Full disclosure — I picked up this stone yesterday, but it got out shadowed by that spectacular sunset yesterday evening. Earlier in my walk, as I reached a clearing in the woods, I could see the last of the sun lighting the tops of the trees. I used to watch the same thing years ago, sitting on the side of the baseball and soccer field watching games when Sam was in middle school. As the sun would go down behind us, the line of light on the trees to the east would move up and up until it slipped off into sky. Here’s a poem from those many years ago, one of many in an unpublished manuscript influenced by my fascination with physics and the way trees manifest the immutable laws of the universe.
Evergreen
The light draws a line on the crowns
that moves down as the sun
rises, or up as it sets.
It’s the world’s line
between is or is not, the world’s
shutter opening and closing
as the globe turns along the loop
that draws all bodies
in the same spinning path, tracking
our groove in the universe so we always
know where we’re going even as we rush
forward into the airless dark.
Grace Mattern 
Love this – your observations and the poem. Physics and mathematics do have their own exquisite beauty and poetry. Great universal stone here!