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The Great Famine of 1315–1322 was the first of a series of large-scale crises that struck Europe early in the 14th century, causing millions of deaths over an extended number of years and marking a clear end to an earlier period of growth and prosperity during the 11th through 13th centuries. Starting with bad weather in the spring of 1315, universal crop failures lasted through 1316 until the summer of 1317; Europe did not fully recover until 1322. It was a period marked by extreme levels of criminal activity, disease and mass death, infanticide, and cannibalism. It had consequences for Church, State, European society and future calamities to follow in the 14th century.

Background
In the spring of 1315, unusually heavy rain began in much of Europe. Throughout the spring and summer, it continued to rain and the temperature remained cool. Under these conditions grain could not ripen. Grain was brought indoors in urns and pots. The straw and hay for the animals could not be cured and there was no fodder for the livestock. The price of food began to rise. Food prices in England doubled between spring and midsummer. Salt, the only way to cure and preserve meat, was difficult to obtain because it could not be evaporated in the wet weather; it went from 30 shillings to 40 shillings. In Lorraine, wheat prices increased by 320 percent and peasants could no longer afford bread. Stores of grain for long-term emergencies were limited to the lords and nobles. Because of the general increased population pressures, even lower-than-average harvests meant some people would go hungry; there was little margin for failure. People began to harvest wild edible roots, plants, grasses, nuts, and bark in the forests.
There are a number of documented incidents that show the extent of the famine. Edward II, King of England, stopped at Saint Alba's on August 10, 1315 and no bread could be found for him or his entourage; it was a rare occasion in which the King of England, the most prosperous nation in Europe, was unable to eat. The French, under Louis X, tried to invade Flanders, but being in the low country of the Netherlands, the fields were soaked and the army became so bogged down they were forced to retreat, burning their provisions where they left them, unable to carry them out.
In the spring of 1316, it continued to rain on a European population deprived of energy and reserve to sustain itself. All segments of society from nobles to peasants were affected, most of all the peasants, who represented 95% of the population and who had no safety nets. To provide some measure of relief, the future was mortgaged by slaughtering the draft animals; eating the seed grain; abandoning children to fend for themselves (see "Hansel and Gretel"); and, among old people, voluntarily refusing food in hopes of the younger generation surviving. The chroniclers of the time wrote of many incidents of cannibalism.
The height of the famine was reached in 1317 as the wet weather hung on. Finally, in the summer the weather returned to its normal patterns. By now, however, people were so weakened by diseases such as pneumonia, bronchitis, tuberculosis, and other sicknesses, and much of the seed stock had been eaten, that it was not until 1325 that the food supply returned to relatively normal conditions and the population began to increase again. Historians debate the toll but it is estimated that between 10%–25% of the population of many cities and towns died. While the Black Death (1338–1375) would kill more, for many the Great Famine was worse. While the plague swept through an area in a matter of months, the Great Famine lingered for years, drawing out the suffering of those who would slowly starve to death, face cannibalism, child-murder and rampant crime.

Great Famine
The famine is called the Great Famine not only because of the number of people who died, or the vast geographic area that was affected, or the length of time it lasted, but also because of the lasting consequences.
The first consequence was for the Church. No amount of prayer seemed effective against the causes of the famine. In a society where the final recourse to all problems had been religion, no amount of prayer was helping and the famine undermined the institutional authority of the Catholic Church. This helped lay the foundations for later movements that were deemed heretical by the Church because they opposed the Papacy.
Second was the increase in criminal activity. Medieval Europe in the 13th century had already been a violent culture where rape and murder were demonstrably more common than in modern times. With the famine even those who were not normally inclined to criminal activity would resort to any means to feed themselves or their family. After the famine, Europe took on a tougher and more violent edge; it had become an even less amicable place than during the 12th and 13th centuries. The effects of this could be seen across all segments of society, perhaps the most striking in the way warfare was conducted in the 14th century during the bloody 100 Years War, versus the 12th and 13th centuries when nobles were more likely to die by accident in tournament games than on the field of battle.
Third was the failure of the Medieval governments to deal with the crisis.
Fourthly, the Great Famine marked a clear end to an unprecedented period of population growth that had started around 1050; although some believe this had been slowing down for a few decades already, there is no doubt the Great Famine was a clear end of high population growth.
Finally, the Great Famine would have consequences for future events in the 14th century such as the Black Death when an already weakened population would be struck again.

Consequences
The evidence for cannibalism during the Great Famine is ambiguous and controversial for historians. There are reports from Livonia and Estonia, as well as Ireland and most other parts of Europe. Many historians have discounted it as being improbable that, in a time when the Renaissance was just starting and Dante was creating one of the greatest works of literature in history, people in Europe were eating one another. However, perhaps it says more about modern values, which attribute cannibalism to "the other", than about the realities of one's ancestors doing whatever it took to survive.

Big Dig is the unofficial name of the Central Artery/Tunnel Project (CA/T), a megaproject that rerouted the Central Artery (Interstate 93), the chief controlled-access highway through the heart of Boston, Massachusetts, into a 3.5 mile (5.6km) tunnel under the city. The project also included the construction of the Ted Williams Tunnel (extending Interstate 90 to Logan International Airport), the Zakim Bunker Hill Bridge over the Charles River, and the Rose Kennedy Greenway in the space vacated by the previous I-93 elevated roadway. Initially, the plan was also to include a rail connection between Boston's two major train terminals.
The final ramp opened 13 January 2006. The project's overall completion is at 99%.
The Big Dig has been the most expensive highway project in the U.S.

Historical background
The project was conceived in the 1970s by the Boston Transportation Planning Review to replace the rusting elevated six-lane Central Artery. The expressway separated downtown from the waterfront, and was increasingly choked with bumper-to-bumper traffic. Business leaders were more concerned about access to Logan Airport, and pushed instead for a third harbor tunnel. In their second terms as governor and secretary of transportation, respectively, Michael Dukakis and Fred Salvucci, came up with the strategy of tying the two projects together—thereby combining the project that the business community supported with the project that they and the City of Boston supported..

Early planning
In addition to these political and financial difficulties, the project faced several environmental and engineering obstacles.
The downtown area through which the tunnels were to be dug was largely landfill, and included existing subway lines as well as innumerable pipes and utility lines that would have to be replaced or moved. Tunnel workers encountered many unexpected geological and archaeological barriers, ranging from glacial debris to foundations of buried houses and a number of sunken ships lying within the reclaimed land.
The project received approval from state environmental agencies in 1991, after satisfying concerns including release of toxins by the excavation and the possibility of disrupting the homes of millions of rats, causing them to roam the streets of Boston in search of new housing. By the time the federal environmental clearances were delivered in 1994, the process had taken some seven years, during which time inflation greatly increased the project's original cost estimates.
Reworking such a busy corridor without seriously restricting traffic flow required a number of state-of-the-art construction techniques. Because the old elevated highway (which remained in operation throughout the construction process) rested on pylons located throughout the designated dig area, engineers first utilized slurry wall techniques to create 120 ft.-deep concrete walls upon which the highway could rest. These concrete walls also stabilized the sides of the site, preventing cave-ins during the excavation process.
The multilane interstates also had to pass under South Station's 7 tracks which carried over 40,000 commuters and 400 trains per day. In order to avoid multiple relocations of the train lines while the tunnelling advanced, as had been initially planned, a specially designed jack was constructed in order to support the ground and tracks to allow the excavation to take place below. Ground freezing was also implemented in order to help stabilise the surrounding ground as the tunnel was excavated. This was the largest tunnelling project undertaken beneath railway lines anywhere in the world. The ground freezing enabled safer, more efficient excavation, and also assisted in environmental issues, as less contaminated fill needed to be exported than if a traditional cut and cover method had been applied.
Other challenges included an existing subway tunnel crossing the path of the underground highway. In order to build slurry walls past this tunnel, it was necessary to dig beneath the tunnel and build an underground concrete bridge to support the tunnel's weight.

Obstacles
The Central Artery/Tunnel Project was managed by the Massachusetts Turnpike Authority with design and construction supervised by a joint venture of Bechtel Corporation and Parsons Brinckerhoff. Due to the enormous size of the project—too large for any company to undertake alone—the design and construction of the Big Dig were broken up into dozens of smaller subprojects with well-defined interfaces between contractors. Major heavy-construction contractors on the project included Jay Cashman, Modern Continental, Obayashi Corporation, Perini Corporation, Peter Kiewit Sons' Incorporated, J.F. White, and the Slattery division of Skanska USA. (Of those, Modern Continental was awarded the greatest gross value of contracts, joint ventures included.)
The nature of the Charles River crossing had been a source of major controversy throughout the design phase of the project. Many environmental advocates preferred a river crossing entirely in tunnels, but this, along with 27 other plans, was rejected as too costly. Finally, with a deadline looming to begin construction on a separate project that would connect the Tobin Bridge to the Charles River crossing, Salvucci overrode the objections and chose a variant of the plan known as "Scheme Z". This plan was considered to be reasonably cost-effective, but had the drawback of requiring highway ramps stacked up as high as 100 feet (30 m) immediately adjacent to the Charles River. The city of Cambridge objected to the visual impact of the chosen Charles River crossing design. It sued to revoke the project's environmental certificate and forced the project to redesign the river crossing again. Meanwhile, construction continued on the Tobin Bridge approach. By the time all parties agreed on the I-93 design, construction of the Tobin connector (today known as the "City Square Tunnel" for a Charlestown area it bypasses) was far along, significantly adding to the cost of constructing the U.S. Route 1 interchange and retrofitting the tunnel.
Boston blue clay and other soils extracted from the path of the tunnel were used to cap many local landfills, fill in the Granite Rail Quarry in Quincy, and restore the surface of Spectacle Island in the Boston Harbor Islands National Recreation Area.
The Zakim Bunker Hill Bridge, designed by Swiss designer Christian Menn, is the terminus of the project, connecting the underground highway with I-93 and US 1. The distinctive cable-stayed bridge is supported by two forked towers connected to the span by cables and girders.
The Leverett Circle Connector, a companion bridge to the Zakim, began carrying traffic from I-93 to Storrow Drive in 1999. The project had been under consideration for years, but was opposed by the wealthy residents of the Beacon Hill neighborhood. However, it finally was accepted because it would funnel traffic bound for Storrow Drive and downtown Boston away from the mainline roadway. The Connector ultimately used a pair of ramps that had been constructed for Interstate 695, enabling the mainline I-93 to carry more traffic that would have used I-695 under the original Master Plan.
When construction began, the project cost, including the Charles River crossing, was estimated at $5.8 billion. Eventual cost overruns were so high that the chairman of the Massachusetts Turnpike Authority, James Kerasiotes, was fired in 2000. His replacement had to commit to an $8.55 billion cap on federal contributions. Total expenses eventually passed $15 billion.

Construction phase
On January 17, 2003, the opening ceremony was held for the I-90 Connector Tunnel, extending the Massachusetts Turnpike (Interstate 90) east into the Ted Williams Tunnel, and onwards to Logan Airport. (The Williams tunnel had been completed and in limited use for commercial traffic and high-occupancy vehicles since late 1995.) The westbound lanes opened on the afternoon of January 18 and the eastbound lanes on January 19.
The next phase, moving the elevated Interstate 93 underground, was completed in two stages: northbound lanes opened in March 2003 and southbound lanes (in a temporary configuration) on December 20, 2003. A tunnel underneath Leverett Circle connecting eastbound Storrow Drive to I-93 North and the Tobin Bridge opened December 19, 2004, easing congestion at the circle. All southbound lanes of I-93 opened to traffic on March 5, 2005, including the left lane of the Zakim Bridge, and all of the refurbished Dewey Square Tunnel.
By the end of December 2004, 95% of the Big Dig was completed. Major construction remained on the surface, including construction of final ramp configurations in the North End and in the South Bay interchange, and reconstruction of the surface streets. Many impact-mitigation projects (transit, pedestrian, bicycle, and parks) also remain, but some are in danger of cancellation due to cost overruns on the rest of the project.
The final ramp downtown—exit 20B from I-93 south to Albany Street—opened January 13, 2006.
In 2006, the two Interstate 93 tunnels were dedicated as the Thomas P. O'Neill Jr. Tunnel, after the former Democratic speaker of the House of Representatives from Massachusetts who pushed to have the Big Dig funded by the federal government.

Final phases

"Thousands of leaks"
Massachusetts State Police searched the offices of Aggregate Industries, the largest concrete supplier for the underground portions of the project, in June 2005. They seized evidence of faked records that hid the poor quality of concrete delivered for the highway project. In May 2006, six executives of the company, including its general manager, were arrested and charged with crimes related to fraud. Immediately after the arrests, Massachusetts Governor Mitt Romney announced he would return $3,900 in political contributions from employees of Aggregate Industries.

Fatal ceiling collapse

Michaelhouse is the name of one of the former colleges of the University of Cambridge, that existed between 1323 and 1546, when it was merged with King's Hall to form Trinity College. Michaelhouse was the second residential college to be founded, after Peterhouse (1284). Though King's Hall was established earlier in 1317, it did not acquire actual premises until its refoundation by Edward III in 1336.

Reformation and Dissolution
The parish church of St Michael probably dates back to the foundation of the city of Cambridge itself, though no written records survive prior to a valuation of the living in 1217 (see William E. Lunt ed., The Valuation of Norwich, Oxford: Clarendon Press, 1926, 218). Substantially rebuilt by Hervey de Stanton in the decorated style, the Church was designed to serve both the parish and the college. The chancel is three bays long, a bay larger than the nave; both chancel and nave have side aisles. In 1324, de Stanton had suggested to the bishop of Ely that the master and fellows, who were all members of the clergy, could provide daily worship for the parish, since they already used the church as their chapel. Consequently, on 18 March 1324/5, the first Master of Michaelhouse, Walter de Buxton was inducted as vicar of St Michael's Church (Trinity Archives MS 25). Until the completion of a chapel for neighbouring Gonville Hall in 1396, both Michaelhouse and Gonville shared in the use of the church.
Michaelhouse clergy contiunued to serve the parish until the dissolution of the College in 1546. Until the completion of Trinity College chapel under Mary Tudor in 1565, the scholars of Trinity continued to use St Michael's Church as its chapel. Indeed, when Trinity College was remodelled between 1708-18, the Tudor scholars' seats were transferred to St Michael's Church where they remain today. As successor of Hervey de Stanton's foundation, Trinity College continues to hold the patronage of the living of St Michael's and, during the sixteenth to eighteenth centuries, fellows in Holy Orders at Trinity College ministered as clergy (so-called 'chaplains') in St Michael's Church. The present minister retains this title.
From the middle of the seventeenth century until the middle of the nineteenth century, the church was used as a venue of the episcopal and archidiaconal visitations for the Diocese of Ely. Similarly, Diocesan confirmation services would be held at St Michael's rather than in Ely Cathedral. On 11 November 1849, as the congregation was gathering for Sunday worship, the heating system caused the church roof to catch fire, resulting in the careful rebuilding of the roof by George Gilbert Scott the following year. Twenty years later, from 1870-2, George Gilbert Scott Junior designed a fine new East Window and matching altarpiece for the chancel, while the ceiling and walls were painted by F.R. Leach.
Ultimately, the parish was too small to be sustainable. Indeed, from as early as 1550, when it was suggested that it should be united with the parish of All Saints in the Jewry, St Michael's parish was threatened with fusion with neighbouring parishes. It was finally united with that Great St Mary's in 1908. Substantially refurbished in 2001-2002, the church now bears the College's name and serves as a weekday church, community centre, art gallery and a café. The chapel adjacent to de Stanton's grave is named in his memory and now, as then, forms the focal point for daily devotions at the church he built.

This article derives some information from an edition of 'Trinity College - An Historical Sketch' by GM Trevelyan, along with information from various individuals associated with the College and the University and Andreas Loewe's 'Michaelhouse: City Church, Cambridge College'.

There are a number of models regarding the ways in which religions come into being and develop. Broadly speaking, these models fall into three categories:
The models are not mutually exclusive. Multiple models may be seen to apply simultaneously, or different models may be seen as applying to different religions.

Models which see religions as social constructions;
Models which see religions as progressing toward higher, objective truth;
Models which see a particular religion as absolutely true; Religions as social construction
This model holds that religion is the byproduct of the cognitive modules in the human brain that arose in our evolutionary past to deal with problems of survival and reproduction. Initial concepts of supernatural agents may arise in the tendency of humans to "over detect" the presence of other humans or predators (momentarily mistaking a vine for a snake). For instance, a man might report that he felt something sneaking up on him, but it vanished when he looked around.

Religion as a Byproduct of Evolutionary Psychology
In this model, held by individuals such as Karl Marx and Bertrand Russell, religion is seen as a tool concocted by the powerful to pacify and oppress the powerless. As Bertrand Russell wrote, "Religion in any shape or form is regarded as pernicious and deliberate falsehood, spread and encouraged by rulers and clerics in their own interests, since it is easier to control over the ignorant." In this model, the development of religion is seen as analogous to the growth of a cancer: and the most "developed" religion would be no religion at all. However, there is some question regarding the meaning of Karl Marx's image due to opium in his time being the only widely available pain killer (which, incidently, he had used). Thus, religion would be likened to a powerful pain killer, an idea that religious people would tend to support but that some of Marx's adepts may have misunderstood.

"Theory of religion" model
In the dogma selection model, religion is a set of beliefs which allow humans to encode useful survival tips and social structures. For example, early populations may not have understood microbes (germs), but thinking of illness as being caused by invisible demons that can hop on nearby people and possess them also supplies a mental model that reminds one to stay away from people that are coughing. The demon is an abstraction or approximation of germs and their infectious nature.
Dogma that increases the survival of a group will spread using a kind of Darwinian selection process (see Natural Selection; meme). The most useful dogmas spread because they keep the population that espouses them alive to bear more children. Over time good ideas may "mutate" as new generations or tribal branches alter them and the best variations spread using the selection process described above. Of course sometimes religious doctrine goes awry and ends up in large numbers of deaths, but it is the net benefits that count in the end.

Dogma selection model
In contrast to the above models, the following models see religion as "progressively true." Proponents of these models state that their models differentiate between major world religions and the cults and false religions which develop in the above ways. Within these models, and in contrast to cults, religions reflect an essential Truth to one degree or another. The development of religion is therefore the course of religions aligning themselves more completely with the Truth, as the benefits of the teachings of each religion take effect within the development of humanity across time and place, as well as dealing with drifts of the religions from their founding principles or standing in need of elaborating the same essential truth in a new specific way - but all in relation to the same mysterious God, that is that this progression is divinely based or directed, rather than simply the occurrence of good people in history.
1) Within these models, religions are developed by prophets and teachers who bring genuine insight to religious thought. This contrasts with the "useful lie" model above, which sees religious thought as merely random changes which spread according to their usefulness.
2) Within these models, prophets such as Jesus and Muhammad are seen as outsiders leading a divine rebellion against the dominant and corrupt power structures to rescue humanity from destruction. Religion is therefore "grass-roots" in origin, rather than "imposed by the powerful." This contrasts strongly with the Opiate of the Masses model which sees religion as originating with the rich and powerful as a means of controlling the powerless.
3) Within these models, prophets are seen as having genuine insight and wisdom. This contrasts with the "Theory of Religion" model, which ascribes religious birth and development to some psychological or moral pathology in religious leaders and believers.

Religions as progressively true
To a lesser degree of "progression in religion" is true within most of the religions - Judaism accepts a series of Prophets, progressively leading the Jews, from Abraham down through Moses down to Malachi: see the Nevi'im. Christianity accepts the same and adds Jesus. Islam accepts those of Judaism and Christianity and adds Muhammad. Hinduism identifies a series of Avatars, to use their own terminology, from Brahma through to Krishna. Buddhism identifies a separate series of earlier Buddhas. Zoroastrians also delineate earlier Saviors, or Saoshyants, who came progressively leading the people forward. There are other examples. However this is a minor recognition because the figures referred to are accepted within the religion, or are partial because their references to other religions are not systematic

Minor Progression
In the Bahá'í view, religion develops through a series of divine interventions from God, in the form of a Manifestation of God. Bahá'ís believe that God has sent a number of messengers in different times and cultures to bring divine revelation to humanity. Each of these messengers taught the truth of God, but later messengers provided more information to humanity, because humanity was ready to receive the more subtle teachings. Bahá'ís believe in Adam, the Jewish prophets, Jesus, and Muhammad, among others, as messengers of God. Bahá'í teachings also extend that progression indefinitely into the future. A particularized form of this is often present in other religions. The Abrahamic religions have a certain heritage and disputed progression among them (clearly if Judaism accepted Christianity as the right progression then it wouldn't stay Judaism as we know it for example - the same is true for most of the religions we have today.) The Dharmic religions similarly have a certain heritage and disputed progression. While often categorized as an Abrahamic religion, the Bahá'í faith claims to be a member of the progression of both Dharmic and Abrahamic categories and that other possible divine teachers may have appeared directly among other cultural traditions as among the Native Americans and Australian aboriginal peoples. For all culturally based categories of religions, Bahá'ís believe Bahá'u'lláh, the founder of Bahá'í Faith, has brought the latest revelation from God.
In summarizing this view, Shoghi Effendi, the Guardian of the Bahá'í Faith stated:
"The fundamental principle enunciated by Bahá'u'lláh, the followers of His Faith firmly believe, is that religious truth is not absolute but relative, that Divine Revelation is a continuous and progressive process, that all the great religions of the world are divine in origin, that their basic principles are in complete harmony, that their aims and purposes are one and the same, that their teachings are but facets of one truth, that their functions are complementary, that they differ only in the nonessential aspects of their doctrines, and that their missions represent successive stages in the spiritual evolution of human society." (Shoghi Effendi in The Promised Day Is Come, preface) [1]
See Progressive Revelation for more information

Bahá'í prophecy model
In A Study of History, Arnold J. Toynbee argues that as civilizations decay, they experience a "schism in the soul," as the creative and spiritual impulse dies. In this environment of spiritual nadir, a few prophets (such as Abraham, Moses, the Prophets, and Christ) are given to extraordinary spiritual insight, born of the spiritual decay in the dying civilization. He describes such prophets as "surveyors of the course of secular civilization who report breaks in the road and breakdowns in the traffic, and plot a new spiritual course which will avoid those pitfalls."
Thus, he argues, the "high points" in secular history coincide with the "low points" in spiritual history, and vice versa. He notes that the call of Abraham followed the defiance of God by the self-confident builders of the Tower of Babel; that the mission of Moses was to rescue God's chosen people from the fleshpots of Egypt; that the prophets of Israel and Judah were inspired to preach repentance from the spiritual backslidings into which Israel lapsed in its 'land flowing with milk and honey' which Yahweh had provided for them; and that the Ministry of Christ, whose passion reflected the anguish of the Hellenic Time of Troubles, was the intervention of God Himself for the purpose of extending to the whole of Mankind the covenant he had made with Israel.
While these new spiritual insights allow for the birth of a new religion and ultimately a new civilization, they are ultimately impermanent. This is due to their tendency to deteriorate after being institutionalized, as men of God degenerate into successful businessmen or men of politics. He describes the worst corruption of all, however, as "idolizing the terrestrial institution in which the Church Militant on Earth is imperfectly though unavoidably embodied. A church is in danger of lapsing into this idolatry insofar as she lapses into believing herself to be, not merely a depository of truth, but the sole depository of the whole truth in a complete and definite revelation."
Of the possibility that a new religion may arise in Western civilization to finally establish a permanent kingdom of heaven, he concludes that it is unlikely or impossible. "The manifest reason is exhibited by the nature of Society and the nature of Man. For Society is nothing but the common ground between the fields of action of personalities, and human personality has an innate capacity for evil as well as for good. The establishment of such a single Church Militant as we have imagined would not purge Man of Original Sin. This World is a province of the Kingdom of God, but it is a rebellious province, and, in the nature of things, it will always remain so."

A Study of History model
In the following models, religions are seen as absolutely and unchangingly True. They contrast with both the first group of models (which held religion to be false), and the second group (which held religion to develop over time).

Religions as absolutely true
Traditional Judaism teaches that God relates to humanity through a series of covenants, which are initiated by him, and in which God promises to perform certain acts on the condition that humans "keep their side of the bargain." Jews believe that they are bound by the Mosaic law, which includes the Ten Commandments and additional teachings, especially those found in Leviticus and the later Sanhedrin. All non-Jews are under the Noahide Laws, established by God after the global flood which wiped out antediluvian civilization. Those who fulfill their part of the covenant are granted the afterlife.

Jewish model
Many religions which claim an exclusive revelation from God assert that theirs is the "One True Religion," and all others are false, because they do not originate from the same source. Exclusivism can be seen in many religions, particularly in certain branches of Christianity and Islam. In such a model, the development of "True Religion" is inexorably tied to a single prophet and/or holy book, and all other religions are described as "non-religion," in that they originate either from human ignorance, or from the evil influence of deceivers, false prophets, or even Satan. However, Judaism is alone in its belief that both the written and oral Torah, the basis of Judaism, was in fact received by the whole Jewish nation, not a single prophet, on mount Sinai by God himself.

Exclusivist models
Many religions have been deeply influenced by charismatic leaders, such as Jesus, Martin Luther, Saint Francis of Assisi, John Calvin, Joseph Smith, etc. These leaders are either the central teacher and founder of the religion (e.g. Muhammad, Jesus, or Gautama) or reformers or prominent persons. Failed or violent new religions were also founded by charismatic leaders, such as Jim Jones.
There is some similarity to the role played by charismatic figures in politics. See list of charismatic leaders.

See also

The special theory of relativity was proposed in 1905 by Albert Einstein in his article "On the Electrodynamics of Moving Bodies". Some three centuries earlier, Galileo's principle of relativity had stated that all uniform motion was relative, and that there was no absolute and well-defined state of rest; a person on the deck of a ship may be at rest in his opinion, but someone observing from the shore would say that he was moving. Einstein's theory generalized Galilean relativity from only mechanics to all laws of physics including electrodynamics. To stress this point, Einstein not only widened the postulate of relativity, but added the second postulate - that all observers will always measure the speed of light to be the same no matter what their state of uniform linear motion is.
This theory has a variety of surprising consequences that seem to violate common sense, but all have been experimentally verified. Special relativity overthrows Newtonian notions of absolute space and time by stating that distance and time depend on the observer, and that time and space are perceived differently, depending on the observer. It yields the equivalence of matter and energy, as expressed in the mass-energy equivalence formula E = mc², where c is the speed of light in a vacuum. Special relativity agrees with Newtonian mechanics in their common realm of applicability, in experiments in which all velocities are small compared to the speed of light.
The theory was called "special" because it applies the principle of relativity only to inertial frames. Einstein developed general relativity to apply the principle generally, that is, to any frame, and that theory includes the effects of gravity. Special relativity does not account for gravity, but it can deal with accelerations.
Although special relativity makes some quantities relative, such as time, that we would have imagined to be absolute based on everyday experience, it also makes absolute some others that we would have thought were relative. In particular, it states that the speed of light is the same for all observers, even if they are in motion relative to one another. Special relativity reveals that c is not just the velocity of a certain phenomenon - light - but rather a fundamental feature of the way space and time are tied together. In particular, special relativity states that it is impossible for any material object to accelerate to light speed.
For history and motivation, see the article: history of special relativity

Postulates
The principle of relativity, which states that there is no stationary reference frame, dates back to Galileo, and was incorporated into Newtonian Physics. However, in the late 19 century, the existence of electromagnetic waves led some physicists to suggest that the universe was filled with a substance known as "aether", which would act as the medium through which these waves, or vibrations traveled. The aether was thought to constitute an absolute reference frame against which speeds could be measured. In other words, the aether was the only fixed or motionless thing in the universe. Aether supposedly had some wonderful properties: it was sufficiently elastic that it could support electromagnetic waves, and those waves could interact with matter, yet it offered no resistance to bodies passing through it. The results of various experiments, including the Michelson-Morley experiment, indicated that the Earth was always 'stationary' relative to the aether — something that was difficult to explain, since the Earth is in orbit around the Sun. Einstein's elegant solution was to discard the notion of an aether and an absolute state of rest. Special relativity is formulated so as to not assume that any particular frame of reference is special; rather, in relativity, any reference frame moving with uniform motion will observe the same laws of physics. In particular, the speed of light in a vacuum is always measured to be c, even when measured by multiple systems that are moving at different (but constant) velocities.

Lack of an absolute reference frame
Main article: Consequences of special relativity
Einstein has said that all of the consequences of special relativity can be derived from examination of the Lorentz transformations.
These transformations, and hence special relativity, lead to different physical predictions than Newtonian mechanics when relative velocities become comparable to the speed of light. The speed of light is so much larger than anything humans encounter that some of the effects predicted by relativity are initially counter-intuitive:

Time dilation — the time lapse between two events is not invariant from one observer to another, but is dependent on the relative speeds of the observers' reference frames (e.g., the twin paradox which concerns a twin who flies off in a spaceship traveling near the speed of light and returns to discover that his twin has aged much more).
Relativity of simultaneity — two events happening in two different locations that occur simultaneously to one observer, may occur at different times to another observer (lack of absolute simultaneity).
Lorentz contraction — the dimensions (e.g., length) of an object as measured by one observer may be smaller than the results of measurements of the same object made by another observer (e.g., the ladder paradox involves a long ladder traveling near the speed of light and being contained within a smaller garage).
Composition of velocities — velocities (and speeds) do not simply 'add', for example if a rocket is moving at ⅔ the speed of light relative to an observer, and the rocket fires a missile at ⅔ of the speed of light relative to the rocket, the missile does not exceed the speed of light relative to the observer. (In this example, the observer would see the missile travel with a speed of 12/13 the speed of light.)
Inertia and momentum — as an object's velocity approaches the speed of light from an observer's point of view, its mass appears to increase thereby making it more and more difficult to accelerate it from within the observer's frame of reference.
Equivalence of mass and energy, E = mc² — The energy content of an object at rest with mass m equals mc. Conservation of energy implies that in any reaction a decrease of the sum of the masses of particles must be accompanied by an increase in kinetic energies of the particles after the reaction. Similarly, the mass of an object can be increased by taking in kinetic energies. Consequences
Full article: Lorentz transformations
Relativity theory depends on "reference frames". A reference frame is an observational perspective in space at rest, or in uniform motion, from which a position can be measured along 3 spatial axes. In addition, a reference frame has the ability to determine measurements of the time of events using a 'clock' (any reference device with uniform periodicity).
An event is an occurrence that can be assigned a single unique time and location in space relative to a reference frame: it is a "point" in space-time. Since the speed of light is constant in relativity in each and every reference frame, pulses of light can be used to unambiguously measure distances and refer back the times that events occurred to the clock, even though light takes time to reach the clock after the event has transpired.
For example, the explosion of a firecracker may be considered to be an "event". We can completely specify an event by its four space-time coordinates: The time of occurrence and its 3-dimensional spatial location define a reference point. Let's call this reference frame S.
In relativity theory we often want to calculate the position of a point from a different reference point.
Suppose we have a second reference frame S', whose spatial axes and clock exactly coincide with that of S at time zero, but it is moving at a constant velocity with respect to S along the -axis.
Since there is no absolute reference frame in relativity theory, a concept of 'moving' doesn't strictly exist, as everything is always moving with respect to some other reference frame. Instead, any two frames that move at the same speed in the same direction are said to be comoving. Therefore S and S' are not comoving.
Let's define the event to have space-time coordinates in system S and in S'. Then the Lorentz transformation specifies that these coordinates are related in the following way:




where is called the Lorentz factor and is the speed of light in a vacuum.
The and coordinates are unaffected, but the and axes are mixed up by the transformation. In a way this transformation can be understood as a hyperbolic rotation.
A quantity invariant under Lorentz transformations is known as a Lorentz scalar.

Reference frames, coordinates and the Lorentz transformation

Main article: Relativity of simultaneity Simultaneity
Writing the Lorentz Transformation and its inverse in terms of coordinate differences we get


and


Suppose we have a clock at rest in the unprimed system S. Two consecutive ticks of this clock are then characterized by Δx = 0. If we want to know the relation between the times between these ticks as measured in both systems, we can use the first equation and find:
for events satisfying
This shows that the time Δt' between the two ticks as seen in the 'moving' frame S' is larger than the time Δt between these ticks as measured in the rest frame of the clock. This phenomenon is called time dilation.
Similarly, suppose we have a measuring rod at rest in the unprimed system. In this system, the length of this rod is written as Δx. If we want to find the length of this rod as measured in the 'moving' system S', we must make sure to measure the distances x' to the end points of the rod simultaneously in the primed frame S'. In other words, the measurement is characterized by Δt' = 0, which we can combine with the fourth equation to find the relation between the lengths Δx and Δx':
for events satisfying
This shows that the length Δx' of the rod as measured in the 'moving' frame S' is shorter than the length Δx in its own rest frame. This phenomenon is called length contraction or Lorentz contraction.
These effects are not merely appearances; they are explicitly related to our way of measuring time intervals between events which occur at the same place in a given coordinate system (called "co-local" events). These time intervals will be different in another coordinate system moving with respect to the first, unless the events are also simultaneous. Similarly, these effects also relate to our measured distances between separated but simultaneous events in a given coordinate system of choice. If these events are not co-local, but are separated by distance (space), they will not occur at the same spacial distance from each other when seen from another moving coordinate system.
See also the twin paradox.

Time dilation and length contraction
In diagram 2 the interval AB is 'time-like'; i.e., there is a frame of reference in which event A and event B occur at the same location in space, separated only by occurring at different times. If A precedes B in that frame, then A precedes B in all frames. It is hypothetically possible for matter (or information) to travel from A to B, so there can be a causal relationship (with A the cause and B the effect).
The interval AC in the diagram is 'space-like'; i.e., there is a frame of reference in which event A and event C occur simultaneously, separated only in space. However there are also frames in which A precedes C (as shown) and frames in which C precedes A. If it was possible for a cause-and-effect relationship to exist between events A and C, then paradoxes of causality would result. For example, if A was the cause, and C the effect, then there would be frames of reference in which the effect preceded the cause. Although this in itself won't give rise to a paradox, one can show that faster than light signals can be sent back into one's own past. A causal paradox can then be constructed by sending the signal if and only if no signal was received previously.
Therefore, one of the consequences of special relativity is that (assuming causality is to be preserved), no information or material object can travel faster than light. On the other hand, the logical situation is not as clear in the case of general relativity, so it is an open question whether or not there is some fundamental principle that preserves causality (and therefore prevents motion faster than light) in general relativity.
Even without considerations of causality, there are other strong reasons why faster-than-light travel is forbidden by special relativity. For example, if a constant force is applied to an object for a limitless amount of time, then integrating F=dp/dt gives a momentum that grows without bound, but this is simply because p = mγv approaches infinity as v approaches c. To an observer who is not accelerating, it appears as though the object's inertia is increasing, so as to produce a smaller acceleration in response to the same force. This behavior is in fact observed in particle accelerators.
See also the Tachyonic Antitelephone.

Causality and prohibition of motion faster than light

Main article: Velocity-addition formula Composition of velocities

Main article: Mass in special relativity Mass, momentum, and energy
Introductory physics courses and some older textbooks on special relativity sometimes define a relativistic mass which increases as the velocity of a body increases. According to the geometric interpretation of special relativity, this is often deprecated and the term 'mass' is reserved to mean invariant mass and is thus independent of the inertial frame, i.e., invariant.
Using the relativistic mass definition, the mass of an object may vary depending on the observer's inertial frame in the same way that other properties such as its length may do so. Defining such a quantity may sometimes be useful in that doing so simplifies a calculation by restricting it to a specific frame. For example, consider a body with an invariant mass m moving at some velocity relative to an observer's reference system. That observer defines the relativistic mass of that body as:

"Relativistic mass" should not be confused with the "longitudinal" and "transverse mass" definitions that were used around 1900 and that were based on an inconsistent application of the laws of Newton: those used f=ma for a variable mass, while relativistic mass corresponds to Newton's dynamic mass in which p=Mv and f=dp/dt.
Note also that the body does not actually become more massive in its proper frame, since the relativistic mass is only different for an observer in a different frame. The only mass that is frame independent is the invariant mass. When using the relativistic mass, the applicable reference frame should be specified if it isn't already obvious or implied. It also goes almost without saying that the increase in relativistic mass does not come from an increased number of atoms in the object. Instead, the relativistic mass of each atom and subatomic particle has increased.
Physics textbooks sometimes use the relativistic mass as it allows the students to utilize their knowledge of Newtonian physics to gain some intuitive grasp of relativity in their frame of choice (usually their own!). "Relativistic mass" is also consistent with the concepts "time dilation" and "length contraction".

Relativistic mass
The classical definition of ordinary force f is given by Newton's Second Law in its original form:

and this is valid in relativity.
Many modern textbooks rewrite Newton's Second Law as

This form is not valid in relativity or in other situations where the relativistic mass M is varying.
This formula can be replaced in the relativistic case by

As seen from the equation, ordinary force and acceleration vectors are not necessarily parallel in relativity.
However the four-vector expression relating four-force to invariant mass m and four-acceleration restores the same equation form


Force

Main article: Minkowski space The geometry of space-time
Here, we see how to write the equations of special relativity in a manifestly Lorentz covariant form. The position of an event in spacetime is given by a contravariant four vector whose components are:

That is, x = z. Superscripts are contravariant indices in this section rather than exponents except when they indicate a square. Subscripts are covariant indices which also range from zero to three as with the spacetime gradient of a field φ:


Physics in spacetime
Having recognised the four-dimensional nature of spacetime, we are driven to employ the Minkowski metric, η, given in components (valid in any inertial reference frame) as:

Its reciprocal is:

Then we recognize that co-ordinate transformations between inertial reference frames are given by the Lorentz transformation tensor Λ. For the special case of motion along the x-axis, we have:

which is simply the matrix of a boost (like a rotation) between the x and t coordinates. Where μ' indicates the row and ν indicates the column. Also, β and γ are defined as:

More generally, a transformation from one inertial frame (ignoring translations for simplicity) to another must satisfy:

where there is an implied summation of and from 0 to 3 on the right-hand side in accordance with the Einstein summation convention. The Poincaré group is the most general group of transformations which preserves the Minkowski metric and this is the physical symmetry underlying special relativity.
All proper physical quantities are given by tensors. So to transform from one frame to another, we use the well known tensor transformation law
Where is the reciprocal matrix of .
To see how this is useful, we transform the position of an event from an unprimed co-ordinate system S to a primed system S', we calculate

which is the Lorentz transformation given above. All tensors transform by the same rule.
The squared length of the differential of the position four-vector constructed using

is an invariant. Being invariant means that it takes the same value in all inertial frames, because it is a scalar (0 rank tensor), and so no Λ appears in its trivial transformation. Notice that when the line element is negative that is the differential of proper time, while when is positive, is differential of the proper distance.
The primary value of expressing the equations of physics in a tensor form is that they are then manifestly invariant under the Poincaré group, so that we do not have to do a special and tedious calculation to check that fact. Also in constructing such equations we often find that equations previously thought to be unrelated are, in fact, closely connected being part of the same tensor equation.

Metric and transformations of coordinates
Recognising other physical quantities as tensors also simplifies their transformation laws. First note that the velocity four-vector U also has an invariant form:

So all velocity four-vectors have a magnitude of c. This is an expression of the fact that there is no such thing as being at coordinate rest in relativity: at the least, you are always moving forward through time. The acceleration 4-vector is given by . Given this, differentiating the above equation by τ produces

So in relativity, the acceleration four-vector and the velocity 4-vector are orthogonal.

Velocity and acceleration in 4D
The momentum and energy combine into a covariant 4-vector:

where m is the invariant mass.
The invariant magnitude of the momentum 4-vector is:

We can work out what this invariant is by first arguing that, since it is a scalar, it doesn't matter which reference frame we calculate it, and then by transforming to a frame where the total momentum is zero.

We see that the rest energy is an independent invariant. A rest energy can be calculated even for particles and systems in motion, by translating to a frame in which momentum is zero.
The rest energy is related to the mass according to the celebrated equation discussed above:

Note that the mass of systems measured in their center of momentum frame (where total momentum is zero) is given by the total energy of the system in this frame. It may not be equal to the sum of individual system masses measured in other frames.

Momentum in 4D
To use Newton's third law of motion, both forces must be defined as the rate of change of momentum with respect to the same time coordinate. That is, it requires the 3D force defined above. Unfortunately, there is no tensor in 4D which contains the components of the 3D force vector among its components.
If a particle is not traveling at c, one can transform the 3D force from the particle's co-moving reference frame into the observer's reference frame. This yields a 4-vector called the four-force. It is the rate of change of the above energy momentum four-vector with respect to proper time. The covariant version of the four-force is:

where is the proper time.
In the rest frame of the object, the time component of the four force is zero unless the "invariant mass" of the object is changing in which case it is the negative of that rate of change times c. In general, though, the components of the four force are not equal to the components of the three-force, because the three force is defined by the rate of change of momentum with respect to coordinate time, i.e. while the four force is defined by the rate of change of momentum with respect to proper time, i.e. .
In a continuous medium, the 3D density of force combines with the density of power to form a covariant 4-vector. The spatial part is the result of dividing the force on a small cell (in 3-space) by the volume of that cell. The time component is the negative of the power transferred to that cell divided by the volume of the cell. This will be used below in the section on electromagnetism.

Force in 4D
Theoretical investigation in classical electromagnetism led to the discovery of wave propagation. Equations generalizing the electromagnetic effects found that finite propagation-speed of the E and B fields required certain behaviors on charged particles. The general study of moving charges forms the Liénard–Wiechert potential, which is a step towards special relativity.
The Lorentz transformation of the electric field of a moving charge into a non-moving observer's reference frame results in the appearance of a mathematical term commonly called the magnetic field. Conversely, the magnetic field generated by a moving charge disappears and becomes a purely electrostatic field in a comoving frame of reference. Maxwell's equations are thus simply an empirical fit to special relativistic effects in a classical model of the Universe. As electric and magnetic fields are reference frame dependent and thus intertwined, one speaks of electromagnetic fields. Special relativity provides the transformation rules for how an electromagnetic field in one inertial frame appears in another inertial frame.

Relativity and unifying electromagnetism

Main article: Formulation of Maxwell's equations in special relativity Electromagnetism in 4D

Main article: Status of special relativity Status

Textbooks

On the Electrodynamics of Moving Bodies, A. Einstein, Annalen der Physik, 17:891, June 30, 1905 (in English translation)
Wolf, Peter and Gerard, Petit. "Satellite test of Special Relativity using the Global Positioning System", Physics Review A 56 (6), 4405-4409 (1997).
Will, Clifford M. "Clock synchronization and isotropy of the one-way speed of light", Physics Review D 45, 403-411 (1992).
Rizzi G. et al, "Synchronization Gauges and the Principles of Special Relativity", Found. Phys. 34 (2005) 1835-1887
Alvager et al., "Test of the Second Postulate of Special Relativity in the GeV region", Physics Letters 12, 260 (1964).
Olivier Darrigol (2004) "The Mystery of the Poincaré-Einstein Connection", Isis 95 (4), 614 - 626. Journal articles
People: Arthur Eddington | Albert Einstein | Hendrik Lorentz | Hermann Minkowski | Bernhard Riemann | Henri Poincaré | Alexander MacFarlane | Harry Bateman | Robert S. Shankland | Walter Ritz
Relativity: Theory of relativity | principle of relativity | general relativity | frame of reference | inertial frame of reference | Lorentz transformations | Bondi k-calculus | Einstein synchronisation | Rietdijk-Putnam Argument
Physics: Newtonian Mechanics | spacetime | speed of light | simultaneity | physical cosmology | Doppler effect | relativistic Euler equations | Aether drag hypothesis | Lorentz ether theory | Moving magnet and conductor problem
Maths: Minkowski space | four-vector | world line | light cone | Lorentz group | Poincaré group | geometry | tensors | split-complex number
Philosophy: actualism | conventionalism | formalism

See also

Original Works

Wikibooks: Special Relativity
Einstein Light An award-winning, non-technical introduction (film clips and demonstrations) supported by dozens of pages of further explanations and animations, at levels with or without mathematics.
Einstein Online Introduction to relativity theory, from the Max Planck Institute for Gravitational Physics.

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