Massachusetts abolishes slavery and grants African-American men the right to vote.

A freedom clause in the Massachusetts constitution is interpreted as an abolishment of slavery. Massachusetts enfranchises all men regardless of race.

Delaware makes it illegal to enslave imported Africans.

Pennsylvania begins gradual emancipation.

Great Hurricane of 1780 — the deadliest Atlantic hurricane on record — kills 20,000 to 30,000 in Caribbean.

William Herschel discovers first binary star, Xi Ursae Majoris.

Abraham Gottlob Werner asserts that all rocks have been deposited by a primordial ocean. This "Neptunian" view is accepted with little question.

Mozart's opera "Idomeneo" premieres in Munich.

Los Angeles, California, is founded by 54 settlers, including 26 of African ancestry.

Immanuel Kant publishes Critique of Pure Reason, a fundamental work of modern philosophy.

Pierre François André Méchain discovers M80 (globular cluster in Scorpio).

Johan Carl Wilcke introduces the concept of SPECIFIC HEAT.

Coloumb's Théorie des machiones simple (Theory of simple machines) is a study of friction.

Britain signs agreement recognizing U.S. independence.

Congress approves Great Seal of U.S. and the eagle as its symbol.

American Revolution Ends Britain and the infant United States sign the Peace of Paris treaty.

Joseph and Jacques Montgolfier make first public balloon flight.

Earthquakes ravage Calabria in Italy, killing 30,000.

The amateur British astronomer John Michell proposes the theoretical idea of an object massive enough that its gravity would prevent even light from escaping (which has since become known as a black hole). He realizes that such an object would not be directly visible, but could be identified by the motions of a companion star if it was part of a binary system. A similar idea was independently proposed by the Frenchman Pierre-Simon Laplace in 1795.

Horace-Bénédict de Saussure's Essais sur l'hygromé (Essay on measuring humidity) describes how to construct a hygrometer from human hair that can measure relative humidity.

John Jay becomes first U.S. Secretary of State.

Russian trappers established a colony on Kodiak Island, Alaska.

Congress narrowly defeats Thomas Jefferson's proposal to ban slavery in new territories after 1800.

Treaty of Paris ratified, officially ending the American Revolutionary War

Congress of the Confederation ratifies the Treaty of Paris on January 14, 1784, formally ending the Revolutionary War.

John Wesley charters Methodist Church.

Historian and naturalist Cosimo Alessandro Collini publishes a description of the first known pterosaur.

George Atwood accurately determines the acceleration of a free-falling body.

Charles Willson Peale establishes a natural history museum in Philadelphia, one of the first successful American museums.

New York frees all slaves who served in the Revolutionary Army.

First balloon flight across English Channel (Jean-Pierre Blanchard and John Jeffries).

French balloonists Jean-François Pilatre de Rozier and Jules Romain are killed when their Royal Balloon crashes near Boulogne, France, June 15, 1785, in what is considered the first aerial disaster.

Napoleon Bonaparte (16) graduates from the military academy in Paris (42nd in a class of 51).

Lazzaro Spallanzani performs artificial insemination on a dog.

In his Theory of the Earth, James Hutton explains the principle of uniformitarianism: all geological features can be explained by changes that can be observed now, taking place over very long periods of time.

Couloumb makes precise measurements of the forces of attraction and repulsion between charged bodies and between magnetic poles, using a torsion balance, demonstrating conclusively that electric charge and magnetism obey inverse-square laws like that of gravity. He also discovers that electrically charged bodies discharge spontaneously. In the 20th century, it is found that cosmic radiation is responsible for this discharge.

Mozart's opera, The Marriage of Figaro, premieres in Vienna.

Frederick the Great, King of Prussia, dies.

Twining's Tea creates a logo that is still in use today, making it the world's oldest, continuous use logo. The founder of Twinings was Thomas Twining from Painswick, Gloucestershire in England. He opened Britain's first known tea room at No. 216 Strand, London, in 1706; it still operates today.

Federalist Papers published, calls for ratification of Constitution. The Federalist (later known as The Federalist Papers) is a collection of 85 articles and essays written (under the pseudonym Publius) by Alexander Hamilton, James Madison, and John Jay promoting the ratification of the United States Constitution. Seventy-seven were published serially in the Independent Journal and the New York Packet between October 1787 and August 1788. A compilation of these and eight others, called The Federalist: A Collection of Essays, Written in Favour of the New Constitution, as Agreed upon by the Federal Convention, September 17, 1787, was published in two volumes in 1788 by J. and A. McLean. The collection's original title was The Federalist; the title The Federalist Papers did not emerge until the 20th century. This book should be carefully read by anyone with an interest in American democracy.

Constitutional convention opens at Philadelphia, George Washington presiding.

The Northwest Ordinance bans slavery in the Northwest Territory (what becomes the states of Ohio, Indiana, Illinois, Michigan, and Wisconsin). The ordinance together with state emancipation laws create a free North.

Austrian emperor Jozef II bans children under 8 from labor.

Herschel discovers Enceladus, a moon of Saturn, and Titania and Oberon, moons of Uranus.

Jacques-Alexandre Charles shows that different gases expand by the same amount for a given rise in temperature (Charles Law).

Thomas Jefferson publishes Notes on the State of Virginia refuting Buffon's claim that America's harsh, moist climate stunts the growth of its inhabitants. He also addresses the issue of race, describing Native Americans favorably, but African slaves unfavorably.

Maryland votes (December 23) to cede a ten-square-mile area for District of Columbia.

New York City becomes first capital of US.

The Massachusetts General Court (legislature), following an incident in which free blacks were kidnapped and transported to the island of Martinique, declares the slave trade illegal and provides monetary damages to victims of kidnappings.

Captain Arthur Phillip forms English colony at Sydney, Botany Bay, New South Wales, Australia.

Kant publishes Critique of Practical Reason.

Juan-Bautista Bru mounts the first relatively accurate fossil reconstruction of an extinct animal from South America. Georges Cuvier classifies it as a giant sloth.

US Congress passes Federal Judiciary Act, creating a six-person Supreme Court.

Bourbon Whiskey is first created by Elijah Craig in Bourbon, Kentucky.

George Washington becomes the first president of the United States.

Fletcher Christian leads Mutiny on HMS Bounty and Captain William Bligh. Mutineers from the Bounty settle on Pitcairn Island.

Former slave Olaudah Equiano publishes his memoirs, and he travels in Britain lecturing against slavery.

The fall of the Bastille marks the beginning of the French Revolution.

Gilbert White's The Natural History and Antiquities of Selborne, a series of notes about animal and plant life in Selborne, England, is the first recognizable work of ecology. It goes through about 300 different editions and is still in print today.

Johann Wolfgang Goethe's Versuch, die Metamorphose der Pflanzen zu erklären (Attempt to explain the metamorphosis of plants) claims incorrectly that all plant structures are modified leaves, but clearly espouses evolution.

French polymath Antoine Lavoisier publishes a paper on French geology defining peacefully deposited pelagic sediments and violently deposited littoral sediments. He argues that these sediments illustrate a fluctuating sea level on an ancient planet.

The French chemist Antoine-Laurent de Lavoisier definitively states the Law of Conservation of Mass (although others had previously expressed similar ideas, including the ancient Greek Epicurus, the medieval Persian Nasir al-Din al-Tusi and the 18th Century scientists Mikhail Lomonosov, Joseph Black, Henry Cavendish and Jean Rey), and identifies (albeit slightly incorrectly) 23 elements which he claims can not be broken down into simpler substances.