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Hour Glass
An hourglass (or sandglass, sand timer, or sand clock) is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated flow of a substance (historically sand) from the upper bulb to the lower one due to gravity. Typically, the upper and lower bulbs are symmetric as they are usually manufactured by pinching a tube. The specific duration of time a given hourglass measures is determined by factors including the quantity and coarseness of the particulate matter and the neck width. Depictions of an hourglass as a symbol of the passage of time are found in art, especially on tombstones or other monuments, from antiquity to the present day. The form of a winged hourglass has been used as a literal depiction of the Latin phrase ("time flies"). History Antiquity The origin of the hourglass is unclear. Its predecessor the ''clepsydra'', or water clock, is known to have existed in Babylon and Egypt as early ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Noon
Noon (also known as noontime or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for '' meridiem'', literally 12:00 midday), 12 p.m. (for ''post meridiem'', literally "after midday"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 ( military time). Solar noon is the time when the Sun appears to contact the local celestial meridian. This is when the Sun reaches its apparent highest point in the sky, at 12 noon apparent solar time and can be observed using a sundial. The local or clock time of solar noon depends on the date, longitude, and time zone, with Daylight Saving Time tending to place solar noon closer to 1:00pm. Etymology The word ''noon'' is derived from Latin ''nona hora'', the ninth canonical hour of the day, in reference to the Western Christian liturgical term Nones (liturgy), (number nine), one of the seven fixed prayer times in traditional Christian denominations. The Roman and Western European medieval monastic day began at 6:00& ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferdinand Magellan
Ferdinand Magellan ( – 27 April 1521) was a Portuguese explorer best known for having planned and led the 1519–22 Spanish expedition to the East Indies. During this expedition, he also discovered the Strait of Magellan, allowing his fleet to pass from the Atlantic into the Pacific Ocean and perform the first European navigation to Asia via the Pacific. Magellan was killed in battle in the Philippines and his crew, commanded by the Spanish Juan Sebastián Elcano, completed the return trip to Spain in 1522 achieving the first circumnavigation of Earth in history. Born around 1480 into a family of minor Portuguese nobility, Magellan became a skilled sailor and naval officer in service of the Portuguese Crown in Asia. King Manuel I refused to support Magellan's plan to reach the Moluccas, or Spice Islands, by sailing westwards around the American continent. Magellan then proposed the same plan to King Charles I of Spain, who approved it. In Seville, he married, fathere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Timer
An egg timer or kitchen timer is a device whose primary function is to assist in timing during cooking; the name comes from the first timers initially being used for the timing of cooking eggs. Early designs simply counted down for a specific period of time. Some modern designs can time more accurately by depending on water temperature rather than an absolute time. Technology Traditionally egg timers were small hourglasses and the name has come to be synonymous with this form. As technology progressed mechanical countdown timers were developed which had an adjustable dial and could be applied to a wide range of timed cooking tasks. Most recently digital timers have also been manufactured and a wide selection of software is available to perform this task on a computer or mobile phone. The task is simple to perform on most microwaves and oven timers. New products have been developed which potentially allow for better egg timing; these use the temperature of the water in which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable nuclide, stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its Amphoterism, amphoteric nature; lead and lead oxides react with acids and base (chemistry), bases, and it tends to form covalent bonds. Lead compounds, Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marble
Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or Dolomite (mineral), dolomite (CaMg(CO3)2) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is typically not Foliation (geology), foliated (Layered intrusion, layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphosed limestone, but its use in stonemasonry more broadly encompasses unmetamorphosed limestone. The extraction of marble is performed by quarrying. Marble production is dominated by four countries: China, Italy, India and Spain, which account for almost half of world production of marble and decorative stone. Because of its high hardness and strong wear resistance, and because it will not be deformed by temperature, marble is often used in Marble sculpture, sculpture and construction. Etymology The word "marble" derives from the Ancient Greek (), from (), "crystalline rock, shin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product. Examples include fused quartz, fumed silica, opal, and aerogels. It is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored. Silicon dioxide is a common fundamental constituent of glass. Structure In the majority of silicon dioxides, the silicon atom shows Tetrahedral molecular geometry, tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ampoule
An ampoule (also ampul and ampule) is a small sealed vial which is used to contain and preserve a sample, usually a solid or liquid. Ampoules are usually made of glass. Modern ampoules are most commonly used to contain pharmaceuticals and chemicals that must be protected from air and contaminants. They are hermetic seal, hermetically sealed by melting the thin top with an open flame, and usually opened by snapping off the neck. The space above the chemical may be filled with an inert gas before sealing. The walls of glass ampoules are usually sufficiently strong to be brought into a glovebox without any difficulty. Glass ampoules are more expensive than bottles and other simple containers, but there are many situations where their superior imperviousness to gases and liquids and all-glass interior surface are worth the extra cost. Examples of chemicals sold in ampoules are hypodermic needle, injectable pharmaceuticals, air-sensitive reagents like tetrakis(triphenylphosphine)pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Chronometer
A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies. When first developed in the 18th century, it was a major technical achievement, as accurate knowledge of the time over a long sea voyage was vital for effective navigation, lacking electronic or communications aids. The first true chronometer was the life work of one man, John Harrison, spanning 31 years of persistent experimentation and testing that revolutionized naval (and later aerial) navigation. The term ''wikt:chronometer, chronometer'' was coined from the Greek words () (meaning time) and (meaning measure). The 1713 book ''Physico-Theology'' by the English cleric and scientist William Derham includes one of the earliest theoretical descriptions of a marine chronome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Harrison
John Harrison ( – 24 March 1776) was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the History of longitude, problem of how to calculate longitude while at sea. Harrison's solution revolutionized navigation and greatly increased the safety of long-distance sea travel. The problem he solved had been considered so important following the Scilly naval disaster of 1707 that the Parliament of Great Britain, British Parliament was offering financial rewards of up to £20,000 (equivalent to £ in ) under the 1714 Longitude Act, though Harrison never received the full reward due to political rivalries. He presented his first design in 1730, and worked over many years on improved designs, making several advances in time-keeping technology, finally turning to what were called sea watches. Harrison gained support from the Board of Longitude, Longitude Board in building and testing his designs. Towards the end of his life, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Museum
The British Museum is a Museum, public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is the largest in the world. It documents the story of human culture from its beginnings to the present.Among the national museums in London, sculpture and decorative art, decorative and applied art are in the Victoria and Albert Museum; the British Museum houses earlier art, non-Western art, prints and drawings. The National Gallery holds the national collection of Western European art to about 1900, while art of the 20th century on is at Tate Modern. Tate Britain holds British Art from 1500 onwards. Books, manuscripts and many works on paper are in the British Library. There are significant overlaps between the coverage of the various collections. Established in 1753, the British Museum was the first public national museum. In 2023, the museum received 5,820,860 visitors, 42% more than the previous y ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
