December 16, 2009
What is going on here? Has the space-time continuum been distorted by a pulse of gravitational waves from a nearby supernova? Well, not quite. Gravity waves (not gravitational waves) are responsible for the shimmer effect: surface gravity waves on the surface of the pond. But why is the distortion most pronounced near the top of the picture? By now you’ll have realized that you’re seeing the distorted reflection of a deciduous hardwood tree in that pond, and as the waves spread out radially, their "curvature" decreases, so the waves at the top of the photograph were in reality nearer to me as I took the picture. By the way, it was only after I photographed this scene that I noticed a sign “Please do not throw rocks in the pond!”
Click here to see the entire pond. Notice how the reflection of the cloudy sky is darker near the bottom than the sky itself – a consequence of the varying reflectivity of light at different angles of incidence on the pond. Photo taken in Lancaster, Pennsylvania on December 4, 2009.
Lancaster coordinates: N40.039722, W76.304444