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

Where Do Butternut Squash Come From?
10:07

How Did the Great Stink of London Work?
12:10

BrainStuff Classics: How Do Blue Whales Work?
08:41