Allow us to set the scene: you’re out walking on a misty mountain. It was clear as day when you set off this morning, but as you’re reaching the peak a thick fog comes rolling in behind you. The Sun is just about still breaking through when you spot it, a great looming “dark watcher” – and not only does it appear to be following you, but it’s mirroring your every movement.
This spectacular optical illusion is what’s known as a “Brocken spectre” as named by German scientist Johann Silberschlag who spotted one while walking in the Harz mountains. Since then, Brocken spectres have become a hit in literature including works from Charles Dickens and Lewis Carroll, while others refer to the looming figures as “dark watchers”.
Deliciously spooky as they are, there’s nothing sinister about dark watchers. Well, beyond being a sign you’re probably not going to be able to see very much when you make it to the top of that mountain you’re climbing.
That’s because dark watchers love fog.
Dark watchers appear when a person creates a shadow that then gets a leg up by casting onto a cloud or mist. It results in an enormous silhouette that looks really far away because, from the position of the person casting it, the magnification appears to be touching far-reaching parts of the landscape.
These spooky figures will also sometimes move even if the person casting the shadow is staying still. Clouds are dynamic entities and as their water droplets shift so too can the shadow, making it move. The effect gives the entire ensemble a rather psychedelic feel as your silhouette creates a groovy, waving shadow giant, but you can imagine it freaked people out in the past back when we didn’t have science communicators to tell us how Brocken spectres work.
The technicolor cherry on top is that sometimes dark watchers also get a halo, or glory, which appears like colorful rings around the shadow of the head. It happens when light interacts with water droplets, creating concentric rings that shift from red to blue resembling something like a rainbow dartboard (you even get glories on other worlds). While glories are formed through a similar process to rainbows, they are different in that the angle of a glory from its source is much smaller, meaning the light diffracts, reflects, and refracts in water droplets at different angles.
So, if you’re out strolling in the coming weeks and find the fog is setting in, keep your eyes peeled for dark watchers. And if the idea of being stalked by your own massive shadow has the hairs on your neck standing up, have you ever wondered if humans can really “feel” when we’re being watched?
Source Link: Super Foggy Outside? Could Be The Perfect Time To Spot “Dark Watchers”
