This summer is shaping up to be a strange one with all the lightning lasers, glowing squid, and shed insect skin fashion. This time dozens of photos were taken of this most recent phenomenon that appeared over the Shonan Coast of Kanagawa Prefecture.

This blue streak is quite easily explained but to appear in this kind of location is still a bit of a mystery.

What this photo shows is called an anticrepuscular ray, but before explaining that let’s look at the easier crepuscular ray.  A crepuscular ray is a fancy egghead name for a ray of sunshine.  We’ve surely all seen one on a cloudy day where a small crack in the clouds reveals a single beam of light, or if the sun is setting behind some clouds or mountains and rays shoot out from the openings.

An anticrepuscular ray is, as its name suggests, is the opposite, meaning that it’s a beam of non-sunlight, kind of like a shadow.  It only occurs during sunrise or sunset when the sky changes hues to orange and purple because of the sun’s angle to the atmosphere.

In this case, the rays, which travel through the thicker atmosphere creating a different color, are blocked by something like a cloud or mountain.  This leaves a “beam” of normal blue sky against a backdrop of sunset tinted sky as seen in these photos.

What’s weird about this vivid anticrepuscular ray in Kanagawa is that there are no mountains in the area and there appears to be a clear sky.  So what’s blocking the sun?

It could just be that the clouds are behind the camera, which makes sense since these rays appear strongest in the sky opposite of the sun.  The other theory is that water molecules not large enough to create a cloud can still be dense enough to create this effect, but it’s rare, especially considering how strongly visible this ray is.

We actually are often in the presence of these rays but they are usually so weak that we hardly take notice of them, so check the sky of your own vacation photos taken at dawn or dusk and you might surprise yourself.

Source: togetter via livedoor news (Japanese)

▼ This, one of the few photos taken towards the sun, reveals the culprit: some distant storm clouds.