Our This Planet video episode Bunny, Billionaire & Pencil starts with Elon Musk. Every age has its genius and Musk could be ours. A millionaire in his 20's and billionaire in his 30's, Musk is a serial tech entrepreneur who seems less interested in money than in his fixations with cars, rocket ships and alternative energy.

Musk attracted lots of attention last summer by "open sourcing" all the battery patents at his electric car company, Tesla Motors. Musk told MSNBC's Chris Hayes that Tesla has too big a lead on other car companies, because "if Tesla succeeds, but the climate is destroyed, I'm not sure that actually helps Tesla."

So Musk wants other car companies to catch up in order to save this planet?

Not so fast, say plenty of commentators, including those at the online economic policy discussion series The Lip, which we used in our video. Not pure altruism but pure genius, because Tesla's rival isn't another electric car company, it's the gas guzzlers.

Enough about Elon Musk! Except that he is also the founder of Solar City, which will sell or rent you solar panels, as well as a way to store the power they generate...and yes, that means batteries.

And batteries are what we care about, because improving batteries means cheaper and more effective use of renewable energy. So we get to the part about the pencil. If every age has its genius, it also has its key material. There was the Bronze Age and the Iron Age. We are living in the Silicon Age. Tomorrow: the Age of graphene. Although our interest in graphine is all about batteries, please allow a brief digression: