I'm not really bringing physics into it -- purely just from a biology standpoint. It's like when I nearly get into a car accident or something and my body ups my adrenaline...time seems to move more slowly, in part (I believe), just from that my brain is processing things more quickly (I crashed my mountain bike a couple years ago, and I was perplexed at how long it took me to actually hit the ground). To me at least, it seems as if I could think twice as fast (similar to when I crashed my bike), that time would appear to run more slowly.