The Daily Omnivore

Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. Turnbull’s blue is essentially identical chemically, excepting that it has different impurities and particle sizes—because it is made from different reagents—and thus it has a slightly different color.

Prussian blue was created in the early 18th century and is the first modern synthetic pigment. It is prepared as a very fine colloidal dispersion, because the compound is not soluble in water. It contains variable amounts of other ions and its appearance depends sensitively on the size of the colloidal particles. The pigment is used in paints, it became prominent in 19th-century aizuri-e Japanese woodblock prints, and it is the traditional ‘blue’ in technical blueprints.

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The dark forest hypothesis is the conjecture that many alien civilizations exist throughout the universe, but they are both silent and hostile, maintaining their undetectability for fear of being destroyed by another hostile and undetected civilization. It is one of many possible explanations of the Fermi paradox, which contrasts the lack of contact with alien life with the potential for such contact. The hypothesis derives its name from Chinese author Liu Cixin’s 2008 novel ‘The Dark Forest,’ although the concept predates the novel. A similar hypothesis, under the name ‘deadly probes,’ was described by astronomer and author David Brin in his 1983 summary of the arguments for and against the Fermi paradox.

The ‘dark forest’ hypothesis presumes that any space-faring civilization would view any other intelligent life as an inevitable threat and thus destroy any nascent life that makes itself known. As a result, the electromagnetic spectrum would be relatively quiet, without evidence of any intelligent alien life.

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