Have a deep view into what people are curious about.

🔗 Climate change 🔗 Engineering

Cold district heating is a technical variant of a district heating network that operates at low transmission temperatures well below those of conventional district heating systems and can provide both space heating and cooling. Transmission temperatures in the range of approx. 10 to 25 °C are common, allowing different consumers to heat and cool simultaneously and independently of each other. Hot water is produced and the building heated by water heat pumps, which obtain their thermal energy from the heating network, while cooling can be provided either directly via the cold heat network or, if necessary, indirectly via chillers. Cold local heating is sometimes also referred to as an anergy network. The collective term for such systems in scientific terminology is 5th generation district heating and cooling. Due to the possibility of being operated entirely by renewable energies and at the same time contributing to balancing the fluctuating production of wind turbines and photovoltaic systems, cold local heating networks are considered a promising option for a sustainable, potentially greenhouse gas and emission-free heat supply.

🔗 Mathematics

An untouchable number is a positive integer that cannot be expressed as the sum of all the proper divisors of any positive integer (including the untouchable number itself). That is, these numbers are not in the image of the aliquot sum function. Their study goes back at least to Abu Mansur al-Baghdadi (circa 1000 AD), who observed that both 2 and 5 are untouchable.

🔗 Mathematics 🔗 Physics

A topological quantum computer is a theoretical quantum computer that employs two-dimensional quasiparticles called anyons, whose world lines pass around one another to form braids in a three-dimensional spacetime (i.e., one temporal plus two spatial dimensions). These braids form the logic gates that make up the computer. The advantage of a quantum computer based on quantum braids over using trapped quantum particles is that the former is much more stable. Small, cumulative perturbations can cause quantum states to decohere and introduce errors in the computation, but such small perturbations do not change the braids' topological properties. This is like the effort required to cut a string and reattach the ends to form a different braid, as opposed to a ball (representing an ordinary quantum particle in four-dimensional spacetime) bumping into a wall. Alexei Kitaev proposed topological quantum computation in 1997. While the elements of a topological quantum computer originate in a purely mathematical realm, experiments in fractional quantum Hall systems indicate these elements may be created in the real world using semiconductors made of gallium arsenide at a temperature of near absolute zero and subjected to strong magnetic fields.

🔗 Mathematics

Gödel's completeness theorem is a fundamental theorem in mathematical logic that establishes a correspondence between semantic truth and syntactic provability in first-order logic. It makes a close link between model theory that deals with what is true in different models, and proof theory that studies what can be formally proven in particular formal systems.

It was first proved by Kurt Gödel in 1929. It was then simplified in 1947, when Leon Henkin observed in his Ph.D. thesis that the hard part of the proof can be presented as the Model Existence Theorem (published in 1949). Henkin's proof was simplified by Gisbert Hasenjaeger in 1953.

🔗 Lists

This is a list of countries and territories by home ownership rate, which is the ratio of owner-occupied units to total residential units in a specified area.

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Law 🔗 Tennessee

The Battle of Athens (sometimes called the McMinn County War) was a rebellion led by citizens in Athens and Etowah, Tennessee, United States, against the local government in August 1946. The citizens, including some World War II veterans, accused the local officials of predatory policing, police brutality, political corruption, and voter intimidation.

🔗 Military history 🔗 Comedy 🔗 Military history/Maritime warfare 🔗 Military history/European military history 🔗 Military history/British military history

The Dreadnought hoax was a practical joke pulled by Horace de Vere Cole in 1910. Cole tricked the Royal Navy into showing their flagship, the battleship HMS Dreadnought, to a fake delegation of Abyssinian royals. The hoax drew attention in Britain to the emergence of the Bloomsbury Group, among whom some of Cole's collaborators numbered. The hoax was a repeat of a similar impersonation which Cole and Adrian Stephen had organised while they were students at Cambridge in 1905.

🔗 California 🔗 National Register of Historic Places

The Forestiere Underground Gardens in Fresno, California are a series of subterranean structures built by Baldassare Forestiere, an immigrant from Sicily, over a period of 40 years from 1906 to his death in 1946. The gardens are operated by members of the Forestiere family through the Forestiere Historical Center, and can be considered an unconventional example of vernacular architecture.

🔗 Biography 🔗 Greater Manchester

Frederick Travis Dibnah, (29 April 1938 – 6 November 2004) was an English steeplejack and television personality, with a keen interest in mechanical engineering, who described himself as a "backstreet mechanic".

When Dibnah was born, Britain relied heavily upon coal to fuel its industry. As a child, he was fascinated by the steam engines which powered the many textile mills in Bolton, but he paid particular attention to chimneys and the men who worked on them. He began his working life as a joiner, before becoming a steeplejack. From age 22, he served for two years in the Army Catering Corps of the British Army, undertaking his National Service. Once demobilised, he returned to steeplejacking but met with limited success until he was asked to repair Bolton's parish church. The resulting publicity provided a boost to his business, ensuring he was almost never out of work.

In 1978, while making repairs to Bolton Town Hall, Dibnah was filmed by a regional BBC news crew. The BBC then commissioned a documentary, which followed the rough-hewn steeplejack as he worked on chimneys, interacted with his family and talked about his favourite hobby—steam. His Lanky manner and gentle, self-taught philosophical outlook proved popular with viewers and he featured in a number of television programmes. Toward the end of his life, the decline of Britain's industry was mirrored by a decline in his steeplejacking business and Dibnah increasingly came to rely on public appearances and after-dinner speaking to support his income. In 1998, he presented a programme on Britain's industrial history and went on to present a number of series, largely concerned with the Industrial Revolution and its mechanical and architectural legacy.

He died from bladder cancer in November 2004, aged 66.

🔗 Economics 🔗 Business 🔗 Politics 🔗 Socialism 🔗 Sociology

Wage slavery is a term describing a situation in which a person's livelihood depends on wages or a salary, especially when the dependence is total and immediate. It has been used to criticise exploitation of labour and social stratification, with the former seen primarily as unequal bargaining power between labour and capital (particularly when workers are paid comparatively low wages, e.g. in sweatshops) and the latter as a lack of workers' self-management, fulfilling job choices and leisure in an economy. The criticism of social stratification covers a wider range of employment choices bound by the pressures of a hierarchical society to perform otherwise unfulfilling work that deprives humans of their "species character" not only under threat of starvation or poverty, but also of social stigma and status diminution. Historically, some socialist organisations and activists have espoused workers' self-management or worker cooperatives as possible alternatives to wage labour.

Similarities between wage labour and slavery were noted as early as Cicero in Ancient Rome, such as in De Officiis. With the advent of the Industrial Revolution, thinkers such as Pierre-Joseph Proudhon and Karl Marx elaborated the comparison between wage labour and slavery, while Luddites emphasised the dehumanisation brought about by machines. The introduction of wage labour in 18th-century Britain was met with resistance, giving rise to the principles of syndicalism. Before the American Civil War, Southern defenders of African American slavery invoked the concept of wage slavery to favourably compare the condition of their slaves to workers in the North. The United States abolished slavery after the Civil War, but labour union activists found the metaphor useful – according to historian Lawrence Glickman, in the Gilded Age "[r]eferences abounded in the labour press, and it is hard to find a speech by a labour leader without the phrase".