"It takes the average human seven minutes to go to sleep, but according to Hand's Human Physiology, it takes the same average human fifteen to twenty minutes to wake up. It is as if sleep is a pool from which emerging is more difficult than entering. When the sleeper wakes, he or she comes up by degrees, from deep sleep to light sleep to what is sometimes called "waking sleep," a state in which the sleeper can hear sounds and will even respond to questions without being aware of it later... except perhaps as fragments of dreams."