Theresa Stimson, age 12, of Spokane, Washington, for her question:

Did man invent time or discover it?

The whole Universe runs on time schedules, pacing the wheeling Galaxy and the motions of separate stars. The earth orbits the sun on time, tilting its axis to alternate the seasons. It also rotates, repeating its rhythm of days and nights. Plants and animals respond and adjust to the earth's daily and seasonal schedules. But they are not aware of these things. Mankind is aware of himself and of things around him. Our earliest ancestors noticed the passage of time.

Later they charted the motions of the sun and the stars    and discovered their relationship to the earth's daily and seasonal schedules. This historic discovery led to the invention of man made systems for keeping track of the passage of time. The wheeling heavens provide a natural clock and a calender. Days and hours, weeks and months were invented to adjust this discovery to a workable time keeping system. Hence "time" can be said to be an invention based on a discovery.