Preparing for the August 2017 Total Solar Eclipse

Scientists from NASA, the University of Texas Arlington and the University of Hawaii presented an overview of the 2017 total solar eclipse at the American Geophysical Union’s Fall Meeting in San Francisco on Dec.14, 2016. They discussed the geometry of eclipses, eclipse science now and throughout the ages, and how to safely view next year’s solar eclipse.A view of the United States during the total solar eclipse of Aug. 21, 2017, showing the umbra (black oval), penumbra (concentric shaded ovals) and path of totality (red). This version includes images of the sun, showing its appearance in a number of locations, each oriented to the local horizon.

Credits: NASA/Goddard Space Flight Center Scientific Visualization StudioSolar eclipses occur when the moon blocks any part of the sun. Total solar eclipses, however, are only possible on Earth because of a cosmic quirk of geometry: The sun’s diameter is 400 times wider than the moon’s, but it is also 400 times farther away. The result is that the sun and the moon appear to be the same size from our perspective. When they line up just right, the moon can obscure the sun’s entire surface, creating a total solar eclipse. This line-up occurs once every 12 to 18 months. Partial solar eclipses, on the other hand, occur when the alignment is such that the moon blocks only part of the sun, and these can occur more frequently.

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