placed a small flash light into the box, tilting it, so it would shine directly through some of the holes, and closed the top of the box.
Finally, we placed the box on one side of the stove, with a burner turned on, and looked at it, from the the other side.
As the light from our little stars passed through the heat rising from the burner, they did seem to shimmer, at least, if not twinkle.
Wood suggests placing a pencil in a glass of water, for further study of the light bending properties of density. And, he goes on to explain this is the same effect, that causes water mirages on the surface of a hot road.
It's great to be a homeschooler.