Dust high in the atmosphere scatters light to the night side of the planet. Atmospheric conditions are best determined at the actual time and place of events. Within the s, 24-hour is encountered in , and twilight literally lasts for weeks in the polar fall and spring. The twilight phases in the morning are often called , while the twilight phases in the evening are referred to as. This is partially due to tactics dating back to the part of the of 1756—1763 , when combatants on both sides would launch attacks at nautical dawn or dusk. Within the , is encountered in summer, and in regions very close to the poles, twilight can last for weeks on the winter side of the. It was twilight by the time I got back home.
Evening civil twilight begins at and ends when the geometric center of the sun reaches 6° below the horizon. This is followed by a few days of nautical twilight as the Sun moves further up the sky. In the evening, it begins at sunset and ends when the Sun reaches 6 degrees below the horizon. This transition ends sometime in October when the Sun sinks more than 18 degrees below the horizon. The most noticeable of these events, and the most significant in regard to ordinary affairs, are the rising and setting of the Sun and Moon. There, small variations in atmospheric refraction can change the time of rise or set by many minutes, since the Sun and Moon intersect the horizon at a very shallow angle. It marks the beginning of nautical twilight.
Under good atmospheric conditions with the absence of other illumination, during nautical twilight, the human eye may distinguish general outlines of ground objects but cannot participate in detailed outdoor operations. During summer months at , there may be no distinction between astronomical twilight after sunset and astronomical twilight before sunrise. Twilight is produced by in the upper atmosphere, illuminating the lower atmosphere so that is neither completely lit nor completely dark. Because the Sun and Moon appear as circular disks and not as points of light, a definition of rise or set must be very specific because not all of either body is seen to rise or set at once. In the morning, civil twilight begins when the Sun is 6 degrees below the horizon and ends at sunrise.
In Europe, it covers much of central. Thus, even under ideal conditions e. The 50-arcminute geometric depression of the Sun's center used for the computations is obtained by adding the average apparent radius of the Sun 16 arcminutes to the average amount of atmospheric refraction at the horizon 34 arcminutes. Often confused with , twilight is specifically defined as the period before or after -time during which it is possible to conduct outdoor activities without the aid of artificial light. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Nautical Twilight, Dawn, and Dusk Nautical twilight occurs when the geometrical center of the Sun is between 6 degrees and 12 degrees below the horizon.
Astronomical twilight can last all night for several weeks as far from the poles as 48. Civil twilight occurs when the Sun is less than 6 degrees below the horizon. As the Earth's atmosphere scatters and reflects much of the Sun's rays, coloring the sky bright yellow and orange, artificial lighting is generally not required in clear weather conditions to carry out most outdoor activities. Morning twilight is when morning prayers are done, while evening twilight is the time for evening prayers. Some outdoor activities may be conducted without artificial illumination during these intervals, and it is useful to have some means to set limits beyond which a certain activity should be assisted by artificial lighting. Created by Rod in 1959. The lowest latitudes at which the various twilights can continue through local midnight are approximately 60.
The sky can take on spectacular colors during the period of twilight. This is because at low latitudes the sun's apparent movement is perpendicular to the observer's horizon. This angle causes a short daily period of astronomical, nautical, or civil twilight, a temporary break from the complete and permanent darkness that envelops polar regions in the winter. How do people think this is okay? North Pole has the experience of this from November 12 to January 30. The time of the day when the sun is just below the horizon, especially the period between sunset and dark. By early March, astronomical twilight becomes visible to observers on the North Pole.
The word twilight is also used to denote the periods of time when this illumination occurs. It was twilight by the time I got back home. Transit: The transit time of a celestial body refers to the instant that its center crosses an imaginary line in the sky - the observer's meridian - running from north to south. The only permanent settlement to experience this condition is , Canada, where it occurs for a week in late February, and again in late October. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. An american mini serie dedicated to strange phenomenon and bizzare events. Sunrise and sunset conventionally refer to the times when the upper edge of the disk of the Sun is on the horizon.
However, in locations around the poles that experience during the winter months, the Sun may reach an angle of less than 18° below the horizon around. Astronomical Twilight, Dawn, and Dusk Astronomical twilight occurs when the Sun is between 12 degrees and 18 degrees below the horizon. That is, the center of the Sun is geometrically 50 arcminutes below a horizontal plane. Before this time, the sky is absolutely dark. The February Full Moon is named after the snow on the ground.