"For millennia, people have thought and written about time: its fundamental nature, how we perceive and experience it, and how we organize our lives in temporal contexts ranging from minutes to days to lifetimes. For the most part, our experience of time seems natural, as it relates to the rhythms of both our planet and our bodies, so that individuals not only share roughly comparable day-night cycles of sleep and wakefulness, and of the coming of the seasons, but on a more local timescale we naturally gravitate toward preferred speeds for walking, clapping, dancing, or singing."--