The vernal equinox is the moment in spring when day and night are nearly equal in length all over Earth. It happens around March 20 each year in the Northern Hemisphere, marking the official beginning of spring there. Vernal comes from a Latin word meaning spring, and equinox means equal night.

Here's what makes it special: Earth tilts as it orbits the sun, which is why we have seasons. During the vernal equinox, Earth's tilt causes the sun to shine directly over the equator. At this moment, if you stood on the equator at noon, the sun would be directly overhead. Many places on Earth get almost exactly twelve hours of daylight and twelve hours of darkness.

After the vernal equinox, the Northern Hemisphere tilts more toward the sun, giving it longer days and warmer weather as spring advances toward summer. Meanwhile, the Southern Hemisphere experiences the opposite: its days grow shorter as it heads into autumn.

Ancient peoples built monuments like Stonehenge to mark the equinoxes, showing how important these moments were for tracking seasons and planning when to plant crops. Today, the vernal equinox reminds us that Earth follows precise, predictable patterns as it travels through space.