September 23 has seen planets discovered, empires challenged, and musical innovations born.
German astronomer Johann Galle discovered Neptune at the Berlin Observatory, based on mathematical predictions by Urbain Le Verrier. It was the first planet found through mathematical calculation rather than observation.
Gaius Octavius, the future Emperor Augustus, was born in Rome. He became the first Roman Emperor and established the Pax Romana, an era of relative peace and stability lasting over 200 years.
The Lewis and Clark Expedition returned to St. Louis after two years and four months exploring the American West to the Pacific Ocean. Their journey provided invaluable knowledge about the continent.
American naval captain John Paul Jones defeated the British warship HMS Serapis in a fierce battle off the English coast. When asked to surrender, he reportedly replied, 'I have not yet begun to fight!'
NASA's Mars Climate Orbiter was lost due to a navigation error caused by a mix-up between metric and imperial units. The $125 million spacecraft burned up in Mars's atmosphere.
Harvard College held its first commencement ceremony, graduating nine students. Founded in 1636, Harvard is America's oldest institution of higher learning.
Mozilla released the first version of the Phoenix browser, later renamed Firefox. The open-source browser challenged Internet Explorer's dominance and helped shape the modern web.