The year has only just begun and yet people across the world are already gearing up for the biggest astronomical event to take place in North America in almost forty years. On Monday, August 21, 2017 a total solar eclipse will sweep across the United States, darkening skies from the West coast all the way to the East coast. Sky watchers, sun chasers, moon gazers, astronomers, and just about everyone else will turn their attention to the cosmos and get a chance to witness this rare and spectacular celestial event. The 2017 eclipse is already being called the “Great American Total Solar Eclipse” and many people are extremely excited for this one, some have even been waiting decades to see it.
If you want to get the most out of the mid-August eclipse, you’ll need to plan ahead first and know all about what to expect from the experience. During a total solar eclipse the moon appears to completely and totally cover the sun. With the sunlight blocked out, it’s prevented from reaching Earth, day suddenly turns into night and darkness falls upon parts of the planet. This occurs when the moon passes between the sun and Earth and like all solar eclipses, it must happen during a new moon. Furthermore, the alignment of the sun, moon, and Earth all must enter into syzergy, meaning they are in conjunction and aligned both straight and evenly. Because the moon’s orbit is slightly tilted and elliptical, rather than circular and on an even orbital plane to that of the Earth, its shadow at new moon almost always misses Earth.
However, when syzergy occurs and the new moon is at a place in its orbit where it’s close enough to appear just as large as the sun is, a total solar eclipse can occur. Yet even still, in order to view it here on Earth, a person needs to be at a location in what is called the path of totality. That is the area where the moon’s shadow tracks along on the Earth’s surface below as it sweeps across the sun. It’s also where viewing is the best and darkest because the sun is totally blocked out by the moon.
For this upcoming great American total solar eclipse the path of totality happens to pass beautifully across a number of states in a narrow arc which will be approximately 75 miles wide. It starts up on the Pacific Northwest coast of Oregon and travels over and down on a southeasterly bend crossing over parts of Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, North Carolina, and Georgia, before ending in South Carolina. According to Space.com skywatching columnist Joe Rao, approximately 12 million people live in the narrow path of totality and a further 220 million live within a one day drive of it.
Those who are lucky enough to experience the eclipse in the path of totality will have anywhere between a few seconds and 2 minutes and 44 seconds of it, which is the longest period of totality according to data provided by the US Naval Observatory on their official eclipse page. In case you’re wondering, the exact spot with the greatest duration is located somewhere within the Shawnee National Forest in Southern Illinois.