The first total solar eclipse in the contiguous United States since 1979 will sweep across the continent Aug. 21 and treat observers to one more example of the beauty God created on this special little planet. The eclipse will cut a 70-mile-wide path of totality, the region where the moon will completely block the sun.
For those fortunate enough to be in the path of totality, a swath that stretches from Oregon to South Carolina, the sun and moon will put on an especially spectacular show. As the moon moves in front of the sun, a narrow band of light around the dark silhouette of the moon will look almost like a beaded necklace due to the ragged terrain of the moon’s surface. When the moon slides directly in front of the sun, the beads will disappear until only one remains and the sun will look like a brilliantly shining diamond ring. Observers will see the diamond ring again when the moon slips away from the sun.
As the moon completely blocks the sun, stars will shine in the sky and several planets, including Saturn, Jupiter, Mars, Venus, and Mercury, should be noticeable.
But by far the most spectacular event during the eclipse will be the twisting, fiery ribbons of light emanating from the sun’s atmosphere. “It’s not just an amorphous glow,” Rick Fienberg, press officer for the American Astronomical Society, told Science.com. “It’s a tangle of streamers and jets and loops and twists and all kinds of stuff, because it’s controlled entirely by the sun’s magnetic field, which is very tangled and twisted.” These streamers are always present but typically the brightness of the sun’s central disc obscures them, he said.
Meanwhile, back on Earth, observers will witness other awe-inspiring phenomena. When the sun disappears behind the moon, the temperature suddenly drops by as much as 15 degrees, birds stop singing, and observers may see the moon’s shadow racing toward them like a dark cone or tornado. They may also see the shadow flee away when the moon uncovers the sun again.
The change in lighting will make shadows appear sharper, so much so that individual hairs on the heads and arms of observers may be apparent.
Some observers may also witness an unpredictable phenomenon called shadow bands, thin undulating lines of alternating light and dark that move in parallel on smooth, light-colored, uniform surfaces. Shadow bands appear for only a few seconds before totality. Scientists are unsure what causes them but believe they are related to turbulence in the Earth’s atmosphere.
And if cloud conditions are right, the sun may give observers a special treat—a 360-degree sunrise and sunset glow around the horizon.