In aesthetics, the sublime is a blend of immense beauty with a hint of darkness. Imagine a sweet mango slice sprinkled with chili powder, or the experience of holding a cute, playful infant, only to be told they haven’t been burped yet.
Weather embodies the sublime. It is beautiful and awe-inspiring, yet sometimes also frightening. Sadly, our focus often dwells on the latter. We spend far more time predicting the weather so we can avoid the associated fates than chasing them. To meteorologists who do it everyday, it can be disheartening and impact their mental health.
But there is one positive atmospheric phenomenon that everyone loves: rainbows.
Seriously, I’ve yet to identify a constituency that is opposed to rainbows. They are nature at its best. I can think of no downside to rainbows - other than possibly contributing to inflation.
In the May 2024 issue of the journal Weather, Thomas Alan Clark and Alan Dyer recently published a study on the differences between rainbows formed from solar or manmade light sources.
Aboard a ship navigating a Norwegian fjord in a heavy rain storm, they were inspired by seeing double rainbows in the searchlight beams. They wondered about how rainbows form in different types of light and rain.
The Birth of a Rainbow
Here's a step-by-step explanation of how a typical rainbow forms:
Sunlight: Rainbows occur when there are water droplets in the air and sunlight shining from behind at a low angle, typically either early in the morning or late in the afternoon.
Refraction #1: When sunlight enters a water droplet, it slows down and bends as it passes from air (less dense) into water (more dense).
Reflection: After refracting upon entering the droplet, the light reflects off the inside surface of the droplet.
Refraction #2, Electric Bugaloo: As the light exits the droplet, it refracts again due to the change in medium from water back to air. This change in direction spreads the light out into its various wavelengths (colors). This happens because of…
Dispersion: The amount of bending (or refraction) depends on the wavelength of the light. Violet light bends the most, and red light bends the least.
The Mark I Eyeball: The light rays enter the observer’s eye at slightly different angles, with the different colors seen at different angles due to their varying degrees of refraction. This arrangement of colors forms a circular arc with red on the outer edge and violet on the inner edge.
Fun fact: Each observer sees their own personal rainbow, as the angle and size depend on the specific angle of light in relation to where they are standing.
(Not) too much of a good thing
In some cases, there are 2 reflections within the water drop. That creates double rainbows, which usually have a dark band between them known as Alexander’s Band.
After applying some basic geometry and algebra to the photo, the researchers produced a light profile of one of the searchlight beams, which clearly separated and measured the positions and widths of its two rainbows.
The researchers then compared the light intensity profiles of these rainbows with those created by sunlight in rain or in the spray of a garden hose. The searchlight rainbows had a stronger secondary bow and also showed more separation between colors.
The searchlight's rainbow displayed a broader (flatter) profile compared to the other two. Typically, smaller water droplets result in more broadened rainbows, which is why the spray from a garden hose appears broader than a rainbow seen in sunlight. However, this does not explain the unusually broad profile of the searchlight's rainbow, which was seen in rain and not mist.
The researchers suggest the cause is due to the searchlight beams emerging from a larger source than sunlight. As seen from Earth, the Sun is typically about 0.5° of arc in width. The searchlight beams were probably around 2.3°. So, it is a much larger light source, allowing for a wider distribution of angles. Another cause could be the raindrops in the intense storm had deformed enough to alter the reflection angles.
Science is driven by curiosity. Sometimes, we just want to know why something is. New knowledge about rainbows, whether from searchlights or sunlight, may not change the world overnight, but it can add beauty to a small part of it. Often associated with storms or flooding, rainbows are, in some ways, the opposite of the sublime. They can take scary situations and add a tinge of beauty to them.
It’s cliche, but I believe I would be breaking either a fundamental law of physics or even a legal law if I didn’t include this clip.
And Now for Something Completely Different
This has been a wild tornado season for North America. In their immediate aftermath, news and social commentary tend to focus (understandably) on damage and destruction. However, in the spirit of this issue of WWAT, we wanted to highlight a positive story.
Johnny Parker was a 16-year-old weather enthusiast living in Smithville, Mississippi, on April 27, 2011, when an EF-5 tornado struck his town. He survived and is credited with saving countless other lives through social media and texting alerts he sent to the community. The town recently named a street after Johnny, who is both a local hero and also now a meteorologist.
His full story is described in this article at Tornado Talk, a website devoted to tornado history. Tornado Talk dives deep into the stories of over 500 tornadoes (and growing). Check it out here, along with their e-mail newsletter and podcast.