This is not really a documentary but it's an incredible, 10-hours-long, video material full of amazing scientific explanations. Don't be discouraged by the length of the playlist because the material is divided in relatively small parts and you can digest them in your own time. This is simply a compilation of the most popular videos of one spectacular YouTube channel - Vsauce.
Michael, the owner of the channel, has a unique talent of presenting scientific facts in a very interesting way. If you think you're familiar with the everyday science, then wait until you see what he has to say. Michael's explanations include a wide spectrum of scientific topics, such as:
What will happen if everyone on Earth jumped at once? Does the mirror have a color? Why do people kiss? Do everyone see the same colors? What's the most fatal place on the planet? How high can our buildings go? Why are things scary? Why are bad words labeled as bad? Does the shadow have a weight? What would happen if the sun disappears? Does anyone own the moon? Can we live forever?
Can you do anything without a brain? Will we ever go to the stars? Can a baby be born in space? How big can a person get? Why do we play video games? What is the most exceptional metal on Earth? Is anything really real? Where do deleted files on our computers go? Why are some things attractive? Why do we wear clothes at all? Why do we need dreams? Why do we have two nostrils when one is totally fine?
Are we ready for the eventual alien appearance? How hot can it get on planet Earth? Why don't we taxidermy humans... like we do with the animals? How many photos have been taken so far in total? Why do we sometimes get bored? How much does the Internet actually weigh? Is yawning contagious?... and many, many more.