Wikipedia:Picture of the day/December 2004

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Liquid water is most dense at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the temperature drops to 0 °C. This is due to hydrogen bonds forming between the water molecules, which line up molecules less efficiently (in terms of volume) when water is frozen. The result is that ice floats on liquid water, an important factor in Earth's climate.

Photo credit: Barfooz
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Modern Formula 1 must be constructed by the racing teams themselves and are required to be powered by 3.0-litre, ten-cylinder naturally aspirated engines. Estimates put the best engines at or about 900 bhp at 19,000 rpm.

Photo credit: Rick Dikeman
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The Damselfly (suborder Zygoptera) is an insect in the order Odonata. They are similar to a dragonfly, but the adults can be differentiated by the fact their wings are held along the body when at rest. They are also usually smaller, and weaker fliers than dragonflies, and the eyes are separated.

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The island Ko Samui has a population of about forty thousand, and survives on a successful tourist industry, as well as exports of coconut and rubber. It even has its own international airport, with flights daily to Bangkok and other major airports in Southeast Asia. It has not forgotten its roots, however, and the people are still by-and-large the same easygoing island folk they were before the world landed on their doorstep.

Photo credit: Tsui
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The blood of Icefish is transparent because they have no haemoglobin and no or only defunct erythrocytes. Their metabolism relies only on the oxygen dissolved in the liquid blood, which is believed to be absorbed directly through the skin from the water. This works, because water can dissolve the most oxygen when it is coldest.

Photo credit: Uwe Kils
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Lake Tanganyika is situated within the Western Rift of the Great Rift Valley and is confined by the mountainous walls of the valley. It is the largest rift lake in Africa and the second largest lake by surface area on the continent. It is the deepest lake in Africa and holds the greatest volume of fresh water.

Photo credit: Worldtraveller
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Zabriskie Point is an area in Death Valley National Park noted for its beautiful erosional landscape. It is called a badlands due to its difficult-to-traverse topography. The area is composed of sediment from Lake Zabriskie, which dried-up 9 million years ago - long before Death Valley existed. Zabriskie Point is named after Christian Brevoort Zabriskie of Wyoming Territory.

Photo credit: Daniel Mayer
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Historically, the first soda waters were prepared by adding sodium bicarbonate to lemonade. A chemical reaction between sodium bicarbonate and citric acid occurred to create carbon dioxide. The person who is usually credited with first successfully creating carbonated water is Joseph Priestley in 1796.

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Although used occasionally in later experimental devices, this nuclear weapon design was used only once as a weapon, in Little Boy, because of the extreme danger of a misfire. A simple crash could drive the "bullet" into the "target" and release lethal radiation doses or even a full nuclear detonation.

Photo credit: Fastfission
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The Wolf spider is a spider of the family Lycosidae. Except for the genus Sosippus, these spiders do not use their silk to make a snare. Some use their silk to line a tubular tunnel in the ground. Some take regular shelter in natural crevices. Still others spend their entire lives wandering around with no fixed abode. Unlike many other spiders, they have good vision and run their prey down.

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Abbey of Senanque, located in France, Provence, Vaucluse, Gordes village. An abbey is a Christian monastery or convent, under the government of an Abbot or an Abbess, who serve as the spiritual father or mother of the community.

Photo credit: Greudin
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The Sydney Opera House in Sydney, New South Wales , Australia. Situated on Bennelong Point at Sydney Harbour, the Sydney Opera House is one of the most distinctive and famous 20th-century buildings, and one of the most famous performing arts venues in the world.

Photo credit: Chmouel
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Crystals of 99.999% gallium. The chemical element gallium is a rare, soft silvery metallic poor metal. It occurs in trace amounts in bauxite and zinc ores. Gallium is notable for its stunning silvery color and its solid metal fractures conchoidally like glass.

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The first ejector seats were developed during the war by Heinkel. Early models were powered by compressed air and the first aircraft to be fitted with such a system was the Heinkel He 280 prototype jet fighter in 1941. One of the He 280 test pilots, Helmut Schenk, became the first person to escape from a stricken aircraft with an ejector seat on January 13, 1942 after his control surfaces iced up and became inoperable. By December 2003, Martin-Baker ejector seats had saved 7028 lives. The total figure for all types of seat is unknown but must be considerably higher.

Photo credit: U.S. Air Force
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The Vitruvian Man is a famous drawing with accompanying notes by Leonardo da Vinci made around the year 1490 in one of his journals. It depicts a naked male figure in two superimposed positions with his arms apart and simultaneously inscribed in a circle and square. The drawing and text are sometimes called the Canon of Proportions. The rediscovery of the mathematical proportions of the human body in the 15th century by Da Vinci and others is considered one of the great achievements leading to the Italian Renaissance.

Photo credit: Leonardo da Vinci
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Io moon taken by NASA's Galileo probe. This image shows two volcanic eruptions. The one on the horizon is 140km high, the other is 75km high. Io is the innermost of the four Galilean moons of Jupiter. It is named after Io, one of Zeus's many love interests in Greek mythology.

Photo credit: NASA
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Darlingtonia (Darlingtonia californica), also called the California Pitcher plant or Cobra Lily, is a carnivorous plant in the family Sarraceniaceae. Darlingtonia is native to California and Oregon and grows in bogs and seeps. The name Cobra Lily is from the resemblance of the tubular leaf to a rearing Cobra, complete with "fangs". The genus Darlingtonia is monotypic.

Photo credit: Daniel Keshet
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Mount Cook, a peak in the Southern Alps is the highest mountain in New Zealand. Mount Cook is also known as Aoraki, meaning "Cloud Piercer" in the Kai Tahu dialect of the Maori language. The mountain is located within the Aoraki/Mount Cook National Park and was formally declared one of the United Nations World Heritage Parks in 1953.

Photo credit: Dynabee
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A mackerel sky is an indicator of moisture and instability at high levels. If the lower atmosphere is stable and no moist air moves in, the weather will most likely remain dry. However, moisture at lower levels combined with temperature instability can lead to spectacular thunderstorms should the rising moist air reach this layer. In weather lore, a mackerel sky portends changeable weather.

Photo credit: Denni Windrim
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The National Gallery at night, illuminated for an event to promote the launch of a Pepsi commercial. The National Gallery in London is an art gallery designed by William Wilkins. It holds part of the National Collection, particularly Western European art from 1250 to 1900. The collection of 2300 paintings belongs to the British public.

Photo credit: Michael Reeve
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Bryce Canyon National Park is distinctive due to its unique geological structures, called hoodoos. In winter, most birds in the park migrate, but jays, ravens, nuthatches, eagles, and owls stay. The Mule Deer, Mountain Lion, and coyotes will migrate to lower elevations. Ground squirrels and marmots pass the winter in hibernation.

Photo credit: National Park Service
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The Emperor Penguin is the largest of all penguins. Like his King Penguin counterpart, a male Emperor Penguin has an abdominal fold—the "brood pouch"—between its legs and lower abdomen. The male will incubate an egg in its brood pouch for 65 days without food by surviving on his fat reserves.

Photo credit: Josh Landis
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Sainte Jeanne d'Arc Church at night. Sainte Jeanne d'Arc Church is a Catholic church in Nice, France which is noticeable for its original architecture. The church was built between 1926 and 1933 by the architect Jacques Dror in reinforced concrete. The style was influenced by Art nouveau.

Photo credit: Ericd
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The airship USS Akron (ZRS-4) flying over the southern tip of Manhattan circa 1931–1933. The Akron was a commissioned 'ship' of the United States Navy, built for them by the Goodyear-Zeppelin Corporation in Akron, Ohio. She cast off for her maiden voyage on 2 November 1931, but crashed less than two years later.

Photo credit: U.S. Naval Historical Center
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The blue ice covering Lake Fryxell in the Transantarctic Mountains, a mountain range in Antarctica, comes from glacial meltwater from the Canada Glacier and other smaller glaciers. The freshwater stays on top of the lake and freezes, sealing in briny water below.

Photo credit: Joe Mastroianni
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A plant's leaves are the primary sites for photosynthesis. The green colour is from chlorophyll, a pigment that absorbs the energy from sunlight falling on the leaf. The veins are the vascular tissue of the leaf, moving water into the leaf and the sap produced by photosynthesis back out.

Photo credit: PDPhoto.org
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Antarctica, the continent surrounding the Earth's South Pole, is the coldest place on earth and is almost entirely covered by ice. Antarctica was discovered in late January 1820. Too cold and dry to support virtually any vascular plants, Antarctica's flora presently consists of around 250 lichens, 100 mosses, 25-30 liverworts, and around 700 terrestrial and aquatic algal species.

Photo credit: NASA
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An 18th century Persian Astrolabe. During the age of sail, the astrolabe was the chief instrument for navigation. It is a precursor of the modern planisphere — the back plate, or mater is engraved with coordinate lines of the celestial sphere in stereographic projection, the points of the curved spikes on the front rete plate, mark the positions of the brightest stars.

Photo credit: Solipsist
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