In honor of the International Day of Light, anthropologist Savannah Mandel takes a sociocultural retrospective to understand the science behind rainbows.
Throughout the 20th and 21st centuries, the Western world witnessed a trailblazing push for increased diversity and inclusion. In recent years, we’ve seen legislative progress in rights for women, individuals with disabilities, the LGBTQ community, minority groups, and people of color. Some of these progressive acts and laws include the Americans with Disabilities Act of 1990; the 1992 United Nations’ Declaration on the Rights of Persons Belonging to National or Ethnic, Religious and Linguistic Minorities; the 1999 landmark Supreme Court decision in Olmstead v. L.C.; the 2010 amendment to the Fair Labor Standards Act; the 2013 removal of the ban against women in combat; the legalization of same-sex marriage across the United States; as well as strides towards a more general equality, such as the United Kingdom’s 2010 Equality Act.
With the International Day of Light just around the corner and the importance of diversity on my mind, my thoughts immediately drifted to the incredible and international history of the rainbow. What could better represent the mission of the International Day of Light (IDL), which states that the goal of IDL is to “celebrate the role light plays in science, culture and art, education, and sustainable development, and in fields as diverse as medicine, communications, and energy?”
Not unlike the residents of planet Earth, rainbows come in a diverse spectrum of shapes and sizes. Did you know that there are 12 types of rainbows? Rainbows also have a rich cultural history as a symbol of cooperation and peace, spanning continental barriers, and they have been studied as a natural and mathematical phenomenon by scientists around the globe for thousands of years.
One of the oldest known depictions of a rainbow is an aboriginal rock painting located near Ubirr Rock in Kakadu National Park in the Northern Territory of Australia. The cave painting is thought to be representative of the Rainbow Serpent, an aboriginal deity, and is dated to be several thousand years old.
Fast forward several millennia to around 384-322 BCE in Greece, where Aristotle was one of the first known scholars to record studying the rainbow. He successfully explained that rainbows existed due to the refraction of light off water droplets, but his theories on color and the mathematics behind other related phenomena, such as double rainbows, remained incomplete.
In the same time frame in what is now western Bolivia, individuals carved the first representation of the Wiphala, a checkered rainbow flag symbolizing native people of the Andes, on vessels which would be found by archaeologists centuries later. In the 1970s, the Wiphala became a political representation of indigenous and peasant movements.
From the 10th century to the 13th century, scientists and philosophers across the Middle East and Asia produced an intense amount of literature on rainbows. In China in the 10th century, mathematicians Shen Kuo and Sun Sikong continued Aristotle’s work, figuring out exactly what occurred when light refracted in water droplets. Likewise, polymath Ibn al-Haytham wrote Magala fi al-Hala wa Qaws Quzah (On the Rainbow and Halo). By 1268, Roger Bacon, an English philosopher and educational reformer, identified the angle at which a rainbow appears and its geometric foundation. At this point, our international group of scientists have now discovered that rainbows are the result of sunlight refracting through raindrops. They are not static objects but are instead an optical phenomenon visible when water droplets are viewed at an angle of 42 degrees from the direction opposite of a light source.
Sir Isaac Newton was the first to establish a true color theory to explain the ROY-G-BIV phenomena we all know and love. In the late 1660s in England, Newton began experimenting with color and optics. He found when white light passed through a prism, a spectrum of color projected through it. Newton identified seven colors, which he compared to the musical scale. These were red, orange, yellow, green, blue, indigo and violet.
In present Western culture, those seven colors together in rainbow form reflect a multicultural history of scientific exploration, and an international movement for the LGBTQ community.
The original rainbow flag, unveiled in 1978, had eight colors, which were each associated with meaning. This flag was commissioned by the first openly gay politician to be elected in California, Harvey Milk, and was designed by Gilbert Baker, known to his friends and family as “the gay Betsy Ross.” In 1979, the colors pink and turquoise were removed for manufacturing reasons and six colors, red, orange, yellow, green, blue and violet, remained. These colors symbolized life, healing, sunlight, nature, peace and spirit respectively. Over the years, the rainbow flag of LGBTQ pride underwent several more changes, adopting a black stripe during the AIDS crisis of the 1980s and changed again in 2017 by adding black and brown stripes for people of color.
In 2003, during the Key West Pride parade, the world’s longest rainbow flag was presented, measuring an unbelievable 1.25 miles long. After its debut, the flag was dismantled and traveled – like the history of the rainbow itself – across the world. Parts of the flag were showcased in Germany, Sweden, Norway, Canada, Australia and across the United States.
Traveling onward throughout time, the rainbow continues to gain more meaning, history and international momentum, proving it is not just an optical phenomenon, but a symbol of international cooperation and peace.