@elonmusk The Fifteen Decisive Battles of the World: from Marathon to Waterloo is a book written by Sir Edward Shepherd Creasy and published in 1851. This book tells the story of the fifteen military engagements, which, according to the author, had a significant impact on world history.
@engineers_feed astronomical unit (AU, or au), a unit of length effectively equal to the average, or mean, distance between Earth and the Sun, defined as 149,597,870.7 km (92,955,807.3 miles).