Why do finals go so late?

Why do finals go so late?
Why do finals go so late?

Two reasons, mainly. You can finish earlier if you start the school year earlier, and some schools do. And there are limits to how many classrooms of a given size there are, so there are limits to how many exams you can have happening at the same time.

Why is the sky blue?

Why is the sky blue?
Why is the sky blue?

Scattering of sunlight is more effective in the short wavelength (blue/violet) part of the spectrum, so the sky appears blue (but not today, because clouds and rain tend to mask that!). See: hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html for a more thorough explanation.