Your ancient ancestors--no matter where they lived--told time by the sky.
You can do this too. Just imagine you're outside at sunrise.
You're facing the sun--east--and pointing at it...
Now you point to where the sun will be
a quarter of an Earth-spin--6 hours--after sunrise...
Next you point to where the sun will be
half of an Earth-spin--12 hours--after sunrise...
And you point to where the sun will be
three quarters of an Earth-spin--18 hours--after sunrise...
Finally, you point to where the sun will be
one whole Earth-spin--24 hours--after sunrise...
Of course, the sun isn't circling you--
you're spinning around our Earth's axis.
So, if you point to a star in the east
and you point to this star every quarter of an Earth-spin later,
you'll move your arm through this same circle.
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