A planetarium is a theatre built for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation. A dominant feature of most planetaria is the large dome-shaped projection screen onto which scenes of stars and other celestial objects can be made to appear and move realistically to simulate the complex'motions of the heavens'; the celestial scenes can be created using a wide variety of technologies, for example precision-engineered'star balls' that combine optical and electro-mechanical technology, slide projector and fulldome projector systems, lasers. Whatever technologies are used, the objective is to link them together to simulate an accurate relative motion of the sky. Typical systems can be set to simulate the sky at any point in time, past or present, to depict the night sky as it would appear from any point of latitude on Earth. Planetariums range in size from the 37 meter dome in St. Petersburg, Russia to three-meter inflatable portable domes where attendees sit on the floor.

The largest planetarium in the Western Hemisphere is the Jennifer Chalsty Planetarium at Liberty Science Center in New Jersey. The Birla Planetarium in Kolkata, India is the largest by seating capacity. Thereafter, the China Science and Technology Museum Planetarium in Beijing, China has the largest seating capacity. In North America, the Hayden Planetarium at the American Museum of Natural History in New York City has the greatest number of seats; the term planetarium is sometimes used generically to describe other devices which illustrate the solar system, such as a computer simulation or an orrery. Planetarium software refers to a software application that renders a three-dimensional image of the sky onto a two-dimensional computer screen; the term planetarian is used to describe a member of the professional staff of a planetarium. The ancient Greek polymath Archimedes is attributed with creating a primitive planetarium device that could predict the movements of the Sun and the Moon and the planets.

The discovery of the Antikythera mechanism proved that such devices existed during antiquity, though after Archimedes' lifetime. Campanus of Novara described a planetary equatorium in his Theorica Planetarum, included instructions on how to build one; the Globe of Gottorf built around 1650 had constellations painted on the inside. These devices would today be referred to as orreries. In fact, many planetaria today have what are called projection orreries, which project onto the dome a Sun with planets going around it in something close to their correct relative periods; the small size of typical 18th century orreries limited their impact, towards the end of that century a number of educators attempted some larger scale simulations of the heavens. The efforts of Adam Walker and his sons are noteworthy in their attempts to fuse theatrical illusions with educational aspirations. Walker's Eidouranion was the heart of theatrical presentations. Walker's son describes this "Elaborate Machine" as "twenty feet high, twenty-seven in diameter: it stands vertically before the spectators, its globes are so large, that they are distinctly seen in the most distant parts of the Theatre.

Every Planet and Satellite seems suspended without any support. Other lecturers promoted their own devices: R E Lloyd advertised his Dioastrodoxon, or Grand Transparent Orrery, by 1825 William Kitchener was offering his Ouranologia, 42 feet in diameter; these devices most sacrificed astronomical accuracy for crowd-pleasing spectacle and sensational and awe-provoking imagery. The oldest, still working planetarium can be found in the Dutch town Franeker, it was built by Eise Eisinga in the living room of his house. It took Eisinga seven years to build his planetarium, completed in 1781. In 1905 Oskar von Miller of the Deutsches Museum in Munich commissioned updated versions of a geared orrery and planetarium from M Sendtner, worked with Franz Meyer, chief engineer at the Carl Zeiss optical works in Jena, on the largest mechanical planetarium constructed, capable of displaying both heliocentric and geocentric motion; this was displayed at the Deutsches Museum in 1924, construction work having been interrupted by the war.

The planets travelled along overhead rails, powered by electric motors: the orbit of Saturn was 11.25 m in diameter. 180 stars were projected onto the wall by electric bulbs. While this was being constructed, von Miller was working at the Zeiss factory with German astronomer Max Wolf, director of the Landessternwarte Heidelberg-Königstuhl observatory of the University of Heidelberg, on a new and novel design, inspired by Wallace W. Atwood's work at the Chicago Academy of Sciences and by the ideas of Walther Bauersfeld and Rudolf Straubel at Zeiss; the result was a planetarium design which would generate all the necessary movements of the stars and planets inside the optical projector, would be mounted centrally in a room, projecting images onto the white surface of a hemisphere. In August 1923, the first Zeiss planetarium projected images of the night sky onto the white plaster lining of a 16 m hemispherical concrete dome, erected on the roof of the Zeiss works; the first official public showing was at the Deutsches Museum in Munich on October 21, 1923.

When Germany was divided into East and West Germany

Shrewsbury is a large market town and the county town of Shropshire, England. The town is on the River Severn and the 2011 census recorded a population of 71,715; the town centre has a largely-unspoilt medieval street plan and over 660 listed buildings, including several examples of timber framing from the 15th and 16th centuries. Shrewsbury Castle, a red sandstone fortification, Shrewsbury Abbey, a former Benedictine monastery, were founded in 1074 and 1083 by the Norman Earl of Shrewsbury, Roger de Montgomery; the town is where he spent 27 years of his life. Located 9 miles east of the Welsh border, Shrewsbury serves as the commercial centre for Shropshire and mid-Wales, with a retail output of over £299 million per year and light industry and distribution centres, such as Battlefield Enterprise Park, on the outskirts; the A5 and A49 trunk roads come together as the town's by-pass, five railway lines meet at Shrewsbury railway station. The town is located 150 miles north-west of London; the town was the early capital of the Kingdom of Powys, known to the ancient Britons as Pengwern, signifying "the alder hill".

This name evolved in three directions, into Sciropscire, which became Shropshire. Its Welsh name Amwythig means "fortified place". Over the ages, the geographically important town has been the site of many conflicts between the English and Welsh; the Angles, under King Offa of Mercia, took possession in 778. Nearby is the village of 5 miles to the south-east; this was once the site of the fourth largest cantonal capital in Roman Britain. As Caer Guricon it is a possible alternative for the Dark Age seat of the Kingdom of Powys; the importance of the Shrewsbury area in the Roman era was underlined with the discovery of the Shrewsbury Hoard in 2009. Shrewsbury's known history commences in the Early Middle Ages, having been founded c. 800 AD. It is believed that Anglo-Saxon Shrewsbury was most a settlement fortified through the use of earthworks comprising a ditch and rampart, which were shored up with a wooden stockade. There is evidence to show; the Welsh were repelled by William the Conqueror. Roger de Montgomery was given the town as a gift from William, built Shrewsbury Castle in 1074, taking the title of Earl.

He founded Shrewsbury Abbey as a Benedictine monastery in 1083. The 3rd Earl, Robert of Bellême, was deposed in 1102 and the title forfeited, in consequence of rebelling against Henry I and joining the Duke of Normandy's invasion of England in 1101. In 1138, King Stephen besieged the castle held by William FitzAlan for the Empress Maud during the period known as the Anarchy, it was in the late Middle Ages. This success was due to wool production, a major industry at the time, the wool trade with the rest of Britain and Europe, with the River Severn and Watling Street acting as trading routes; the Shrewsbury Drapers Company dominated the trade in Welsh wool for many years. Despite its commercial success, Shrewbury was not immune from the effects of the Black Death. Records suggest the plague arrived in the spring of 1349, was devastating. Examining the number of local church benefices falling vacant due to death, 1349 alone saw twice the vacancies as the previous ten years combined, suggesting a high death toll in Shrewsbury.

In 1403 the Battle of Shrewsbury was fought a few miles north at Battlefield. Shrewsbury's monastic gathering was disbanded with the Dissolution of the Monasteries and as such the Abbey was closed in 1540. However, it is believed that Henry VIII thereafter intended to make Shrewsbury a cathedral city after the formation of the Church of England, but the citizens of the town declined the offer. Despite this, Shrewsbury thrived throughout the 17th centuries; as a result, a number of grand edifices, including the Ireland's Mansion and Draper's Hall, were constructed. It was in this period that Edward VI gave permission for the foundation of a free school, to become Shrewsbury School. During the English Civil War, the town was a Royalist stronghold and only fell to Parliament forces after they were let in by a parliamentarian sympathiser at the St Mary's Water Gate. After Thomas Mytton captured Shrewsbury in February 1645; this prompted Prince Rupert to respond by executing Parliamentarian prisoners in Oswestry.

Shrewsbury Unitarian Church was founded in 1662. By the 18th century Shrewsbury had become an important market town and stop off for stagecoaches travelling between London and Holyhead on their way to Ireland. Local soldier and statesman Robert Clive was Shrewsbury's MP from 1762 until his death in 1774. Clive served once

Bagillt is a small town and community overlooking the Dee Estuary, near Holywell in Flintshire, Wales. At the 2001 Census the population was recorded as 3,918; the community includes the villages of Walwen and Whelston. Bagillt was part of the Kingdom of Gwynedd in the early medieval period. In the 12th century, Owain Gwynedd and his forces retreated to Bryn Dychwelwch, the "Hill of Retreat", above Bagillt while being pursued by superior numbers of Henry II's forces. Castell Hen Blas, a motte-and-bailey castle, lies within the boundaries of Bagillt, it was the birthplace of Dafydd ap Llywelyn, Prince of Wales around Easter 1212. The castle ruins were excavated in the mid-1950s. Dafydd's birth was commemorated by the unveiling of a plaque on the wall of the Upper Shippe Inn in the centre of the village on 25 July 2010. Mostyn Hall, the seat of one of the oldest Welsh families, lies close to Bagillt. Parts of the building date from the time of Henry VI in the 15th century; the future Henry VII is said to have been concealed in the Hall by the lord of Mostyn, Richard ap Howel, during the reign of Richard III.

The Hall now houses antiquities and manuscripts pertaining to British and Welsh history that were brought from Gloddaeth Hall, Llanrhos. The Gadlys Lead Smelting Works was established by Edward Wright and his associates, who were Quakers, in 1704. Organised as the London Lead Company, they kept the workshop open until 1799. John Freame, one of the founders of Barclays Bank, was involved in this initiative. By the late 18th century, Bagillt had become a centre of mineral manufacturing. Hundreds of men laboured in eleven collieries. There was a factory and works that produced and refined zinc and iron. Bagillt had several quays on the banks of the River Dee, where fishing boats had moored for centuries, but by the early 19th century, these had grown into docks where cargo destined for the factories and foundries of England were loaded. In 1846, navvies laying track for the North Wales Coast Line reached Bagillt; the Chester and Holyhead Railway opened on 1 May 1848. The local mines and works that had used these wharves now switched to haulage by steam train.

Bagillt railway station had goods yard. It closed in 1966. In 1879 a working men's club and cocoa house was built on the High Street in the Pentre area by public subscription; the building was named the Foresters Hall. It was built to promote temperance and was associated with the Foresters Friendly Society, it was the first cocoa house built in Wales. But the industrial age created problems: in 1848, the same year the railway opened, a book was published in London entitled Reports of the Commissioners of Inquiry into the state of Education in Wales, it detailed the poverty and hard living of many people in Bagillt and the Flintshire coalfields in the 19th century: In some of the collieries the men are paid every other Saturday, do not return to their work till the following Tuesday or Wednesday. In Bagillt and in the adjoining town of Flint the old Welsh custom of keeping a merry night is still prevalent, being reserved for a Saturday, is protracted to the following Sunday, during which drinking never ceases.

The custom is represented by the others as involving the most pernicious consequences. I saw two men stripped and fighting in the main street of Bagillt, with a ring of men and children around them. There is no policeman in the township; the women are represented as being for the most part ignorant of domestic economy. The girls are early sent to service, but marry as early as 18, have large families. Women are not employed in or about the mines, but spend most of their time in cockling, or gathering cockles on the beach, they have low ideas of domestic comfort, living in small cottages dirty and ill-ventilated, at night are crowded together in the same room, sometimes in the same bed, without regard to age or sex. Bagillt remained a hard-working boom town for more than a century. For instance on 31 May 1873, a local newspaper, the Wrexham Advertiser, reported that so many new coal workings had opened near Bagillt that it was becoming difficult to find enough miners to work in them: No less than four new collieries have been started near Mold, it is becoming a serious question how to get labour to work them, all the men available in the district being engaged.

The colliery nearest the town on the north side is named Hard Struggle from the difficulty experienced in obtaining water to get up steam. Another to the east side is named Slap Bang from the fact. To the south the Linger and Die company are doing their best to reduce the price of coal and to enhance that of labour. While to the south east the Strip and at it company are showing the world how to make the most of it. We hear of numberless other ventures. In July 1897 work commenced at Boot End, Bagillt, on the huge Milwr Tunnel which would drain water from the mines working the lead lodes under Pentre Halkyn. Digging started at a point 9 feet below high-water mark on the Dee foreshore; the tunnel was driven southwest at a gradient of 1:1000. It was brick-lined where it passed through coal measures and shale but unlined after the first 1.5 miles where it passed through chert and limestone. In 1908 the tunnel was draining more than 1.7 million gallons of water per day through the drainage channel a