James Galambos, age 16, of Lake Nelson, New Brunmrick, N. J., for his question:

How often do we get an equinox?

The equinox is a date on which day and night are equal all over the world. This event happens twice each year, which means We get two equinoxes every year. The vernal equinox is on March 21, which is the first day of spring. After this date, the days in the Northern Hemisphere get longer until June 22; the longest day of the year.

Then the days get shorter until We reach the autumnal equinox. This second equinox of the year falls on or near Sept. 22. Day and night again are equal all over the globe. After this, our days north of the equator get shorter until dec. 21, when we get the shortest day of the year.