Rationally Explanation Of Red/Blood Rain

Blood rain is a phenomenon where blood is perceived to fall from the sky in the form of rain. Cases have been recorded since Homer's Iliad, composed ca eighth century BC, and are widespread. Before the 17th century it was generally believed that the rain was actually blood. Literature mirrors cult practice, in which the appearance of blood rain was considered a bad omen, and was used as a tool foreshadowing events, but while some of these may been literary devices, some occurrences are historic.

Recorded instances of blood rain usually cover small areas. The duration can vary, sometimes lasting only a short time, others several days. By the 17th century, explanations for the phenomenon had moved away from the superstitious and attempted to provide natural reasons. In the 19th century blood rains were scientifically examined and theories that dust gave the water its red colour gained ground.

Today, the dominant theories are that the rain is caused by red dust dissolved in the water, or due to the presence of micro-organisms. Alternative explanations include sunspotsaurorae, and in the case of the red rain in Kerala in 2001, dust from meteorites and extraterrestrial cells in the water. and

In Germany, a shower of blood was one of several portents for the arrival of the Black Death in 1348–1349. The phenomenon gained exposure to a wide audience in the 16th century, during the Renaissance, when it was used as an example of the power of God; a form of literature using prodigies such as blood rain as cautions against immorality proliferated across Europe having originated in Italy. In Germany, such works were particularly popular amongst Protestants.

Although unusual events such as rains of blood were still treated with superstition, often as demonstrations of godly power, Nicolas-Claude Fabri de Peiresc (1580–1637) was one of the few who proposed natural causes; after hearing of a bloody rain in Aix-en-Provence, he suggested it was caused by butterflies. Although his theory would later be rejected, he helped the likes of Pierre Gassendi and René Antoine Ferchault de Réaumur to lay the foundations for removing superstition from explanations of the phenomenon.

In Europe, there were fewer than thirty recorded cases of blood rain in the 13th, 14th, and 15th centuries altogether. There were 190 instances across the 16th and 17th centuries; there was a decline in the 17th century when only 43 were recorded, but this picked up again with 146 in the 19th century. There is little literature on the subject of blood rain, although it has gained the attention of some naturalists. The phenomenon received international coverage in 2001, after red rain fell in Kerala, India.

Photomicrograph of particles from a sample of red rain from Kerala

Tatlock, in a study of some medieval cases of blood rain, notes that the medieval cases of blood rain "agree well" with their classical counterparts. Although there are variables – for example the rain sometimes lasted only for a short period, while on other occasions it can last days – they were widely considered to be bad omens, and warnings of events to come. He also suggests that the phenomenon may only be recorded in small areas because the colour of the rain would not always be noticed, and may only be obvious against pale backgrounds. In the classical period, events such as a shower of blood was seen a demonstration of godly power; in the medieval period, Christians were less inclined to attribute the phenomenon to such reasons, although followers of nature-religions were happy to do so.

In the 19th century, there was a trend of examining events such as rains of blood more scientifically; Ehrenberg conducted experiments at the Berlin Academy, attempting to recreate "blood rain" using dust mixed with water. He concluded that blood rain was caused by water mixing with a reddish dust mostly composed of animal and vegetable matter. He was unclear on the origin of the dust, stating that it lacked the characteristics of African dust which might have indicated it came from the Sahara Desert.

Instead, he suggested that the dust came from dried swamps where it was picked up by violent winds and would later fall as rain. This explanation has persisted, and the Academic Press Dictionary of Science and Technology (1992) attributes the colour of blood rain to the presence of dust containing iron oxide.

Other reasons for blood rain aside from dust are sometimes given. Schove and Peng-Yoke have suggested that the phenomenon may be connected to sunspots and aurorae. When red rain fell in Kerala, dust was the suspected cause. Alternative theories included dust from a meteorite and extraterrestrial cells in the water. These were later dismissed. The particles causing the red colour in Kerala were "morphologically similar" to algae and fungal spores.