quote:
Yet if clouds block the sun from view, the sky that is not obscured is still bright. Obviously the sun is a light source, but the day sky is, too. Unless you know about optics.
I suppose the entire sky could be viewed as a huge light source - by a completely naive viewer. I guess I was thinking of people in general who had contemplated this stuff for a little while.
When the sun is obscured (via clouds, rain, etc..) , a better way to express it is the light gets dimmer, it is not "still bright".
People also realized that obstructing a bright thing (fire, sun) cast lack of light where it "blocked" the light. The sun itself cast a shadow, the sky did not. Hence the sundial.
People could also see that "blocking" one's view of a lightsource did not stop all light from hitting them. I'm sure they understood reflections (mirrors) from a basic sense.
But I can't back any of this up. It's just my gut feeling. I could be wrong! Very wrong! :-)