Beyond being one of the greatest scientists to have ever lived, Richard Feynman revelled in challenging the received notions and flawed assumptions that underpin most of our understandings about how the world is put together.
He was an educator as much as a scientist, a man who believed that even the most complex of ideas should be able to be expressed to a teenager.
In this video he argues with himself, in typically articulate fashion, over how we should best understand those heavy, imposing, bark-covered entities called trees. The answer: as being made of the air itself. A worthy reminder that science is often the art of proving that what we can see is usually completely wrong.