Mysterious hole in California sky

The image of a strange bright blue hole in the cloud of Northern California - USA is attracting the attention of the online community with the question: What is the truth?

Strange bright cloud in California sky

The cloud image with an unusually bright blue hole appears throughout social networking sites like Twitter, Facebook started on May 9 and spread quickly in the past few days.

The picture made people curious in California state and many places guessing old and unpredictable. Many people believe that this is "auspicious" or derived from some strange cause.

According to many netizens, a cloud of bright holes is a UFO (an unidentified flying object) or an alien. Many more realistic people hypothesize that the cloud is only a warning sign of bad weather, while others with rich imagination guess this is a "deep hole" like in the horror film Donnie Darko.

Many netizens believe this is a trace of aliens

However, most of the opinions identified here are cloud holes (Fallstreak) , which is a large circular space that can appear in cirrus clouds (Cirrocumulus) or medium clouds (Altocumulus) . As for CBS13, these images are not rare in the world, especially in warm places like Stockton, California.

The cloud hole formed when the water temperature in the cloud was lower than the freezing point but the water was still not frozen due to the lack of ice seeds.

When a part of the cloud begins to freeze, it will cause a chain effect that causes the surrounding steam to freeze and fall. This phenomenon causes a hole, usually circular, in the cloud.

Cloud holes form when part of the cloud freezes and falls.(Photo: BBC)

It is believed that the turbulence in the cloud, for example by aircraft, can activate the chain evaporation effect and create cloud holes. Specifically, the air passing through the propeller or two wings of the plane will expand and cool quickly. Ice crystals begin to form and after the plane passes, these crystals remain, falling out of the cloud and forming round holes, sometimes very large.