Long TextExercise 3 of 83

If you can read a clock, you can tell the time of day. But no one really knows what time itself is. We cannot see it. We cannot touch it. We cannot hear it. We know it only by the way we mark its passing. For all our success in measuring even the smallest parts of time, time remains one of the great mysteries of the…

• Why is time such a difficult concept to understand?
• How were early humans able to begin measuring time?