No Shadow Bands 2024

 

In 2017 Christine dragged me on the Katy Trail near St. Louis to see the eclipse. We were not in the totality. The first effect I noticed was the sickling. People were making pinhole viewers with blades of grass or a circle with thumb and forefinger. Sickling, the crescent moon shadow, was everywhere. The next was shadow bands. The sickling turned off and shadow bands, alternations of light and dark, appeared on the ground. They were straight and went on forever. Towards maximum darkness, and stillness, the shadow bands clicked off and then reappeared on the other side of the eclipse. Then the bands turned off and sickling reappeared. The shadow bands did not move. I don’t know if their position was the same on both sides of the eclipse.

I had not heard of shadow bands before. Shadow bands are an interference pattern. An interference pattern occurs when a light is split, and then subsequent two slits create a wave interference pattern. The question is where the interference comes from. One slit is obvious, even if curved, the eclipse of the sun. Some think the two following slits are an atmospheric effect. Another possibility is a quantum effect, sufficient light bending around the other edge of the moon. Sneer in whichever way you like.

In 2024 Christine dragged me to the totality, Thornwood preserve near Indianapolis. I brought a tape measure to see if I could better observe the shadow bands. There was no sickling. Other people in the totality noticed this as well. There was sickling everywhere else. It was as though there was too much light. I didn’t see shadow bands. Fortunately, Speedway sold us eclipse glasses. I saw the pearls where the light peeps around the moon’s mountains. When it was too dark to see through the glasses, I looked at the totality and saw the flare near the bottom. I didn’t see a quantum dot at the center.

Rather than quantum, is the moons gravity sufficient to bend enough light at an angle? Other observers see flickering and motion. Once the pattern appears, the flickering sounds atmospheric.

Neither quantum nor gravity is sufficient. An interferometer is an elaborate instrument that takes precision and engineering to get its effect.  The lack of angle at the totality explains the lack of crescent. The crescent shows when there is enough angle to spread it out.  The first slit in the Young double slit experiment is obviously when the light is squeezed to the edge of the moon. At that moment the crescents disappear and the bands show. The second slit can only be when the line of light hits the atmosphere. Refraction requires the line of light hit the atmosphere at an angle. The difficulty is that the refraction is slight. Interference requires a third slit, with enough light. Rather than the main beam the line pattern could be interference between the refracted and ambient light. The ambient light is diffused from the main beam.  

A systemic error is that everyone is looking up and doesn’t see the other effects. Another is that the cool kids with the equipment head for the totality.