Welcome to another episode of the Bizarre Natural Phenomena series! I know it's been a while since the last episode on the majestic Lençóis Maranhenses National Park, but today I got something really rare and awesome to make it up to you!
Image from: wikipedia.org - Courtesy of: Heikki Immonen - License: CC BY 3.0
If you remember, we have discussed two types of rainbows here: moonbows and fogbows, with the first being a rainbow created by the moonlight and not the sun; and the latter being the result of fog droplets in the atmosphere that create a faint, most times white, rainbow. We have also talked about the beautiful glory phenomenon, a phenomenon that looks a lot like a big, full-circle rainbow, but is somehow different than a rainbow.
Let's bring out some of the basics to freshen up our knowledge
To have a rainbow we need:
Water in the air: we need water droplets in the air, from rain or mist, at a direction opposite the sun, that's the reason you can see it to the west in the morning time and to the east in the evening.
and
The sun at the right place: to see a rainbow the sun must be low in the sky. You will spot it if you look at an angle of about 40° from the ground.
From Bizarre Natural Phenomena Vol. 47 - Rainbows In The Night (Moonbows)
The floating droplets as prisms
Each water droplet acts like a single prism, when they all combine the final result is a colorful circular band across the sky (with a pot of gold on its end and a leprechaun guarding it). Sunlight enters the suspending water droplets, the rays are refracted (bent due to the change in the medium), internally reflected (bounce back) on the walls of the droplet and then refracted again as they exit the water medium and return to the air; but the incoming ray won't be the same coming out, as some of it will be reflected once more at the time of the second refraction and will exit the droplet from the opposite side or keep reflecting inside the droplet (double refraction).
From Bizarre Natural Phenomena Vol. 47 - Rainbows In The Night (Moonbows)
Inside those tiny floating prisms the white light will be separated at angles depending on the wavelength of each color, but the angle forming from the original white light beam and the exiting red light beam, will always be 42 o . The rest of the colors exit the droplet at different angles, with violet being the one higher than the all the others. The cool trick here is that each of those droplets send only one color beam to our eyes depending on their height in the sky. Those higher will deliver red to our eyes and as we lower towards the horizon, droplets will send all the other colors, with violet being the last one. All this complex "information" will be processed and finally form the image of a colorful rainbow in our brain! [3]
Physics Girl will give you a better idea in this video:
And let's make things a little creepy now!
Sometimes it is possible for a rainbow to appear... red, painting the skies scarlet, as if a gruesome celestial massacre has just occurred!
Image from: wikipedia.org - Courtesy of: Astronautilus, www.rodjonesphotography.co.uk - License: CC BY 2.0
Relax, this is not a horror movie we're in! It's just a rainbow where no other colors than red... survived!
How did it happen?
It is possible after the rain and near sunrise or sunset, for a rainbow to lose all its colors but red and sometimes maybe yellow. During this time, the sun is very close to the horizon, so light has a longer distance to travel through the atmosphere in order to make it to our eyes. On this journey, shorter wavelengths (like blue, green and yellow) are scattered and only red is left (the prevalent color of sunrises and sunsets). This means that our floating prisms don't have much of a variety of colors to use and paint the beautiful arcs in the sky a warm, red color! The sight can be really awe-inspiring and, why not, eerie, combined with the dim surrounding light at this time of day. [1, 2, 3]
Red rainbows are really not easy to spot, as the right conditions to form might be met, but surrounding lights may ruin it for you. You need a really dark background to actually see the "magic" picture, otherwise the color just fades away. [4]
Have you ever seen a weird rainbow?
Do you have any cool videos or shots to share? I'd be more than happy to see them! ☺
References
[1] wikipedia.org
[2] wikivividly.com
[3] worldatlas.com
[4] telegraph.co.uk
Thank you so much for your time!
Until my next post,
Steem on and keep smiling, people!
