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300 BC -400 AD: Glacier retreat in the Alps  

Großer Sonnblick in southern Austria. Map (left) and photo seen from the south-east (right). The peak seen to the left in the photo is Goldzechkopf, while Großer Sonnblick is to the right.


Many glaciers in the Alps apparently retreated from about 300 BC to about 400 AD (Delibrias et al. 1975). At that time they probably were comparable in size or even less extensive as today, as is indicated by Roman gold mines established high up in the Alps in the Sonnblick area (Austria). 

Traffic over Alpine passes at that time continued even in winter time, and actual reports of winters in central and northwestern Europe that are recorded from those times indicate only few that were notable for snows (Lamb 1977).

Gold and Silver have been mined in this region for several thousands of years, and the the Greek geographer Strabo gives the first record for gold mining in the region. Most probably mining activities started in Pre-Roman time like in many other places in the Salzburg region (copper in Muehlbach and salt at Hallein/Duerrnberg). 

At Hocharn the mines at the Goldzeche and at Grieswies-Schwarzkogel were most important. The underground workings reached heights of more than 3000m and are considered to be the highest gold mines in Europe.

It appears that after the collapse of the Roman Empire in AD 476 some of the mines were blocked by advancing glaciers, and therefore given up. The entrance to some of these mines are probably still covered by glacier ice while others have only recently come to light as the glacier retreated in the 20th century (Lamb 1977, 1995).

However, several of the mine entrances apparently again became free of ice during the Medieval warm period, and in late medieval times the Salzburg region became the world´s largest producer of gold. In the 19th century advancing glaciers blocking the entrance to the mines (many glaciers in the eastern Alps reached their Little Ice Age maximum around 1860) and falling gold price and caused the closure of many gold mines in this region of Austria. Mining finally ceased at the end of World War II.

Nowadays many topographic names remind of the historic gold mining (Hoher Goldberg, Goldzeche, Goldzechkopf, Goldlacklschneid, Pochkar, Silberpfennig, Erzwies, Huettwinkel). Gold can still be found at Hocharn and Großer Sonnblick. The Großer Sonnblick reaches a height of 3,030 m and is the easternmost peak of the Alps that exceeds an altitude of 3,000 metres.

There are still unmined economic ore bodies beneath both Hocharn and Sonnblick. But as the impact of gold mining on nature and tourism would be large the gold will presumably remain in these mountains.


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9 AD: Battle of the Teutoburg Forest  

Topography of Germany (left) with insert showing location of map section to the right. Detailed map showing the location of the Battle at Teutoburg Forest (right).


The name of the Teutoburg Forest (Teutoburger Wald) in northwestern Germany is connected to one of the most famous battles from ancient history, the clades Variana, the defeat of the Roman general Varus. In September 9 AD, a coalition of Germanic tribes, led by a nobleman named Arminius, defeated a bir Roman army consisting of three legions and other units, and forced their commander Publius Quintilius Varus to commit suicide.

The result of the battle in Teutoburg Forest was that Germania remained independent and was never included in the Roman Empire. Presumably the Roman defeat was indeed one of the most decisive and influential battles in world history. Weather played no small role in the outcome of this battle.

In the last decade of the second century BC, the expanding Romans first encountered Germanic tribes. The Cimbri and Teutones were considered dangerous enemies, but ultimately defeated by the Roman commander Marius in two battles in BC 102 and 101. For two generations, all was then quiet on the northern front, but in BC 58, when Julius Caesar was waging war in eastern Gaul, he got involved in a conflict with the Germanic leader Ariovistus. At Colmar, Caesar defeated his enemy, and Caesar subsequently bridged the Rhine and invaded the country east of the river, which he called Germania.

Following his successful campaign, Caesar declared the river Rhine as a natural boundary between the Gallic barbarians ("Celts") and the Germanic tribes, which in his official opinion were even more barbarous. In reality, Caesar needed a well-defined theatre of operations and the Rhine was, from a military point of view, a fine frontier. But from a cultural or ethnic point of view, it was not a natural frontier at all. The Celtic culture also existed on the east bank of the Rhine, and people speaking a Germanic language had already settled on the west bank.

In BC 39-38, Marcus Vipsanius Agrippa was governor of Gaul, and fought a war on the east bank of the Rhine on behalf of the Ubians against the Suebians, a Germanic tribe that was notorious for its aggressiveness. After this campaign, Agrippa resettled the Ubians on the west bank of the Rhine, and founded Cologne. The Rhine was now changing into being a frontier between an increasingly Roman Gaul and an increasingly Germanic Germania.

During this dynamic age, the tribes of the east bank sometimes raided the Roman empire west of the Rhine. This happened in the winter of BC 17-16, where the governor of Gallia Belgica, Marcus Lollius, was defeated by the Sugambri. At this occasion the Fifth legion Alaudae lost its eagle standard: the ultimate disgrace to a Roman army unit. The emperor Augustus then understood that the Rhine frontier was still highly unstable and therefore sent his adoptive son Drusus to the north, to pacify the region and create a more stable frontier.

In the years BC 16-13, the Romans reorganized the strip of land along the Rhine. The region now became a military zone, where the army of Germania Inferior defended the Roman Empire against invaders from Germania. A second army group was called the army of Germania Superior was stationed further south along the Middle Rhine. In the summer of BC 11, Drusus managed to reach the river Elbe with his army. However, on his way back home, he fell from his horse and died. The Roman conqueror of Germania was only 29 years old.

Drusus was succeeded by his brother Tiberius, a capable general who held the opinion that Germania was too cold and poor to ever represent a valuable part of the Roman Empire. On the other hand, the armies could not be recalled immediately after the death of Drusus, as this would look as if the Romans had been defeated. In the years BC 9 and 8, Tiberius therefore attacked the Sugambri and deported thousands of them to the west bank of the Rhine.

After this operation all now seemed quiet for a while along the upper reaches of the Rhine, and  in AD 4, Augustus ordered Tiberius to advance northeast again, to finish the conquest of Germania. The whole of Germania was to become a normal, tax-paying province, cold climate or not. The army of Germania Inferior therefore was ordered to march from the Rhine to the sources of the river Lippe, where a camp was built at Anreppen. Next year, the legions had a rendez-vous with the Roman navy at the mouth of the Elbe, and Tiberius marched with his army along the Elbe, which was to become the new northeastern frontier of the Roman Empire.

Meanwhile, the army of Germania Inferior was commanded by Publius Quinctilius Varus, one of the most important senators of his age and a personal friend of Augustus. Varus was ordered to make a normal province of the country between the Lower Rhine and Lower Elbe, and indeed had some initial success in doing this. Then, everything suddenly went wrong, probably because Varus decided to impose tribute in the new Roman Province.

The taxes imposed by Varus provoked resistance among a population that had at first been willing to accept Roman rule, but was not prepared to pay this amount of tribute. Presumably Varus did not take the gathering storm seriously, and as usual sent smaller groups of Roman troops to various places in Germania, which asked for them for the alleged purpose of guarding various positions, arresting robbers, or escorting provision trains.  Thereby Varus did not keep his legions together, as would have been the proper procedure in a hostile country.

Next there came an uprising, first on the part of those who lived at large distances away from the Roman headquarter, deliberately so arranged, in order that Varus should march against them and so be more easily overpowered while proceeding through what was supposed to be friendly country. Varus, on hearing the first news about the revolt of a far-away tribe, sensibly decided to regroup his army before taking any action.

All sources agree that the Germanic leader of the uprising was Arminius, a member of the Cheruscan tribe and until then a loyal supporter of Rome. The rebels (or freedom fighters) must have made their preparation during the late summer of 9 AD. However, not all Germanic leaders agreed with Arminius' policy, and his plan was apparently betrayed to Varus. What happened next is not entirely clear. Presumably Varus refused to listen, and instead rebuked the person(s) that could have saved him.

The battle in Teutoburg Forest took place in the year 9 AD, most likely in September. The battles final stage took part at the northern foot of the Kalkriese hill, a site remarkably well-suited for an ambush. Although only 157 meters high, the Kalkriese is difficult to pass on its northern slope, because a traveller then has to cross many deep brooks and rivulets, and in the level terrain north of the Kalkriese extends a difficult wetland for large distances. However, in between this great bog and the hill exists a more accessible zone up to several hundred meters wide, consisting of stable, Quaternary sandy deposits. The most accessible part of this corridor has a width of only 220 meters. It therefore comes as no big surprise that much later, in the 19th century, German engineers choose this natural east-west corridor along the northern slope of Kalkriese for the construction of both the main road B218 and the Mittelland Canal further to the north.

In September 9 AD, Varus' forces included three legions (Legio XVII, Legio XVIII, and Legio XIX), six cohorts of auxiliary troops (non-citizens or allied troops) and three squadrons of cavalry. The Roman forces were not marching in combat formation, and were interspersed with large numbers of camp-followers.

As they entered the forest shortly northeast of the modern town Osnabrück, they found the forest track narrow and muddy, and at the same time a violent rainstorm began. Apparently Varus neglected to send out advance reconnaissance parties, but instead advanced with all his forces along the narrow track in one long formation.


Overview illustration of the Kalkriese Battlefield from Mike Anderson’s Ancient History Blog (left). The Mittelland Canal is seen in the foreground (direction of view towards SW).  Overview map showing the main features of the battlefield (right).


On this narrow track the Roman line soldiers rapidly became stretched out perilously long; estimates are somewhere between 15 and 20 km in total. The Roman forces were then suddenly attacked by Arminius's Germanic warriors armed with light swords, large lances and narrow-bladed short spears. The Germanic warriors quickly managed to surround the entire Roman army and rained down javelins on the intruders from the surrounding forest.

The German leader, Arminius, had grown up in Rome as a citizen and became a Roman soldier, understood Roman tactics very well and could thus direct his troops to counter them effectively, using locally superior numbers against the dispersed Roman legions. Indeed, the German warriors presumably used a very efficient tactic of isolating individual, manageable parts of the extended Roman column, to defeat them one by one. 1930 years later similar efficient ‘motti’ tactics were successfully employed by the Finnish army against the much bigger Red Army during the Finnish-USSR winter war 1939-40, again assisted by the prevailing weather.

The Roman main force however managed to set up a fortified night camp near Engter, and the next morning the remaining Roman soldiers managed to break out into the open country north of the Wiehen Hills, near the modern town of Ostercappeln. The break-out cost heavy losses, as did a further attempt to escape by marching through another forested area, with the torrential rains continuing.

According to Cassius Dio, Roman History (Historia Romana, in 80 books):

They were still advancing when the fourth day dawned, and again a heavy downpour and violent wind assailed them, preventing them from going forward and even from standing securely, and moreover depriving them of the use of their weapons. For they could not handle their bows or their javelins with any success, nor, for that matter, their shields, which were thoroughly soaked. Their opponents, on the other hand, being for the most part lightly equipped, and able to approach and retire freely, suffered less from the storm.

The continuing rain prevented the Roman forces from using their otherwise efficient bows, because their sinew strings become slack when wet. This rendered the Roman soldiers virtually defenceless as their shields also became waterlogged and soft.

The Romans then undertook a night march to escape, but marched into another trap that Arminius had set, at the foot of Kalkriese Hill north of Osnabrück. There, the sandy, open strip on which the Romans could march easily was constricted by the hill to the south, so that there was a gap of only about 2-300 m between the woods and swampland with high vegetation at the edge of the Great Bog to the north. The Roman soldiers probably expected nothing at this stage, but were suddenly attacked on their left flank by part of the Germanic forces hiding in the swamp. Moreover, the Roman forces found the road ahead blocked by a fortified trench, and, towards the forest, an earthen wall had been built along the roadside, permitting the Germanic tribesmen to attack the Romans from cover. The Roman forces was surrounded on three sides.

The Romans made a desperate attempt to storm the wall to break one part of the Germanic pincer, but failed. The highest-ranking officer next to Varus, Legatus Numonius Vala, abandoned the troops by riding off with the cavalry; however, he too was overtaken by the Germanic cavalry and killed. The Germanic warriors then stormed the field and slaughtered the now disintegrating Roman forces.

Varus did what the Romans considered the honorable thing: he committed suicide. One commander, Praefectus Ceionius, shamefully surrendered and later took his own life, while his colleague Praefectus Eggius heroically died leading his doomed troops to the bitter end. The Roman defeat was a major one, and at that time it rarely happened that legionary soldiers lost a battle, and the loss of no less than three legions was one of the worst defeats in Roman history.

Archeological excavations in the area north of Kalkriese have shown that the staff of at least one legion was present, and the presence of cavalry and auxiliary infantry is also attested. There were also noncombatants and perhaps women at Kalkriese mountain battlefield. In total, around 15,000–20,000 Roman soldiers must have died; not only Varus, but also many of his officers are said to have taken their own lives by falling on their swords in the approved manner.

Other Roman soldiers from Germania had already reached the Rhine, and the news that something terrible had happened spread upstream along the river. Even in Rome, the populace was afraid, and the emperor Augustus ordered that watch be kept by night throughout the city.

According to Suetonius, Augustus, 23.4:

He (Augustus) was so greatly affected that for several months in succession he cut neither his beard nor his hair, and sometimes he could dash his head against a door, crying "Quintilius Varus, give me back my legions!"

The battle in the Teutoburg Forest had a profound effect on 19th century German nationalism; the Germans, at that time still divided into many individual German states, identified with the Germanic tribes as shared ancestors of one "German people" and came to associate the imperialistic Napoleonic French and Austro-Hungarian forces with the invading Romans who were destined for defeat. This was part of the background on which Bismarck, the German statesman, could unify numerous German states into a powerful German Empire under Prussian leadership, and thereby create a "balance of power" that preserved peace in Europe from 1871 until 1914. Today, the place where the final battle at Kalkriese took place has been transformed into a museum and an archaeological park, Varusschlacht (Varus Battle).


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23-79 AD: Gaius Plinius Secundus and Naturalis Historia  

Naturalis Historia, 1669 edition, title page (left picture). The title at the top reads: "Volume I of the Natural History of Gaius Plinius Secundus. Mount Vesuvius during the 79 AD eruption (centre left). Plaster casts of the casualties of the pumice-fall, whose remains vanished leaving cavities in the pumice (centre right). Pliny the Elder (to the right): an imaginative 19th century portrait. No contemporary picture shoving Gaius Plinius Secundus has survived.


Gaius Plinius Secundus (23 AD – August 25, 79 AD) is also known as Pliny the Elder. He was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian. Spending most of his spare time studying, writing or investigating natural and geographic phenomena in the field, he wrote an encyclopedic work, Naturalis Historia, which became a model for all such works written subsequently, and contributed to the survival in Europe of knowledge collected by Aristotle and his students.

Gaius Plinius was highly interested in agriculture, which he considered being the single most important human type of activity. Agriculture depended on correct planning of seasonal activities, and Gaius Plinius therefore collected much of what was believed to be known about weather. Much of this knowledge on weather phenomena is collected in volume two of his Naturalis Historia, which consisted of no less than 37 volumes in total.

Below is reproduced (in extract) the English translation of some examples of Gaius Plinius writings on meteorological phenomena, all taken from volume two of Naturalis Historia. The Latin version of volume two can be found here.

Chap. XLII. The causes of raine, showers, winds, and clouds.

I CANNOT denie, but without these causes there arise raines and winds: for that certaine it is, how there is sent forth from the earth a mist sometimes moist, otherwhiles smokie, by reason of hote vapours and exhalations. Also, that clouds are engendred by vapours which are gone up on high, or els of the aire gathered into a waterie liquor: that they bee thicke, grosse, and of a bodily consistence, wee guesse and collect by no doubtfull argument, considering that they overshaddow the Sunne, which otherwise may be seene through the water, as they know well, that dive to any depth whatsoever.

Chap. XLVII. Many sorts of Winds.

MEN in old time observed foure Winds only, according to so many quarters of the world (and therefore Homer nameth no more:) a blockish reason this was, as soone after it was judged. The Age ensuing, added eight more; and they were on the other side in their conceit too subtile and concise. The Moderne sailers of late daies, found out a meane betweene both: and they put unto that short number of the first, foure winds and no more, which they tooke out of the later. Therefore every quarter of the heaven hath two winds apeece...

…The coldest winds of all other, be those which we said to blow from the North pole, and together with them their neighbour, Corus. These winds doe both allay and still all others, and also scatter and drive away clouds. Moist winds are Africus, and especially the South wind of Italie, called Auster…

…The North wind also bringeth in haile, so doth Corus. The South wind is exceeding hote and troublous withall. Vulturnus and Favonius bee warme. They also bee drier than the East: and generally all winds from the North and West, are drier than from the South and East. Of all winds the Northerne is most healthfull: the Southerne wind is noisome, and the rather when it is drie; haply, because that when it is moist, it is the colder. During the time that it bloweth, living creatures are thought to bee lesse hungrie. …

Chap. LX. Of Haile, Snow, Frost, Mist, and Dew.

HAILE is engendred of Raine congealed into an Ice: and Snow of the same humour growne togither, but not so hard. As for Frost, it is made of dewe frozen. In winter Snowes fall, and not Haile. It haileth oftner in the day time than in the night, yet haile sooner melteth by farre than snow. Mists be not seene neither in Summer, nor in the cold weather. Dewes shew not either in frost, or in hote seasons; neither when winds be up, but only after a calme and cleere night. Frostes drie up wet and moisture; for when the yce is thawed and melted, the like quantitie of water in proportion is not found.

  Quite interesting, Gaius Plinius in volume 2 of  Naturalis Historia also comments on the effects of sea level changes:

Chap. LXXXVIII. What Lands the Seas have broken in betweene.

EVEN within our kenning and neare to Italie, betweene the Ilands Æoliæ; in like manner neare to Creta, there was one shewed it selfe with hote fountaines out of the sea, for a mile and a halfe: and another in the third yeere of the 143 Olympias, within the Tuscane gulfe, and this burned with a violent wind. Recorded it is also, that when a great multitude of fishes floted ebbe about it, those persons died presently that fed therof. So they say, that in the Campaine gulfe, the Pithecusæ Ilands appeared. And soone after, the hill Epopos in them (at what time as sodainly there burst forth a flaming fire out of it) was laid level with the plain champion. Within the same also there was a towne swallowed up by the sea: and in one earthquake there appeared a standing poole; but in another (by the fall and tumbling downe of certaine hils) there grew the Iland Prochyta: For after this manner also Nature hath made Ilands. Thus, she disjoyned Sicilie from Italie, Cyprus from Syria, Eubœa from Bœotia, Atalante and Macris from Eubœa, Besbycus from Bithynia, Leucostia from the promontorie and cape of the Syrenes.

Chap. XC. What Lands have been turned wholly into Sea.

NATURE hath altogether taken away certaine Lands: and first and formost where as now the sea Atlanticum is, it was sometime the Continent for a mightie space of ground; if wee give credit to Plato. And soone after in our Mediteranean sea, all men may see at this day how much hath been drowned up, to wit, Acamania by the inward gulfe of Ambracia; Achaia within that of Corinth; Europe and Asia within Propontis and Pontus. Over and besides, the sea hath broken through Leucas, Antirrhium, Hellespont, and the two Bosphori.

Chap. XCII. What Citties have been drowned with the Sea.

THE sea Pontus hath overwhelmed Pyrrha and Antyssa about Mæotis, Elice, and Bura, in the gulfe of Corinth: whereof, the markes and tokens are to be seene in the deepe. Out of the Iland Cea, more than 30 miles of ground was lost sodainly at once, with many a man besides. In Sicilie also the sea came in, and had away halfe the citie Thindaris, and whatsoever Italy nourseth, even all betweene it and Sicilie. The like it did in Bœotia and Eleusina.

Pliny the Elder died on August 25, 79 AD, while attempting the rescue by ship of a friend and his family from the eruption of Mount Vesuvius that had just destroyed the cities of Pompeii and Herculaneum. The prevailing wind would not allow his ship to leave the shore, and after a while Pliny collapsed. His companions attributed his collapse and death to toxic volcanic fumes, although they were themselves unaffected by these gasses

Gaius Plinius apparently managed to publish the first ten volumes of Naturalis Historia in 77 and was engaged on revising and enlarging the rest during the two remaining years before his death.

Gaius Plinius Secundus enjoyed high recognition in Europe long time after his death. Pliny's encyclopedic work Naturalis Historia was held in high esteem in the Middle Ages, and were to be printed in no less than 128 editions until 1669 AD. With all due respect for Pliny the Elder this also to some degree indicates the lack of significant scientific progress in Europe for more than 1000 years after the death of Gaius Plinius in 79 AD.

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101-106 AD: Bridge constructed across the River Danube at the Iron Gate  

Map showing the location of the Iron Gate (black arrow) in south-east Europe.


An indication of the benign climate of Roman times with a rather long immunity from cold winters in Europe may be seen in the building between AD 101 and 106 of a bridge with many stone piers across the River Danube at the Iron Gate in south-east Europe, between Serbia and the Transylvian highlands in Romania (cf. Lamb 1995).

The bridge was designed by Appolodorus of Damascus for the Emperor Trajan for efficient passage of the Roman armies and administration across the Danube, preceding Trajan's subsequent conquest of Dacia, a large region broadly corresponding to modern Romania and Moldova

Trajan's bridge apparently stood for no less than about 170 years Lamb (1977, 1995). This must be considered an amazing fact, as in any recent century such a construction would rapidly have been carried away by river ice during a cold winter. In the end the bridge is said to have been destroyed by the Dacian tribes when the Romans later withdrew from this part of Europe (Lamb 1977, 1995).


Artistic reconstruction of Trajan's bridge across the river Danube (source: Wikimedia Commons).


Trajan's bridge was 1,135 m in length (the Danube is about 800 m wide at the place of crossing), 15 m in width, and 19 m in height above the average water level. At each end of the bridge was a Roman castrum, each built around an entrance to the bridge. In other words, in order to cross the bridge you had first to pass through a Roman military camp.

For the bridge's construction Appolodorus of Damascus used wooden arches set on twenty masonry pillars (made of bricks, mortar and pozzolana cement) that spanned 38 m each. The entire bridge was built quickly within two years only (between 103 and 105 AD), employing the construction of a wooden caisson for each pier. For more than 1000 years Trajan's bridge was the longest arch bridge ever constructed, in both total and span length, and it apparently survived for no less than about 170 years (Lamb 1975, 1977), before being demolished by the Dacian people. Although representing an impressive engineering feat, relative mild winters with little river ice presumably contributed to the long survival time of the bridge. 

A relief on Trajan's Column shows the Roman bridge across the River Danube (see figure below). Noteworthy on this illustration are the unusually flat segmental arches on high-rising concrete piers; in the foreground of the relief Emperor Trajan sacrificing by the Danube can be seen.



The River Danube and the Kazan gorge at its narrowest point (left), and relief showing the Roman bridge across Danube on Trajan's Column in Rome (right). Source: Wikimedia Commons.


The Iron Gate gorge(s) lies between Romania in the north and Serbia in the south. At this point, the river separates the southern Carpathian Mountains from the northwestern foothills of the Balkan Mountains. The Romanian, Hungarian, Slovakian, Turkish, German and Bulgarian names literally mean "Iron Gates" and are used to name the entire range of gorges. The Romanian side of the gorge now constitutes the Iron Gates natural park, whereas the Serbian part constitutes the Đerdap national park.

The Great Kazan (kazan meaning "boiler") is the most famous and the narrowest gorge of the Iron Gate route (photo above): the river here narrows to 150 m and reaches a depth of up to 53 m (174 ft). Shortly downstream is the site where the Roman Emperor Trajan had the legendary military bridge erected between 103 and 105 AD, preceding his conquest of Dacia. On the right (Serbian) bank of the river a Roman memorial plaque (Tabula Trajana) commemorates Emperor Trajan's military road into Dacia. The Tabula was originally located 50 meters lower than now. The original site was flooded with the construction of a major hydroelectric dam in late 1960s and the monument was moved to a new position just above the waterline. On the opposite Romanian bank, at the Small Kazan, a statue of Trajan's Dacian opponent Decebalus was carved in rock from 1994 through 2004 (see photos below).


Rock carving showing Decebalus on the Romanian side of the Iron Gate (left), and a plate commemorating the roman Emperor Trajan on the Serbian bank (right). Source: Wikimedia Commons.

The twenty pillars carrying Trajan's bridge were still visible in 1856, when the level of the Danube hit a record low. In 1906, the International Commission of the Danube however decided to destroy two of the pillars, to ensure safe navigation on the river. In 1932, there were 16 remaining pillars underwater, but in 1982 archaeologists only manage to find 12 of these. Presumably the missing four had been swept away by river ice following the relative cold period 1960-1980 in Europe. Today, only the entrance pillars are visible on either bank of the Danube. 

In 1979, Trajan's Bridge was added to the Monument of Culture of Exceptional Importance, and in 1983 it was added to the Archaeological Sites of Exceptional Importance list, and by that it is protected by Republic of Serbia.

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90-168 AD: Claudius Ptolemaeus  

An early Baroque artist's rendition of Claudius Ptolemaeus (left). To the right is shown a 15th-century manuscript copy of the Ptolemy world map, reconstituted from Ptolemy's Geographia, indicating the countries of "Serica" and "Sinae" (China) at the extreme east, beyond the island of "Taprobane" (Sri Lanka, oversized) and the "Aurea Chersonesus" (Malay Peninsula).


Claudius Ptolemaeus (AD90-168) was a Greek-Roman citizen, who lived in Alexandria, working at the big scientific library.  He was a philosopher, mathematician, astronomer, geographer, and astrologist. Much of the summary below is adopted from different sources in Wikepedia and from Rasmussen 2010, from where additional information is available.

Ptolemaeus was the author of several scientific treatises, at least three of which were of continuing importance to later Islamic and European science. The first is the astronomical treatise now known as the Almagest, the Great Treatise. The second is the Geography, which is a thorough discussion of the geographic knowledge of the Greco-Roman world. The third is an astrological treatise usually known in Greek as the Tetrabiblos, and in Latin as the Quadripartitum (or four books). Here Ptolemaeus attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day.

The first treatise, Almagest, is usually considered as the main work of Ptolemaeus, and is the only surviving comprehensive ancient treatise on astronomy. Babylonian astronomers had developed arithmetical techniques for calculating astronomical phenomena, while Greek astronomers such as Hipparchus had produced geometric models for calculating celestial motions. Ptolemaeus, however, claimed to have derived his geometrical models from selected astronomical observations by his predecessors spanning more than 800 years, though astronomers have for long time suspected that his models' parameters were adopted mainly independently of observations.

Ptolemaeus presented his astronomical models in convenient tables, which could be used to compute the future or past position of the planets. The Almagest also contains a star catalogue, which is an appropriated version of a catalogue created by Hipparchus. Its list of forty-eight constellations is ancestral to the modern system of constellations, but unlike the modern system they did not cover the whole sky, but only the sky Hipparchus could see from Alexandria.

Ptolemy's model, like those of his predecessors, was geocentric, assuming that that the Earth is the center of the universe, and that all other objects orbit around it.

Two commonly made observations supported the idea that the Earth was the center of the Universe. The first observation was that the stars, sun, and planets appear to revolve around the Earth each day, making the Earth the center of that system. Further, every star was on a "stellar" or "celestial" sphere, of which the earth was the center, that rotated each day, using a line through the north and south pole as an axis. The second common notion supporting the geocentric model was that the Earth does not seem to move from the perspective of an Earth bound observer, and that it is solid, stable, and unmoving. In other words, it is completely at rest.

Ptolemaeus was convinced that conditions on Earth were influenced by the orbiting celestial objects. The influence of the Sun and the Moon on seasons and tide water, respectively, was obvious, and it was therefore assumed that also the other five planets (Sun and Moon were considered planets) had influence on the conditions on Earth.

In his thesis Tetrabiblos Ptolemaeus outline a series of astrology based rules for weather forecasts, while admitting that that many mistakes are made in its practice - partly because of "evident rascals" who profess to practice it without due knowledge and pretend to foretell things which cannot be naturally known. His conclusion is that this kind of study is only able to give reliable knowledge in general terms.


Ptolemy instructing Regiomontanus under an image of the zodiac encircling the celestial spheres (left). Frontispiece from Ptolemy's Almagest, (Venice, 1496). To the right an illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568 (Bibliothèque Nationale, Paris).


One of the unique features of the Tetrabiblos, amongst the astrological texts of its period, is the extent to which the first book not only introduces the basic astrological principles, but also attempts to explain the reasoning behind their reported associations in line with Aristotelian philosophy. Chapter four in Tetrabiblos, explains the "power of the planets" through their associations with the creative qualities of warmth or moisture, or cold and dryness. Hence Mars is described as a destructive planet because its association is excessive dryness, whilst Jupiter is defined as temperate and fertilising because its association is moderate warmth and humidity.

Chapter nine in Tetrabiblos discusses the "power of the fixed stars". Here, rather than give direct humoral associations, Ptolemy describes their "temperatures" as being like that of the planets he has already defined. Hence Aldebaran (called the Torch) is described as having "a temperature like that of Mars", whilst other stars in the Hyades are "like that of Saturn and moderately like that of Mercury". At the end of this chapter Ptolemy clarifies that these are not his proposals, but are drawn from historical sources, being "the observations of the effects of the stars themselves as made by our predecessors".

His Planetary Hypotheses went beyond the mathematical model of the Almagest to present a physical realization of the universe as a set of nested spheres, in which he used the epicycles of his planetary model to compute the dimensions of the universe. He estimated the Sun was at an average distance of 1210 Earth radii while the radius of the sphere of the fixed stars was 20,000 times the radius of the Earth.

Ptolemaeus presented a useful tool for astronomical calculations in his Handy Tables, which tabulated all the data needed to compute the positions of the Sun, Moon and planets, the rising and setting of the stars, and eclipses of the Sun and Moon. Ptolemy's Handy Tables provided the model for later astronomical tables. In the Phaseis (Risings of the Fixed Stars) Ptolemy gave a parapegma, a star calendar or almanac based on the hands and disappearances of stars over the course of the solar year.

Through the Middle Ages the Almagest was considered as the authoritative text on astronomy, with its author becoming an almost mythical figure. Like most of the Classical Greek science the Almagest was preserved in Arabic manuscripts. Because of its reputation, it was widely sought and was translated twice into Latin in the 12th century, once in Sicily and again in Spain.

The astronomical predictions of Ptolemy's geocentric model were used to prepare astrological charts for over 1500 years. The geocentric model survived into the early modern age, but was gradually replaced from the late 16th century onward by the heliocentric model of Copernicus, Galileo and Kepler. However, the transition between these two theories met stiff resistance, not only from the Catholic Church, which was reluctant to accept a theory not placing God's creation at the center of the universe, but also from those who saw geocentrism as a fact that could not be subverted by a new and apparently weakly justified theory.


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476 AD: Collapse of the Roman Empire    

Karl Bruillov's 'Sack of Rome' (left). Map of the "barbarian" invasions of the Roman Empire showing the major incursions from 100 to 500 AD (right).


The decline of the Roman Empire refers to the gradual societal collapse of the Western Roman Empire. This slow decline occurred over a period of four centuries, culminating on September 4, 476 AD, when Romulus Augustus, the last Emperor of the Western Roman Empire, was deposed by Odoacer, a Germanic chieftain. The following text is based mainly on Büntgen et al. (2011), Lubick 2011 and Wikipedia

The decline of the Roman Empire is one of the events traditionally marking the end of Classical Antiquity and the beginning of the European Middle Ages. Throughout the 5th century, the Empire's territories in western Europe and northwestern Africa, including Italy, fell to various invading or indigenous peoples in what is often known as the Migration period, a 250 year period of turmoil in Europe. Although the eastern half of the original Roman Empire still survived with borders essentially intact for several centuries, the Empire as a whole had initiated major cultural and political transformations since the Crisis of the Third Century, with the shift towards a more openly autocratic and ritualized form of government, the adoption of Christianity as the state religion, and a general rejection of the traditions and values of Classical Antiquity.

The European Middle Ages following the decline of the Roman Empire is important, as it witnessed the first sustained urbanisation of northern and western Europe. Many modern European states owe their origins to events unfolding in the Middle Ages; present European political boundaries are, in many regards, the result of the military and dynastic achievements during this tumultuous period.

By the late 3rd century, the city of Rome no longer served as an effective capital for the Emperor and various cities were used as new administrative capitals. Successive emperors, starting with Constantine, privileged the eastern city of Byzantium, which he had entirely rebuilt after a siege. Later renamed Constantinople, and protected by formidable walls in the late 4th and early 5th centuries, it was to become the largest and most powerful city of Christian Europe in the Early Middle Ages. Since the Crisis of the Third Century, the Roman Empire was intermittently ruled by more than one emperor at once (usually two), presiding over different regions. At first a haphazard form of power sharing, this eventually settled on an East-West administrative division between the Western Roman Empire (centred on Rome, but now usually presided from other seats of power such as Trier, Milan, and especially Ravenna), and the Eastern Roman Empire, also known as the Byzantine Empire.

Throughout the 5th century, Western emperors were usually figureheads, while the Eastern emperors maintained more independence. For most of the time, the actual rulers in the West were military strongmen who took the titles of magister militum (master of the soldiers), patrician, or both. Although Rome was no longer the capital in the West, it remained the West's largest city and its economic centre. But the city was sacked by rebellious Visigoths in 410 AD and by the Vandals in 455 AD, events that shocked contemporaries and signalled the disintegration of Roman authority.

In June 474 AD, Julius Nepos became Western Emperor but in the next year the magister militum Orestes revolted and made his son Romulus Augustus emperor. Romulus, however, was not recognized by the Eastern Emperor Zeno, who used to have good connections to Nepos. Romulus, therefore, was technically a usurper, and Nepos still being the legal Western Emperor. Nevertheless, Romulus Augustus is often known as the last Western Roman Emperor. In 476 AD, after being refused lands in Italy, Orestes' Germanic mercenaries under the leadership of the chieftain Odoacer captured and executed Orestes and took Ravenna, the Western Roman capital at the time, deposing Romulus Augustus. The whole of Italy was quickly conquered, and Odoacer was granted the title of patrician by Zeno, effectively recognizing his rule in the name of the Eastern Empire. Odoacer returned the Imperial insignia to Constantinople and ruled as King in Italy. Although Roman political authority in the West was lost, Roman culture would last in most parts of the former Western provinces into the 6th century and beyond.

The English historian Edward Gibbon, author of The History of the Decline and Fall of the Roman Empire (1776) made the concept of the decline of the Roman Empire part of the framework of the English language. In six volumes, Gibbon painstakingly charted the Empire’s final demise, using original reference material where possible. Gibbon blamed the fall on several factors: a loss of civic virtue, the use of barbarians as mercenaries rather than Roman soldiers, and the rise of Christianity, which led to increased pacifism and widespread beliefs that a better life awaited Roman citizens after death.

Gibbon, however, was not the first to speculate on why and when the Empire collapsed. In 1984, the German professor Alexander Demandt published a collection of 210 theories on why Rome fell, and new theories have emerged since then. One of the last was recently proposed by Büntgen et al. (2011).

The Büntgen research team compared modern tree-ring data with instrumental climate records to quantify the relationship between tree-ring growth and climate (precipitation and summer temperature). They used this relationship to reconstruct climate information from the ancient tree rings before instrumental records became available. To avoid getting strong local signals from one or a handful of trees in a particular forest or mountain site, Büntgen et al. (2011) used data for thousands of pieces of oak wood across Central Europe. Precipitation was reconstructed by using over 7000 oak trees across France and Germany. And about 1500 stone pine trees from the Austrian Alps region provided information about temperature.


Reconstructed precipitation (upper panel) and summer (JJA) temperature anomaly, with respect to the average of the 1901-2000 period (Büntgen et al. (2011)).


From these data interesting climate information emerge. From the beginning of the Roman Empire to its peak (c. 50 BC to AD 250), the climate was relatively stable, with warm and dry summers. During the two-and-half centuries or so that followed Europe apparently experienced very unfavourable conditions for agriculture, with summers being wet and cool. This time period corresponds to what today is known as the Migration period - a 250-year-period of turmoil and waves of migration in Europe.

Wet weather apparently may have made harvest conditions very difficult around the end of the Roman Empire in the fifth century. In this way cool and moist summer climate may have contributed to the Decline of the Roman Empire. Later climate then transitioned to an very dry and cold period around AD 550. Better conditions returned again around AD 700, and the subsequent reduced climate variability from AD 1000 to 1200 was coincident with prosperity and a growing population.


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