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Rømer's determination of the speed of light was the demonstration in 1676 that light has a finite speed and so does not travel instantaneously. The discovery is usually attributed to Danish astronomer Ole Rømer, who was working at the Royal Observatory in Paris at the time.

By timing the eclipses of the Jovian moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun. This would give light a velocity of about 220,000 kilometres per second, about 26% lower than the true value of 299,792 km/s.

Rømer's theory was controversial at the time that he announced it and he never convinced the director of the Paris Observatory, Giovanni Domenico Cassini, to fully accept it. However, it quickly gained support among other natural philosophers of the period such as Christiaan Huygens and Isaac Newton. It was finally confirmed nearly two decades after Rømer's death, with the explanation in 1729 of stellar aberration by the English astronomer James Bradley.

In multi-objective optimization, the Pareto front (also called Pareto frontier or Pareto curve) is the set of all Pareto efficient solutions. The concept is widely used in engineering.^{: 111–148} It allows the designer to restrict attention to the set of efficient choices, and to make tradeoffs within this set, rather than considering the full range of every parameter.^{: 63–65 : 399–412}

The axial twist theory (a.k.a. axial twist hypothesis) is a proposed scientific theory to explain a range of unusual aspects of the body plan of vertebrates (including humans). It states that the rostral part of the head is "turned around" regarding the rest of the body. This end-part consists of the face (eyes, nose, and mouth) as well as part of the brain (cerebrum and thalamus). According to the theory, the vertebrate body has a left-handed chirality.

The axial twist theory competes with a number of other proposals that focus on more limited, specific aspects, most of which explain contralateral forebrain organization, the phenomenon that the left side of the brain mainly controls the right side of the body and vice versa. None of the proposed theories explaining this phenomenon, including axial twist theory, have gained general recognition. The genetic basis underlying the proposed developmental twist is not yet understood.

The axial twist theory would explain various anatomical phenomena, and addresses how and when the proposed twist between the end of the head and the rest of the body develops. It also addresses the possible evolutionary history. One prediction of the theory was the aurofacial asymmetry, which was then found empirically, albeit by one of the authors of the original theory.

Phenomena the theory can explain include:

• Contralateral organization of the brain
• Left-sided orientation of the heart
• Asymmetric position of the gastrointestinal tract, the liver, and the pancreas
• Optic chiasm
• Chiasm of the trochlear nerve
• Non-crossed olfactory tract
• Aurofacial asymmetry
• Yakovlevian torque
• Asymmetry of the thoracal vertebra

According to the axial twist developmental model, the anterior part of the head turns against the rest of the body, except for the inner organs. Due to this twist, the forebrain and face are turned around such that left and right, but also anterior and posterior are flipped in the adult vertebrate.

The Ambassadors (1533) is a painting by Hans Holbein the Younger. Also known as Jean de Dinteville and Georges de Selve, it was created in the Tudor period, in the same year Elizabeth I was born. As well as being a double portrait, the painting contains a still life of several meticulously rendered objects, the meaning of which is the cause of much debate. It also incorporates a much-cited example of anamorphosis in painting. It is part of the collection at the National Gallery in London.

A Penrose tiling is an example of an aperiodic tiling. Here, a tiling is a covering of the plane by non-overlapping polygons or other shapes, and aperiodic means that shifting any tiling with these shapes by any finite distance, without rotation, cannot produce the same tiling. However, despite their lack of translational symmetry, Penrose tilings may have both reflection symmetry and fivefold rotational symmetry. Penrose tilings are named after mathematician and physicist Roger Penrose, who investigated them in the 1970s.

There are several different variations of Penrose tilings with different tile shapes. The original form of Penrose tiling used tiles of four different shapes, but this was later reduced to only two shapes: either two different rhombi, or two different quadrilaterals called kites and darts. The Penrose tilings are obtained by constraining the ways in which these shapes are allowed to fit together. This may be done in several different ways, including matching rules, substitution tiling or finite subdivision rules, cut and project schemes, and coverings. Even constrained in this manner, each variation yields infinitely many different Penrose tilings.

Penrose tilings are self-similar: they may be converted to equivalent Penrose tilings with different sizes of tiles, using processes called inflation and deflation. The pattern represented by every finite patch of tiles in a Penrose tiling occurs infinitely many times throughout the tiling. They are quasicrystals: implemented as a physical structure a Penrose tiling will produce diffraction patterns with Bragg peaks and five-fold symmetry, revealing the repeated patterns and fixed orientations of its tiles. The study of these tilings has been important in the understanding of physical materials that also form quasicrystals. Penrose tilings have also been applied in architecture and decoration, as in the floor tiling shown.

The Southern Television broadcast interruption was a broadcast signal intrusion that occurred on 26 November 1977 in parts of southern England in the United Kingdom. The audio of a Southern Television broadcast was replaced by a voice claiming to represent the 'Ashtar Galactic Command', delivering a message instructing humanity to abandon its weapons so it could participate in a 'future awakening' and 'achieve a higher state of evolution'. After six minutes, the broadcast returned to its scheduled programme.

Subsequent investigations showed that the Hannington transmitter of the Independent Broadcasting Authority had rebroadcast the signal from a small but nearby unauthorised transmitter, instead of the intended source at Rowridge transmitting station. The hoaxer was never identified.

The event prompted hundreds of telephone calls from concerned members of the public, and was widely reported in British and American newspapers. These are sometimes contradictory, including differing accounts of the name used by the speaker and the wording of their message.

From its beginnings in the 1960s, writing software has evolved into a profession concerned with how best to maximize the quality of software and of how to create it. Quality can refer to how maintainable software is, to its stability, speed, usability, testability, readability, size, cost, security, and number of flaws or "bugs", as well as to less measurable qualities like elegance, conciseness, and customer satisfaction, among many other attributes. How best to create high quality software is a separate and controversial problem covering software design principles, so-called "best practices" for writing code, as well as broader management issues such as optimal team size, process, how best to deliver software on time and as quickly as possible, work-place "culture", hiring practices, and so forth. All this falls under the broad rubric of software engineering.

Fumifugium, or, The inconveniencie of the aer and smoak of London dissipated together with some remedies humbly proposed by J.E. esq. to His Sacred Majestie, and to the Parliament now assembled is a pamphlet published in London, 1661 (see 1661 in literature), by John Evelyn. It is one of the earliest known works on air pollution and is broken down into three parts which explain the problem, a proposed solution, and a way of improvement upon the air in London. The letter was specifically addressed to King Charles II of England and discussed problems with the capital's air pollution dating back to medieval times. Evelyn refers to Greek philosophers, who once believed that air was the principle of the earth and primary substance of the soul up until the time that air pollution began to cause ill health.

Evelyn was appointed to the newly formed Royal Society, and both Society and pamphlet are celebrated in the 1663 "Ballad of Gresham College". Stanza 23 (given here in modern English) describes how Evelyn

[...] shows that 'tis the sea-coal smoke

That always London does environ,
Which does our lungs and spirits choke,
Our hanging spoil, and rust our iron.
Let none at Fumifuge be scoffing

Who heard at Church our Sunday's coughing.

The sea-coal to which Evelyn referred was appropriately named because it came by sea from Newcastle. When burned, it gave off a terrible smell because of high amounts of sulfur in its composition. When burned the sea coal released sulfur dioxide, carbon dioxide, nitric oxide, soot, and particulates of organic matter into the atmosphere. The pamphlet suggests that burning wood, particularly aromatic woods, will be less harmful to the lungs and recommends relocating some of London's more polluting industries outside the capital, in particular lime-burning and brewing.

Kriegspiel is a chess variant invented by Henry Michael Temple in 1899 and based upon the original Kriegsspiel (German for war game) developed by Georg von Reiswitz in 1812. In this game each player can see their own pieces, but not those of their opponent. For this reason, it is necessary to have a third person (or computer) act as an umpire, with full information about the progress of the game. When it is a player's turn he or she will attempt a move, which the umpire will declare to be 'legal' or 'illegal'. If the move is illegal, the player tries again; if it is legal, that move stands. Each player is given information about checks and captures. They may also ask the umpire if there are any legal captures with a pawn. Since the position of the opponent's pieces is unknown, Kriegspiel is a game of imperfect information. The game is sometimes referred to as blind chess.