The human eye is basically only limited by the curvature of the Earth and stuff that gets in its way. (Well, and various medical conditions.) Learn how far we can see in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/question198.htm

How Did the Penn Center Become a Civil Rights Sanctuary?
09:53

BrainStuff Classics: Why Is Cramming the Worst Way to Study?
05:55

How Can We Separate Ninja Fact from Ninja Fiction?
07:38