Hippocrates (460–377 BC) postulated that the imbalance or excess of four fluids (called humors) within the body play a role in ones emotional and physical state. The chart below shows the four humors (row 1), the condition created by too much of each (row 2), and their respective emotions (row 3):


The Hippocratic theory of personality popularized the practice of bloodletting — opening a vein or applying leeches to "drain off" excessive amounts of the troublesome humor. In medieval Europe, it was common for barber-surgeons (whose professional practice relied on sharp instruments like knives and razors) to advertise their bloodletting services by posting a sign depicting a pale human arm traced with a crimson spiral of blood. (Remember that a ...

Known by tourists as the Eyes of God, the Prohodna cave is a typical karst cave in the north of Bulgaria and lies within one of the largest karst regions of the country. It is 262 meters long and easily accessible due to its two entrances on both sides of the cave. Prohodna cave is naturally lit because of these huge entrances and various holes in the ceiling.
Two of these holes are situated next to each other and their almond-like symmetrical shape gave them the striking resemblance to giant eyes. Seen from a certain angle they resemble a face looking down and during the rain it even seems as if the eyes were crying.

Not only is the cave a popular site for tourists and movie makers, it is also a good location for speleology (the scientific ...

The lake Leitisvatn/Sørvágsvatn sits about 30 metres above sea level.

The Faroe Islands are an archipelago between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Norway and Iceland, 320 kilometres (200 mi) north-northwest of mainland Scotland. The area is approximately 1,400 km2 with a 2010 population of 50,000.

Here's another look.

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On the Mediterranean island of Cyprus, you might be lucky to find a black flamingo. Normal flamingoes are born white and grey, and turn their iconic shade of pinky orange around the age of two, as a result of the high carotenoid content of the algae and crustaceans that they eat.

Experts believe that this individual (and potentially the other bird spotted in Israel) has a genetic condition that causes it to overproduce melanin, changing its feathers to black.

Where is it found? In Russia! How deep is it? About 12 kilometers! That's deeper than the deepest point of the ocean, and it's the deepest hole humans have ever dug into the Earth. Watch this informative video,

This perfect little cloud-covered island looks like an area of a game that you’re not allowed to access just yet. In reality it's Lítla Dímun, a small island in the Faroe Islands of Denmark.

In the catacombs of Sicily, there's a creepy child mummy named Rosalia Lombardo who appears to open and close her eyes on a regular basis. Here's how a scientist solved the mystery of this little "sleeping beauty". (Hint: she's not actually undead.)

Smoking was compulsory for schoolboys in the 17th century at England's famous Eton school because it was thought to prevent the plague.

Trampe is the world's first bicycle lift intended for urban areas. The prototype was built in 1993. During its 15 years of operation, Trampe pushed more than 200.000 cyclists up the 130 m long hill Brubakken in Trondheim, Norway.

A new report has ranked the world’s 16 major economies according to their energy efficiency, and Germany - who set a world record in May for generating 74% of their power needs from renewable energy - came out on top.

Lake Baikal in eastern Siberia is the oldest freshwater lake on Earth, and one of the largest and deepest, containing around one-fifth of the world's freshwater. In winter, it freezes over, and these beautiful transparent, turquoise masses of broken ice appear momentarily in March, caused by the unequal structure, temperature and pressure in the main body of the packed ice.