It is now one of my two favorite times of the day: twilight. Celtic lore holds that the “veil” between the human world and the fairy world “lifts” during these magical times of day, allowing for fairies to be seen by humans. I’ve investigated what gives twilight its magical blue color in the sky. It turns out that during morning and evening twilight, the Sun is from 4 to 8 degrees beneath the horizon. During these times, the Sun’s blue wavelengths dominate because the ozone layer absorbs the  yellow, orange, and red parts of the light spectrum. This kind of absorption is known as the Chappuis absorption, named after the French chemist James Chappuis. As a result, a magical teal color dominates the sky. The sun sets pretty late here in Barcelona, at aroun 9 p.m. I say late because I’m used to the sun setting at 6:30 p.m. in Puerto Rico, where I’m from. Photographers love to take photos during the blue hour because the blue light is magnificent, as you can see here. It’s almost as if they’re hoping to catch a fairy.

W.B. Yeats once wrote: “At Howth, a great colony of otherworld creatures travel nightly.” The Irish Times has a great article about fairies still living in the Irish imagination. From the article and being quoted from Irish Fairies (1890) by W.B. Yeats:

“When I tell people that the Irish peasantry still believe in fairies, I am often doubted. They think that I am merely trying to weave a forlorn piece of gilt thread into the dull grey worsted of this century. They do not imagine it possible that our highly thought of philosophies so soon grow silent outside the walls of the lecture room, or that any kind of ghost or goblin can live within the range of our daily papers. If the papers and the lectures have not done it, they think, surely at any rate the steam-whistle has scared the whole tribe out of the world. They are quite wrong. The ghosts and goblins do still live and rule in the imaginations of the innumerable Irish men and women, and not merely in remote places, but close even to big cities. 

At Howth, for instance, ten miles from Dublin, there is a ‘fairies path’, whereon a great colony of otherworld creatures travel nightly from the hill to the sea and home again.”