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National Science Foundation Network

The National Science Foundation Network (NSFNET) was a program of coordinated, evolving projects sponsored by the National Science Foundation (NSF) from 1985 to 1995 to promote advanced research and education networking in the United States. The program created several nationwide backbone computer networks in support of these initiatives. It was created to link researchers to the NSF-funded supercomputing centers. Later, with additional public funding and also with private industry partnerships, the network developed into a major part of the Internet backbone.

The National Science Foundation permitted only government agencies and universities to use the network until 1989 when the first commercial Internet service provider emerged. By 1991, the NSF removed access restrictions and the commercial ISP business grew rapidly.

History
Following the deployment of the Computer Science Network (CSNET), a network that provided Internet services to academic computer science departments, in 1981, the U.S. National Science Foundation (NSF) aimed to create an academic research network facilitating access by researchers to the supercomputing centers funded by NSF in the United States.

In 1985, NSF began funding the creation of five new supercomputing centers:
 * John von Neumann Center at Princeton University
 * Cornell Theory Center at Cornell University
 * Pittsburgh Supercomputing Center (PSC), a joint effort of Carnegie Mellon University, the University of Pittsburgh, and Westinghouse
 * National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana–Champaign
 * San Diego Supercomputer Center (SDSC) on the campus of the University of California, San Diego (UCSD)

Also in 1985, under the leadership of Dennis Jennings, the NSF established the National Science Foundation Network (NSFNET). NSFNET was to be a general-purpose research network, a hub to connect the five supercomputing centers along with the NSF-funded National Center for Atmospheric Research (NCAR) to each other and to the regional research and education networks that would in turn connect campus networks. Using this three tier network architecture NSFNET would provide access between the supercomputer centers and other sites over the backbone network at no cost to the centers or to the regional networks using the open TCP/IP protocols initially deployed successfully on the ARPANET.

56kbit/s backbone

The NSFNET initiated operations in 1986 using TCP/IP. Its six backbone sites were interconnected with leased 56-kbit/s links, built by a group including the University of Illinois National Center for Supercomputing Applications (NCSA), Cornell University Theory Center, University of Delaware, and Merit Network. PDP-11/73 minicomputers with routing and management software, called Fuzzballs, served as the network routers since they already implemented the TCP/IP standard.

This original 56kbit/s backbone was overseen by the supercomputer centers themselves with the lead taken by Ed Krol at the University of Illinois at Urbana–Champaign. PDP-11/73 Fuzzball routers were configured and run by Hans-Werner Braun at the Merit Network and statistics were collected by Cornell University.

Support for NSFNET end-users was provided by the NSF Network Service Center (NNSC), located at BBN Technologies and included publishing the softbound "Internet Manager's Phonebook" which listed the contact information for every issued domain name and IP address in 1990. Incidentally, Ed Krol also authored the Hitchhiker's Guide to the Internet to help users of the NSFNET understand its capabilities. The Hitchhiker's Guide became one of the first help manuals for the Internet.

As regional networks grew the 56kbit/s NSFNET backbone experienced rapid increases in network traffic and became seriously congested. In June 1987 NSF issued a new solicitation to upgrade and expand NSFNET.

1.5Mbit/s (T-1) backbone
As a result of a November 1987 NSF award to the Merit Network, a networking consortium by public universities in Michigan, the original 56kbit/s network was expanded to include 13 nodes interconnected at 1.5Mbit/s (T-1) by July 1988. Additional links were added to form a multi-path network, and a node located in Atlanta was added. Each of the backbone nodes was a router called the Nodal Switching System (NSS). The NSSes were a collection of multiple (typically nine) IBM RT PC systems connected by a Token Ring local area network. The RT PCs ran AOS, IBM's version of Berkeley UNIX, and was dedicated to a particular packet processing task.

Under its cooperative agreement with NSF the Merit Network was the lead organization in a partnership that included IBM, MCI, and the State of Michigan. Merit provided overall project coordination, network design and engineering, a Network Operations Center (NOC), and information services to assist the regional networks. IBM provided equipment, software development, installation, maintenance and operations support. MCI provided the T-1 data circuits at reduced rates. The state of Michigan provided funding for facilities and personnel. Eric M. Aupperle, Merit's President, was the NSFNET Project Director, and Hans-Werner Braun was Co-Principal Investigator.

From 1987 to 1994, Merit organized a series of "Regional-Techs" meetings, where technical staff from the regional networks met to discuss operational issues of common concern with each other and the Merit engineering staff.

During this period, but separate from its support for the NSFNET backbone, NSF funded:
 * the NSF Connections Program that helped colleges and universities obtain or upgrade connections to regional networks;
 * regional networks to obtain or upgrade equipment and data communications circuits;
 * the NNSC, and successor Network Information Services Manager (aka InterNIC) information help desks;
 * the International Connections Manager (ICM), a task performed by Sprint, that encouraged connections between the NSFNET backbone and international research and education networks; and
 * various ad hoc grants to organizations such as the Federation of American Research Networks (FARNET).

The NSFNET became the principal Internet backbone starting in the Summer of 1986, when MIDnet, the first NSFNET regional backbone network became operational. By 1988, in addition to the five NSF supercomputer centers, NSFNET included connectivity to the regional networks BARRNet, JVNCNet, Merit/MichNet, MIDnet, NCAR, NorthWestNet, NYSERNet, SESQUINET, SURAnet, and Westnet, which in turn connected about 170 additional networks to the NSFNET. Three new nodes were added as part of the upgrade to T-3: NEARNET in Cambridge, Massachusetts; Argone National Laboratory outside of Chicago; and SURAnet in Atlanta, Georgia. NSFNET connected to other federal government networks including the NASA Science Internet, the Energy Science Network (ESnet), and others.

Connections were also established to research and education networks in other countries starting in 1988 with Canada, France, NORDUnet (serving Denmark, Finland, Iceland, Norway, and Sweden), the Netherlands, and many other countries in subsequent years.

Two Federal Internet Exchanges (FIXes) were established in June 1989 under the auspices of the Federal Engineering Planning Group (FEPG). FIX East, at the University of Maryland in College Park and FIX West, at the NASA Ames Research Center in Mountain View, California. The existence of NSFNET and the FIXes allowed the ARPANET to be phased out in mid-1990.

Starting in August 1990 the NSFNET backbone supported the OSI Connectionless Network Protocol (CLNP) in addition to TCP/IP. However, CLNP usage remained low when compared to TCP/IP.

Traffic on the network continued its rapid growth, doubling every seven months. Projections indicated that the T-1 backbone would become overloaded sometime in 1990.

A critical routing technology, Border Gateway Protocol (BGP), originated during this period of Internet history. BGP allowed routers on the NSFNET backbone to differentiate routes originally learned via multiple paths. Prior to BGP, interconnection between IP network was inherently hierarchical, and careful planning was needed to avoid routing loops. BGP turned the Internet into a meshed topology, moving away from the centric architecture which the ARPANET emphasized.

45Mbit/s (T-3) backbone

During 1991, an upgraded backbone built with 45Mbit/s (T-3) transmission circuits was deployed to interconnect 16 nodes. The routers on the upgraded backbone were IBM RS/6000 servers running AIX UNIX. Core nodes were located at MCI facilities with end nodes at the connected regional networks and supercomputing centers. Completed in November 1991, the transition from T-1 to T-3 did not go as smoothly as the previous transition from 56kbit/s DDS to 1.5 mbit/s T-1, as it took longer than planned. As a result, there was at times serious congestion on the overloaded T-1 backbone. Following the transition to T-3, portions of the T-1 backbone were left in place to act as a backup for the new T-3 backbone.

In anticipation of the T-3 upgrade and the approaching end of the 5-year NSFNET cooperative agreement, in September 1990 Merit, IBM, and MCI formed Advanced Network and Services (ANS), a new non-profit corporation with a more broadly based Board of Directors than the Michigan-based Merit Network. Under its cooperative agreement with NSF, Merit remained ultimately responsible for the operation of NSFNET, but subcontracted much of the engineering and operations work to ANS. Both IBM and MCI made substantial new financial and other commitments to help support the new venture. Allan Weis left IBM to become ANS's first President and Managing Director. Douglas Van Houweling, former Chair of the Merit Network Board and Vice Provost for Information Technology at the University of Michigan, was Chairman of the ANS Board of Directors.

The new T-3 backbone was named ANSNet and provided the physical infrastructure used by Merit to deliver the NSFNET Backbone Service.

Regional networks
In addition to the five NSF supercomputer centers (which operated regional networks, e.g., SDSCnet and NCSAnet ), NSFNET provided connectivity to eleven regional networks and through these networks to many smaller regional and campus networks. The NSFNET regional networks were:
 * BARRNet, the Bay Area Regional Research Network in Palo Alto, California;
 * CERFnet, California Education and Research Federation Network in San Diego, California, serving California and Nevada;
 * CICNet, the Committee on Institutional Cooperation Network via the Merit Network in Ann Arbor, Michigan and later as part of the T-3 upgrade via Argonne National Laboratory outside of Chicago, serving the Big Ten Universities and the University of Chicago in Illinois, Indiana, Iowa, Michigan, Minnesota, Ohio, and Wisconsin;
 * JVNCNet, the John von Neumann National Supercomputer Center Network in Princeton, New Jersey, connected the universities that made up the Consortium for Scientific Computing as well as a few New Jersey Universities. There were 1.5Mbit/s (T-1) links to Princeton University, Rutgers University, Massachusetts Institute of Technology, Harvard University, Brown University, University of Pennsylvania, University of Pittsburgh, Yale University, The Institute for Advanced Study, Pennsylvania State University, Rochester Institute of Technology, New York University, The University of Colorado and The University of Arizona.
 * Merit/MichNet in Ann Arbor, Michigan serving Michigan, formed in 1966, still in operation as of 2013;
 * MIDnet in Lincoln, Nebraska the first NSFNET regional backbone to become operational in the Summer of 1986, serving Arkansas, Iowa, Kansas, Missouri, Nebraska, Oklahoma, and South Dakota, later acquired by Global Internet, which was acquired by Verio, Inc.;
 * NEARNET, the New England Academic and Research Network in Cambridge, Massachusetts, added as part of the upgrade to T-3, serving Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont, established in late 1988, operated by BBN under contract to MIT, BBN assumed responsibility for NEARNET on 1 July 1993;
 * NorthWestNet in Seattle, Washington, serving Alaska, Idaho, Montana, North Dakota, Oregon, and Washington, founded in 1987;
 * NYSERNet, New York State Education and Research Network in Ithaca, New York;
 * SESQUINET, the Sesquicentennial Network in Houston, Texas, founded during the 150th anniversary of the State of Texas;
 * SURAnet, the Southeastern Universities Research Association network in College Park, Maryland and later as part of the T-3 upgrade in Atlanta, Georgia serving Alabama, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia, sold to BBN in 1994; and
 * Westnet in Salt Lake City, Utah and Boulder, Colorado, serving Arizona, Colorado, New Mexico, Utah, and Wyoming.

Commercial traffic
The NSF's appropriations act authorized NSF to "foster and support the development and use of computer and other scientific and engineering methods and technologies, primarily for research and education in the sciences and engineering." This allowed NSF to support NSFNET and related networking initiatives, but only to the extent that that support was "primarily for research and education in the sciences and engineering." And this in turn was taken to mean that use of NSFNET for commercial purposes was not allowed.

Acceptable use policy
To ensure that NSF support was used appropriately, NSF developed the NSFNET Acceptable Use Policy (AUP) that outlined in broad terms the uses of NSFNET that were and were not allowed. The AUP was revised several times to make it clearer and to allow the broadest possible use of NSFNET, consistent with Congress' wishes as expressed in the appropriations act.

A notable feature of the AUP is that it cites acceptable uses of the network that are not directly related to who or what type of organization is making that use. Use from for-profit organizations is acceptable when it is in support of open research and education. Additionally, some uses, such as fundraising, advertising, public relations activities, extensive personal or private use, for-profit consulting, and all illegal activities were never acceptable, even when that use is by a non-profit college, university, K-12 school, or library. While these AUP provisions seem reasonable, in some specific cases, they often proved difficult to interpret and enforce. NSF did not monitor the content of traffic that was sent over NSFNET or actively police the use of the network. Further, NSF did not require Merit or the regional networks to do so. NSF, Merit, and the regional networks did investigate possible cases of inappropriate use, when such use was brought to their attention.

An example may help to illustrate the problem. Is it acceptable for a parent to exchange e-mail with a child enrolled at a college or university, if that exchange uses the NSFNET backbone? It would be acceptable, if the subject of the e-mail was the student's instruction or a research project. Even if the subject was not instruction or research, the e-mail still might be acceptable as private or personal business as long as the use was not extensive.

The prohibition on commercial use of the NSFNET backbone meant that some organizations could not connect to the Internet via regional networks that were connected to the NSFNET backbone, while to be fully connected other organizations (or regional networks on their behalf), including some non-profit research and educational institutions, would need to obtain two connections, one to an NSFNET attached regional network and one to a non-NSFNET attached network provider. In either case the situation was confusing and inefficient. It prevented economies of scale, increased costs, or both. And this slowed the growth of the Internet and its adoption by new classes of users, something no one was happy about.

In 1988, Vint Cerf, then at the Corporation for National Research Initiatives (CNRI), proposed to the Federal Networking Council (FNC) and to MCI to interconnect the commercial MCI Mail system to NSFNET. MCI provided funding and FNC provided permission and in the summer of 1989, this linkage was made. In effect, the FNC permitted experimental use of the NSFNET backbone to carry commercial email traffic into and out of the NSFNET. Other email providers such as Telenet's Telemail, Tymnet's OnTyme and CompuServe also obtained permission to establish experimental gateways for the same purpose at about the same time. The interesting side effect of these links to NSFNET was that the users of the heretofore disconnected commercial email services were able to exchange email with one another via the Internet. Coincidentally, three commercial Internet service providers emerged in the same general time period: AlterNet (built by UUNET), PSINet and CERFnet.

Commercial ISPs, ANS CO+RE, and the CIX
During the period when NSFNET was being established, Internet service providers that allowed commercial traffic began to emerge, such as Alternet, PSINet, CERFNet, and others. The commercial networks in many cases were interconnected to the NSFNET and routed traffic over the NSFNET nominally accordingly to the NSFNET acceptable use policy Additionally, these early commercial networks often directly interconnected with each other as well as, on a limited basis, with some of the regional Internet networks.

In 1991, the Commercial Internet eXchange (CIX, pronounced "kicks") was created by PSINet, UUNET and CERFnet to provide a location at which multiple networks could exchange traffic free from traffic-based settlements and restrictions imposed by an acceptable use policy.

In 1991, a new ISP, ANS CO+RE (commercial plus research), raised concerns and unique questions regarding commercial and non-commercial interoperability policies. ANS CO+RE was the for-profit subsidiary of the non-profit Advanced Network and Services (ANS) that had been created earlier by the NSFNET partners, Merit, IBM, and MCI. ANS CO+RE was created specifically to allow commercial traffic on ANSNet without jeopardizing its parent's non-profit status or violating any tax laws. The NSFNET Backbone Service and ANS CO+RE both used and shared the common ANSNet infrastructure. NSF agreed to allow ANS CO+RE to carry commercial traffic subject to several conditions:
 * that the NSFNET Backbone Service was not diminished;
 * that ANS CO+RE recovered at least the average cost of the commercial traffic traversing the network; and
 * that any excess revenues recovered above the cost of carrying the commercial traffic would be placed into an infrastructure pool to be distributed by an allocation committee broadly representative of the networking community to enhance and extend national and regional networking infrastructure and support.

For a time ANS CO+RE refused to connect to the CIX and the CIX refused to purchase a connection to ANS CO+RE. In May 1992 Mitch Kapor and Al Weis forged an agreement where ANS would connect to the CIX as a "trial" with the ability to disconnect at a moment's notice and without the need to join the CIX as a member. This compromise resolved things for a time, but later the CIX started to block access from regional networks that had not paid the $10,000 fee to become members of the CIX.

Meanwhile, Congress passed its Scientific and Advanced-Technology Act of 1992 that formally permitted NSF to connect to commercial networks in support of research and education.

An unfortunate state of affairs
The creation of ANS CO+RE and its initial refusal to connect to the CIX was one of the factors that lead to the controversy described later in this article. Other issues had to do with:
 * differences in the cultures of the non-profit research and education community and the for-profit community with ANS trying to be a member of both camps and not being fully accepted by either;
 * differences of opinion about the best approach to take to open the Internet to commercial use and to maintain and encourage a fully interconnected Internet; and
 * differences of opinion about the correct type and level of involvement in Internet networking initiatives by the public and the private sectors.

For a time this state of affairs kept the networking community as a whole from fully implementing the vision for the Internet as a worldwide network of fully interconnected TCP/IP networks allowing any connected site to communicate with any other connected site. These issues would not be fully resolved until a new network architecture was developed and the NSFNET Backbone Service was turned off in 1995.

Privatization and a new network architecture
The NSFNET Backbone Service was primarily used by academic and educational entities, and was a transitional network bridging the era of the ARPANET and CSNET into the modern Internet of today. With its success, the "federally-funded backbone" model gave way to a vision of commercially operated networks operating together to which the users purchased access.

On April 30, 1995, the NSFNET Backbone Service had been successfully transitioned to a new architecture and the NSFNET fiber optic backbone was decommissioned. At this point the NSFNET regional backbone networks were still central to the infrastructure of the expanding Internet, and there were still other NSFNET programs, but there was no longer a central NSFNET optical networking service.

After the transition, network traffic was carried on the NSFNET fiber optic regional backbone networks and any of several commercial backbone networks, internetMCI, PSINet, SprintLink, ANSNet, and others. Traffic between networks was exchanged at four Network Access Points or NAPs. Competitively established, and initially funded by NSF, the NAPs were located in New York (actually New Jersey), Washington, D.C., Chicago, and San Jose and run by Sprint, MFS Datanet, Ameritech, and Pacific Bell. The NAPs were the forerunners of modern Internet exchange points.

The NSFNET regional backbone networks could connect to any of their newer peer commercial backbone networks or directly to the NAPs, but in either case they would need to pay for their own connection infrastructure. NSF provided some funding for the NAPs and interim funding to help the regional networks make the transition, but did not fund the new commercial backbone networks directly.

To help ensure the stability of the Internet during and immediately after the transition from NSFNET, NSF conducted a solicitation to select a Routing Arbiter (RA) and ultimately made a joint award to the Merit Network and USC's Information Science Institute to act as the RA.

To continue its promotion of advanced networking technology the NSF conducted a solicitation to create a very high-speed Backbone Network Service (vBNS) which, like NSFNET before it, would focus on providing service to the research and education community. MCI won this award and created a 155Mbit/s (OC3c) and later a 622Mbit/s (OC12c) and 2.5Gbit/s (OC48c) ATM network to carry TCP/IP traffic primarily between the supercomputing centers and their users. NSF support was available to organizations that could demonstrate a need for very high speed networking capabilities and wished to connect to the vBNS or to the Abilene Network, the high speed network operated by the University Corporation for Advanced Internet Development (UCAID, aka Internet2).

At the February 1994 regional techs meeting in San Diego, the group revised its charter to include a broader base of network service providers, and subsequently adopted North American Network Operators' Group (NANOG) as its new name. Elise Gerich and Mark Knopper were the founders of NANOG and its first coordinators, followed by Bill Norton, Craig Labovitz, and Susan Harris.

Controversy
For much of the period from 1987 to 1995, following the opening up of the Internet through NSFNET and in particular after the creation of the for-profit ANS CO+RE in May 1991, some Internet stakeholders were concerned over the effects of privatization and the manner in which ANS, IBM, and MCI received a perceived competitive advantage in leveraging federal research money to gain ground in fields in which other companies allegedly were more competitive. The Cook Report on the Internet, which still exists, evolved as one of its largest critics. Other writers, such as Chetly Zarko, a University of Michigan alumnus and freelance investigative writer, offered their own critiques.

On March 12, 1992 the Subcommittee on Science of the Committee on Science, Space, and Technology, U.S. House of Representatives, held a hearing to review the management of NSFNET. Witnesses at the hearing were asked to focus on the agreement(s) that NSF put in place for the operation of the NSFNET backbone, the foundation's plan for recompetition of those agreements, and to help the subcommittee explore whether the NSF's policies provided a level playing field for network service providers, ensured that the network was responsive to user needs, and provided for effective network management. The subcommittee heard from seven witnesses, asked them a number of questions, and received written statements from all seven as well as from three others. At the end of the hearing, speaking to the two witnesses from NSF, Dr. Nico Habermann, Assistant NSF Director for the Computer and Information Science and Engineering Directorate (CISE), and Dr. Stephen Wolff, Director of NSF's Division of Networking & Communications Research & Infrastructure (DNCRI), Representative Boucher, Chairman of the subcommittee, said:

"… I think you should be very proud of what you have accomplished. Even those who have some constructive criticism of the way that the network is presently managed acknowledge at the outset that you have done a terrific job in accomplishing the goal of this NSFNET, and its user-ship is enormously up, its cost to the users has come down, and you certainly have our congratulations for that excellent success."

Subsequently, the subcommittee drafted legislation, becoming law on October 23, 1992, which authorized the National Science Foundation

"… to foster and support access by the research and education communities to computer networks which may be used substantially for purposes in addition to research and education in the sciences and engineering, if the additional uses will tend to increase the overall capabilities of the networks to support such research and education activities (that is to say, commercial traffic)."

This legislation allowed, but did not require, NSF to repeal or modify its existing NSFNET Acceptable Use Policy (AUP) which restricted network use to activities in support of research and education.

The hearing also led to a request from Rep. Boucher asking the NSF Inspector General to conduct a review of NSF's administration of NSFNET. The NSF Office of the Inspector General released its report on March 23, 1993. The report concluded by:
 * stating that "[i]n general we were favorably impressed with the NSFNET program and staff";
 * finding no serious problems with the administration, management, and use of the NSFNET Backbone Service;
 * complimenting the NSFNET partners, saying that "the exchange of views among NSF, the NSFNET provider (Merit/ANS), and the users of NSFNET [via a bulletin board system], is truly remarkable in a program of the federal government"; and
 * making 17 "recommendations to correct certain deficiencies and strengthen the upcoming re-solicitation."

title: National Science Foundation Network


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Talk:Dial-up

we have Dial-up access too. yuck!

Redirect
I changed this to a redirect because the other meanings besides dial-up access didn't have articles or even red links and it is unclear whether articles will ever be created on those subjects. Here's part of the manual of style for disambiguation pages.

 * Redlinks (links to articles not yet written) may be included only if you are confident that an encyclopedia article could be written on the subject. Don't include dictionary definitions (see below for how to include Wiktionary links).

The articles are unwritten and the disambiguation page was just giving dictionary definitions of the other subjects. -- Kjkolb 08:50, 4 October 2005 (UTC)

Redirection
It's a pity that dial-up (and/or "dial-up access") redirect to the sole "internet connection". uucp, bbs and many other lemmas look less reliable if the "dial-up" lemma refers only to internet access. --Xoristzatziki (talk) 15:38, 31 January 2014 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:Dial-up


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Ribhus

Ribhus (Sanskrit: ऋभु, ṛbhu, also Arbhu, Rbhus, Ribhuksan) is an ancient Indian word whose meaning evolved over time. In early layers of the Vedic literature, it referred to a sun deity. It evolved to being a wind deity, thereafter referred to three male artisans whose abilities and austerities make them into divinities in later Vedic texts. Their individual names were Ribhu (or Rhibhu), Vaja and Vibhvan (also called Vibhu), but they were collectively called Rhibhus or Ribhus (, pl. ṛbhava, also called Ribhuksan). Their name's meaning is "clever, skillful, inventive, prudent", cognate to Latin labor and Gothic arb-aiþs "labour, toil", and perhaps to English elf.

Ribhus are depicted in some legends of the Vedic literature as three sons of the goddess of morning light named Saranyu and Hindu god Indra. In other legends, such as in the Atharvaveda, they are sons of Sudhanvan, which means good archer. In either legends, they are famous for their creative abilities, innovation and they design chariots, the magic cow of plenty, channels for rivers, and tools for Indra and other gods, which makes many envious. In later Hindu mythology, the Ribhus are born in human form who then bring their innovation to earth, remain humble and kind. This makes some gods angry and the Ribhus are refused entry back to heaven. Other gods intervene and make the inventive Ribhus immortal. They are revered in ancient Hindu texts as sages, as stars, or rays of the sun.

Origin and meaning
The Ribhus were first mentioned in the oldest Hindu scriptures of the Rigveda, wherein eleven hymns are dedicated to them (RV 1.20, 110, 111, 161, RV 3.60, RV 4.33-37, RV 7.48), and the Atharvaveda. They are said to be the sons of Sudhanvan, a descendant of Angiras. In later Hindu mythology (Vishnu Purana Book 2, Chapters 15 - 16 and the Song of Ribhu ) Ribhu, supposed to be the leader of them, is said to be a son of Brahma. Unlike that identification the "Puranic Encyclopedia" states that this Ribhu is not identical with the leader of the Ribhus whose name therein is Rbhuksan. They are supposed to dwell in the solar sphere; Aitareya Brahmana III, 30 describes them as "sun's neighbours or pupils".

Works
The Ribhus are artists who formed the horses of Indra, the carriage of the Ashvins, and the miraculous cow of Brihaspati, made their parents young, and performed other wonderful works which according to RV 4.51.6 were "done by the dawn". According to Yaska they also founded the sacrifices. They are supposed to take their ease and remain every year for twelve days idle in the house of Agohya (an appellation of Aditya which means "one who cannot be concealed", therefore the Sun). When the Devas (gods) heard of their skill, they sent Agni to them, bidding them, to construct four cups from the one cup of Tvashtar, the artificer of the devas. When the Ribhus successfully had executed this task, the devas received them among themselves, gave them immortality and allowed them to partake of their sacrifices.

Three Seasons
According to Yaska and Sayana the Ribhus represent the rays of the sun. David Frawley states about that notion, that "Vedic gods, like the Adityas, Maruts, Vasus and Rhibhus, often appear as rays of the sun, as stars or constellations" Bal Gangadhar Tilak, stating that the interpretation of Yaska and Sayana could not explain their number, interpreted them 1893 referring to "several European scholars" as representing the three seasons of the year of the early Vedic period. The Satapata Brahmana XIV.I.1.28 mentions "three divisions of the year" and in RV 1.164.48 the "three spokes" are supposed to mean this three seasons. But Tilak didn't show a relation of their name and works to this interpretation. So Arthur Berriedale Keith 1925 mentioned that "the assertion that the Rbhus are really the Rthus" (the seasons) "is not 'in the slightest degree plausible'".

Description
According to Bal Gangadhar Tilak referring to RV 1.161.13 the twelve days, when the Ribhus rested at the house of Agohya, took place "at the end of the year". He describes them as the holiest days of the year of which the ancestors of today's Indians believed, that the devas then would leave heaven to visit the homes of the humans. As David Frawley mentioned in context of the seasons, according to RV 7.103.7 - 8 also as the long Atiratra rite of Soma was celebrated at this time.

Bal Gangadhar Tilak further interpreted the hound or dog, which according to RV 1.161.13 woke the Ribhus, as the "dogstar" Sirius, which appears at the vernal equinox "at the end of the Pitriyana". The "Pitriyana" (meaning "the path of the fathers", called Pitrs), are the six southern signs of the Zodiak, by Tilak also called "the eternal waters of Yamaloka". Illustrative Maitrayani Upanishad VI, 1 describes the year as divided into two halfes, one of which belongs to Agni (Fire) and the other to Varuna (Water). Thus according to Bal Gangadhar Tilak in 1893 the year started at the time of the Rigveda at the vernal equinox and the Ribhus recommenced working after their awakening in the beginning of the new year. William Dwight Whitney 1895 rejected this interpretation by Tilak. In this context Tilak also pointed to the fact that because of RV 1.161.13 not the solar year but the anticlockwise movement of the precession of the equinoxes must be meant which he calls an "equinoctial year", but he didn't refer to this in his further interpretation.

Interpretation
Bal Gangadhar Tilak then interpreted also in 1893 the Period of twelve days as the twelve intercalary days, to fix the difference between the lunar year of 354 days and the solar year of 366 days. While he interpreted the beginning of the year at the vernal equinox, Arthur Anthony Macdonell 1917 stated that the twelve intercalary days "in all probability" were inserted at the winter solstice. A.B. Keith 1925 also criticized Tilak's interpretation by pointing to "... the fact that a year of 360 days and 12 months is ... the only year clearly known to the whole of Vedic literature prior to the late Sutras". Because he also "admits that ancient Indians had knowledge of intercalation" his statements on that point are considered "confused". But already 1895 a similar view in terms of the length of the year was stated by George Thibaut and W.D. Whitney in Indian Antiquity. In 1960 Narendra Nath Law wrote in Indian Antiquity Quarterly that: "W would be correct if the 7th season or the 13th month (presumably for intercalation) had not been mentionend." He was referring to RV 1.164.15 which was interpreted by H.H. Wilson as describing seven seasons. But according to the translation of Ralph Thomas Hotchkin Griffith RV 1.164.15 means the seven Rishis, which according to David Frawley were actually eight seers, representing the Big Dipper. The eighth star of the big dipper is according to his later reference to RV 3.56.2 in connexion with RV 1.164.15 not the unseen fourth star of the handle forming a double star system but the Pole Star around which the big dipper rotates. Already Moritz Winternitz 1907 pointed "to the fact that there are certain passages in the Vedic texts which admid of various interpretations." So A.B. Keith's and A.A. Macdonell's 1912 statement is still applicable, the 12 days were "merely the 'reflexion of the year' (samvatsarasya pratima) in the same way that they represent the twelve months and have no relation to chronology at all."

title: Ribhus


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Arjuna

Arjuna (अर्जुन, ) was a legendary ancient prince of the Kuru Kingdom, located in the present-day India. His story is discussed in the epic, the Mahabharata. He was the third of five Pandava brothers, from the lineage of the Kuru. In the Mahabharata War, Arjuna was a key warrior from the Pandava side in the battle of Kurukshetra. Before the beginning of the war, his mentor Krishna gave him the supreme knowledge of the Bhagavad Gita to overcome his moral dilemmas. In the epic, Arjuna is a hero and a close companion of Krishna. He was also an incarnation of Nara from the Nara Narayan duo a twin incarnation of Vishnu.

Arjuna was the son of Kunti, the wife of Kuru King Pandu, and the god Indra, who fathered him due to Pandu's curse. In the Mahabharata, Arjuna is depicted as a skilled archer from an early age, as a student who earns the favor of his preceptor Drona, as the primary adversary of Kauravas, and the betrothed of Draupadi, who became the common wife of the Pandavas. Arjuna is twice exiled, first for breaking a pact with his brothers, and again with his brothers after his oldest brother is tricked into gambling away the throne. During his first exile, Arjuna married Ulupi, Chitrāngadā and Subhadra. From his four wives, Arjuna had four sons, one from each wife — Shrutakarma, Iravan, Babhruvahana and Abhimanyu. During his second exile, Arjuna gained many celestial weapons. Apart from being a warrior, Arjuna also possessed skills in music and dance. At the end of the epic the Pandavas, accompanied by Draupadi, retire to the Himalayas, where everyone in time passes away to arrive in heaven.

Etymology and epithets
According to Monier Monier-Williams, the word Arjuna means white, clear or silver. But Arjuna is known by many other names, such as:

 * Dhanañjaya (धनञ्जय) – one who conquered wealth and gold
 * Guḍākesha (गुडाकेश) – one who has conquered sleep (the lord of sleep, Gudaka+isha) or one who has abundant hair (Guda-kesha).
 * Vijaya (विजय) – always victorious, invincible and undefeatable
 * Savyasāchī (सव्यसाची)– one who can shoot arrows using the right and the left hand with equal activity;Ambidextrous.
 * Shvetavāhana (श्वेतवाहन) – one with milky white horses mounted to his pure white chariot
 * Anagha (अनघ) – one who is sinless
 * Bībhatsu (बीभत्सु) – one who always fights wars in a fair, stylish and terrific manner and never does anything horrible in the war
 * Kirīṭī (किरीटी) – one who wears the celestial diadem presented by the King of Gods, Indra
 * Jiṣṇu (जिष्णु) – triumphant, conqueror of enemies
 * Phālguṇa (फाल्गुण) – born under the star Uttara Phalguni (Denebola in Leo)
 * Mahābāhu (महाबाहु) – one with large and strong arms
 * Gāṇḍīvadhārī (गाण्डीवधारी) – holder of a bow named Gandiva
 * Pārtha (पार्थ) – son of Pritha (or Kunti) – after his mother
 * Kaunteya (कौन्तेय) – son of Kunti – after his mother
 * Pāṇḍuputra (पाण्डुपुत्र) – son of Pandu – after his father
 * Pāṇḍava (पाण्डव) – son of Pandu – after his father
 * Kṛṣṇā (कृष्णा) – He who is of dark complexion and conducts great purity.
 * Bṛhannalā (बृहन्नला) – another name assumed by Arjuna for the 13th year in exile

Literary background
The story of Arjuna is told in the Mahabharata, one of the Sanskrit epics from the Indian subcontinent. The work is written in Classical Sanskrit and is a composite work of revisions, editing and interpolations over many centuries. The oldest parts in the surviving version of the text may date to near 400 BCE.

The Mahabharata manuscripts exist in numerous versions, wherein the specifics and details of major characters and episodes vary, often significantly. Except for the sections containing the Bhagavad Gita which is remarkably consistent between the numerous manuscripts, the rest of the epic exists in many versions. The differences between the Northern and Southern recensions are particularly significant, with the Southern manuscripts more profuse and longer. Scholars have attempted to construct a critical edition, relying mostly on a study of the "Bombay" edition, the "Poona" edition, the "Calcutta" edition and the "south Indian" editions of the manuscripts. The most accepted version is one prepared by scholars led by Vishnu Sukthankar at the Bhandarkar Oriental Research Institute, preserved at Kyoto University, Cambridge University and various Indian universities.

Birth and early life
Arjuna was one of the five Pandava brothers of royal lineage, whose collective name derives from their father, and heir to the Lunar dynasty, Pandu. However, Pandu was under a curse whereby he would die if he had sexual relations with a woman, and so his sons were born using a mantra given to Kunti by sage Durvasa during her maiden days. His wives—Madri and Kunti—invoked different gods and were also blessed with children. According to the legend, Arjuna was a demigod, who was born as a blessing after his mother Kunti invoked the god Indra on her husband's request. The Mahabharata and Puranas such as Devi Bhagavata also records Arjuna as a reincarnation of a rishi called Nara.

Despite being the younger brother of Dhritarashtra, it was Pandu who succeeded their father as king of Bharata. This was because Dhritarashtra was blind, a disability that caused him to forfeit his right to the royal succession. Dhritarashtra fathered 100 sons, known as the Kaurava brothers, and ascended the throne on the death of Pandu. The Pandava brothers were then brought up with their cousins, the Kauravas, and the education of all these boys was supervised by Bhishma. Among their teachers was the brahmin warrior called Drona, who considered Arjuna to be his favourite. According to Swami Parmeshwaranand, Arjuna was Drona's most accomplished pupil. He notes an incident where Drona deemed that out of all his students, none but Arjuna had the steadfast focus to shoot the eye of a toy bird on a tree using a bow and arrow, and that Drona was proven right.

After the princes completed their training, Arjuna defeated Drupada of Panchala, who was impressed by the prince's skills, as the gurudakshina for his beloved teacher Drona. Later, Duryodhana and his maternal uncle Shakuni planned to burn Pandavas alive along with their mother Kunti. They built a palace out of lac in a village named Varanāvata. The Pandavas, though, managed to escape the house of lac with the help of Vidura through a secret tunnel.

Marriages and children
Arjuna married Draupadi, the fire born daughter of Drupada, who was the king of Panchala.

After the event of Lakshagriha, Arjuna, his mother and brothers decide to hide from Hastinapura. One day, Arjuna learns that Drupada is holding an archery tournament to determine who should marry his daughter. The tournament was to lift and string a bow, and fire arrows to pierce the eye of a golden fish only by looking at its reflection in the water. At the Swayamvara, almost all the assorted monarchs were unable to complete the challenge. In the end, Arjuna, dressed as a Brahmin, wins the tournament. Annoyed by their defeat, the kings attack Arjuna, but he defeats them and runs home to tell his mother of his success, shouting "look what we have found". Commentators vary as to whether Kunti thought he was referring to alms found in the forest or to some great prize unknown to her. She tells him that the find must be shared with his brothers, as they had always shared such things in the past.

This misunderstanding, combined with the protocol that the oldest of the brothers, Yudhishthira, should marry first, leads to the agreement that all five brothers marry her. This is one of the rare examples of polyandry in Sanskrit literature. The brothers agreed that none should intrude if Draupadi was alone with one of the others, the penalty for doing so is a year to be spent in exile during which the culprit must remain celibate.

When Arjuna, his siblings, mother and Draupadi returned to Hastinapura, Dhritarashtra determined to avoid a rivalry developing for control of Hastinapur by splitting the kingdom, with half of it being left to his own eldest son, Duryodhana, and half to the eldest son of Pandu, Yudhishthira.

Arjuna inadvertently broke the pact with his brothers, intruding as he sought to collect weapons whilst Yudhishthira, was alone with Draupadi. He felt obliged to go into exile despite Yudhishthira's attempts to dissuade him. It was this event that led to him forming a close relationship with his cousin Krishna. He ignored the celibacy condition of the pact and married three people on his travels, the first of whom was a Naga princess named Ulupi, with whom he had a son called Iravan. His second marriage was with a princess of Manipura, Chitrangada, who bore a son named Babhruvahana. The third was with Subhadra, the sister of Krishna. This last event, which took place in Dvaraka, is not the first meeting between Krishna and the Pandavas in the story but it does mark the start of a bond, sealed with the birth of the couple's child, Abhimanyu, whom Krishna adores.

Burning of Khandava Forest
It was while at Indraprastha, the capital city of the Pandavas, for the birth of Abhimanyu that Arjuna and Krishna become involved in what Alf Hiltebeitel describes as "one of the strangest scenes of the epic", this being the burning of the Khandava Forest. This story within a story has been interpreted in various ways.

The essence of this part of the myth is that Arjuna and Krishna are in the forest when they are approached by a hungry person. They agree to help satisfy his hunger, at which point he reveals himself to be Agni, the god of fire. Agni's hunger can only be sated by consuming the entire forest and everything in it but his previous attempts to do this were thwarted by Indra, who is a protector of the forest and sent down rains to quench the fire. The cousins agree to fend off Indra and anyone else who might interfere; to this end, Arjuna armed himself with the Gandiva bow and Krishna with his Sudarshana Chakra, weapons suitable for a fight with the gods. They then begin to destroy the forest, battling against Indra and other gods, as well as demons, animals and snakes. Once the forest has gone, after six days of fire and slaughter, Arjuna and Krishna receive thanks from Indra, who had retreated with the other gods partway through the proceedings on being commanded by a mysterious voice to step back and watch.

The game of dice
As heir to the lordship of Kurukshetra, Yudhishthira had attracted the unwelcome attention of his Kaurava cousin, Duryodhana, who sought the throne. The royal consecration involved an elaborate Vedic ceremony called rajasuya which extended over several years and included the playing of a ritualised game of dice. This particular game, described as "Indian literature's most notorious dice game" by Williams, was rigged by Duryodhana, causing Yudhishthira to gamble and lose everything, including his kingdom and his shared wife Draupadi. He and his brothers only obtained their freedom because Draupadi offered herself to the Kauravas in exchange. She was then humiliated by them so much that revenge for her treatment became a further motivation for the Pandavas in the rivalry with their cousins. During her humiliation, Karna called her an unchaste for marrying five men. This led Arjuna to take a vow of killing Karna. The brothers, including Arjuna, were forced into a 12-year exile, to be followed by a year living incognito if Yudhishthira was to regain his kingdom.

Exile of the Pandavas
While in this exile, Arjuna visited the Himalayas to get celestial weapons that he would be able to use against the Kauravas. Thereafter, he honed his battle skills with a visit to Swarga, the heaven of Indra, where he emerged victorious in a battle with the Daityas and also fought for Indra, his spiritual father, with the Gandiva.

After the battle at Khandava, Indra had promised Arjuna to give him all his weapons as a boon for matching him in battle with the requirement that Shiva is pleased with him. During the exile, following the advice of Krishna to go on meditation or tapasya to attain this divine weapon, Arjuna left his brothers for a penance on Indrakeeladri Hill (Koppal, Karnataka).

When Arjuna was in deep meditation, a wild boar ran towards him. He realized it and took out an arrow and shot it at the boar. But, another arrow had already pierced the boar. Arjuna was furious and he saw a hunter there. He confronted the hunter and they engaged in a fight. After hours of fighting, Arjuna was not able to defeat him and realized that the hunter was Shiva. Shiva was pleased and took his real form. He gave him Pashupatastra and told that the boar was Indra as he wanted to test Arjuna. After gaining the weapon, Indra took him to heaven and gave him many weapons.

During his exile, Arjuna was invited to the palace of Indra, his father. An apsara named Urvashi was impressed and attracted to Arjuna's look and talent so she expresses her love in front of him. But Arjuna did not have any intentions of making love to Urvashi. Instead, he called her "mother". Because once Urvashi was the wife of King Pururavas the ancestor of Kuru dynasty. Urvashi felt insulted and cursed Arjuna that he will be a eunuch for the rest of his life. Later on Indra's request, Urvashi curtailed the curse to a period of one year.

At Matsya Kingdom
Arjuna spent the last year of exile as a eunuch named Brihannala at King Virata’s Matsya Kingdom. He taught singing and dancing to the princess Uttarā. After Kichaka humiliated and tried to molest Draupadi, Arjuna consoled her and Bhima killed Kichaka. When Duryodhana and his army attacked Matsya, Uttara, Uttarā's brother, with Brihannala as his charioteer went to the army. Later that day, the year of Agyatavasa was over. Arjuna took Uttara away from the army to the forest where he had kept his divine bow, Gandiva, and revealed his identity to Uttara.He then fought Kaurava army and single-handedly defeated them including warriors like Bheeshma, Drona, Ashwatthama,Karna, Duryodhana etc. When Arjuna's identity was revealed to the court, Uttarā was married to Arjuna's son Abhimanyu.

Bhagavat Gita
The Bhagavad Gita is a book within the Mahabharata that depicts a dialogue between Arjuna and Krishna immediately prior to the commencement of the Kurukshetra War between the Pandavas and Kauravas. According to Richard H. Davis, "The conversation deals with the moral propriety of the war and much else as well. The Gita begins with Arjuna in confusion and despair, dropping his weapons; it ends with Arjuna picking up his bow, all doubts resolved and ready for battle."

In the war
Arjuna was a key warrior in Pandava's victory in the Kurukshetra. Arjuna's prowess as an archer was demonstrated by his success in slaying numerous warriors, including his own elder brother Karna and grandfather Bhishma.

 * Fall of Bhishma: On the 10th day of battle, Shikhandi accompanied Arjuna on the latter's chariot and they faced Bhishma who did not fire arrows at Shikhandi. He was then felled in battle by Arjuna, pierced by innumerable arrows. With Sikhandi in front, Bhishma did not even look in that direction, Arjuna shot arrows at Bhishma, piercing his entire body.
 * Death of Bhagadatta: On the 12th day of the war, Arjuna killed powerful king of Pragjyotisha Bhagadatta, along with his mighty elephant Supratika.
 * Death of Jayadratha: Arjuna learns that Jayadratha blocked the other four Pandavas, at the entrance of Chakravyuha, due to which Abhimanyu entered alone and was killed unfairly by multiple Kaurava warriors on the 13th day of the war. Arjuna vowed to kill him the very next day before sunset, failing which he would kill himself by jumping in a fire. Arjuna pierced into the Kaurava army on the 14th day, killing 2 aukshohinis (4.2 Lakh soldiers) of their army, and finally beheaded Jayadratha on 14th day of the war.
 * Death of Sudakshina: He killed Sudakshina the king of Kambojas on the 14th day using Indrastra killing him and a large part of his army. He also killed Shrutayu, Ashrutayu, Niyutayu, Dirghayu, Vinda, and Anuvinda during his quest to kill Jayadratha.
 * Death of Susharma: Arjuna on the 18th day, killed king Susharma of Trigarta Kingdom, the main Kaurava ally.
 * Death of Karna: The much anticipated battle between Arjuna and Karna took place on the 17th day of war. The battle continued fiercely and Arjuna killed Karna by using Anjalikastra when Karna was weaponless.

Later life and death
After the Kurukshetra War, Yudhishthira appointed Arjuna as the Prime Minister of Hastinapur. Yudhishthira performed Ashvamedha. Arjuna followed the horse to the land of Manipura and encountered Babhruvahana, one of his sons. None of them knew one another. Babhruvahana asked Arjuna to fight and injured his father during the battle. Chitrāngadā came to the battlefield and revealed that Arjuna was her husband and Babhruvahana's father. Ulupi, the second wife of Arjuna, revived Arjuna using a celestial gem called Nagamani.

After Krishna left his mortal body, Arjuna took the remaining citizens of Dwaraka to Indraprastha. On the way, they were attacked by a group of bandits. Arjuna desisted fighting seeing the law of time.

Upon the onset of the Kali Yuga, and acting on the advice of Vyasa, Arjuna and other Pandavas retired, leaving the throne to Parikshit (Arjuna's grandson and Abhimanyu's son). Giving up all their belongings and ties, the Pandavas, accompanied by a dog, made their final journey of pilgrimage to the Himalayas. The listener of the Mahabharata is Janamejaya, Parikshit's son and Arjunaś great-grandson.

Indonesia
In the Indonesian archipelago, the figure of Arjuna is also known and has been famous for a long time. Arjuna especially became popular in the areas of Java, Bali, Madura and Lombok. In Java and later in Bali, Arjuna became the main character in several kakawin, such as Kakawin Arjunawiwāha, Kakawin Pārthayajña, and Kakawin Pārthāyana (also known as Kakawin Subhadrawiwāha. In addition, Arjuna is also found in several temple reliefs on the island of Java, for example the Surawana temple.

Wayang story
Arjuna is a well-known figure in the world of wayang (Indonesian Puppetry) in Javanese culture. Some of the characteristics of the wayang version of Arjuna may be different from that of Arjuna in the Indian version of the Mahābhārata book in Sanskrit. In the world of puppetry, Arjuna is described as a knight who likes to travel, meditate, and learn. Apart from being a student of Resi Drona at Padepokan Sukalima, he is also a student of Resi Padmanaba from the Untarayana Hermitage. Arjuna was a Brahman in Goa Mintaraga, with the title Bagawan Ciptaning. He was made the superior knight of the gods to destroy Prabu Niwatakawaca, the giant king of the Manimantaka country. For his services, Arjuna was crowned king in Dewa Indra's heaven, with the title King Karitin and get the gift of magical heirlooms from the gods, including: Gendewa (from Bhatara Indra), Ardadadali Arrow (from Bhatara Kuwera), Cundamanik Arrow (from Bhatara Narada). After the Bharatayuddha war, Arjuna became king in Banakeling State, the former Jayadrata kingdom.

Arjuna has a smart and clever nature, is quiet, conscientious, polite, brave and likes to protect the weak. He leads the Madukara Duchy, within the territory of the state of Amarta. For the older generation of Java, he was the embodiment of a whole man. Very different from Yudhisthira, he really enjoyed life in the world. His love adventures always amaze the Javanese, but he is strangely different from Don Juan who always chases women. It is said that Arjuna was so refined and handsome that such princesses, as well as the ladies-in-waiting, would immediately offer themselves. They are the ones who get the honor, not Arjuna. He is very different from Wrekudara. He displayed a graceful body and a gentleness that was appreciated by the Javanese of all generations.

Arjuna also has other powerful heirlooms, among others: The Kiai Kalanadah Keris was given to Gatotkaca when he married Dewi Gowa (Arjuna's son), Sangkali Arrow (from Resi Drona), Candranila Arrow, Sirsha Arrow, Sarotama Kiai Arrow, Pasupati Arrow (from Batara Guru), Panah Naracabala, Arrow Ardhadhedhali, Keris Kiai Baruna, Keris Pulanggeni (given to Abhimanyu), Terompet Dewanata, Cupu filled with Jayengkaton oil (given by Bagawan Wilawuk from Pringcendani hermitage) and Ciptawilaha Horse with Kiai Pamuk's whip. Arjuna also has clothes that symbolize greatness, namely Kampuh or Limarsawo Cloth, Limarkatanggi Belt, Minangkara Gelung, Candrakanta Necklace and Mustika Ampal Ring (formerly belonging to King Ekalaya, the king of the Paranggelung state).

In popular culture

 * The American astronomer Tom Gehrels named a class of asteroids with low inclination, low eccentricity and earth-like orbital period as Arjuna asteroids.
 * The Arjuna Award is presented every year in India to one talented sportsperson in every national sport.
 * Arjun is a third generation main battle tank developed for the Indian Army.
 * Mayilpeeli Thookkam is a ritual art of dance performed in the temples of Kerala. It is also known as Arjuna Nrithyam (‘Arjuna's dance’) as a tribute to his dancing abilities.
 * Arjuna is also an Archer class Servant in the mobile game Fate/Grand Order. He is a minor antagonist in the "E Pluribus Unum" story chapter, where he wishes to fight Karna again. Arjuna also appears as a rogue Archer servant in the game Fate/Samurai Remnant as one of servants recruitable by the protagonist Iori.
 * The protagonist in Steven Pressfield's 1995 book The Legend of Bagger Vance and its 2000 film adaptation, Rannulph Junuh, is based in part on Arjuna (R. Junuh).
 * Arjuna (地球少女アルジュナ, Chikyū Shōjo Arujuna, lit. "Earth Maiden Arjuna") is a Japanese anime television series created by Shoji Kawamori. The series follows Juna Ariyoshi, a high school girl chosen to be the "Avatar of Time" and entrusted with saving the dying Earth.

In television and films
There have been serials and films based on Arjuna's life and exploits.

 * "Arjuna" is a character in Orson Scott Card's Earth Afire (2013) and Earth Awakens (2014).

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Svarga

Svarga (स्वर्गम्, ), also known as Indraloka and Svargaloka, is the celestial abode of the devas in Hinduism. Svarga is one of the seven higher lokas (esoteric planes) in Hindu cosmology. Svarga is often translated as heaven, though it is regarded to be dissimilar to the concept of the Abrahamic Heaven.

Description
Svarga is a set of celestial worlds located on and above Mount Meru, where those who had led righteous lives by adhering to the scriptures delight in pleasures, before their next birth on earth. It is described to have been built by the deity Tvashtar, the Vedic architect of the devas. The king of the devas, Indra, is the ruler of Svarga, ruling it with his consort, Indrani. His palace in the abode is called Vaijayanta. This palace holds the famous hall, Sudharma, unrivalled among all the princely courts. The capital of Svarga is Amaravati, and its entrance is guarded by the legendary elephant, Airavata. Svarga is described to be the home of Kamadhenu, the cow of plenty, as well as Parijata, the tree that grants all wishes. The legendary Kalpavriksha tree grows in the centre of the Nandana gardens, which was planted there by Indra after it emerged from the Samudra Manthana, the churning of the ocean. Due to its location, Svarga is called Tridiva, the third highest heaven.

In Hindu mythology, the devas' dominion over Svarga is often the primary point of contention in their eternal war with their rivals, the asuras. A common theme in these legends is an asura king, such as Hiranyakashipu, usurping the realm for himself. The preserver deity, Vishnu, often intervenes to restore the status quo. He sometimes assumes an avatar, such as Narasimha, to vanquish the asura king, restoring Indra and the devas to their place. During each pralaya (the great dissolution), the first three realms, Bhuloka, Bhuvarloka, and Svargaloka are destroyed. In contemporary Hinduism, Svarga itself is often relegated to the status of a lower heaven, one that is spiritually as well as physically beneath Vaikuntha and Kailasha, the celestial abodes of Vishnu and Shiva.

Vedas
In the hymns of the Atharvaveda, Svarga is conceptualised as Pitrloka, the land where one hopes to meet one's departed ancestors. It is the abode that is rewarded for the one who performs sacrifices. The sacrifices that one performs are stated to journey directly to heaven, and are stored to await the sacrificer on his arrival. One hymn describes Svarga to be a realm that contains water-lilies and lotuses, lakes of butter with banks of honey, along with streams flowing with a number of foods such as wine, milk, curds, and water. Offering gifts to guests is also stated to be a path that secures heaven.

The Vedanta Shutra explains the concept of transmigration from Svarga to Bhuloka. It indicates that a jiva (life force) that has performed sacrifices and charitable acts ascends to Svarga, and when departing the abode and returning to earth, it descends as a raincloud, and is precipitated upon the earth as rain. When man consumes the food that is watered by the rain, it enters his semen, and during intercourse, enters a woman, to be reborn. It described "sampata" to be the term for the concept that allows one to ascend to heaven. It also states that the one who was of good conduct in Svarga attains the birth of a Brahmin, Kshatriya, or a Vaishya, and that others are condemned to lesser births, such as other animals or outcastes.

The Mundaka Upanishad affirms that the performance of Vedic rituals is necessary to attain Svarga.

Puranas
The Bhagavata Purana states that Svarga is the realm for the one who is able to discriminate between right and wrong acts, and loves other people, engaging in good deeds for them. The good, the virtuous, and the devoted are described to be able to achieve the abode. It is stated to be a realm of gratification, where one is able to appreciate divine music, divine beauty, and divine objects, all of which are enough for any man. The duration of one's stay in this loka is determined by the punya (virtue) one has accumulated. High intellect is not deemed to be sufficient to enter the abode if one lacks the necessary level of spirituality.

Ramayana
The acquisition of punya and the performance of good deeds is stated to be a prerequisite of attaining Svarga in the Ramayana.

The epic describes the legend of King Trishanku, who had been promised a place in Svarga by the sage Vishvamitra. The sage engaged in a solitary yajna to achieve this, not joined by other sages due to instructions from Sage Vasishta. Due to the power of the sage's ceremony, the king ascended to the gates of Svarga. The devas reported this to Indra, who angrily kicked Trishanku from the abode because of his low birth, sending him hurtling towards the earth. Vishvamitra was able to halt his fall mid-way during his descent, and so the king was left suspended in the air. Indra opted to create a new Svarga below his own Svarga as a compromise, just for the residence of Trishanku. In retort, Vishvamitra created a new Indra and devas to occupy the new heaven with the king. Terrified of the powers of the sage, Indra relented, and personally carried Trishanku to the real Svarga on his own golden vimana.

Mahabharata
In the epic Mahabharata, the prince Arjuna is escorted to Svarga by Matali, the charioteer of Indra, the prince's father. During the journey, he witnesses thousands of flying celestial cars, vimanas. He observes that there is neither sun nor moon that is necessary to offer light in this realm, as it is entirely self-luminous. He takes note of the residents of Svarga: rishis, heroes who had died in battle, those who had performed severe austerities, gandharvas, guhyakas, as well as apsaras. He passes through the several successive regions of heaven until he arrives at Amaravati, the capital of Indra.

In Amaravati, Arjuna beholds the gardens of Nandana, the favourite resort of the apsaras. He observes that sacred trees and flowers of all seasons bloom. He is eulogised by various classes of beings, such as deities like the Ashvins and the Maruts, the royal sages, headed by Dilipa, and exalted Brahmanas. He is treated to the most sacred and profane music of the finest gandharva, Tumvuru, and observes the dances of the most enticing apsaras, such as Menaka, Rambha, and Urvashi.

The Mahabharata suggests the existence of several forms or regions of Svarga, each headed by a deity, such as Surya, Kubera, and Varuna. Indra is stated to sate all the desires of the residents. Men and women enjoy each other's pleasures without restriction, and there is no form of jealousy between the sexes.

In the text, Nahusha opines to Yudhisthira that offering charity, speaking pleasing words, honesty, and ahimsa allows one to achieve heaven.

Bhagavad Gita
In the Bhagavad Gita, it is indicated that Svarga is not the everlasting destination of those who had accumulated punya.

"'They, having enjoyed that spacious world of Svarga, their merit (punya) exhausted, enter the world of the mortals; thus following the Dharma of the Triad, desiring (objects of) desires, they attain to the state of going and returning.'"

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Amaravati (disambiguation)

Amaravati is the legislative capital and the de facto seat of government of the Indian state of Andhra Pradesh.

Amaravati, Amaravathi or Amravati may also refer to:

Religion

 * Amaravati, a Pali word meaning "Abode of the Deathless", which refers to nirvana
 * Amaravati Stupa, Ruined Buddhist stupa near the village of Amaravathi
 * Amaravati style or school, regional style of sculpture, 1st century BC to 4th century CE, after the stupa
 * Amaravati (mythology), the capital of Svarga, one of the seven planes of Hinduism
 * Amaravathi mandal, Andhra Pradesh, a mandal in Guntur district headquartered at Amaravathi
 * Amaravati Buddhist Monastery, a Theravada Buddhist monastery located in Hertfordshire, UK

India

 * Amaravathi (village), Palnadu district in Andhra Pradesh, modern village near the stupa
 * Amravati, a city in the state of Maharashtra, India
 * Amravati district, a district of Maharashtra state
 * Amravati division, a division of Maharashtra state
 * Amaravathinagar, a town in Tamil Nadu state
 * Amaravathi Dam, a dam at Amaravathinagar, 25 km south of Udumalpet, Tamil Nadu, India
 * Amaravathi Reservoir, the Amaravathi Dam impoundment on the edge of Indira Gandhi Wildlife Sanctuary
 * Amaravati River, a river in the states of Kerala and Tamil Nadu, India

Others

 * Amaravati, principality in the ancient kingdom of Champa in Central Vietnam

Railways

 * Amravati railway station, in Maharashtra, India
 * Amaravati Express, express train operated by Indian Railways

Entertainment

 * Amaravathi (1993 film), a 1993 Indian Tamil-language film
 * Amaravathi (2009 film), a 2009 Indian Telugu-language film

title: Amaravati (disambiguation)


text:
Meru

Meru may refer to:

Kenya

 * Meru, Kenya, city in Meru County in the republic of Kenya
 * Meru County, one of Kenya's 47 counties that was created by the 2009 merger of 3 districts:
 * Meru Central District
 * Meru North District
 * Meru South District
 * ...the three of which had been split in 1992 from Meru District, Kenya
 * Meru National Park, a Kenyan wildlife park

Tanzania

 * Meru District, a district in Arusha Region, Tanzania
 * Meru, Tanzania, a village in northern Tanzania (Meru District)
 * Mount Meru (Tanzania), a volcano near Arusha in northern Tanzania

Other places

 * Mary, Turkmenistan, a city in the Karakum Desert, formerly named Meru
 * Meru, Hazaribagh, a small town in Jharkhand, India
 * Meru, Malaysia, a town in Klang, located in Selangor
 * Meru, Western Australia, a locality near Geraldton
 * Méru, a commune of the Oise département in France
 * Meru Peak, a mountain in the Indian Himalayas, not to be confused with Mount Meru (see the section Other below)

Entertainment

 * Meru (film), a 2015 documentary about climbing Meru Peak
 * Prince Meru (Sgt. Frog), main character from the anime movie Keroro Gunso the Super Movie 2: The Deep Sea Princess
 * Meru (Legend of Dragoon), a playable character from the video games The Legend of Dragoon

Ethnic groups

 * Meru people, also known as Amîîrú, are a people of Kenya
 * Meru, another name for the Aboriginal Australian Erawirung people of South Australia
 * Wameru, Bantu for the Meru people of northern Tanzania

Individuals

 * Meru (overseer of sealers), an Ancient Egyptian official under king Mentuhotep II in the Eleventh Dynasty
 * Vatsu Meru, politician from Nagaland, India

Organizations

 * Meru Networks, a supplier of wireless local area networks that was acquired by and integrated into Fortinet in 2015
 * Meru Cabs, a taxi aggregator company based in Mumbai, India.
 * Maharishi European Research University (MERU), a school that researches transcendental meditation
 * MERU, Holland, the current location in Vlodrop, Netherlands

Other uses

 * Meru (beetle), a family of aquatic beetles
 * Meru language, the language spoken by the Meru people (Ameru)
 * Milli Earth Rate Unit, an angular velocity equal to 1/1000 of Earth's rotation rate; see inertial navigation system
 * Maha Meru, a 3-dimensional Sri Chakra Yantra
 * Mount Meru, a mountain in Hindu, Jain and Buddhist mythology
 * Pelinggih meru, the multiple tiered roofs similar to pagoda in Balinese temple
 * An alternate (erroneous) name for Mount Kailash

title: Meru


text:
Mount Meru

Mount Meru (Sanskrit/Pali: मेरु), also known as Sumeru, Sineru, or Mahāmeru, is the sacred five-peaked mountain of Hindu, Jain, and Buddhist cosmology and is considered to be the centre of all the physical, metaphysical, and spiritual universes. The mountain is also mentioned in some scriptures of non-Indian based religions such as Taoism, which was influenced by the arrival of Buddhism in China. There is no clear identification of Mount Meru with a particular geophysical location but it is always located in Himalayan or Aravali ranges.

Many famous Hindu, Jain, and Buddhist temples have been built as symbolic representations of this mountain. The "Sumeru Throne" 須彌座 xūmízuò style base is a common feature of Chinese pagodas. The highest point (the finial bud) on the pyatthat, a Burmese-style multi-tiered roof, represents Mount Meru.

Etymology
Etymologically, 'meru' in Sanskrit means 'high'. The proper name of the mountain is Meru (Sanskrit: Meruparvata), to which is added the approbatory prefix su-, resulting in the meaning "excellent Mount Meru" or "sublime Mount Meru". Meru is also the name of the central bead in a mālā.

In other languages
In other languages, Mount Meru is pronounced:
 * Assamese: মেৰু পর্বত (Meru Pôrbôt)
 * Bengali: মেরু পর্বত (Meru Porbot)
 * Burmese: မြင်းမိုရ်တောင်
 * Cebuano: Bukid Meru
 * Chinese: 須彌山 (Xūmíshān)
 * Gujarati: મેરૂ પર્વત (Meru Parvat)
 * Sanskrit, Marathi, Hindi: मेरु पर्वत (Meru Parvat)
 * Ilocano: Bantay Meru
 * Japanese: 須弥山 (Shumisen)
 * Javanese: ꦱꦼꦩꦺꦫꦸ (Semeru)
 * Kannada: ಮೇರು ಪರ್ವತ (Meru Parvata)
 * Khmer: ភ្នំព្រះសុមេរុ (Phnom Preah Someru) or (Phnom Preah Somae)
 * Korean: 수미산 (Sumisan)
 * Malayalam: മഹാമേരു പർവ്വതം (Mahameru Parvatham)
 * Mongolian: Сүмбэр Уул (Sümber Uul)
 * Nepali: सुमेरु पर्वत (Sumeru Parwat)
 * Odia: ମେରୁ ପର୍ବତ (“Meru Pôrbôtô”)
 * Old Maldivian: ސުމޭރު-މަންދަރަ "Sumēru-Mandara" (sometimes spelt as Ṣumeru-Mandara)
 * Pāli: Sineru
 * Punjabi: ਮੇਰੂ ਪਰਬਤ (Meru Parbat)
 * Tagalog: Bulkang Meru
 * Tamil: மகா மேரு மலை (Maha Meru Malai)
 * Telugu: మేరు పర్వతం (Meru Parvatam)
 * Sinhala: මහා මේරු පර්වතය (Maha Meru Parvathaya)
 * Tibetan: ཪི་རྒྱལ་པོ་རི་རབ་ (Wylie: ri gyal po ri rab)
 * Thai: เขาพระสุเมรุ (Khao phra sumen)
 * Vietnamese: Núi Tu-di

Geography
The dimensions attributed to Mount Meru — which all refer to it as a part of the Cosmic Ocean, along with several other statements that describe it in geographically vague terms (e.g., "the Sun along with all the planets circle the mountain") — make the determination of its location most difficult, according to most scholars.

Several researchers identify Mount Meru or Sumeru with the Pamirs, northwest of Kashmir.

The Suryasiddhanta mentions that Mt. Meru lies at the centre of the Earth ("bhuva-madhya") in the land of the Jambunad (Jambudvīpa). Narapatijayacharyasvarodaya, a ninth-century text, based on mostly unpublished texts of Yāmal Tantr, mentions:
 * " Prithvī-madhye shrūyate drishyate na tu"
 * (Sumeru is heard to be at the centre of the Earth, but is not seen there).

Several versions of cosmology can be found in existing Hindu texts. In all of them, cosmologically, the Meru mountain was also described as being surrounded by Mandrachala Mountain to the east, Suparshva Mountain to the west, Kumuda Mountain to the north, and Kailasha to the south.

In Buddhism
According to Buddhist cosmology, Mount Meru (or Sumeru) is at the centre of the world, and Jambūdvīpa is south of it. It is 80,000 yojanas wide and 80,000 yojanas high according to the Abhidharmakośabhāṣyam and 84,000 yojanas high according to the Long Āgama Sutra. Trāyastriṃśa is at its peak, where Śakra resides. The Sun and the Moon revolve around Mount Meru, and as the Sun passes behind it, it becomes nighttime. The mountain has four faces — each one made of a different material; the northern face is made of gold, the eastern one is made of crystal, the southern one is made of lapis lazuli, and the western one is made of ruby.

In Vajrayāna, maṇḍala offerings often include Mount Meru, as they in part represent the entire universe. It is also believed that Mount Meru is the home of the Buddha Cakrasaṃvara.

In Hinduism
Hindus believe Mount Meru to be a stairway to Svarga, a heaven where the devas reside. Meru is considered as the center of the universe and is described as 84,000 yojanas high, about 1082000 km, which would be 85 times the Earth's diameter. One yojana can be taken to mean about 11.5 km (9 miles), though its magnitude seems to differ over periods — for example, the Earth's circumference is 3,200 yojanas according to Varahamihira and slightly less so in the Aryabhatiya, but is said to be 5,026.5 yojanas in the Suryasiddhānta. The Matsya Purana and the Bhagavata Purana, along with some other Hindu texts, consistently give the height of 84,000 yojanas to Mount Meru, which translates into 672,000 miles or 1,082,000 kilometers. The Sun and Moon along with all the planets revolve around Mount Meru which connects the earth with the under world and heaven with Shiva residing on top of the mountain at Kailasha. Gods and devas are described as frequenting Mount Meru.

According to the Mahabharata, Meru is located amidst the Himavat range between Malayavat and Gandhamadhana mountains. Some scriptures indicate that Shiva resides in a horn of the mountains called as Saivatra. Mahabharata further states that the mountain gleans of gold when the rays of the sun fall on it and is said to contain lovely woods, lakes, rivers adorned with fruit trees, precious stones and life saving herbs. It also describes Meru as the means to reach heaven and only a being without any sins would be able to scale it. Meru is also said to be the residence of Kubera who lives near a golden gate with a lake called Alaka adorned with golden lotuses and sweet tasting water from which Mandakini river arises. As per the Mahabharata, the Pandavas along with their wife Draupadi, traveled towards the summit of the mountain as a means to reach the heaven but only Yudhishthira who was accompanied by a dog, was able to make it.

The Hindu epic Ramayana describes Kailash and Lake Manasarovar located in the Mount Meru as places unlike anywhere in the world.

Vishnu Purana states that Meru is a pillar of the world, located at the heart of six mountain ranges symbolizing a lotus. It also states that the four faces of Mount Kailash are made of crystal, ruby, gold, and lapis lazuli. It further talks about Shiva sitting in a lotus position, engaged in deep meditation within the confines of the mountain. The mountain is home to four lakes, whose water is shared by the gods and four rivers that originate from the Ganges and flow to the earth. The Vayu Purana describes similarly with the mountain located close to a lake consisting of clear water with lotuses and lilies decked with water birds. Bhagavata Purana places Kailash as located south of Mount Meru. Skanda Purana mentions that the mountain is located amongst the highest peaks, perpetually covered with snow. Mount Meru was said to be the residence of King Padmaja Brahma in antiquity.

This mythical mountain of gods was mentioned in the Tantu Pagelaran, an Old Javanese manuscript written in the 15th-century Majapahit period. The manuscript describes the mythical origin of the island of Java, as well as the legendary movement of portions of Mount Meru to Java. The manuscript explains that Batara Guru (Shiva) ordered the gods Brahma and Vishnu to fill Java with human beings. However, at that time, Java island was floating freely on the ocean, always tumbling and shaking. To stop the island's movement, the gods decided to nail it to the Earth by moving the part of Mahameru in Jambudvipa (India) and attaching it to Java. The resulting mountain is Mount Semeru, the tallest mountain in Java.

In Jainism

According to Jain cosmology, Mount Meru (or Sumeru) is at the centre of the world surrounded by Jambūdvīpa, in the form of a circle forming a diameter of 100,000 yojanas. There are two sets of sun, moon, and stars revolving around Mount Meru; while one set works, the other set rests behind Mount Meru.

Every Tirthankara is taken to the summit of Meru by Indra shortly after his birth, after putting the Tirthankara child's mother into a deep slumber. There, he is bathed and anointed with precious unctions. Indra and other Devas celebrate his birth.

Architecture
The concept of a holy mountain surrounded by various circles was incorporated into ancient Hindu temple architecture with a Shikhara (Śikhara) — a Sanskrit word translating literally to "peak" or "summit". Early examples of this style can be found at the Harshat Mata Temple and Harshnath Temple from the 8th century CE in Rajasthan, Western India. This concept also continued outside India, such as in Bali, where temples feature Meru towers.

In Buddhist temples, the Mahabodhi Temple in Bodh Gaya is the earliest example of the 5th- to 6th-century depiction. Many other Buddhist temples took on this form, such as the Wat Arun in Thailand and the Hsinbyume Pagoda in Myanmar.

title: Mount Meru


text:
Talk:Four color theorem

Re: the recent added images of colorings of different countries
I agree with that adding an entire section as a gallery to simply present different countries with their colorings is a bit overkill (especially with the map of America's at the beginning). I was thinking, though, of re-adding at least one of them to the section "Use outside of mathematics," since it seems apt. I was originally just going to place the Germany one in, but maybe adding a picture of a real-life exclave forcing 5-colors would be nice. In any case, I don't think it hurts to add a second picture illustrating how it works, since non-math inclined people are probably going to be interested in (more than one) examples of these type. I didn't want to just make the edit immediately though since the similar one had just been reverted. What do other people think? Integral Python click here to argue with me 21:58, 24 May 2023 (UTC)

Equivalence to torus coloring is wrong
The article says "Forcing two separate regions to have the same color can be modelled by adding a 'handle' joining them outside the plane. Such construction makes the problem equivalent to coloring a map on a torus (a surface of genus 1), which requires up to 7 colors for an arbitrary map." That seems to imply that there's a planar map with just one noncontiguous region that requires 7 colors. But you can 4-color the contiguous countries and then use 1 more color for the noncontiguous one, so you only need 5 colors. I don't know how this should be rewritten. Nylimb (talk) 14:41, 23 August 2023 (UTC)

 * I don't follow "4-color the contiguous countries and then use 1 more color for the noncontiguous one". The problem in this section is that both regions marked "A" are constrained to have the same color. Under that constraint, there should be a map which requires 7 colors (although we don't draw it using the "handle" style of visualization). There's probably a clearer way to say all this, for example expanding on the example in the section in "Generalizations" describing the torus coloring problem, but I'm not sure quite what this would look like and whether it would be an improvement. Kingdon (talk) 10:40, 14 July 2024 (UTC)

 * "Forcing two separate regions to have the same color can be modelled by adding a 'handle' joining them outside the plane" -- true.
 * "Such construction makes the problem equivalent to coloring a map on a torus" -- false, because a torus map can require seven colors, while five colors suffice for a planar map with a single two-region country.
 * Proof: Consider the map obtained by removing both of the "A" regions. That map is planar, so it can be four-colored.  Apply that four-coloring to the original map, and use a fifth color for "A".
 * Should we just delete that paragraph? Joule36e5 (talk) 21:20, 14 July 2024 (UTC)
 * Another falsehood: "A similar construction also applies if a single color is used for multiple disjoint areas, as for bodies of water on real maps ... In such cases more colors might be required with a growing genus of a resulting surface.", because all the bodies of water can be given a single color, regardless of how much the genus would grow by adding handles connecting them all. Anyway, I would be fine with deleting from "Forcing two separate regions" to "(See the section Generalizations below.)". —David Eppstein (talk) 06:26, 15 July 2024 (UTC)
 * Should we just delete that paragraph? Joule36e5 (talk) 21:20, 14 July 2024 (UTC)
 * Another falsehood: "A similar construction also applies if a single color is used for multiple disjoint areas, as for bodies of water on real maps ... In such cases more colors might be required with a growing genus of a resulting surface.", because all the bodies of water can be given a single color, regardless of how much the genus would grow by adding handles connecting them all. Anyway, I would be fine with deleting from "Forcing two separate regions" to "(See the section Generalizations below.)". —David Eppstein (talk) 06:26, 15 July 2024 (UTC)
 * Another falsehood: "A similar construction also applies if a single color is used for multiple disjoint areas, as for bodies of water on real maps ... In such cases more colors might be required with a growing genus of a resulting surface.", because all the bodies of water can be given a single color, regardless of how much the genus would grow by adding handles connecting them all. Anyway, I would be fine with deleting from "Forcing two separate regions" to "(See the section Generalizations below.)". —David Eppstein (talk) 06:26, 15 July 2024 (UTC)

Cubic map
In the section on three-coloring, it is stated that "A cubic map can be colored with only three colors if and only if each interior region has an even number of neighboring regions." but I can't find any easily available explanation of what a cubic map is. Maybe this should be explained, rather than requiring people to pass a paywall to read the cited article before they can understand what that sentence means? MasterHigure (talk) 11:33, 4 January 2024 (UTC)

 * I've added a wikilink. Joule36e5 (talk) 00:23, 20 February 2024 (UTC)

Isn't this section just plain misleading? It states that "A cubic map can be colored with only three colors if and only if each interior region has an even number of neighboring regions." But then it gives the US map as an example of an application of this statement when the US map is in fact not cubic! Moreover, since planar graph 3-colorability is NP-complete, it cannot be that the simple cubic map criterion used for testing if three colors suffice can be applied in general to all planar maps (that are not cubic). --Litmus58 (talk) 18:40, 14 March 2024 (UTC)

Alternative non-mathematical explanation
Maybe a sentence added to the lead, to the effect of "It is impossible to draw five bodies that are all touching each other, which would be required for the theorem to be disproven", would help more practically-minded people to grasp it intuitively. :) --Kraligor (talk) 16:07, 19 February 2024 (UTC)

 * That would be incorrect. It is a very standard misunderstanding of the theorem. The actual theorem is not about the impossibility of five regions touching each other (for which see Kuratowski's theorem). Minimal graphs that require five colors do not have to have five vertices, just as minimal graphs that require three colors can be cycles of any odd length, not just triangles. —David Eppstein (talk) 18:15, 19 February 2024 (UTC)

title: Talk:Four color theorem