Today is a cross-quarter day, meaning that the Sun is halfway between an equinox and a solstice. The word “equinox” is a combination of “equal” and “nox” (which means night), and it occurs when the Sun is directly overhead at the equator. The solstice is when the Sun reaches its greatest distance from the equator at approximately 23.5 degrees. Then it is directly overhead at the Tropic of Cancer in the north or the Tropic of Capricorn in the south. Today, the Sun is at its halfway point between the equator and the Tropic of Capricorn.
For the Northern Hemisphere, the autumn cross-quarter day falls near Halloween. In the spring, it is near “Groundhog Day.” For those of us interested in astronomy and Earth’s climate and weather, that gives Halloween and Groundhog Day a significance different from what most people consider.
For us, a cross-quarter day is another reminder that our planet is extraordinary. The reason for equinoxes and solstices is Earth’s 23.5-degree tilt. That tilt is also vital to our survival. The Sun doesn’t overheat any section of the planet because Earth’s tilt changes the latitude where the Sun is overhead. It also avoids over-cooling as the Sun returns soon enough to avoid the extreme cold temperatures we observe on other celestial objects. This design also generates weather systems, the movement of ocean currents, winds to distribute plant seeds, and many other factors needed for life.
Indeed “the heavens declare the glory of God; the skies proclaim the work of His hands. Day after day they pour forth speech. Night after night they display knowledge” (Psalms 19:1-2). Happy cross-quarter day!
— John N. Clayton © 2021
Reference: Archaeoastronomy.com