On the 21st of August, 2017, there will be a Solar Eclipse. Along a swath of the US from the Pacific Northwest to the Southeast, the Eclipse will appear as "total," meaning that the sky will acutally go dark, during the day, for a couple of minutes as the Moon passes exactly between the Sun and the Earth, casting a shadow. (In other parts of the US, there will be "partial" eclipse, which is also impressive to watch with the right equipment.)
Two great tours have been made using WorldWide Telescope to explain the 2017 Eclipse.
...
Read more about 2017 Eclipse of the Sun