In China, a staggering blood-red sky has residents fearing the worst

In China, a staggering blood-red sky has residents fearing the worst

There was a very simple explanation for the dramatic hue in the sky that worried the people of Zhoushan for a few moments.

The situation in certain Chinese municipalities is currently quite tense, in the context of the government’s merciless fight against Covid-19 which sometimes has a heavy impact on the inhabitants.

Recently, the inhabitants of the city of Zhoushan, in the east of Zhejiang province, witnessed a downright apocalyptic spectacle: the sky turned a decidedly threatening scarlet red color. Very quickly, witnesses began to offer dozens of explanations, some of them extremely pessimistic. Some expected this unusual color to be the result of a large-scale fire. Others even suspected a chemical cloud, or even the beginning ofa nuclear conflict.

Many observers also saw it as a sort of prophecy. The Science Times reports several comments from locals who saw it as a harbinger of a catastrophe such as an earthquake, or even the beginnings of the last judgment. Others, however, were more optimistic, preferring to interpret it as a sign of “good luck and prosperity”.

No apocalypse, only trawlers

The most superstitious will perhaps continue to see it as a sign of fate, but what is certain is that this blood red sky was not due neither to a large-scale catastrophe, nor to a war, nor to a demonic supernatural force. The answer is actually much simpler and less dramatic.

But the explanations are far less dramatic than early observers had suggested. The little wind of panic that threatened to blow over the country quickly subsided following explanations from local meteorologists; it was simply a or several trawlers which would have turned on powerful searchlights in order to hunt the Cololabis sairaa small local fish.

The specialists explained that if the phenomenon took such proportions, it is above all because of the particular meteorological conditions which reigned in the zone. Indeed, the weather was particularly gloomy in Zhoushan. A very dense fog hovered over parts of the city, which itself was covered in thick cloud cover. Add that to an uninterrupted fine rain and possibly a dose of atmospheric pollutants, and you have the ideal conditions for studying certain optical phenomena like the Tyndall effect which is at play here.

A combination of refraction and diffusion

Remember that the latter is neither more nor less than an electromagnetic wave, ie a flow of charged particles which oscillate more or less quickly. The distance between these oscillations materializes what is called the wavelength, a parameter which will give its properties to the wave in question.

When this wavelength is between about 380 and 750 nanometers, this electromagnetic wave belongs to the visible range; at our scale, we interpret this range as light whose color varies according to the wavelength.

But these waves can also encounter obstacles in their path in the form of tiny particles of matter in suspension (microscopic drops of water, dust particles, etc.). And when a ray of light passes through a medium particularly charged with particles of this type, we witness a phenomenon of diffusion coupled with a phenomenon of refraction.

This means that when they enter a cloud of particles, the rays of light which previously traveled in a precise direction from the projector of the boat find themselves deflected in all directions: it is said to be diffuse, hence the red sky visible at long distance.

This phenomenon has also been amplified by the phenomenon of refraction, which modifies the trajectory of rays when they pass through a medium of different density – from air to a microdroplet, for example.

When the conditions are good, there is more water in the atmosphere which creates aerosols. They then refract and diffuse the light from the trawlers and create the red sky observed by the public.”, explains the staff of the Zhoushan Meteorological Bureau interviewed by the Global Times.

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