jeudi 16 mai 2013

General Information To Know About Sunsets

By Antoinette Quinn

Sunsets, also known as sundowns, describe the daily occurrence that is the Sun disappearing below the western horizon. This natural behavior is the result of a rotating Earth. Many people enjoy watching the star go down because of the beautiful atmosphere that is created, including the intense red and orange colors.

A sunset, in the field of astronomy, is known as the time when the edge of the Sun disappears below the line of horizon. The light that is given off from the star as it sets is distorted by the horizon because of what is known as atmospheric refraction. This makes it appear that sundown is occurring when in reality the disk has fallen below the horizon.

This is different from dusk, the time when the sky becomes completely dark. This occurs only after the star is more than 15 degrees below horizon. The time period between sundown and dusk is known as twilight. Certain areas near the Arctic Circle and Antarctic Circle do not experience sunrise or sunset at least once during the year. This is when polar night or polar day lasts for 24 hours.

Nicolaus Copernicus, an astronomer during the sixteenth century, was the first person to present the world with a mathematical model to support the truth that the Earth moves and the Sun does not. During his time, many believed that this large star moved. His model is still widely accepted in modern times.

The time for the Sun to go down will vary throughout the year. It is also based on the position of a viewer on Earth. That is, the elevation level, latitude and longitude of a particular location. Changes in sunset timing, whether small or noticeable, occur because the axial tilt of our planet, its revolution paired with the Moon, rotation and its orbital movement around the Sun.

During the spring and winter, days are longer and sundown occurs later each day until the last sunset, which occurs after the summer solstice. In the Northern Hemisphere, June or early July is when the latest sundown usually takes place. Rarely is it on the summer solstice, but it will vary based on latitude. Furthermore, the earliest of sunsets does not usually take place on the winter solstice but instead, two weeks earlier. Typically this takes place in late November or early December but is also based on latitude.

This same phenomenon takes place in the Southern Hemisphere, but the dates are reversed. The early sunsets occur before the summer solstice in winter and the latest of sunsets take place after the winter solstice in summer. Still, it all depends on the exact latitude.

Sunsets are known for the beautiful atmospheric changes they create. The intense colors in the sky, surrounding clouds and Sun make this natural occurrence a thing of marvel. The time and duration of sunsets is based on the longitude, latitude and elevation of a person. There are changes that occur over the course of a year because the movements, revolutions, rotation and tilt of planet Earth.

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