soupsandwich
Roofer
A simple explanation so that you can concentrate on other stuff ....
I understand, but how can you prove that without being in both places?Assuming both of our appendages are the same length, if I measure the shadow cast by mine at midday while laying down here in southern Leics and you measure yours, laying down, in wherever, providing it's in a northerly or southerly direction from where I am, then your shadow cast will be bigger than mine if you're north of me, my shadow cast will be bigger than yours if I am North of you.
Or we could agree on equal lengths sticks which would be a lot easier and more decent.