Have a deep view into what people are curious about.

🔗 Meteorology 🔗 Chemicals 🔗 Soil 🔗 Weather 🔗 Weather/Weather

Petrichor () is the earthy scent produced when rain falls on dry soil. The word is constructed from Greek petra (πέτρα), meaning "stone", and īchōr (ἰχώρ), the fluid that flows in the veins of the gods in Greek mythology.

🔗 Mathematics

In mathematics, tetration (or hyper-4) is an operation based on iterated, or repeated, exponentiation. It is the next hyperoperation after exponentiation, but before pentation. The word was coined by Reuben Louis Goodstein from tetra- (four) and iteration.

Under the definition as repeated exponentiation, the notation ${\displaystyle {^{n}a}}$ means ${\displaystyle {a^{a^{\cdot ^{\cdot ^{a}}}}}}$, where n copies of a are iterated via exponentiation, right-to-left, I.e. the application of exponentiation ${\displaystyle n-1}$ times. n is called the "height" of the function, while a is called the "base," analogous to exponentiation. It would be read as "the nth tetration of a".

Tetration is also defined recursively as

${\displaystyle {^{n}a}:={\begin{cases}1&{\text{if }}n=0\\a^{\left(^{(n-1)}a\right)}&{\text{if }}n>0\end{cases}}}$,

allowing for attempts to extend tetration to non-natural numbers such as real and complex numbers.

The two inverses of tetration are called the super-root and the super-logarithm, analogous to the nth root and the logarithmic functions. None of the three functions are elementary.

Tetration is used for the notation of very large numbers.

🔗 Novels 🔗 Books 🔗 Novels/Short story 🔗 Horror

The King in Yellow is a book of short stories by American writer Robert W. Chambers, first published by F. Tennyson Neely in 1895. The British first edition was published by Chatto & Windus in 1895 (316 pages).

The book contains nine short stories and a sequence of poems; while the first stories belong to the genres of supernatural horror and weird fiction, The King in Yellow progressively transitions towards a more light-hearted tone, ending with romantic stories devoid of horror or supernatural elements. The horror stories are highly esteemed, and it has been described by critics such as E. F. Bleiler, S. T. Joshi, and T. E. D. Klein as a classic in the field of the supernatural. Lin Carter called it "an absolute masterpiece, probably the single greatest book of weird fantasy written in this country between the death of Poe and the rise of Lovecraft", and it was an influence on Lovecraft himself.

The book is named for the eponymous play within the stories which recurs as a motif through the first four stories, a forbidden play which induces madness in those who read it.

🔗 Visual arts

Iron gall ink (also known as common ink, standard ink, oak gall ink or iron gall nut ink) is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources. It was the standard ink formulation used in Europe for the 1400-year period between the 5th and 19th centuries, remained in widespread use well into the 20th century, and is still sold today.

I have edited thousands of articles so that they do not contain the phrase "comprised of". Edit summaries for those edits usually refer to this page.

This page explains the purpose of these edits and the project in general.

🔗 Computing 🔗 Trains 🔗 Trains/Rail transport modelling

The Tech Model Railroad Club (TMRC) is a student organization at the Massachusetts Institute of Technology (MIT). Historically it has been a wellspring of hacker culture and the oldest such hacking group in North America. Formed in 1946, its HO scale layout specializes in automated operation of model trains.

🔗 Computing 🔗 Computing/Software 🔗 Microsoft

Internet Explorer for UNIX is a discontinued graphical web browser that was available free of charge and produced by Microsoft for use in the X Window System on Solaris or HP-UX. Development ended with a version of Internet Explorer 5 in 2001 and support for it was completely discontinued in 2002.

🔗 Biology 🔗 Astronomy 🔗 Color 🔗 Evolutionary biology 🔗 Project-independent assessment

The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin-based chlorophyll, making the surface biosphere appear purplish rather than its current greenish color. It is estimated to have occurred between 3.5 and 2.4 billion years ago during the Archean eon, prior to the Great Oxygenation Event and Huronian glaciation.

Retinal-containing cell membranes exhibit a single light absorption peak centered in the energy-rich green-yellow region of the visible spectrum, but transmit and reflect red and blue light, resulting in a magenta color. Chlorophyll pigments, in contrast, absorb red and blue light, but little or no green light, which results in the characteristic green reflection of plants, green algae, cyanobacteria and other organisms with chlorophyllic organelles. The simplicity of retinal pigments in comparison to the more complex chlorophyll, their association with isoprenoid lipids in the cell membrane, as well as the discovery of archaeal membrane components in ancient sediments on the Early Earth are consistent with an early appearance of life forms with purple membranes prior to the turquoise of the Canfield ocean and later green photosynthetic organisms.

🔗 Espionage 🔗 Books 🔗 Computer Security 🔗 Computer Security/Computing

The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionage is a 1989 book written by Clifford Stoll. It is his first-person account of the hunt for a computer hacker who broke into a computer at the Lawrence Berkeley National Laboratory (LBNL).

Stoll's use of the term extended the metaphor Cuckoo's egg from brood parasitism in birds to malware.

🔗 Education

Underwater basket weaving is an idiom referring pejoratively to supposedly useless or absurd college or university courses and often generally to refer to a perceived decline in educational standards.

The term also serves as an intentionally humorous generic answer to questions about an academic degree. It is also used to humorously refer to any non-academic elective course, specifically one that does not count towards any graduation requirements.