Khan Academy (and Time)

I recently discovered the Khan Academy. Sal Khan began creating 10-minute Youtube videos to tutor his cousins in various school subjects. Five years and over 2200 videos later his website is now an invaluable resource for learning, and great for anyone with a passing interest in subjects ranging from Physics, Finance, Astronomy, History, Calculus, Biology, Stocks, Chemistry, etc. I've recently been watching his videos on Astronomy and found them fascinating. Here are two of my favorites which emphasize the vast scale of the universe in both time and space (similar to my own "How Big Is a Billion" post).

Visualizing the age of the universe


Visualizing the scale of the universe