why it is that the young have the keys to cool...
They have (to crudely generalise):
Naivety - they don't know what came before them, they believe anything is possible, they are utopian
Energy - self-explanatory
Libido - related to energy but different, they're biologically primed to show off and shag
Reckessness - they don't care about the adult world of responsibilities, the adult world appears like a protracted decline, they don't believe in death
Rebelliousness: they want to shake things up, they view adult institutions with scepticism/hostility
Malleability: they're not stuck in their ways yet, or they are at least open to exploring new ways
Intense feeling - Is this a biological fact? Not sure, but I'd warrant that their hormones are causing them to feel things intensely. They're not as prone to conceptualising in the dry scientific way the adults do.