– How do we actually know when the earth does a full orbit of the sun and why are our years based off of it?

Question

– How do we actually know when the earth does a full orbit of the sun and why are our years based off of it?

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Answer 1

Stonehenge and similar ancient structures line up with the solstices. This was probably for this exact reason- to track the seasons and similar events, such as the start of the year.

The sun rises at a slightly different part of the sky each morning, moving until it returns to it’s start point, which takes exactly one solar year