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The Shell Grotto, sometimes called the Shell Temple, is an ornate underground shell grotto in the seaside town of Margate, Kent, England. The grotto, which has a passageway and main room, was dug out from chalk, a soft limestone common in the region. Almost all the surface area of the walls and roof is covered in mosaics created entirely of seashells, totalling about 2,000 square feet (190 m²) of mosaic, with approximately 4.6 million shells. Its age, creators, and purpose are unknown, which has inspired a wide range of speculation, although several other shell grottos in England were made in the 18th century. This grotto was rediscovered in about 1835 and first opened to the public as a privately-owned tourist attraction in 1837. The grotto is a Grade I-listed building and remains open to the public. Attached to the grotto is a modern museum room, cafe, and gift shop.

Lee Felsenstein (born April 27, 1945) is an American computer engineer who played a central role in the development of personal computers. He was one of the original members of the Homebrew Computer Club and the designer of the Osborne 1, the first mass-produced portable computer.

Before the Osborne, Felsenstein designed the Intel 8080 based Sol-20 computer from Processor Technology, the PennyWhistle modem, and other early "S-100 bus" era designs. His shared-memory alphanumeric video display design, the Processor Technology VDM-1 video display module board, was widely copied and became the basis for the standard display architecture of personal computers.

Many of his designs were leaders in reducing costs of computer technologies for the purpose of making them available to large markets. His work featured a concern for the social impact of technology and was influenced by the philosophy of Ivan Illich. Felsenstein was the engineer for the Community Memory project, one of the earliest attempts to place networked computer terminals in public places to facilitate social interactions among individuals, in the era before the commercial Internet.

A glass knife is a knife with a blade made of glass, with a fracture line forming an extremely sharp cutting edge.

Glass knives were used in antiquity due to their natural sharpness and the ease with which they could be manufactured. In modern electron microscopy glass knives are used to make the ultrathin sections needed for imaging.

SETL (SET Language) is a very high-level programming language based on the mathematical theory of sets. It was originally developed at the New York University (NYU) Courant Institute of Mathematical Sciences in the late 1960s, by a group including (Jack) Jacob T. Schwartz, R.B.K. Dewar, and E. Schonberg. Schwartz is credited with designing the language.

Ondol (ON-dol; , Korean: 온돌; Hanja: 溫突/溫堗; Korean pronunciation: [on.dol]) or gudeul (구들; [ku.dɯl]) in Korean traditional architecture is underfloor heating that uses direct heat transfer from wood smoke to heat the underside of a thick masonry floor. In modern usage, it refers to any type of underfloor heating, or to a hotel or a sleeping room in Korean (as opposed to Western) style.

The main components of the traditional ondol are an agungi (아궁이; [a.guŋ.i]), a firebox or stove, accessible from an adjoining room (typically kitchen or master bedroom), a raised masonry floor underlain by horizontal smoke passages, and a vertical, freestanding chimney on the opposite exterior wall providing a draft. The heated floor, supported by stone piers or baffles to distribute the smoke, is covered by stone slabs, clay and an impervious layer such as oiled paper.

Bertie the Brain is one of the first games developed during the early history of video games. It was built in Toronto by Josef Kates for the 1950 Canadian National Exhibition. The four meter (13 foot) tall computer allowed exhibition attendees to play a game of tic-tac-toe against an algorithm, presented by its creators as artificial intelligence. The player entered a move on a keypad in the form of a three-by-three grid, and the game played out on a grid of lights overhead. The machine had an adjustable difficulty level. After two weeks on display by Rogers Majestic, the machine was disassembled at the end of the exhibition and largely forgotten as a curiosity.

Kates built the game to showcase his additron tube, a miniature version of the vacuum tube, though the transistor overtook it in computer development shortly thereafter. Patent issues prevented the additron tube from being used in computers besides Bertie before it was no longer useful. Bertie the Brain is a candidate for the first video game, as it was potentially the first computer game to have any sort of visual display of the game. It appeared only three years after the 1947 invention of the cathode-ray tube amusement device, the earliest known interactive electronic game to use an electronic display. Bertie's use of light bulbs rather than a screen with real-time visual graphics, however, much less moving graphics, does not meet some definitions of a video game.

Sonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound.

In early 2025, beaver activity in the Brdy Protected Landscape Area, Czech Republic, contributed to the restoration of a wetland ecosystem. A family of beavers constructed a series of dams that accomplished environmental goals set by the Czech government, which had delayed its proposed project since 2018 for bureaucratic and financial reasons. The beaver-built dams saved the Czech government approximately US$1.2 million, providing ecological benefits including improved water quality, enhanced biodiversity, and better water retention.

The great horse manure crisis of 1894 refers to the idea that the greatest obstacle to urban development at the turn of the century was the difficulty of removing horse manure from the streets. More broadly, it is an analogy for supposedly insuperable extrapolated problems being rendered moot by the introduction of new technologies. The phrase originates from a 2004 article by Stephen Davies entitled "The Great Horse-Manure Crisis of 1894".

The supposed problem of excessive horse-manure collecting in the streets was solved by the proliferation of cars, buses and electrified trams which replaced horses as the means of transportation in big cities. The term great horse manure crisis of 1894 is often used to denote a problem which seems to be impossible to solve because it is being looked at from the wrong direction.

The name refers to a supposed 1894 publication in The Times, which said "In 50 years, every street in London will be buried under nine feet of manure". The reasoning was that more horses are needed to remove the manure, and these horses produce more manure. An urban planning conference in 1898 supposedly broke up before its scheduled end due to a failure to find an answer to this problem. No such statement in the Times, nor conference result, is known, but in 1893 London there was a complaint that horse manure, formerly an economic good that could be sold, had become a disposal problem, an economic bad.

The supposed crisis has since taken on life as a useful analogy.

Electromagnetically induced acoustic noise (and vibration), electromagnetically excited acoustic noise, or more commonly known as coil whine, is audible sound directly produced by materials vibrating under the excitation of electromagnetic forces. Some examples of this noise include the mains hum, hum of transformers, the whine of some rotating electric machines, or the buzz of fluorescent lamps. The hissing of high voltage transmission lines is due to corona discharge, not magnetism.

The phenomenon is also called audible magnetic noise, electromagnetic acoustic noise, lamination vibration or electromagnetically induced acoustic noise, or more rarely, electrical noise, or "coil noise", depending on the application. The term electromagnetic noise is generally avoided as the term is used in the field of electromagnetic compatibility, dealing with radio frequencies. The term electrical noise describes electrical perturbations occurring in electronic circuits, not sound. For the latter use, the terms electromagnetic vibrations or magnetic vibrations, focusing on the structural phenomenon are less ambiguous.

Acoustic noise and vibrations due to electromagnetic forces can be seen as the reciprocal of microphonics, which describes how a mechanical vibration or acoustic noise can induce an undesired electrical perturbation.