If the stick was lined up with the sunrise, it would be laying on the ground. However, an ancient civilization might have noted that the the tip of the shadow from a vertical stick stuck in the ground followed a straight line throughout a sunny day on either equinox, while following curved lines during a sunny day at other times of the year.
But if the ancient civilization could do that accurately enough with a stick in the ground, why did they spend the time and effort to build all the Towers of Chankillo to do the same thing?
“If the stick was lined up with the sunrise, it would be laying on the ground.”
I mean putting a stick in the ground between the sunrise and a fixed observation point, like these towers are laid out. In that case, you would end up with a line of sticks similar to the line of towers.
“But if the ancient civilization could do that accurately enough with a stick in the ground, why did they spend the time and effort to build all the Towers of Chankillo to do the same thing?”
They probably got along just fine with sticks for a few decades until a really strong wind came along and blew the sticks away. Then they realized they might need something more permanent than sticks.