Connie Boldra, age 9, of Aurelia, Iowa, for her question:

What is the meaning of a.m. and p.m?

In both cases, the letter m stands for the word meridian which comes to us for an older word for noon. Since noon occurs when the sun reaches its highest point in the sky, the word meridian is given to an imaginary line over which the sun crosses at midday. This celestial line arches over the sky from pole to pole. It corresponds with a meridian, or line of longitude, on the face of the earth.

The sun reaches its greatest glory when it crosses the meridian, so it seems only proper to divide the hours of the day at this point. From midnight to noon, the hours are followed by letters a.m. which is short for ^nte meridian, meaning before noon. The hours from midday to midnight are followed by the letters p,m,, short for post meridian, meaning after noon,