On August 21, 2017, people in a large swath of North America had the opportunity to view a total solar eclipse for the first time in nearly 40 years. How rare is a total solar eclipse? Let’s look at the facts.
How Often Does a Total Solar Eclipse Occur?
A total solar eclipse is visible from somewhere on Earth about every 18 months. However, many of these events can be seen only from remote locales where travel is difficult.
In terms of the United States, the August 21, 2017 total solar eclipse was the first to traverse the country in nearly a century. The last time a total solar eclipse occurred in the Lower 48 was 1979—and that was only visible from a few states in the Pacific Northwest. In comparison, the 2017 eclipse crossed the country from coast to coast.
The next time a total solar eclipse will traverse from coast to coast will be in 2045.
How About the Town Where You Live?
A better question is: How often is a total solar eclipse visible from any given location, such as the town where you live?
The answer is about once every 375 years, on average.
Every location, however, is different. By chance, some locations are treated to total solar eclipses only a few years apart.
- In the last 100 years, some areas have been in the paths of multiple eclipses: New England, for example, saw five.
- In New York City, the last total solar eclipse was in 1925.
- Chicago has not seen a total solar eclipse in the last 100 years.
- On the west coast, San Diego was last eclipsed in 1923.
- The city of Los Angeles is in the midst of a “dry spell” of more than 1,500 years without a total solar eclipse.
- The location with the longest dry spell is near Tucson; the last solar eclipse was in the year 797.
Total Solar Eclipse Path
While the 2017 Total Solar Eclipse did cross the entire United States, only viewers fortunate enough to be in the narrow Path of Totality saw a TOTAL eclipse.
The approximately 100-mile wide shadow of the Moon swept across the continent from Oregon (10:15 a.m.) to South Carolina (2:45 p.m.) and completely hid the Sun for more than two minutes.
Outside the Path of Totality, the rest of North America saw a PARTIAL eclipse. The Sun appears to have a dark shadow on only a small part of its surface. You might not even have even noticed this event.
NASA prepared an excellent Interactive Total Solar Eclipse Map displaying the Path of Totality as well as locations that will see partial eclipses. For a general idea of the eclipse’s path, see the simplified map, below.
Total Solar Eclipse Safety
The only time it is ever safe to look at the Sun with your “naked” eyes is during the brief minutes of totality, when the Moon has completely covered the Sun.
WARNING: NEVER LOOK AT THE SUN WITH YOUR UNPROTECTED EYES. NEVER LOOK AT THE SUN THROUGH AN UNMODIFIED TELESCOPE OR BINOCULARS—BOTH CAN RESULT IN PERMANENT EYE DAMAGE AND EVEN BLINDNESS.
How do you safely view an eclipse, then? Here are three ways, none costing more than a few dollars.
- Watch on the Web. Many web sites offer live coverage of eclipses. If it happens to be cloudy in your area during an eclipse, the web may be your only option.
- Use Eclipse Glasses. For direct viewing, consider getting a pair of inexpensive eclipse glasses, which are readily available across the internet.
- Build an Eclipse Viewer. Essentially a pinhole camera, it’s as simple as two pieces of cardboard and a small square of aluminum foil. See NASA’s guide: How to Make a Pinhole Camera.
Do not be tempted to use sunglasses. They will NOT protect your eyes enough! Read more about how to safely view a total solar eclipse without damaging your eyes.
Did you watch the 2017 total solar eclipse? Was it as magnificent as expected? Let us know your thoughts in the comments below!