[citation needed] As sunrise and sunset are calculated from the leading and trailing edges of the Sun, respectively, and not the center, the duration of a daytime is slightly longer than nighttime (by about 10 minutes, as seen from temperate latitudes).These phenomena occur due to Earth’s axial tilt, causing continuous sunlight or darkness at certain times of the year.This symmetry becomes clear if the hemispheric relation in sunrise equation is applied to the x- and y-components of the solar vector presented in Ref.The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange.[19] Ash from volcanic eruptions, trapped within the troposphere, tends to mute sunset and sunrise colors, while volcanic ejecta that is instead lofted into the stratosphere (as thin clouds of tiny sulfuric acid droplets), can yield beautiful post-sunset colors called afterglows and pre-sunrise glows.A number of eruptions, including those of Mount Pinatubo in 1991 and Krakatoa in 1883, have produced sufficiently high stratus clouds containing sulfuric acid to yield remarkable sunset afterglows (and pre-sunrise glows) around the world.Depending on weather conditions and the types of clouds present, these colors have a wide spectrum, and can produce unusual results.[citation needed] In some languages, points of the compass bear names etymologically derived from words for sunrise and sunset.The word "levant", related e.g. to French "(se) lever" meaning "lift" or "rise" (and also to English "elevate"), is also used to describe the east.Instead, the air is full of red dust, blown into the atmosphere by high winds,[22] so its sky color is mainly determined by a Mie Scattering process, resulting in more blue hues than an Earth sunset.One study also reported that Martian dust high in the atmosphere can reflect sunlight up to two hours after the Sun has set, casting a diffuse glow across the surface of Mars.
Evening
twilight
in
Joshua Tree, California
, displaying the separation of yellow colors in the direction from the Sun below the
horizon
to the observer, and the blue components scattered from the surrounding sky