The last time a total solar eclipse was visible to most of the continental U.S., Richard Nixon was president and the Beatles had just released ‘Let It Be’ in the U.K. The 2017 total solar eclipse on Aug. 21 follows a long tradition of captivating people’s imaginations that’s been going on for thousands of years.
Oral and written histories tell us of fear and trepidation at the sight of a comet or meteor, while other cultures celebrated the same sight with dancing and feasts. But the disappearance of the sun or the moon -- an eclipse -- was an exceptional event.
People started paying more attention to the skies and created accurate calendars to both establish a coherent society and to organize the planting and harvesting of crops. By tracking the lunar and solar calendars they also began to predict eclipses.
But a total solar eclipse - like the one that will take place over the continental U.S. Aug. 21, 2017 - was very difficult for ancient people to predict. That’s because you can be just about anywhere on the side of the Earth facing the moon and still see a lunar eclipse, but for a solar eclipse you have to be in a very specific geographic location. It all has to do with the size of the shadow. According to NASA's website:
The diameter of Earth's shadow upon the moon is over 12,000 kilometers during a LUNAR eclipse. Compare this with the 300 km shadow of the moon on Earth during a SOLAR eclipses. This makes predicting lunar eclipses a forgiving enterprise even when you do not know the precise details of the moon's orbit.
In other words, you need to know precise details of the lunar orbit to predict where the moon’s shadow will fall across the Earth’s surface - where you would see a solar eclipse. Surviving written records suggest that only the ancient Chinese and Greeks managed this degree of accuracy.
“Solar eclipses happen just as frequently [as lunar eclipses] the only difference is the moon is between us and the sun, and the moon will cover some or all of the sun’s disk. And only those of you within the shadow can see the actual solar eclipse,” said Matt Benjamin, education program director at Fiske Planetarium.
“They do have this perception that they are more rare -- they happen just as often, it’s just that fewer people are in the path to see it.”
That’s what makes the 2017 total solar eclipse so special. A huge swath of the country -- including Colorado -- will be able to see it.
“It hasn't happened in 47 years,” Benjamin said. “This is likely a once in a generation astronomical event in the United States.”
With that in mind, here are his tips for the best view of this spectacular event.
Get to center line.
“Just 2 percent of the sun’s light is enough for you to not see the dramatic nature of a total solar eclipse,” Benjamin said.
Depending on where you are in the continental U.S., you could see anywhere from 30 to 100 percent totality -- how much of the sun will be obscured. Benjamin recommends viewing the eclipse from center line or umbra, a vantage point that changes as the moon’s shadow moves across the continent.
“You see streamers that seem to sort of emanate from the sun’s surface, animals will act strange because they are habituated to when it goes from morning to the evening,” he said. “ It is a very very strange phenomenon. Get to center line so you can see totality.”
You better hurry though, hotels in those areas are already booking up.
Wear eclipse glasses
No matter where you are viewing the eclipse, looking directly at the sun will harm your eyes.
“It is an absolute must to have eclipse glasses,” Benjamin said. “They’re like a thousand times darker than sunglasses, and they really help protect your eyes from the remaining light from the sun.”
You’ll also have a more nuanced view of the otherwise hidden solar corona (the sun’s outer atmosphere).
Where were you 47 years ago?
The last total solar eclipse to be viewed in the continental U.S. was in March 7, 1970. They don’t come around often. It’s a rare chance to connect with past peoples and cultures.
“It’s a really beautiful phenomenon that isn’t driving cultural change in modern society, but certainly did hundreds and thousands of years ago,” Benjamin said.