What the Romans observed as Solis Occasum is scientifically explained by the scattering of light within Earth’s atmosphere.
Together, they describe the moment the solar disk descends below the horizon—an event defined in modern astronomy by atmospheric refraction, which makes the sun visible even when its geometric center is technically below the horizon line. Scientific Phenomenon Solis Occasum
Derived from occasus , signifying "falling," "setting," or "decline". What the Romans observed as Solis Occasum is