Your recent discussion about rainbows was interesting. Isn’t it true that if you go high enough up, say in an airplane, the rainbow will be a full circle?
—Mike Boyajian, Homewood
Yes, it is true. In theory, every rainbow is actually a full circle. The central point of a rainbow is directly opposed to the sun’s position in the sky. There- fore, more of the rainbow’s circle becomes visible as the sun approaches the horizon. This means the largest portion of the rainbow’s circle (50 percent) is seen at sunrise or sunset. The lower half of the rainbow lies below the horizon. However, as one goes up, such as from a very high building or an aircraft, a full-circle rainbow can be seen. It is possible to produce a full-circle rainbow by spraying water from a garden hose when facing away from the sun.