September 27

William the Conqueror sets sail from the mouth of the Somme River, beginning the Norman conquest of England.

William, Duke of Normandy, set sail from the mouth of the Somme River with his invasion fleet after weeks of unfavorable winds had delayed the crossing, beginning the campaign that would culminate in his decisive victory at the Battle of Hastings weeks later.

Ottoman forces under Suleiman the Magnificent begin their siege of Vienna.

Ottoman forces under Suleiman the Magnificent began their siege of Vienna, an ambitious campaign that ultimately failed to capture the Habsburg capital before winter weather and logistical difficulties forced an Ottoman withdrawal, marking the furthest extent of Ottoman expansion into Central Europe.

Pope Paul III grants official papal authorization to the newly founded Society of Jesus, the Jesuits.

Pope Paul III formally recognized the Society of Jesus, founded by Ignatius of Loyola and a small group of companions, granting the new religious order papal authorization that allowed the Jesuits to grow into one of the Catholic Church's most influential missionary and educational institutions.

Jean-Francois Champollion announces his decipherment of the Rosetta Stone's hieroglyphic text to the French Academy.

French scholar Jean-Francois Champollion announced to the French Academy that he had successfully deciphered the ancient Egyptian hieroglyphic script using the trilingual Rosetta Stone, a breakthrough that opened the door to modern Egyptology and the study of ancient Egyptian civilization.

The Stockton and Darlington Railway opens in England as the first public steam-powered railway.

The Stockton and Darlington Railway in northern England opened as the world's first public railway to use steam locomotives for both passenger and freight transport, built primarily by engineer George Stephenson. The line's success demonstrated steam railways' commercial viability and directly inspired the rapid expansion of railway construction across Britain and eventually the rest of the industrializing world.

The ocean liner Queen Elizabeth is launched in Glasgow, Scotland.

The ocean liner Queen Elizabeth, at the time the largest passenger ship ever built, was launched from a Glasgow shipyard, though its planned maiden voyage was delayed by the outbreak of World War II, and it initially served as a troop transport instead.

Germany, Japan, and Italy sign the Tripartite Pact in Berlin, formalizing their wartime alliance.

Germany, Japan, and Italy formalized their wartime alliance by signing the Tripartite Pact in Berlin, committing to mutual military assistance if any signatory was attacked by a power not already involved in the European war or the Sino-Japanese conflict, a provision primarily aimed at deterring American intervention. The pact cemented the Axis powers' coordinated strategy during World War II.

Rachel Carson's environmental book "Silent Spring" is published, helping launch the modern environmental movement.

Marine biologist Rachel Carson published "Silent Spring," a meticulously researched book detailing the environmental dangers of widespread pesticide use, particularly DDT, and its devastating effects on bird populations and broader ecosystems. Despite fierce opposition from chemical industry interests, the work is widely credited with launching the modern environmental movement and eventually leading to a nationwide ban on DDT.

Google later designates this date as its official founding anniversary.

Though the company was actually incorporated the previous May, Google later designated this date as its official "birthday," a date now widely recognized and celebrated by the technology company and its users each year despite the discrepancy with its true legal founding date.

Climate activists worldwide participate in coordinated strikes protesting climate change across thousands of locations.

Millions of people across thousands of cities worldwide participated in coordinated climate strikes demanding urgent government action on climate change, inspired partly by teenage Swedish activist Greta Thunberg's solo protests outside her country's parliament the previous year. The demonstrations formed one of the largest coordinated climate protest actions in history, drawing significant international media attention.