Playing in the Unknown
This is a fantastic video, by TED-ED. In this, the reality of observation and thought are shown to be the means of pushing human knowledge and scientific discovery. In such, it is the "unknown" that is the most intriguing area to play.
Adam Savage walks through two spectacular examples of profound scientific discoveries that came from simple, creative methods anyone could have followed -- Eratosthenes' calculation of the Earth's circumference around 200 BC and Hippolyte Fizeau's measurement of the speed of light in 1849. (Launching a series on Inventions that Shaped History)