The brain is like a muscle. When it is in use we feel very good. Understanding is joyous.
This is one of my foremost favourite lectures by cosmologist Carl Sagan who might also happen to be within the higher levels of my own pantheon of personal heroes. In this video, Sagan explains physical dimensions beyond our familiar three-dimensional perception, and does it in such a way that even a child could grasp the concept. The only problem is that the more curious of us might be led to delve much deeper. Get ready for a serious mind job.