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0th law of thermodynamics: the hypothesis of comparative thermodynamics among systems: that if 2 thermodynamic systems each are in thermal equilibrium with a 3rd system, then they are in thermal equilibrium with each other.
1st Baron’s War (1215–1216): a civil war against King John I by major landowners (barons) (who were backed by France) for John’s refusal to abide by the Magna Carta.
1st law of thermodynamics: the hypothesis that the total energy in an isolated system is immutable: that energy can be neither created nor destroyed in a closed system.
2,4–D (2,4-Dichlorophenoxyacetic acid: C8H6Cl2O3): an herbicide.
2-round voting system (aka 2nd ballot, runoff voting, ballotage): a voting method to elect a person via ballot votes. If no candidate receives the requisite vote count in the 1st round, the top 2 vote-getters face off in a runoff election round. The 2-round system is used worldwide for electing members of legislative bodies and directly elected presidents.
2nd law of thermodynamics: the hypothesis of there being a tendency over time toward entropy in an isolated physical system. The 2nd law outlaws perpetual motion machines.
2nd messenger: a molecule that relays a signal from a cell surface receptor to a target molecule inside the cell.
3-age system: an archeological sequential periodization of human prehistory and early history, comprising the Stone Age, Bronze Age, and Iron Age.
3-center 2-electron bond: a covalent bond between 3 atoms sharing 2 electrons.
3PAR (1999–2010): American computer data storage and cloud computing company.
3rd law of thermodynamics: the hypothesis that the entropy of a system approaches a constant value as its temperature approaches absolute zero.
4D (aka spacetime): the 4 dimensions of everyday experience: 3 of space (3d) + 1 of time. See HD and ED.
4th estate: the news media, particularly in regard to political coverage. Historically, the 3 groups, or estates, that had political representation were: the nobility, the clergy, and commoners. The 4th estate, coined by Edmund Burke in 1787, meant those without an official voice, but with influence on public affairs. In the 19th century, the term came to exclusively refer to the press. It now refers to all forms of news media.
7 Years’ War (1756–1763): the largest-scale European war since the 30 Years’ War in the 17th century, involving every great power of the time except the Ottoman Empire. There were 2 coalitions: one led by Great Britain, the other France. France lost, and thereby Britain gained the bulk of French colonies in the New World, as well as colonies in Africa, and superior trading outposts on the Indian subcontinent.
9/11: the aerial suicide bombing via hijacked commercial airliners by Saudi Arabians on 11 September 2001 of select US targets, including the twin World Trade Center towers in New York City (demolished), the Pentagon (damaged), and the White House (unscathed).
12 Tables (~450 BCE): the legislation that served as the foundation of Roman law. The Romans venerated the 12 Tables.
30 Years’ War (1618–1648): a series of wars principally waged in Central Europe; one of the longest and most destructive wars in modern history.
80 Years’ War (1568–1648): the Dutch war of independence from Spain.
100 Years’ War (1337–1453): an intermittent series of conflicts between England and France for control of France. The struggle involved several generations of English and French claimants to the crown of France.
p (3.14159…): the ratio of a circle’s circumference to its diameter.