To King and Ann Inett is born another son, named Sydney, in 1790.

King, following the wreck of Sirius at Norfolk Island in March 1790, returns to England to report on the difficulties of the settlements at New South Wales.

Ann is left in Sydney with the boys; she will later marry another man in 1792, and will go on to lead a comfortable and respected life in the colony.

King, who had probably arranged the marriage, will also arrange for their two sons to be educated in England, where they will become officers in the navy.

The Sydney region comprises a variety of nations that are united by a common language.

These nations are the Eora, who live along the coast; the Tharawal to the south; the Dharug to the northwest; and the Gandagara to the southwest.

Within the language groups there are several clans.

The Eora people generally comprise three main clans known as the Cadigal, Wanegal, and the Cammeraygal, and several smaller ones.

The Dharug people, however, are the largest dialect of the Sydney region and consist of the Wangal, Kurrajong, Boorooberongal, Cattai, Bidjigal, Gommerigal, Mulgoa, Cannemegal, Bool-bain-ora, Cabrigal, Muringong and the Dural clans.

A clan typically numbers between fifty to one hundred people.

The British penal colony that has been established at Port Jackson (present-day Sydney) is the traditional land of the Cadigal people.

The penal colony has a population of around one thousand and for the first few years struggles to adapt to the Australian climate.

The new governor-general of the British East India Company, Charles Cornwallis, makes it clear that he cannot be party to Sultan Abdullah's disputes with the other Malay princes, or promise to protect him against the Siamese or Burmese.

Unbeknown to the Sultan, Light had decided to conceal the facts of the agreement from both parties.

When Light reneges on his promise of protection, the Sultan unsuccessfully attempts to recapture the Prince of Wales Island in 1790, and the Sultan is forced to officially cede the island to the British for an honorarium of six thousand Spanish dollars per annum.

Peking Opera—a form of Chinese opera that combines music, vocal performance, mime, dance, and acrobatics—has its precursor on September 25, when the "Four Great Anhui Troupes" introduce Anhui opera (Huiju) to Beijing, in honor of the Qianlong Emperor's eightieth birthday.

The performance is originally staged for the court and will only later be made available to the public.

Mozart's circumstances had worsened toward the end of the decade.

He had ceased to appear frequently in public concerts around 1786, and his income shrank.

This is a difficult time for musicians in Vienna because of the Austro-Turkish War: both the general level of prosperity and the ability of the aristocracy to support music have declined.

By mid-1788, Mozart and his family had moved from central Vienna to the suburb of Alsergrund.

Although it has been suggested that Mozart's aim was to reduce his rental expenses, research shows that by moving to the suburb, Mozart had not in fact reduced his expenses (as claimed in his letter to his friend and fellow Mason Michael Michael Puchberg), but merely increased the housing space at his disposal.

Mozart had begun to borrow money, most often from Puchberg.

Major works of the period include the last three symphonies (Nos. 39, 40, and 41, all from 1788), and the last of the three Da Ponte operas, Così fan tutte, premiered in 1790.

Mozart makes some long journeys around this time, hoping to improve his fortunes: to Leipzig, Dresden, and Berlin in the spring of 1789, and to Frankfurt, Mannheim, and other German cities in 1790.

Pál Kitaibel, a Hungarian botanist and chemist, discovers Reichenstein's aurum paradoxicum (now known as tellurium) in the mineral wehrlite in 1790.

The Romanians and other minority nations in the Habsburg domains, threatened by both Germanization and Magyarization, are meanwhile experiencing a cultural awakening.

Cagliostro is arrested in 1790 by the Inquisition of Rome.

Subsequent studies show the new gas recognized by Scheele, Priestley, and Rutherford to be a constituent of nitre, a common name for potassium nitrate (KNO₃).

Accordingly, the French chemist Jean-Antoine-Claude Chaptal names it nitrogen (from nitre and Greek gen, bearing or forming) in 1790.

Lavoisier, whose explanation of the role of oxygen—the “fire air”—in combustion, eventually overthrew the popular but erroneous phlogiston theory, considers nitrogen a chemical element, and names it azote, after what he deems its apparent inability to support life, and which today remains the French equivalent of nitrogen.

Alexander von Humboldt, introduced at an early age by his tutor to a group of learned intellectuals including the philosopher Moses Mendelssohn, attends the University of Gottingen, where he studies archaeology, physics, and philosophy from 1789.

Here, he meets Georg Forster, recently returned from his voyage around the world with Captain Cook, a meeting which serves to heighten Humboldt’s already keen interest in botany and exploration.

In the summer of 1790 he pays a short visit to England in the company of Forster.

Humboldt leaves Gottingen in 1790 to study geology under A. G. Werner at the school of mines in Freiburg.