Total Solar Eclipse, 2017

Ηλιακή έκλειψη | Total solar eclipse | summa defectionem solis

On 21 August 2017, Columbia, SC, will experience a total solar eclipse that will last about two and a half minutes. A solar eclipse occurs when the Moon passes between the Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon’s apparent diameter is larger than the Sun’s, thereby occulting the Sun and blocking all direct sunlight, obscuring daylight, and shrouding the affected area in darkness. Totality occurs in a narrow path across the Earth’s surface, with a corresponding partial solar eclipse visible over a surrounding region thousands of kilometers wide. The narrow path of totality occurs within the umbra (Latin for “shadow”), which is the innermost and darkest part of a shadow, where the light is completely blocked by the Moon’s occulting of the Sun. Neighboring areas will experience a partial eclipse due to their falling under the penumbra (from the Latin paene “almost, nearly”), the region in which only a portion of the Sun’s light is obscured by the Moon. During the period of totality, the corona (Latin for “crown”), the Sun’s outer atmosphere of plasma, will be visible with the naked eye.

Columbia, SC, will experience the longest total solar eclipse for a metro area on the East Coast, with 2 minutes and 36 seconds of darkness in the middle of the afternoon. This will be the first transcontinental total solar eclipse to cross the United States in 99 years (the last one crossed the U.S. in 1918 and the last visible eclipse in the U.S. occurred in 1979). There are many city-wide events planned from Friday, August 18th, through Monday, August 21st, the day of the eclipse. The Irvin Department of Rare Books and Special Collections will have highlights from the Robert B. Ariail Collection of Historical Astronomy on display throughout the month of August, with extended hours during eclipse weekend. The partial eclipse will begin around 1:13 pm, on August 21, 2017, and totality will last from about 2:41-2:44 pm; afterward, the Moon will begin to move out from the path of sunlight, with the Sun fully emerging around 4:06 pm.

A total solar eclipse is a rare natural phenomena to witness and has a variety of effects. While solar eclipses occur about every year and a half, given the narrow width of the Moon’s umbra, a total solar eclipse is visible in a given spot only about once in every few hundred years. During totality, the sky will go completely dark, the temperature will drop a few degrees, diurnal animals will be confused while nocturnal animals may wakeup as if it were night, and a variety of optical phenomena that are otherwise obscured by sunlight will become visible. Those who have experienced a total solar eclipse report that it is an awe inspiring spectacle and an emotionally overwhelming experience not to be missed. It is the Irvin Department’s pleasure to be able to share our rich holdings in the history of natural science and astronomy during this astonishing event, and we hope that all who come to visit the collections will find the books on display as inspiring as the eclipse itself.