Tree Leaf Shadows to the Sun's Density: A Surprising Route

Rays of sunlight that strike raindrops produce rainbows that provide information about the spectrum of sunlight. Rays of sunlight that strike airborne ice crystals produce halos, sun pillars, and many other patterns of light and color in the sky. Analysis of those patterns makes it possible to determine the types and orientations of the ice crystals. Rays of sunlight that strike opaque objects produce shadow patterns that can be seen on any clear day. I was surprised to discover that the shadow patterns produced when sunlight strikes tree leaves provide all the information needed to determine the average density of the Sun. It seems unlikely that the Sun's density could be determined without knowing its mass or its volume. And, although it may seem even more unlikely, the density of the Sun can be determined using only information available in the shadows of tree leaves.