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The Alcubierre drive, Alcubierre warp drive, or Alcubierre metric (referring to metric tensor) is a speculative idea based on a solution of Einstein's field equations in general relativity as proposed by Mexican theoretical physicist Miguel Alcubierre, by which a spacecraft could achieve apparent faster-than-light travel if a configurable energy-density field lower than that of vacuum (that is, negative mass) could be created.

Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. Objects cannot accelerate to the speed of light within normal spacetime; instead, the Alcubierre drive shifts space around an object so that the object would arrive at its destination faster than light would in normal space without breaking any physical laws.

Although the metric proposed by Alcubierre is consistent with the Einstein field equations, construction of such a drive is not necessarily possible. The proposed mechanism of the Alcubierre drive implies a negative energy density and therefore requires exotic matter. So if exotic matter with the correct properties cannot exist, then the drive could not be constructed. At the close of his original article, however, Alcubierre argued (following an argument developed by physicists analyzing traversable wormholes) that the Casimir vacuum between parallel plates could fulfill the negative-energy requirement for the Alcubierre drive.

Another possible issue is that, although the Alcubierre metric is consistent with Einstein's equations, general relativity does not incorporate quantum mechanics. Some physicists have presented arguments to suggest that a theory of quantum gravity (which would incorporate both theories) would eliminate those solutions in general relativity that allow for backwards time travel (see the chronology protection conjecture) and thus make the Alcubierre drive invalid.

Atmos is the brand name of a mechanical torsion pendulum clock manufactured by Jaeger-LeCoultre in Switzerland which does not need to be wound manually. It gets the energy it needs to run from temperature and atmospheric pressure changes in the environment, and can run for years without human intervention.

The clock is driven by a mainspring, which is wound by the expansion and contraction of liquid and gaseous ethyl chloride in an internal hermetically sealed bellows. The ethyl chloride vaporises into an expansion chamber as the temperature rises, compressing a spiral spring; with a fall in temperature the gas condenses and the spring slackens. This motion constantly winds the mainspring. A temperature variation of only one degree in the range between 15 °C (59 °F) and 30 °C (86 °F), or a pressure variation of 3 mmHg, is sufficient for two days' operation.

In order to run the clock on this small amount of energy, everything inside the Atmos has to work in as friction-free a manner as possible. For timekeeping it uses a torsion pendulum, which consumes less energy than an ordinary pendulum. The torsion pendulum has a period of precisely one minute; thirty seconds to rotate in one direction and thirty seconds to return to the starting position. This is thirty times slower than the 0.994 m (39.1 in) seconds pendulum typically found in a longcase clock, where each swing (or half-period) takes one second.

On 24 October 1975, Icelandic women went on strike for the day to "demonstrate the indispensable work of women for Iceland’s economy and society" and to "protest wage discrepancy and unfair employment practices". It was then publicized domestically as Women's Day Off (Kvennafrídagurinn). Participants, led by women's organizations, did not go to their paid jobs and did not do any housework or child-rearing for the whole day. Ninety percent of Iceland's female population participated in the strike. Iceland's parliament passed a law guaranteeing equal pay the following year.

The Jumbo Stay (formerly named the Jumbo Hostel) is a hostel located inside a decommissioned Boeing 747-200 jetliner at Stockholm Arlanda Airport. It opened in 2009.

A sex drive-in or sex box is a car garage (or similarly shielded location) that is designed to allow prostitution to take place using cars, and can be found in a few countries in Europe. Generally the facilities are created by local authorities to put some control on where prostitution occurs and to provide increased safety.

This is a list of present-day cities by the time period over which they have been continuously inhabited as a city. The age claims listed are generally disputed. Differences in opinion can result from different definitions of "city" as well as "continuous habitation" and historical evidence is often disputed. Caveats (and sources) to the validity of each claim are discussed in the "Notes" column.

OK (spelling variations include okay, O.K., and ok) is an English word (originally American English) denoting approval, acceptance, agreement, assent, acknowledgment, or a sign of indifference. OK is frequently used as a loanword in other languages. It has been described as the most frequently spoken or written word on the planet. The origins of the word are disputed.

As an adjective, OK principally means "adequate" or "acceptable" as a contrast to "bad" ("The boss approved this, so it is OK to send out"); it can also mean "mediocre" when used in contrast with "good" ("The french fries were great, but the burger was just OK"). It fulfills a similar role as an adverb ("Wow, you did OK for your first time skiing!"). As an interjection, it can denote compliance ("OK, I will do that"), or agreement ("OK, that is fine"). It can mean "assent" when it is used as a noun ("the boss gave her the OK to the purchase") or, more colloquially, as a verb ("the boss OKed the purchase"). OK, as an adjective, can express acknowledgement without approval. As a versatile discourse marker or back-channeling item, it can also be used with appropriate intonation to show doubt or to seek confirmation ("OK?", "Is that OK?").

A stack-oriented programming language is one that relies on a stack machine model for passing parameters. Several programming languages fit this description, notably Forth, RPL, PostScript, BibTeX style design language and many assembly languages (on a much lower level).

Stack-oriented languages operate on one or more stacks, each of which may serve a different purpose. Thus, programming constructs in other programming languages may need to be modified for use in a stack-oriented system. Further, some stack-oriented languages operate in postfix or Reverse Polish notation, that is, any arguments or parameters for a command are stated before that command. For example, postfix notation would be written 2, 3, multiply instead of multiply, 2, 3 (prefix or Polish notation), or 2 multiply 3 (infix notation).

The need for cognition (NFC), in psychology, is a personality variable reflecting the extent to which individuals are inclined towards effortful cognitive activities.

Need for cognition has been variously defined as "a need to structure relevant situations in meaningful, integrated ways" and "a need to understand and make reasonable the experiential world". Higher NFC is associated with increased appreciation of debate, idea evaluation, and problem solving. Those with a high need for cognition may be inclined towards high elaboration. Those with a lower need for cognition may display opposite tendencies, and may process information more heuristically, often through low elaboration.

Need for cognition is closely related to the five factor model domain openness to experience, typical intellectual engagement, and epistemic curiosity (see below).

Snottite, also snoticle, is a microbial mat of single-celled extremophilic bacteria which hang from the walls and ceilings of caves and are similar to small stalactites, but have the consistency of nasal mucus. In the Frasassi Caves in Italy, over 70% of cells in Snottite have been identified as Acidithiobacillus thiooxidans, with smaller populations including an archaeon in the uncultivated 'G-plasma' clade of Thermoplasmatales (>15%) and a bacterium in the Acidimicrobiaceae family (>5%).

The bacteria derive their energy from chemosynthesis of volcanic sulfur compounds including H₂S and warm-water solution dripping down from above, producing sulfuric acid. Because of this, their waste products are highly acidic (approaching pH=0), with similar properties to battery acid. Researchers at the University of Texas have suggested that this sulfuric acid may be a more significant cause of cave formation than the usual explanation offered of the carbonic acid formed from carbon dioxide dissolved in water.

Snottites were brought to attention by researchers Diana Northup and Penny Boston studying them (and other organisms) in a toxic sulfur cave called Cueva de Villa Luz (Cave of the Lighted House), in Tabasco, Mexico. Snottites were first discovered in this cave by Jim Pisarowicz in 1986, who also coined the term.

The BBC series Wonders of the Solar System saw Professor Brian Cox examining snottites and positing that if there is life on Mars, it may be similarly primitive and hidden beneath the surface of the Red Planet.