No Warmth, No Fun,

November - or something like that

November may not be the cheeriest month, but it's certainly not as dreary as the above verse would indicate, well not always anyway. Across some parts of the country, the leaves are showing off and Indian Summer days are being enjoyed. It may even be possible to see a rainbow on a stormy November afternoon. Interestingly enough, it is not possible to seea rainbow in the early afternoon in June or July for most places in the U.S.. If you think about it, you almost always see a rainbow during the late afternoon or evening. If the sun is too high in the sky, a rainbow will not be seen. The reason for this has to do with the geometry of how sunlight interacts with raindrops. Sunlight enters a raindrop and is refracted (bent) and reflected (at least once) before it exits the drop. Most light rays emerge at angles of about 41 or 42 degrees from the axis of the raindrop (the axis is the imaginary line that a light ray takes if it enters the drop at it's center and is reflected back along the same line). Because of this fact, rainbows can only be seen if the sun is not higher than about 42 degrees above the horizon. This is approximately half the distance from the horizon to the zenith, or the point highest in the sky. At 3pm in July the sun is too high to produce a rainbow (in late June or early July the sun does not set until after 8pm). However, in November the sun is much lower in the sky and so rainbows can be seen in the afternoon (in mid November the sun sets about 5pm or so for most places in the U.S.).

The rainbow is actually a circle which is broken by the horizon. From an airplane it is possible to see a full circle rainbow. When the sun is very low in the sky, near sunset for example, if a rainbow occurs it will appear as a triumphant arch, however, if the sun is about 40 degrees from the horizon, then the resulting rainbow will be barely visible, just peeking over the horizon.