it took 15 years to build the terracotta army
720,000 people
well they were found in 1974 by 7 farmers digging a well in china. the emperor made the soldiers in about 220 bc so like 2030 years. :)
37 years
50 million years
It took about 150 days for each one
There possibly were written records originally. However, remember this happened over 2,000 years ago and China has had many rulers and governing systems in that time. -More pointedly , take a look at how terrorist groups like Taliban and ISIS are NOW eradicating history .
How long does it take to change a front coil spring on a Peugeot 206
It was not the Terracotta Army that Qin Shihuang used to take the whole country, but the soldiers who the Terracotta Army modelled after. Thus the unification of China by Qin Shihuang was happened in 221 BCE.
In the related links box below, I posted Building A 250,000 Volt Tesla Coil.
7000000
days maybe weeks