toptics
A
Highlights
Parallel Rays
Peter Ross imaged these 'crepuscular' rays and shadows at Tai Mo Shan, Hong Kong. They show, if proof be needed, that the sun's rays are indeed parallel. Looked at in the direction towards the sun they would appear to radiate in all directions
Images ©Peter Ross, shown with permission
Not quite parallel. The sun's 0.5° diameter in the sky causes the dark (umbra) of shadows to taper.
A pea casts an umbra about 700 mm long.
A mountain's umbra can extend over 300km when the sun is very low
Earth's umbra is 1,400,000km long, three and a half times the distance of the moon.
