The science of the rainbow and the rebirth of a place marked by history: the Vajont
On 9 October 1963 the Vajont tragedy has profoundly marked Italian history, not only for the loss of thousands of human lives, but also for the enormous lesson that emerged from it in terms of responsibility and management of the territory. That disaster, built by thearrogance and inability of man to respect the forces of naturehas become a indelible warning in ours collective memory. Vajont is not just the scene of a catastrophe, but a place where nature continues to demonstrate its extraordinary beauty and complexity. May 7, 2016 a primary rainbowaccompanied by supernumerary arches rare characterized by blue, purple and bands yellowcolored the sky right above the Vajont dam. The shape of the landscape made the heart of the phenomenon perfectly visible.
Some details:
The photo was taken from the location of Villanova (approximate coordinates of 46.27° N and 12.32° E), fraction of Longarone (Bl), the height of the Sun (not refracted) was about 29.0° and the azimuth was about 264.6° (W) . The top of the primary rainbow then appeared at 13° in the sky at the dam.
A photo that shows and demonstrates both natures of light:
This phenomenon is an example of the wave-particle dualism of light, which is the basis of modern physics:
- The corpuscular nature in the refraction and reflection of light in water drops, which gives rise to the primary rainbow.
- The wave nature in the formation of supernumerary arcs, due to the interference of light waves.
What do supernumerary bows look like?
The supernumerary arches are pale colored bands additional colours, in particular blue and purplewhich are formed in continuation of the violet band of the primary rainbow and, sometimes, also of the secondary rainbow. They repeat themselves weaker and weaker as you move away from the main rainbow.
How are supernumerary arches formed?
These arcs, weaker than the main rainbow, are formed thanks to the interference of light within raindrops of very similar size, a phenomenon that exploits the wave nature of light. The light, entering the drop, behaves like athen. Inside the drops, light waves of different wavelengths (corresponding to the various colors of the visible spectrum) overlap. This type of interference produces the chromatic bands distinctive, usually weaker, visible just after the violet color of the primary rainbow, which alternate with each other until they vanish.
Why are these supernumerary arches on the Vajont dam special?
In the specific case observed above the Vajont dam, it was detected a wider echo of the spectrum with the presence of an unexpected intense yellow banda very rare occurrence.
Which suggests that there was a particular configuration in the size of the water drops that allowed the formation of a supernumerary arc with a wider repetition of colors. The Professor Raymond Leeobserving the photo, believed that the average radius of the drops was approximately 0.5 mman ideal size to produce these distinctive and clearly visible arcs, vivid and with the addition of the yellow band. This level of uniformity is rareas rain often has a variety of droplet sizes, which reduces the visibility of supernumerary arcs.
Final reflections: the Vajont between science, memory and rebirth:
When we think of a place, we must remember that it is never the same point in the universe but that the Earth is like a spacecraft wandering in space, making its movements around the to the galaxy, with the local group and every point in space it touches is always different also because, theuniverse is expanding. A place is that place only the instant it is and will never return there a second time. This is why we should not think of Vajont only as the place of catastrophe, but remember that it is catastrophe is the result of human negligencewhere he has permanent residence. The Vajont is therefore no longer the same place as the 1963 catastrophe, but it continues to evolve, just as our way of remembering it and our relationship with it should evolve. The Vajont message therefore cannot be locked away within the confines of a physical location. That disaster belongs to each of us and that is where it must reside, inside everyone’s consciences. The inhabitants of Longarone, Erto e Casso, Castellavazzo and Ponte nelle Alpi, trapped in a past that seems to necessarily continue in their daily lives, have the right to don’t just be the custodians of a tragedy. For those who live in the places of the Vajont disaster it is a reality that accompanies them every single day, not only because this event is part of their experience, but the tourists and passers-by who visit these lands rarely miss the opportunity to ask and request something about that tragedy. We must keep the memory of the tragedy alive, but at the same time recognize and celebrate the rebirth of these lands. Life has returned to these places and it proved extraordinary resilience capacity of man and nature. Through a reflection that unites science and memoryI want to think of the Vajont as a place of rebirth and again luceas symbolized by this atmospheric phenomenon: the rainbow with its special supernumerary arches.
Thanks:
I thank the group of photographers Pictores Caeli, of which I am part, together with, , , , , for having extracted the best of this image and the video.
I thank Professor Raymond Lee for having analyzed our photographic and film material and given ideas for the description and definition of the phenomenon.
