Sun

Hazy conditions, atmospheric dust, and high humidity contribute to this atmospheric attenuation.
. During sunrise and sunset, sunlight is attenuated by a particularly long passage through Earth's atmosphere, and the direct Sun is sometimes faint enough to be viewed directly without discomfort or safely with binoculars. Moreover, Dresden hosts many world-class research institutes:. Viewing the partially eclipsed Sun with the naked eye can cause permanent localized damage to the retina, resulting in small, permanent blind spots for the viewer.^[20] This is an especially insidious hazard for inexperienced observers and for children, because there is no immediate perception of pain and it is tempting to stare at the spectacle of the eclipsing Sun, compounding any damage. Dresden is home to a number of renowned universities:. Each retinal cell that is exposed to the partially-eclipsed solar image thus receives about ten times as much light as it would looking at the normal, non-eclipsed Sun. Between five and eight thousand Neo-Nazis took part, mourning for the victims of what they call the Allied bomb-holocaust (German: Alliierter Bombenholocaust).

In the dim overall light, the pupil tends to dilate from about 2 mm to perhaps 6 mm diameter, increasing the eye's collecting area by a factor of nearly 10. In 2005, Dresden was host to the largest Neo-Nazi demonstration in the post-war history of Germany. During partial eclipses, most sunlight is blocked by the Moon passing directly in front of the Sun, but the uncovered parts of the photosphere have the same surface brightness as during a normal day. Affiliated with the radical right National Democratic Party of Germany (NPD), they cite the bombing of Dresden in order to portray Germans as the real victims of the Second World War, and try to take advantage of anti-American sentiment to do it. The pupil is controlled by the total amount of light in the visual field, not by the brightest object in the field. In recent years, however, right-wing extremist skinheads have tried to instrumentalize the event for their own political ends. During partial eclipses of the Sun, another hazardous condition exists because of the way the eye responds to bright light. Since reunification, the tone of the ceremonies has taken on a more neutral and pacifist tone.

Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness.^[19]. Similar ceremonies held during the period of communism were specifically directed at demonizing the Western Allies, above all the United States. Viewing the Sun through unfiltered 7x50 mm binoculars can deliver as much as 2.5 watts of sunlight into each eye, over 300 times more power than naked eye viewing. Every year on February 13, the anniversary of the major British fire-bombing raid that destroyed most of the city, tens of thousands of demonstrators gather to commemorate the event. Using a proper filter is very important as some improvised filters reduce visible light while passing either infrared or ultraviolet rays that can still damage the eye. Dresden remains a major cultural epicenter of historical memory, owing to the city's destruction in World War II. Suitable filters are available at welding supply shops and camera stores. In 2004 the United Nation's cultural organization UNESCO declared Dresden and the surrounding section of Elbe river valley to be a "World Heritage" site.

Viewing the Sun through light-concentrating optics such as binoculars is hazardous without an attenuating (ND) filter to dim the sunlight. Disaster relief for the millennial flood came from around the world. Brief viewing of the full direct Sun with the naked eye is unpleasant but generally safe.^[18]. The destruction from this “millennium flood” is no longer visible, due to the rapidity of reconstruction. Direct viewing of the Sun with the naked eye delivers about 4 milliwatts of sunlight to the retina that is in the solar image, heating it up and potentially (though not normally) damaging it. In 2002, torrential rains caused the Elbe to flood 9 m past its 1845 record height, damaging many landmarks (See 2002 European flood). Looking directly at the Sun when it is high in the sky causes temporary bleaching of the photosensitive pigments in the retina, which makes phosphene visual artifacts and may cause temporary partial blindness. Volkswagen is currently manufacturing its Phaeton car model and the Bentley "flying spur" model at a modern factory located in central Dresden, delivered by city tramway.

Sunlight is very bright, and looking directly at the Sun is painful to the eyes. The city has also attracted many new firms to the region (including AMD, Motorola, net-linx, Toppan Photomasks, Infineon Technologies, and Airbus Industries). The energy stored in petroleum is thought to have been converted from sunlight by photosynthesis in the distant past. Many of the industries that made Dresden rich before the Second World War and disappeared under communism have resettled in the city including the optical industry, the high quality foodstuffs industries, and the watchmaking industries (including the Glashütte brand). Photosynthesis by plants captures the energy of sunlight and converts it to chemical form (oxygen and reduced carbon compounds), while direct heating or electrical conversion by solar cells are used by solar power equipment to generate electricity or do other useful work. Dresden as a major urban center has developed much faster and more consistently than most other regions in the former East Germany, but the city still faces many social and economic problems which stem from the collapse of the communist system, including high unemployment levels. This energy can be harnessed through several natural and synthetic processes. After 1990 a completely new law and currency system was introduced in the wake of Communism’s downfall, and eastern Germany's infrastructure was largely rebuilt with funds from western Germany.

Sunlight on the surface of Earth is attenuated by the Earth's atmosphere, so that less power arrives at the surface — closer to 1000 watts per directly exposed square meter in clear conditions when the Sun is near the zenith. East Germany had been the richest Communist country but was faced with competition from western Germany after reunification. near Earth. In 1990 Dresden--an important industrial centre of East Germany--had to struggle with the economic collapse of the Soviet Union and the other export markets in eastern Europe. from the Sun, i.e. The urban renewal process in Dresden will continue for many decades but public and government interest remains high and there are numerous large budget projects underway - both historic reconstructions and modern plans - that will continue the city's recent architectural renaissance. It is about 1370 watts per square meter of area, one A.U. Despite the inner city’s almost total destruction in World War II, many areas in the central city have been restored to their former glory.

The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. The new Frauenkirche was rebuilt according to historical drawings and photographs and is now open to public service since Reformation Day 2005. Sunlight — that is, light radiated from the surface of the Sun — is thought to be the main source of energy near the surface of Earth. It was completed in 2005, a year before Dresden's 800th birthday. Thus, the Sun was considered by Greek astronomers to be one of the seven planets (Greek planetes "wanderer"), after which the seven days of the week are named in some languages. The church, once the city's symbol and considered the world's finest Protestant church, was rebuilt following German reunification in 1991 from the remaining pile of rubble of the original church's ruins thanks to private and corporate donations. With respect to the fixed stars, the Sun appears from Earth to revolve once a year along the ecliptic through the zodiac. The most important urban renewal/reconstruction project was the reconstruction of the Frauenkirche (“Church of Our Lady”) and the surrounding Neumarkt district.

It was only after Einstein's theory of mass-energy convertibility in the early 20th century that it was finally understood that the sun runs on nuclear fusion and is billions of years old, with several other billion to go. The city still has many of its wounds from the bombing raids of 1945 but Dresden has undergone significant reconstruction in recent years. In the early years of the modern scientific era, it was proposed that the Sun extracted its energy from friction of its gas masses, which would yield a Sun no older than a few million years, with a few more million years to go. Dresden has experienced dramatic changes since the reunification of Germany in the early 1990s. For teaching this heresy he was imprisoned by the authorities and sentenced to death (though later released through the intervention of Pericles). Local activists and residents, joined in the growing civil disobedience movement spreading across East Germany by staging demonstrations and demanding the removal of the undemocratically-elected communist government. One of the first people in the Western world to offer a scientific explanation for the sun was the Greek philosopher Anaxagoras, who reasoned that it was a giant flaming ball of metal even larger than the Peleponessus, and not the chariot of Helios. On 3 October 1989, (the so-called “battle of Dresden”), a convoy of trains carrying East German refugees from Prague passed through Dresden on its way to West Germany.

In many prehistoric and ancient cultures, the Sun was thought to be a deity or other supernatural phenomenon. Among East Germans, Dresden also earned the nickname "the valley of the clueless" because the city's location in a valley prevented its residents from watching West German TV, an illegal but popular pastime among East Germans. Mankind's most fundamental understanding of the Sun is as the luminous disk in the heavens whose presence above the horizon creates day, and whose absence causes night. However, many of the bombed-out ruins of churches were razed by Soviet authorities in the 1960s instead of being repaired. This stellar evolution scenario is typical of low to medium mass stars. Many important historic buildings were rebuilt, although the communists leaders of the city chose to reconstruct large areas of the city in a bland socialist modern style for economical and ideological reasons, namely to break away from the city's past as the royal capital of Saxony and a stronghold of the German bourgeoisie. The Sun will then evolve into a white dwarf, slowly cooling over eons. After the Second World War, Dresden became a major industrial center in socialist East Germany with a great deal of research infrastructure.

Following the red giant phase, giant thermal pulsations will cause the Sun to throw off its outer layers forming a planetary nebula. The comradery is deeply supported by the populace in both cities. While it is likely that the expansion of the outer layers of the Sun will reach the current position of Earth's orbit, recent research suggests that mass lost from the Sun earlier in its red giant phase will cause the Earth's orbit to move further out, preventing it from being engulfed. Today Dresden has a strong partnership with the English city Coventry, which was heavily damaged by German air attacks. Helium fusion will begin when the core temperature reaches about 3×10⁸ K. Fortunately, much of the city's beauty has been restored, thanks to the zeal of the populace in recreating the architecture of ‘old Dresden'. Instead, in 4-5 billion years it will enter its red giant phase, its outer layers expanding as the hydrogen fuel in the core is consumed and the core contracts and heats up. Others see it as a necessary military action taken to support the Red Army.

Our Sun does not have enough mass to explode as a supernova, and its mass is below the Chandrasekhar limit. While some think that the bombing of Dresden was a tragic occurrence that Nazi Germany brought upon itself, others feel it should be treated as a war crime. This is suggested by a high abundance of heavy elements such as iron, gold and uranium in the solar system: the most plausible ways that these elements could be produced are by endothermic nuclear reactions during a supernova or by transmutation via neutron absorption inside a massive first generation star. It states definite figures of between 18,000 and 22,000 with estimates of final numbers of 25,000 and includes the interesting sentence "Since rumours far exceed the reality, open use can be made of the actual figures.". The Sun is thought to be a second-generation star, whose formation may have been triggered by shockwaves from a nearby supernova. "TB47" is probably a reasonable guide to the order of casualty numbers. It returned to Earth in 2004 and is undergoing analysis, but it was damaged by crash-landing when its parachute failed to deploy on reentry to Earth's atmosphere. The official "Final Report and Situation (TB47)" produced by Reich Commander of the Order Police a month after the bombings.

A solar wind sample return mission, Genesis, was designed to allow astronomers to directly measure the composition of solar material. However the West German Federal Archive in Koblenz discovered a genuine copy of TB47. Elemental abundances in the photosphere are well known from spectroscopic studies, but the composition of the interior of the Sun is much less well known. Many of the higher estimates are based on a fake TB47 report (which has been visibly altered). It has proved so useful that a follow-on mission, the Solar Dynamics Observatory, is planned for launch in 2008. The entire inner city (15 square kilometres) was utterly devastated, and other quarters were damaged to some degree, the many villa quarters, however, on average much less than others. Originally a two-year mission, SOHO is now over ten years old (as of late 2005). At that time, Dresden's population was 600,000, but up to 200,000 refugees were living in cramped apartments and passing through Dresden as the Russians were now only fifty miles away.

To obtain an uninterrupted view of the Sun, the European Space Agency and NASA cooperatively launched the Solar and Heliospheric Observatory (SOHO) on December 2, 1995. Numbers between 25,000 - 140,000 have been used in official statistics with the communist authorities of Dresden increasing their estimates across time; estimates in Nazi Germany by the Ministry of Propoganda varied between 350,000 and 400,000. The North/South swing in apparent angle is the main source of seasons on Earth. Civilian death estimates vary wildly largely as a result of propaganda figures which received widespread publicity at the time, however the most recently available evidence from Friedrich Reichart of Dresden City Museum points to 25,000 deaths, which is less than the number that died in Hamburg, but Dresden was a smaller city. The most obvious variation in the Sun's apparent position through the year is a North/South swing over 47 degrees of angle, due to the 23.5 degree tilt of the Earth, but there is an East/West component as well. Although key industrial facilities were destroyed by the bombing (much of their capacity was quickly restored), the main goal of the "area bombing" was to create a fire storm (an objective inspired by the Luftwaffe's raids on Coventry, Bath and London but refined by Britain's Royal Air Force). The shape described by the Sun's position, considered at the same time each day for a complete year, is called the analemma, and resembles a figure 8, aligned along the North/South direction. The Red Army was approaching from the East and Dresden was one of two key rail routes with marshalling yards.

Observed from Earth, the path of the Sun across the sky varies throughout the year. However these targets were not the main reason for the city being bombed. the interplanetary medium) in a magnetic field, induces electric currents which in turn generates magnetic fields, and in this respect it behaves like an MHD dynamo. Some 300 Jews were kept slave laborers at a camp in Dresden, of these the majority were killed before the war ended, along with almost all of the 6,000 Jews who lived in Dresden before the war (a famous survivor was Dresden native and writer Victor Klemperer). Magnetohydrodynamic (MHD) theory predicts that the motion of a conducting fluid (e.g. These factories employed mainly local workers but also used Jewish slave labour. But satellite observations show that it is about 100 times greater at around 10^-9 tesla. In addition many peacetime factories, such as the cigarette factories, had been converted to ammunition factories as part of the policy of "total war".

If space were a vacuum, then the Sun's 10^-4 tesla magnetic dipole field would reduce with the cube of the distance to about 10^-11 tesla. Dresden's reputation for culture is better known than its highly developed optics industry (Carl Zeiss later Praktica), which produced precision aiming devices during the war. The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth being over 100 times greater than originally anticipated. Evidence uncovered after the war shows that Germany's Anti-Aircraft batteries employed "a flak militia of Juveniles" (Führer-Order 20/90/42). The influence of the Sun's rotating magnetic field on the plasma in the interplanetary medium creates the largest structure in the Solar System, the Heliospheric current sheet. Early in the war it had been considered too distant for the Allied bombers to reach in safety, but even when it had been bombed the majority of Dresden's anti-aircraft defences were redeployed elsewhere in Germany. The magnetic field of the sun reverses once for each 11-year sunspot cycle. The city was not particularly well defended, because as a European cultural center, lacking industry, it was not seen as militarily strategic.

The solar activity cycle includes old magnetic fields being stripped off the Sun's surface starting from one pole and ending at the other. However at the time Allied forces had only recently regrouped from a German counteroffensive. (See magnetic reconnection). In hindsight it is clear that the end of the war was approaching. The differential rotation of the Sun's latitudes causes its magnetic field lines to become twisted together over time, causing magnetic field loops to erupt from the Sun's surface and trigger the formation of the Sun's dramatic sunspots and solar prominences. Because the raging fires stopped at the river, the newer Neustadt ("new town") ironically became the older side of modern-day Dresden sustaining less damage. This makes it possible for the Sun to rotate faster at its equator (about 25 days) than it does at higher latitudes (28 days near its poles). The Altstadt ("old town") side of the Elbe River full of its historical cultural treasures was the most damaged, and left smoldering.

All matter in the Sun is in the form of gas and plasma due to its high temperatures. It was carpet bombed on the early hours of Valentine's Day, February 13-14 1945. Others suggest that cosmic rays might strongly influence the Earth's climate, and that their flux was much higher in the early history of the solar system ^[17]. Dresden was not the only German city devastated by World War II bombing, but the bombing of Dresden in 1945 has become one of the most controversial events of that war. Some scientists have suggested that the young Earth's atmosphere contained much larger quantities of greenhouse gases such as carbon dioxide and/or ammonia than are present today ^[16]. Main article: Bombing of Dresden in World War II. In fact, the young Earth was actually warmer than it is today. The city has suffered repeated destruction: by fire in 1491, from bombardment by the Kingdom of Prussia in 1760, and during the suppression of the constitutionalist May Uprising in 1849 and the destructive Allied bombing raid of February 1945.

However, the geologic record shows that the Earth has remained at a fairly constant temperature throughout its history. In the early 20th century Dresden was particularly well-known for its camera works, such as Ihagee and Pentacon, which produced the Praktica , and the cigarette factories, one of which was in the impressive Yenidze, a building with a multicoloured glass roof shaped like a mosque which still stands today. Such a weak star would not have been able to sustain liquid water on the Earth's surface, and thus life should not have been able to develop. The city’s population quadrupled from 95,000 in 1849 to 396,000 in 1900 as a result of industrialization. Theoretical models of the sun's development suggest that 3.8 to 2.5 billion years ago, during the Archean period, the Sun was only about 75 percent as bright as it is today. The city also developed into an important center for the international sale of art works and antiques. One possible candidate to explain coronal heating is continuous flaring at small scales ^[15], but this is still an open topic of investigation. During the 19th century, the city became a major center of industry, including automobile production, food processing, and the production of medical equipment.

Current research focus has therefore shifted towards flare heating mechanisms. During the Napoleonic Wars the French emperor made it his base of operation, winning here a famous battle on August 27 of that year. In addition, Alfven waves do not easily dissipate in the corona ^[14]. Between 1806 and 1918 it was the capital of the Kingdom of Saxony (which was from 1871 a part of the German Empire). All waves except Alfven waves have been found to dissipate or refract before reaching the corona (^[12], ^[13]). His son Frederick August II also reigned from Dresden as Augustus III of Poland from 1734-1763: during his reign the city was seat of a treaty that ended the Second Silesian War, and suffered heavy destructions in the Seven Years' War (1756-1763). Currently, it is unclear whether waves are an efficient heating mechanism. His reign marked the beginning of Dresden's emergence as a leading European city for technology and art.

^[8], ^[9], ^[10], ^[11]. He also gathered many of the best architects and painters from all over Europe to Dresden. The other proposed mechanism is flare heating, in which magnetic energy is continuously built up by photospheric motion and released through magnetic reconnection in the form of solar flares and waves. Because he planned to make Dresden the most important royal residence, Augustus set out to discover the Chinese secret of porcelain (‘white gold’); under his rule, European porcelain was invented in Dresden and Meißen. These waves travel upward and dissipate in the corona, depositing their energy in the ambient gas in the form of heat. From 1697-1706 and 1709-1733 Elector Frederick Augustus I ruled from Dresden as King August the Strong of Poland; the city is also known as Drezno in Poland. Two main mechanisms have been proposed to explain coronal heating: Wave heating, in which sound, gravitational and magnetohydrodynamic waves are produced by turbulence in the convection zone. From 1485 it was the seat of the dukes of Saxony, and from 1547 the electors as well.

It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere. It was restoered to the Wettin dynasty about 1319. The high temperature of the corona shows that it is heated by something other than the photosphere. After the death of the former, however, the city became property of the King of Bohemia and , later, the Margrave of the Brandenburg. Above it lies the solar corona with a temperature of one million kelvins. Since 1270, starting with Henry the Illustrious, Dresden became the capital of the margravate. The optical surface of the Sun (the photosphere) is known to have a temperature of about 6,000 K. Founder of the city was Dietrich of Meißen, Margrave of Meißen.

Thus, measurement and theory have been reconciled. An ancient Slavic settlement known as Drežďany ("alluvial forest dwellers") on the northern bank of the river was joined in 1206 by a German town on the southern bank, the heart of the present day Altstadt (“old town”), while the Slavic part is called Neustadt ("new town"). It has recently been found that neutrinos have rest mass, and can therefore transform into harder-to-detect varieties of neutrinos while en route from the Sun to Earth in a process known as neutrino oscillation ^[7]. Meißen is situated to the west of Dresden, most famous for the invention as well as production of European porcelain. Several neutrino observatories were constructed, including the Sudbury Neutrino Observatory and Kamiokande to try to measure the solar neutrino flux. More east is Saxon Switzerland, a large prime climbing destination. For some time it was thought that the number of neutrinos produced by the nuclear reactions in the Sun was only a third of the number predicted by theory, a result that was termed the solar neutrino problem. In the northeast is the Bühlau quarter; in the east Kleinzschachwitz, another villa quarter.

The temperature of the corona is several megakelvins. Nearby, at a higher elevation, are the villages Bannewitz and Rundteil at the foot of the Erzgebirge mountains. The low corona, which is very near the surface of the Sun, has a particle density of 10¹¹/m³ (Earth's atmosphere near sea level has a particle density of about 2x10²⁵/m³). The major sights of Dresden include:. The corona merges smoothly with the solar wind that fills the solar system and heliosphere. The city now once again features a wealth of tourist attractions. The corona is the extended outer atmosphere of the Sun, which is much larger in volume than the Sun itself. Many of the city's greatest monuments were rebuilt in the decades following the war; this process was given new impetus and funding after the reunification of Germany in 1990.

It is called the chromosphere from the Greek root chroma, meaning color, because the chromosphere is visible as a colored flash at the beginning and end of total eclipses of the Sun. The city area also reportedly had in some quarters the highest living costs in Europe before World War II. Above the visible surface of the Sun is a thin layer, about 2,000km thick, that is dominated by a spectrum of emission and absorption lines. The style of architecture that predominated under August I of Saxony is known as Dresden Baroque. This part of the Sun is cool enough to support simple molecules such as carbon monoxide and water which can be detected by their absorption spectra. Before the bombing raid of World War II, Dresden with its unmatched collection of baroque architecture was famous as one of the most beautiful cities in Europe. It is about 4,000 K. The Großer Garten (“big garden”) is the largest urban park in the city.

The coolest layer of the Sun is the temperature minimum region about 500km above the photosphere. In 2002 Dresden was listed as one of Europe's greenest (large) cities: a third of its area is covered by the forested areas called Dresdner Heide. They can be viewed with telescopes operating across the electromagnetic spectrum, from radio through visible light to gamma rays. Because of its location in a relatively narrow river valley, Dresden's climate is much more characteristic of southern Germany and is considerably warmer than most other places in eastern Germany. The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. The Dresden University of Technology, is one of the world's oldest technical universities. The photosphere has a particle density of about 10²³/m³ (this is about 1% of the particle density of Earth's atmosphere at sea level). The city is often called the "Silicon Valley of Germany" because numerous computer hardware and hi-tech development firms have opened offices and research facilities in the region.

Sunlight has approximately a black-body spectrum that indicates its temperature is about 6,000 K, interspersed with atomic absorption lines from the tenuous layers above the photosphere. Dresden is also an important center of the sciences and is home to many researchers. Conversely, the visible light we see is produced as electrons react with hydrogen atoms to produce H^- ions. Often seen as an important culture center, it is called the "Florence of the Elbe" (Elbflorenz in German) because of that. The change in opacity has to do with the decreasing amount of H^- ions, which absorb visible light easily. Unlike many large cities in Germany, which feature a clearly defined inner city, Dresden has several important centers of social and economic activity spread throughout the city's area. Above the photosphere, sunlight is free to propagate into space and its energy escapes the Sun entirely. About an hour northwest of Dresden is Leipzig, another big city in Saxony.

The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Dresden is located at 51°03′N 13°45′E, in the southeastern corner of eastern Germany; about two hours south of Germany's capital, Berlin, and about two hours north of Prague, capital of the Czech Republic. The turbulent convection of this outer part of the solar interior gives rise to a 'small-scale' dynamo that produces magnetic north and south poles all over the surface of the Sun. . The thermal columns in the convection zone form an imprint on the surface of the Sun, in the form of the solar granulation and supergranulation. Today, Dresden is an important cultural, political, and economic center in the Eastern part of the Federal Republic of Germany. Convective overshoot is thought to occur at the base of the convection zone, carrying turbulent downflows into the outer layers of the radiative zone. The controversial Bombing of Dresden in World War II and 40 years of GDR changed the face of the city dramatically.

Once the material cools off at the surface, it plunges back downward to the base of the convection zone, to receive more heat from the top of the radiative zone. Dresden has a long history as capital and Royal residence for the Kings of Saxony with centuries of extraordinary cultural and artistic splendor. As a result, thermal convection occurs as thermal columns carry hot material to the surface (photosphere) of the Sun. Dresden is part of the metropolitan area Saxon Triangle with a population of over 3.2 million. From about 0.7 solar radii to 1.0 solar radii, the material in the Sun is not dense enough or hot enough to transfer the heat energy of the interior outward via radiation. The city’s population is 480,347 (as of December 2004) and the population in its agglomeration is 800,000. Because of this, it can take a photon nearly 1,000,000 years to reach the photosphere. Dresden is the capital city of the German Federal State of Saxony and situated in a valley on the River Elbe.

Heat is transferred by ions of hydrogen and helium emitting photons, which travel a brief distance before being re-absorbed by other ions. - Columbus, Ohio; United States. In this zone, there is no thermal convection: while the material grows cooler with altitude, this temperature gradient is slower than the adiabatic lapse rate and hence cannot drive convection. - Salzburg; Austria. From about 0.2 to about 0.7 solar radii, the material is hot and dense enough that thermal radiation is sufficient to transfer the intense heat of the core outward. - Strasbourg; France. Neutrinos are also released in the fusion reactions in the core, but unlike photons they very rarely interact with matter, and so almost all are able to escape the Sun immediately. - Rotterdam; Netherlands.

Upon reaching the surface after a final trip through the convective outer layer, the photons escape as visible light. - Hamburg; Germany. 65) to as little as 17,000 years [6]. - Florence; Italy. Lewis, The Illustrated Encyclopedia of the Universe, Harmony Books, New York, 1983, p. - Brazzaville; Republic of the Congo. Estimates of the "photon travel time" range from as much as 50 million years (Richard S. - Ostrava; Czech Republic.

The high-energy photons (gamma and X rays) released in fusion reactions take a long time to reach the Sun's surface, slowed down by the indirect path taken, as well as constant absorption and re-emission at lower energies in the solar mantle (see below). - Skopje; Macedonia. All of the energy of the interior fusion must travel through the successive layers to the solar photosphere, before it escapes to space. - St.Petersburg; Russia. The core extends from the center of the Sun to about 0.2 solar radii, and is the only part of the Sun where an appreciable amount of heat is produced by fusion: the rest of the star is heated by energy that is transferred outward. - Wroclaw; Poland. About 8.9×10³⁷ protons (hydrogen nuclei) are converted to helium nuclei every second, releasing energy at the matter-energy conversion rate of 4.26 million tonnes per second or 383 yottawatts (9.15×10¹⁶ tons of TNT per second). - Coventry; United Kingdom.

At the center of the Sun, where its density reaches up to 150,000 kg/m³ (150 times the density of water on Earth), thermonuclear reactions (nuclear fusion) convert hydrogen into helium, producing the energy that keeps the Sun in a state of equilibrium. Leibniz Gemeinschaft: IÖR - Leibniz Institute of Ecological and Regional Development, IPF - Leibniz Institute for Polymer Research, IFW - Leibniz Institute for Solid State and Materials Research and FZR - Research Centre Rossendorf. Computer modeling of the Sun is also used as a theoretical tool to investigate its deep layers. Max-Planck-Gesellschaft: MPI of Molecular Cell Biology and Genetics, MPI for Chemical Physics of Solids and MPI for the Physics of Complex Systems. However, just as the study of the waves generated by earthquakes (seismology) can be used to study the interior structure of the Earth, helioseismology, the study of sound waves that travel through the Sun's interior, has also contributed greatly to our understanding of the Sun's structure. Fraunhofer Society: Fraunhofer Institute for Ceramic Technologies and Sintered Materials IKTS, Fraunhofer Institute for Electron and Plasma Technology FEP, Fraunhofer Institute for Integrated Circuits IIS, Fraunhofer Institute for Material and Beam Technology IWS, Fraunhofer Center Nanoelectronic Technologies CNT, Fraunhofer Institute for Photonic Microsystems IPMS, Fraunhofer Applications Center for Processing Machinery and Packaging Technology AVV, Fraunhofer Institute for Transport and Infrastructure Systems IVI as well as branches of other Fraunhofer Institutes headquartered elsewhere in Germany. The solar interior is not directly observable and the Sun itself is opaque to electromagnetic radiation. The Palucca Dance School is the only college of Fine Arts in Germany devoted exclusively to the academic study of dance.

Most of the mass is within about 0.7 radii. The Dresden International University is a private foundation, postgradual, university, founded few years ago in cooperation with the Dresden University of Technology; most students there have to prove some years of successful practise. This is simply the layer above which the gases are too cool or too thin to radiate a significant amount of light. Other universities include the Hochschule für Kirchenmusik, a school specializing on church music, the Evangelische Hochschule fuer Sozial Arbeit, the Fachhochschule der Wirtschaft and the Offizierschule des Heeres. The Sun's radius is measured from centre to the edges of the photosphere. University of Music - Carl Maria von Weber, founded in 1856. Nevertheless, the Sun has a well-defined interior structure, described below. The Palucca School of Dance, founded by Gret Palucca in 1925.

The Sun does not have a definite boundary as rocky planets do, as the density of its gases drops off following an approximately exponential relationship with distance from the centre of the Sun. The Dresden Academy of Art, founded in 1764, known for its former professors and artists like Otto Dix, Oskar Kokoschka, Canaletto or Caspar David Friedrich. The mass of the Sun is so comparatively great that the center of mass of the solar system is generally within the bounds of the Sun itself. The University of Applied Sciences Dresden, founded in 1992, with 5.000 students (2005). Tidal effects from the planets do not significantly affect the shape of the Sun, although the Sun itself orbits the center of mass of the solar system, which is offset from the Sun's center mostly because of the large mass of Jupiter. Dresden University of Technology with almost 35.000 students (2004), founded in 1828, is one of the oldest and largest technical universities in Germany. This is because the centrifugal effect of the Sun's slow rotation is 18 million times weaker than its surface gravity (at the equator). The Transparent Factory, Volkswagen's luxury car assembly plant with a glass exterior opened in 2002.

The Sun is a near-perfect sphere, with an oblateness estimated at about 9 millionths, which means the polar diameter differs from the equatorial by about 10 km. Unfortunately the observation deck is closed. The astronomical symbol for the Sun is a circle with a point at its centre: . Fernsehturm Dresden-Wachwitz - TV Tower of Dresden. Compared to the average movement of other stars in the area, the Sun is moving with a speed of 20 km/s toward the star Vega. Standseilbahn Dresden - the funicular cable railway in Dresden. The orbital speed is 217 km/s, equivalent to one light year every 1400 years, and one AU every 8 days. Schwebebahn Dresden an aerial cable car similar to the Schwebebahn Wuppertal.

The Sun orbits the center of the Milky Way galaxy at a distance of about 25,000 to 28,000 light-years from the galactic centre, completing one revolution in about 226 million years. Blue Wonder historic bridge considered a "wonder" of 19th century engineering. Its current age is thought to be about 4.5 billion years, a figure which is determined using computer models of stellar evolution, and nucleocosmochronology ^[5]. The German military history museum (with exhibits dating back to the Stone Age). The Sun has a predicted main sequence lifetime of about 10 billion years. Many of these hold world records in collection sizes, just as an example the biggest porcelain collection of the world can be found in the Zwinger.