The word equinox can also refer to the position of the sun at this moment. Technically speaking, an equinox is one of the two specific moments in time when the sun is exactly above the celestial equator. For this reason, the terms March equinox and September equinox are sometimes used to avoid a Northern Hemisphere bias.Ĭontrary to popular usage, an equinox doesn’t last for a full 24 hours. In the Southern Hemisphere, it’s the reverse. The autumnal equinox occurs around September 22 or 23, when the sun crosses the celestial equator going south. In the Northern Hemisphere, the spring equinox, or vernal equinox, occurs around March 21, when the sun moves northward across the celestial equator. The two equinoxes occur around March 20–21 and September 22–23, marking the onset of both spring and autumn.ĭuring the equinox, the sun crosses the plane of Earth’s equator, making nighttime and daytime (roughly) equal length all over the world. What is an equinox?Īn equinox is one of the two times of the year when the amount of daylight and nighttime hours are just about of equal length. Solstices mark the start of summer and winter. A solstice is one of the two times of the year resulting in the most amount of daylight time or the least amount of daylight time in a single day. The vernal equinox marks the start of spring, and the autumnal equinox marks the start of fall. An equinox is one of the two times of the year when the amount of daylight and nighttime hours are just about of equal length.

Conclusion the summer solstice pdf