Eli5: How did ancient civilizations in 45 B.C. with their ancient technology know that the earth orbits the sun in 365 days and subsequently create a calender around it which included leap years?

Question

Eli5: How did ancient civilizations in 45 B.C. with their ancient technology know that the earth orbits the sun in 365 days and subsequently create a calender around it which included leap years?

In: 6494

Answer 1

There are various ways they did it, but let’s go for one of the simplest: A stick.

Stick it upright in the ground. When the sun is highest, record where the shadow ends. Repeat all year, and you can tell when the longest and shortest days of the year are. Measure from one shortest day to the next and you have a year.

Repeat for a few years, and you’ll realize it’s around about 365 days. You probably want something more sturdy like an obelisk, though.

The more advanced technology after that is sundials, which can start to tell the time roughly. Earliest one we know that is around 1500 BCE.