Ok, we will get into some basics......it gives me a feeling that people here are mixing up brightness/darkness with radiation. These are qualitative words....
See, the clear sun light is of the order of 100,000 Lux (measure of visible light intensity per unit area), the full moon brightness is of the order of 0.1 and moonless night brightness is of the order of 0.001, thats star light (we are not getting into further bifurcation here).
The point is simple.....that the sun could directly create 100000 lux, reflected light from moon can create a brightness of 0.1 Lux, then why trillions of trillions of stars could not even create 0.1 Lux ? This issue was known much before Big Bang was proposed.
Big Bang (a huge problem in itself) created a related problem of its own, but it got sorted out by the huge redshift (z = 1100 of BB light....The original question demanded an answer...
It was proposed that..
a. Universe is finite not infinite, thus not every line of sight from earth goes to a visible star.
b. Universe is expanding...redshift.
c. Finite speed of light.
This is well cateloged, answering this way is nothing but parrotising.......one particular poster messed up the same with radiation awashed, without understanding the definition of brightness/darkness. These three points do not prove a fact that visible light would be less than 0.001 lux in the clear night......one star is able to create 100000 lux, one moon is able to create 0.1 (both are in finite universe, expanding universe, with finite speed of light)....so caluclation is required that why 10^31 stars total brightness input to earth is << 0.1 ? That would be the answer, those three parrotised lines are just the lines.