It is true that spring has once again arrived. The Latin reference, Vernal Equinox, has been used for centuries and has a high degree of hemispherical bias associated with it. The word vernal, is derived from the Latin word Ver for spring, literally meaning ‘green’. It is indeed a green(ing) time of year. Equinox simply means equal-night. Those persons residing in the southern hemisphere are obviously not having spring, but are now experiencing autumn. The approximate day-length, and therefore night-length, are equal. Notice I used the word approximate. While the official beginning of spring is March 20, the actual ‘equinox’ occurs for us, closer to March 16th.
Day is usually defined as the period when sunlight reaches the ground in the absence of any obstacle. On the day of the equinox, the center of the Sun spends approximately an equal amount of time above and below the horizon at every location on the Earth, so you would assume that night and day are the same length. Actually, the day is longer than the night at an equinox, for a couple of reasons.
From the Earth, the Sun appears as a disc rather than a point of light, so when the center of the Sun is below the horizon, its upper edge is visible. Sunrise, which begins daytime, occurs when the top of the Sun's disk rises above the horizon, even though the center of the sun is well below.
Earth's atmosphere also refracts, or bends, sunlight. As a result, we see daylight before the top of the Sun's disk rises above the horizon. When the upper edge of the Sun is still below the horizon, its rays curve over the horizon to the ground. It may be confusing, but as it turns out, it doesn’t matter because spring happens anyway!
This Saturday be prepared to learn all about azaleas from Tom Smith of Flowerwood Nurseries, the developers of Encore® Azaleas. Reservations are recommended for either the 11am or 1pm talks; contact: Anne via email or calling: 615-876-1014