📞
1-800 — toll-free number
1-800 numbers (in the US) and 8-800 (in Russia) are free for the caller. The system was introduced by AT&T in 1967. The toll-free number became a symbol of customer service and a mass business tool.
Culture
👑
800 AD — coronation of Charlemagne
On December 25, 800, Pope Leo III crowned Charlemagne Emperor of the West in St. Peter's Basilica in Rome. This event laid the foundation of the Holy Roman Empire and changed the political map of Europe.
History
🌡️
800°C — metal glowing temperature
At around 800°C, metal begins to glow dark red — this is called 'cherry red heat'. Blacksmiths have judged temperature by metal color for millennia. Today this is the basis of pyrometry.
Science