Why is the sky dark at night?

So, the sky looks blue because of the particular gases in our atmosphere reflect and scatter the blue wavelengths of light from the Sun. Fair enough. But that leads directly to a second question that, I'm ashamed to say, I never really thought to ask — why doesn't the light from all the stars in the Universe reflect and scatter off our atmosphere, producing a blue sky, all the time?

This Minute Physics video provides a great explanation, which is grounded in both the timey-wimeyness of astrophysics and the limitations of our own human biology.

Via BrainPickings

Read the rest