On August 21, 2017 a total solar eclipse will be visible along a relatively narrow path of the United States, staring near Salem, Oregon and ending just north of Charleston, South Carolina. Along the way total eclipse will be visible from just south of St. Louis. Here’s a map:
While total solar eclipses are not all that rare – one is visible from somewhere on Earth about every 18 months – it is quite rare for a total solar eclipse to occur near your home (70% of the Earth is covered by ocean). A total solar eclipse will be visible from any specific location only about every 400 – 500 years. The last total solar eclipse visible to Americans outside of Hawaii occurred in 1979. And that was only visible to residents of Washington, Oregon, Idaho, Montana, and North Dakota. Everywhere else experienced a partial eclipse (I remember viewing it thru a pinhole viewer at school as a child). So, if you live anywhere near the path of this eclipse – it may be a once-in-lifetime experience to view it.
A total solar eclipse occurs when the moon passes in front of the sun so that it completely blocks out the sun. The diameter of the sun is about 400 times that of the moon, but the moon is about 400 times closer to the Earth than the sun. Thus, the moon occasionally is able to block out the sun and it’s quite the sight.
Here is a description from Space.com describing what you can expect to see: “During a total solar eclipse, the moon casts its umbra upon Earth’s surface; that shadow can sweep a third of the way around the planet in just a few hours. Those who are fortunate enough to be positioned in the direct path of the umbra will see the sun’s disk diminish into a crescent as the moon’s dark shadow rushes toward them across the landscape. During the brief period of totality, when the sun is completely covered, the beautiful corona — the tenuous outer atmosphere of the sun — is revealed.”
Here’s a great site from NASA all about the 2017 Solar Eclipse: https://eclipse2017.nasa.gov/
If you plan on viewing the eclipse, please note all the safety precautions recommended by NASA.
Finally, here’s a map from NASA of the eclipse’s path across Missouri (the NASA site has ones for all the states that are affected):