Iron Age Archaeological period The Iron Age is the final epoch of the three-age system, preceded by the Stone Age (Neolithic) and the Bronze Age. It is an archaeological era in the prehistory and protohistory of Europe and the Ancient Near East, and by analogy also used of other parts of the Old World. The three-age system was introduced in the first half of the 19th century for the archaeology of Europe in particular, and by the later 19th century expanded to the archaeology of the Ancient Near East. As its name suggests, Iron Age technology is characterized by the production of tools and weaponry by ferrous metallurgy (ironworking), more specifically from carbon steel. The duration of the Iron Age varies depending on the region under consideration. The Iron Age is taken to end, also by convention, with the beginning of the historiographical record. The extension of the term "Iron Age" to the archaeology of South, East and Southeast Asia is more recent,[year needed] and may be used loosely.
Carbon dioxide Carbon dioxide (chemical formula CO2) is a naturally occurring chemical compound composed of 2 oxygen atoms each covalently double bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state, as a trace gas at a concentration of 0.039 per cent by volume. The environmental effects of carbon dioxide are of significant interest. Atmospheric carbon dioxide is the primary source of carbon in life on Earth and its concentration in Earth's pre-industrial atmosphere since late in the Precambrian eon was regulated by photosynthetic organisms. Carbon dioxide is an important greenhouse gas; burning of carbon-based fuels since the industrial revolution has rapidly increased the concentration, leading to global warming. It is also a major source of ocean acidification since it dissolves in water to form carbonic acid, which is a weak acid as its ionization in water is incomplete. History Chemical and physical properties . Uses
Global-warming potential Global-warming potential (GWP) is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time interval, commonly 20, 100 or 500 years. GWP is expressed as a factor of carbon dioxide (whose GWP is standardized to 1). For example, the 20 year GWP of methane is 86, which means that if the same mass of methane and carbon dioxide were introduced into the atmosphere, that methane will trap 86 times more heat than the carbon dioxide over the next 20 years. The substances subject to restrictions under the Kyoto protocol either are rapidly increasing their concentrations in Earth's atmosphere or have a large GWP. The GWP depends on the following factors: Thus, a high GWP correlates with a large infrared absorption and a long atmospheric lifetime. Calculating the global-warming potential
Ancient Rome In its approximately 12 centuries of existence, Roman civilization shifted from a monarchy to a classical republic and then to an increasingly autocratic empire. Through conquest and assimilation, it came to dominate Southern and Western Europe, Asia Minor, North Africa, and parts of Northern and Eastern Europe. Rome was preponderant throughout the Mediterranean region and was one of the most powerful entities of the ancient world. Ancient Roman society has contributed to modern government, law, politics, engineering, art, literature, architecture, technology, warfare, religion, language and society. By the end of the Republic, Rome had conquered the lands around the Mediterranean and beyond: its domain extended from the Atlantic to Arabia and from the mouth of the Rhine to North Africa. Founding myth The Roman poet Virgil recounted this legend in his classical epic poem the Aeneid. Kingdom Main article: Roman Kingdom Republic Main article: Roman Republic Punic Wars
Ozone Ozone /ˈoʊzoʊn/ (systematically named 1λ1,3λ1-trioxidane and μ-oxidodioxygen), or trioxygen, is an inorganic molecule with the chemical formula O 3(μ-O) (also written [O(μ-O)O] or O 3). It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O 2, breaking down in the lower atmosphere to normal dioxygen. Ozone's odor is sharp, reminiscent of chlorine, and detectable by many people at concentrations of as little as 10 ppb in air. Ozone is a powerful oxidant (far more so than dioxygen) and has many industrial and consumer applications related to oxidation. Nomenclature The trivial name ozone is the most commonly used and preferred IUPAC name. In appropriate contexts, ozone can be viewed as trioxidane with two hydrogen atoms removed, and as such, trioxidanylidene may be used as a context-specific systematic name, according to substitutive nomenclature. History ozonometer, 1865 Structure 
Global climate model Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To “run” a model, scientists divide the planet into a 3-dimensional grid, apply the basic equations, and evaluate the results. Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points. Note on nomenclature The initialism GCM stands originally for general circulation model. History: general circulation models Atmospheric vs oceanic models There are both atmospheric GCMs (AGCMs) and oceanic GCMs (OGCMs). Modelling trends A recent trend in GCMs is to apply them as components of Earth system models, e.g. by coupling to ice sheet models for the dynamics of the Greenland and Antarctic ice sheets, and one or more chemical transport models (CTMs) for species important to climate. Model structure Coupled atmosphere–ocean GCMs (AOGCMs) (e.g.
Slavs The Slavs are an Indo-European ethno-linguistic group living in Central Europe, Eastern Europe, Southeast Europe, North Asia and Central Asia, who speak the Indo-European Slavic languages, and share, to varying degrees, certain cultural traits and historical backgrounds. From the early 6th century they spread to inhabit most of Central and Eastern Europe and Southeast Europe. Slavic groups also ventured as far as Scandinavia, constituting elements amongst the Vikings; whilst at the other geographic extreme, Slavic mercenaries fighting for the Byzantines and Arabs settled Asia Minor and even as far as Syria. Later, East Slavs (specifically, Russians and Ukrainians) colonized Siberia and Central Asia. Every Slavic ethnicity has emigrated to other parts of the world. Over half of Europe's territory is inhabited by Slavic-speaking communities. Ethnonym European countries where a Slavic language is the official one on the entire territory History
Photosynthesis Schematic of photosynthesis in plants. The carbohydrates produced are stored in or used by the plant. Overall equation for the type of photosynthesis that occurs in plants Composite image showing the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation. Dark red and blue-green indicate regions of high photosynthetic activity in ocean and land respectively. Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the sun, into chemical energy that can be later released to fuel the organisms' activities. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. Overview Photosynthesis changes sunlight into chemical energy, splits water to liberate O2, and fixes CO2 into sugar. The general equation for photosynthesis is therefore: Z scheme The "Z scheme"
Climateprediction.net The project relies on the volunteer computing model using the BOINC framework where voluntary participants agree to run some processes of the project at the client-side in their personal computers after receiving tasks from the server-side for treatment. CPDN, which is run primarily by Oxford University in England, has harnessed more computing power and generated more data than any other climate modelling project. It has produced over 100 million model years of data so far. As of December 2010[update], there are more than 32,000 active participants from 147 countries with a total BOINC credit of more than 14 billion, reporting about 90 teraflops (90 trillion operations per second) of processing power. Aims IPCC graphic of uncertainty ranges with various models over time. As shown in the graph above, the various models have a fairly wide distribution of results over time. The experiments Climateprediction.net screensaver under BOINC 5.4.9 History Explanation
High Middle Ages The High Middle Ages was the period of European history around the 11th, 12th, and 13th centuries (c. 1001–1300). The High Middle Ages were preceded by the Early Middle Ages and followed by the Late Middle Ages, which by convention end around 1500. The key historical trend of the High Middle Ages was the rapidly increasing population of Europe, which brought about great social and political change from the preceding era. By 1250 the robust population increase greatly benefited the European economy, reaching levels it would not see again in some areas until the 19th century. This trend was checked in the Late Middle Ages by a series of calamities, notably the Black Death but also including numerous wars and economic stagnation. From about the year 780 onwards, Europe saw the last of the barbarian invasions and became more socially and politically organized. The Carolingian Renaissance led to scientific and philosophical revival of Europe. Historical events and politics