It is those moments that occur at fleeting passage of time leave a profound impact on your psyche. Some of them make you yearn to relive them and would inspire you to produce your masterful work just to relive that fleeting moment again. At the other extreme, they take you to your deepest introspection and make you much wiser.
Just finished the reading Big Bang by Simon Singh, the entire experience reminded me of the awe, joy, fun and excitement I had when I was first introduced to the concepts of structure of atom, relativity theory and others when in school. Big Bang Theory, in my opinion, is The greatest achievement, so far, of human intellect. Grab a copy of the above mentioned book if you can, you wont be disappointed.