1500 years of lost knowledge.

The idea that we're constantly moving forward is... quaint.  Antikythera mechanism - Wikipedia, the free encyclopedia: "The Antikythera mechanism is an ancient analog computer designed to predict astronomical positions and eclipses for calendrical and astrological purposes, as well as the Olympiads, the cycles of the ancient Olympic Games...

 The artifact was recovered in 1900–1901 from the Antikythera shipwreck off the Greek island of Antikythera. Believed to have been designed and constructed by Greek scientists, the instrument has been dated either between 150 and 100 BCE, or, according to a more recent view, at 205 BCE.  After the knowledge of this technology was lost at some point in Antiquity, technological artifacts approaching its complexity and workmanship did not appear again in Europe until the development of mechanical astronomical clocks in the fourteenth century."

Lost history is a thing.  We know so little.