Was very confused by the shadows on the ground in Singapore yesterday until I realized that, below 23.50 of latitude, shadows in the northern hemisphere can (in the summer) move both clockwise *and* counterclockwise, depending on the time of day. 
(See http://andrewmarsh.com/apps/staging/sunpath3d.html ….)
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This was predicted by the Portuguese mathematician Pedro Nunes in 1537 at the time of the portuguese discoveries. It was also the first natural phenomenon to be predicted by math before being observed :)https://thatsmaths.com/2017/10/12/pedro-nunes-and-solar-retrogression/ …
Are we saying that shadows move counter-clockwise during the summer in latitudes below 23.50 (which makes sense to me) or are we saying that, depending on the time of day shadows can go counter or clockwise (which does not).
