Many eyes will be trained on a clock tonight as midnight signals the change from 2003 to 2004. Humans have been marking time--well, since the beginning of time. Ancient civilizations relied on celestial bodies, other cultures developed the sun dial--today we count time on atomic clocks. Dr. Michael Kearl is a professor of sociology at Trinity University in Texas. He says humans developed a sense of time so they could begin to coordinate their activities.