The history of the Internet has its origin in the efforts to build and interconnect computer networks that arose from research and development in the United States and involved international collaboration, particularly with researchers in the United Kingdom and France.

Computer science was an emerging discipline in the late 1950s that began to consider time-sharing between computer users, and later, the possibility of achieving this over wide area networks. Independently, Paul Baran proposed a distributed network based on data in message blocks in the early 1960s and Donald Davies conceived of packet switching in 1965 at the National Physical Laboratory (NPL) and proposed building a national commercial data network in the UK. The Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense awarded contracts in 1969 for the development of the ARPANET project, directed by Robert Taylor and managed by Lawrence Roberts. ARPANET adopted the packet switching technology proposed by Davies and Baran, underpinned by mathematical work in the early 1970s by Leonard Kleinrock at UCLA. The network was built by Bolt, Beranek, and Newman.

Early packet switching networks such as the NPL network, ARPANET, Merit Network, and CYCLADES researched and provided data networking in the early 1970s. ARPA projects and international working groups led to the development of protocols for internetworking, in which multiple separate networks could be joined into a network of networks, which produced various standards. Bob Kahn, at ARPA, and Vint Cerf, at Stanford University, published research in 1974 that evolved into the Transmission Control Protocol (TCP) and Internet Protocol (IP), the two protocols of the Internet protocol suite. The design included concepts from the French CYCLADES project directed by Louis Pouzin.

In the early 1980s, the National Science Foundation (NSF) funded national supercomputing centers at several universities in the United States, and provided interconnectivity in 1986 with the NSFNET project. Thus creating network access to these supercomputer sites for research and academic organizations in the United States. International connections to NSFNET, the emergence of architecture such as the Domain Name System, and the adoption of TCP/IP internationally on existing networks marked the beginnings of the Internet. Commercial Internet service providers (ISPs) began to emerge in the very late 1980s. The ARPANET was decommissioned in 1990.Limited private connections to parts of the Internet by officially commercial entities emerged in several American cities by late 1989 and 1990. The NSFNET was decommissioned in 1995, removing the last restrictions on the use of the Internet to carry commercial traffic.

Research at CERN in Switzerland by British computer scientist Tim Berners-Lee in 1989–90 resulted in the World Wide Web, linking hypertext documents into an information system, accessible from any node on the network. Since the mid-1990s, the Internet has had a revolutionary impact on culture, commerce, and technology, including the rise of near-instant communication by electronic mail, instant messaging, voice over Internet Protocol (VoIP) telephone calls, video chat, and the World Wide Web with its discussion forums, blogs, social networking services, and online shopping sites. Increasing amounts of data are transmitted at higher and higher speeds over fiber-optic networks operating at 1 Gbit/s, 10 Gbit/s, or more. The Internet’s takeover of the global communication landscape was rapid in historical terms: it only communicated 1% of the information flowing through two-way telecommunications networks in the year 1993, 51% by 2000, and more than 97% of the telecommunicated information by 2007.

The Internet continues to grow, driven by ever greater amounts of online information, commerce, entertainment, and social networking services. However, the future of the global network may be shaped by regional differences.

The history of medicine shows how societies have changed in their approach to illness and disease from ancient times to the present. Early medical traditions include those of Babylon, China, Egypt and India. Sushruta, from India, introduced the concepts of medical diagnosis and prognosis. The Hippocratic Oath was written in ancient Greece in the 5th century BCE, and is a direct inspiration for oaths of office that physicians swear upon entry into the profession today. In the Middle Ages, surgical practices inherited from the ancient masters were improved and then systematized in Rogerius’s The Practice of Surgery. Universities began systematic training of physicians around 1220 CE in Italy.

Invention of the microscope was a consequence of improved understanding, during the Renaissance. Prior to the 19th century, humorism (also known as humoralism) was thought to explain the cause of disease but it was gradually replaced by the germ theory of disease, leading to effective treatments and even cures for many infectious diseases. Military doctors advanced the methods of trauma treatment and surgery. Public health measures were developed especially in the 19th century as the rapid growth of cities required systematic sanitary measures. Advanced research centers opened in the early 20th century, often connected with major hospitals. The mid-20th century was characterized by new biological treatments, such as antibiotics. These advancements, along with developments in chemistry, genetics, and radiography led to modern medicine. Medicine was heavily professionalized in the 20th century, and new careers opened to women as nurses (from the 1870s) and as physicians (especially after 1970).

The ability to practice diplomacy is one of the defining elements of a state, and diplomacy has been practiced since the formation of the first city-states. Originally diplomats were sent only for specific negotiations, and would return immediately after their mission concluded. Diplomats were usually relatives of the ruling family or of very high rank in order to give them legitimacy when they sought to negotiate with the other state.
One notable exception involved the relationship between the Pope and the Byzantine Emperor. Papal agents, called apocrisiarii, were permanently resident in Constantinople. After the 8th century, however, conflicts between the Pope and the Emperor (such as the Iconoclastic controversy) led to the breaking down of these close ties.

Modern diplomacy’s origins are often traced to the states of Northern Italy in the early Renaissance, with the first embassies being established in the thirteenth century. Milan played a leading role, especially under Francesco Sforza who established permanent embassies to the other cities states of Northern Italy. It was in Italy that many of the traditions of modern diplomacy began, such as the presentation of an ambassador’s credentials to the head of state.

The practice spread from Italy to the other European powers. Milan was the first to send a representative to the court of France in 1455. Milan however refused to host French representatives fearing espionage and possible intervention in internal affairs. As foreign powers such as France and Spain became increasingly involved in Italian politics the need to accept emissaries was recognized. Soon all the major European powers were exchanging representatives. Spain was the first to send a permanent representative when it appointed an ambassador to the Court of England in 1487. By the late 16th century, permanent missions became the standard.

Many of the conventions of modern diplomacy developed during this period. The top rank of representatives was an ambassador. An ambassador at this time was almost always a nobleman – the rank of the noble varied with the prestige of the country he was posted to. Defining standards emerged for ambassadors, requiring that they have large residences, host lavish parties, and play an important role in the court life of the host nation. In Rome, the most important post for Catholic ambassadors, the French and Spanish representatives sometimes maintained a retinue of up to a hundred people. Even in smaller posts, ambassadors could be very expensive. Smaller states would send and receive envoys who were one level below an ambassador.

Ambassadors from each state were ranked by complex codes of precedence that were much disputed. States were normally ranked by the title of the sovereign; for Catholic nations the emissary from the Vatican was paramount, then those from the kingdoms, then those from duchies and principalities. Representatives from republics were considered the lowest envoys.

The history of the scientific discovery of climate change began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect was first identified. In the late 19th century, scientists first argued that human emissions of greenhouse gases could change the climate. Many other theories of climate change were advanced, involving forces from volcanism to solar variation. In the 1960s, the evidence for the warming effect of carbon dioxide gas became increasingly convincing. Some scientists also pointed out that human activities that generated atmospheric aerosols (e.g., “pollution”) could have cooling effects as well.

During the 1970s, scientific opinion increasingly favored the warming viewpoint. By the 1990s, as a result of improving fidelity of computer models and observational work confirming the Milankovitch theory of the ice ages, a consensus position formed: greenhouse gases were deeply involved in most climate changes and human-caused emissions were bringing discernible global warming. Since the 1990s, scientific research on climate change has included multiple disciplines and has expanded. Research has expanded our understanding of causal relations, links with historic data and ability to model climate change numerically. Research during this period has been summarized in the Assessment Reports by the Intergovernmental Panel on Climate Change.

Climate change, broadly interpreted, is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (such as more or fewer extreme weather events). Climate change is caused by factors that include oceanic processes (such as oceanic circulation), biotic processes (e.g., plants), variations in solar radiation received by Earth, plate tectonics and volcanic eruptions, and human-induced alterations of the natural world. The latter effect is currently causing global warming, and “climate change” is often used to describe human-specific impacts.