Stanley Perry, age 10, of Grande Prairie,, Texas, for his question:

What is the vernal equinox?

The word vernal means green. The word equinox means equal night. An equinox occurs when day and night are equal all over the earth. This does not happen very often. For, as you know, our summer days are longer than the nights and our winter days are shorter than the nights.

North of the equator June 21 is the longest day of the year. After this, each day gets shorter until December 21, the shortest day of the year. After this each day gets longer until the next June 21. Between June and December there is a day when night and day are equal. There is another equal night and day between December and June. South of the equator the reverse is true.

The autumnal equinox comes when you would expect it, in autumn. The date is September 23. The vernal equinox comes when the world is ready to burst forth with green spring leaves. The date is March 21.