The concept of parallel rays and divergent rays, in relation to the light source, is necessary to validate hypothesis 2 of Eratosthenes.

Hypothesis 1: The Earth is flat and the Sun is close		Hypothesis  2: The Earth is curved and the Sun is very far away.

Observations 

parallelism of the solar rays (for a distant source)

2019 photos with Aigio, Athens, Ioannina, Petroupoli, Busteni, Ubeda, Rio de Janeiro, Jajjah Abbasian