What is an Equinox?

• A. Moon phase cycle
• B. Days of equal day and night
• C. The shortest day of the year
• D. The longest day of the year

Answer: (B)

An equinox is when the Sun appears directly above the Earth’s equator, so the daylight period is about the same as the night. This happens twice a year, around the dates of March and September, marking the times we switch between seasons (spring and autumn). The tilt of the Earth's axis, about 23.5 degrees, means most days are longer or shorter, but on these two days the tilt lines up so that the Sun rises roughly due east and sets roughly due west, giving roughly equal day and night lengths. It’s not the Moon phase cycle, and it’s not the longest or shortest day of the year—that distinction belongs to the solstices.