The perception of time is intricately related to our state of mind. To clarify, just think of one of Einstein's quote about relativity...
<paraphrased>
"A second with your hand placed on a hot burner seems like an hour, but an hour with a beautiful woman seems like a second... that's relativity."
It's potentially related to processing speed within the brain. When we are interested in something we naturally understand it better and more parts of the brain are brought into the process. Perhaps there is greater synaptic involvement and the stimuli are organized, quantized, interpreted, etc. more efficiently.
How many times have you hung out with a friend and had a great time, only to realize that your time was up too soon? And how many times have you engaged in a boring or monotonous task only to feel the seconds tick by so slowly?
Time Dilation and Contraction on a neurophysiological level... hmmm...
"Psychotemporal morphology..." Careful, I'm gonna trademark that!
Oh... the quick answer is because the clock has wings, and the air flow below it moves faster than the air flow above it and it creates a negative pressure pushing it upward.
