A decade and a half into the 21st century, it's tempting to ask: Where are all the robots? In the vein of "Where's my jetpack" thinking, it sure seems like robots would be more present in our homes and offices by now. Granted, I do have a floor-cleaning robot, but it's fussy enough that it doesn't seem like the future I had imagined. (His name is Dusty, and he likes to eat electrical cords.)

In this 10-minute video, Hank Green breaks down the basic history of robotics—the parts of the machines, how those parts interact, and why we don't have robotic butlers opening our doors (or forcing us to mine tungsten for them). Enjoy:

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