On Monday August 21, 2017, the heavens will declare the glory of physics as the Moon passes in front of the Sun creating a total solar eclipse. The Moon will block out the incredibly bright light of the surface of the Sun, revealing one of the most amazing sights in all of nature - the delicate and subtle solar corona, the Sun's outer atmosphere. The Moon will appear as a black disk in the center of the corona, a vision that has been described as "the Eye of God."
About the Eclipse
The solar corona is about 1 million times fainter than the Sun's photosphere, its normally visible surface. This is why the corona is normally invisible - it is lost in the blinding glare of the Sun's brilliance. But during totality, the Moon covers up all of the Sun's photosphere, and the corona becomes visible. The corona is about as bright as the full Moon and is safe to look when the Sun is completely covered by the Moon.
Just as you see your shadow on the ground on a clear sunny day because your body is blocking the Sun's light, the Moon casts a shadow when it blocks the Sun's light. It is this shadow of the Moon that you are standing in during a total solar eclipse.
The Path of Totality
This shadow, called the "umbra", is very small where it lands on the face of the Earth. For this eclipse, it is only 60 to 70 miles wide. To see a total eclipse you have to be located in the "path of totality" where the umbra falls. If you are just outside of this path, you will not see a total eclipse at all, you will only see a partial eclipse. You may think "how much of a difference could that make?" Well, all of the difference in the world. The difference between saying "shrug," and screaming "OH MY GOD!"
Here is the first critical thing you need to know - you absolutely must be within the path of totality to see the corona, prominences and chromosphere. Xavier Jubier's 2017 Eclipse Path of Totality Google Map overlay with local circumstances is the perfect tool to find a place to see the eclipse in the path of totality.