[youtube=http://www.youtube.com/watch?v=Y9KT4M7kiSw&w=700]
Clarity is one of the toughest things to learn and apply, yet some people are blessed with an extraordinary knack for helping others understand things.

Even if I already know the basics of what something is or how it might work, it's always fascinating to see a real expert explain it in their own way. I always learn something more from it.

Take a few minutes to watch this video of the American astronomer Carl Sagan explaining the 4th dimension (and his little soap opera about the square from the second dimension going on a mind bending trip and seeing inside his friends).

Sagan sounds amazing. He wrote and spoke about the dangers of nuclear winter during the Reagan days, was UFO-sceptic, had legal wranglings with Apple, all sorts. Turns out he also used to teach a course on critical thinking, which would have been fascinating. Check his biog on Wikipedia too - he must have been a truly inspirational character.

Some things he said:

A celibate clergy is an especially good idea, because it tends to suppress any hereditary propensity toward fanaticism.

The fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown.

Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense.

The universe is not required to be in perfect harmony with human ambition.

For small creatures such as we the vastness is bearable only through love.