Day and night get equal billing Monday as fall equinox arrives. Here's what to know

The day and night will have an equal time for a brief moment as the equinox arrives. The earth will know about the same quantity of day and night on Monday when the fall equinox arrived. From there, the northern hemisphere plunges in the fall as night becomes more and more, and the southern hemisphere is heading for summer. Solstices are the opposite. They occur in December and March, when the earth is tilted most strongly towards or far from the sun, so day and night are very different lengths.