Why is the sky dark at night?

At http://blogs.discovermagazine.com/badastronomy/2012/10/01/why-is-the-sky-dark-at-night/

Why is the sky dark at night?

One thing educators like to say is that there are no stupid questions. I disagree, mildly: unasked questions might fit that category. Still and all, even basic questions are worth asking, and sometimes can lead to profound insight.

You may find the video at http://blogs.discovermagazine.com/badastronomy/2012/10/01/why-is-the-sky-dark-at-night/