On This Day: August 24

August 24 brings together a buried city, a declaration of independence, and a new definition of a planet. Three stories show how history changes when the ground shifts, a country names its future, or science redraws a category. 1

The date of Vesuvius is not as certain as the story. Mount Vesuvius is traditionally said to have erupted on August 24, 79 CE, burying Pompeii and Herculaneum. But Britannica notes that another reading of Pliny the Younger's damaged manuscript places the eruption on October 24. The disaster remains vivid: a midday eruption sent ground-hugging clouds of hot gas and rock toward the cities, while later excavations helped give rise to modern archaeology. 2

Ukraine's independence began with a vote, then faced the test of public consent. On August 24, 1991, Ukraine declared independence from the Soviet Union, shortly after the failed coup against Mikhail Gorbachev. The decision became a crucial step toward the USSR's collapse later that year. In December, about 90 percent of voters backed independence in a referendum, turning a parliamentary act into a broad public mandate. 13

Pluto's change was a change of definition. On August 24, 2006, the International Astronomical Union adopted Resolution 5A. A planet had to orbit the Sun, be nearly round, and clear the neighbourhood around its orbit. Pluto met the first two conditions but not the third, so the IAU placed it in the new category of dwarf planets. The decision did not erase Pluto; it reflected a solar system that had become more complicated as astronomers found more objects beyond Neptune. 45