Answers to 8 Questions About the August 2017 Solar Eclipse
It’s August and one of the most highly-anticipated astronomical events of the 21st century is nearly upon us: the August 21 solar eclipse, which will be visible as a total eclipse literally across the entire United States…but that doesn’t mean everywhere in the United States. Totality will pass across the U.S. in a narrow band about 60 miles wide starting along the northern coast of Oregon at 10:18 a.m. local time (PDT) and ending along the coast of South Carolina at 2:48 p.m. EDT. But that’s just totality—the full eclipse event will actually begin much earlier than that and end later, and its visibility won’t be limited to only that path. And while it’ll be happening overhead in the daytime sky you’ll need the right equipment to view it safely, whether you’re in totality or not.
Wait, you say, what’s the difference between totality and…not totality? And how is it caused? And why is this a big deal at all? If you’re wondering those things (and perhaps others) then this post is just for you. Below are answers to some common—and certainly not dumb—questions about the solar eclipse, brought to you by yours truly (with a little help from NASA and other eclipse specialists.)
What is even happening?
In a nutshell, on August 21, 2017, the Moon will pass in front of the Sun during its orbit around Earth. The angles will line up just right so that the Moon’s shadow lands on the Earth, and this time the continental United States just happens to be right in the path of where the deepest part of that shadow—the umbra—will fall.
Because our Moon is decently-sized (as moons go) it’s large enough to fully cover the disk of the Sun in the sky, even from 230,000 miles away…but only juuuust barely. This means that for some places in the U.S. the Sun will be totally covered for a brief period—like a minute or two—but for many other places totality won’t be achieved because of viewing angles. It’s like a group of friends trying to watch a movie and someone with a big head sits right in front of one of them. That person’s view of the screen will be blocked, but those to the right or left of them will have better views. In the case of the eclipse, those north and south of the path of totality will see a partial eclipse (but still a really good one!)
Watch a video of how eclipses occur below:
What will I see?
Weather permitting (yes your eclipse could very well be ruined by clouds—hopefully not) the first thing you’ll notice is a small “bite” being taken out of the Sun. This is the Moon moving into position (yes, you are watching the Moon moving!) Because the Sun is so bright compared to the Moon—and that it’s technically a new Moon phase anyway, which means the Moon’s unlit night side (but not the far side) is fully facing Earth—you can’t see the Moon itself before the eclipse starts or even during the partial phases. At this point you’re inside the Moon’s penumbra, or the outer part of its shadow. It’s still bright as day, but the Sun is gradually being covered.
NOTE: It is not safe to watch this part of the eclipse without proper eyewear or some sort of projection viewing device. The Sun is still very much bright enough to permanently damage your eyes. Regular sunglasses—even polarized or multiple layered ones—are not sufficient.
If you are in the path of totality, you’re in for a treat! The Moon will eventually fully cover the Sun, and for that brief few moments the sky will go dark, the air temperature will noticeably cool (especially where conditions are clear, calm, and dry) and the Sun’s normally-hidden outer corona will become visible around the silhouetted disk of the Moon. This is the moment that eclipse-hunters around the world yearn for, one that awakens you to the grand clockwork of the Solar System and can supposedly even “change your outlook on life.” (I don’t know personally, this will be my first experience with totality myself!)
According to Rice University space scientist Patricia Reiff, who has witnessed dozens of eclipses around the world: “Totality (when the sun is completely obscured) is a full-body experience. Although there are many excellent photos of totality, seeing it for yourself is much more dramatic. As totality approaches, the sky gets darker. It’s really hard to notice the difference until the sun is 90 percent covered. Then you notice the sky seems gray, not blue, and the shadows all seem very sharp. Birds may start to roost. The temperature may fall by several degrees, and the wind may pick up. Street lights come on. It’s an eerie feeling, and for many, a spiritual experience. The eclipse looks huge in the sky, because the corona adds up to several times the sun’s diameter.” (Source)
This magical moment is fleeting, however, as the Moon just as quickly moves out of the way and then the eclipse in effect runs “in reverse.”
Isn’t it dangerous to look at an eclipse?
Bottom line: it’s always dangerous to gaze at the Sun without protection. During an eclipse is no different as far as what the Sun is doing is concerned (it’s still happily fusing hydrogen into helium, 93 million miles away) but people tend to think that because it’s getting darker, then it’s OK to look at the Sun longer and see what’s happening. This is wrong. Even with nearly all of the Sun blocked by the Moon there’s still enough UV radiation coming in to damage the sensitive tissues of your eyes—and, because it’s darker, your pupils will actively open up to let more of it in. You can’t see or feel UV so you don’t sense it and instinctively shut your eyes like you do with visible light from an unblocked Sun…UV radiation can just pour in and painlessly roast your retinas. So during an eclipse your eye safety is completely your responsibility—be smart and get a pair of ISO-certified safety glasses so you can watch without worry.
Also, be cautious of “knockoff” eclipse glasses that don’t actually provide adequate protection. If you can see anything other than the Sun through the lenses, they’re not dark enough!
(If you happen to enjoy welding as a hobby you can also use welding goggles, but with a shade rating of at least 14. NOTE: this previously said 3; that was incorrect.)
Also, never ever ever look at the Sun through conventional binoculars or a telescope without having protection on the primary lens first (i.e., don’t put the glasses on and then look through.) This can completely and permanently ruin your eyes, which isn’t worth any type of view.
During totality you CAN view the eclipse safely with the naked eye—in fact, you should! You won’t be able to see anything at all through safety glasses during totality anyway. But as soon as the Sun begins to reappear, you should put your glasses back on.
(This is, of course, only necessary for looking at the Sun and Moon. There’s nothing dangerous about the ambient outdoor lighting during an eclipse. If anything, be sure to explore that too—I hear it’s a unique sort of illumination that greatly enhances contrast and detail as if the world were being lit by a “ring light.”)
I won’t be in or near the “path of totality.” Will I see anything?
If you’re at all able to get into the totality area, I suggest giving it a shot. If it’s truly not possible (and many places are already booked up) then don’t worry—you will still see a partial eclipse! In fact ALL of the United States will see the eclipse, in some form if not in totality, as well as will Canada, Mexico, Central and parts of South America, and even parts of Europe and the UK.
Partial eclipses are still very cool!
Fact: The longest duration of totality will be 2 minutes 44.3 seconds occurring south of Carbondale, Illinois. Explore an Interactive Map of the eclipse in the U.S. here
For an idea of where and when the eclipse will be visible, check out the maps below:
Is this a “once-in-a-lifetime” event?
Not at all—based on the average human lifespan, that is. While the last total solar eclipse visible in America was in 1979, and the last time one crossed the entire country was in 1919 (which had some major implications for physics in general) the next total solar eclipse for our country will happen on April 8, 2024…less than seven years from now. And then another one in 2045, and then four more after that.
Eclipses are fairly common events as astronomy goes, you just need to be in the right place to experience them. (They’re even seen from the Space Station!)
If the Moon is orbiting the Earth, why don’t we have total eclipses all the time?
This makes total sense and would be the case if the Earth, Moon, and Sun were all positioned along the same exact plane. But the Moon orbits at a bit of an angle to Earth—about five degrees—and that plane wobbles as well compared to our orientation around the Sun. So even though the Moon always casts a shadow when it’s between Earth and the Sun, that shadow doesn’t always fall onto Earth; five out of six times it misses. When it doesn’t, we get a solar eclipse somewhere on the planet.
Also the Moon isn’t always the same distance from Earth either, so if a solar eclipse happens when it’s more far than near we end up with an annular eclipse where otherwise it would have been total—a ring of Sun is still visible around the Moon. (Annular is from the Latin word for “ring.”) The May 2012 eclipse was annular (although I only saw it from a partial viewpoint.)
What’s the difference between a solar eclipse and a lunar eclipse?
A solar eclipse is when the Moon’s shadow falls onto the Earth; a lunar eclipse is when the Earth’s shadow falls onto the Moon (more accurately, the Moon is passing through Earth’s shadow.) Solar eclipses only happen at new Moon phases, lunar eclipses only occur during full Moons. As Earth’s shadow is much larger than the Moon’s, lunar eclipses are more common but can also be of the partial and total varieties depending on how deeply into the Earth’s shadow the Moon happens to pass.
They may lack the daytime drama of a total solar eclipse but they are beautiful to witness in their own right!
Will the eclipse make anything bad happen?
No. The eclipse itself has no direct effects on the Earth-Moon system other than changes in illumination. There’s no extra gravitational pull (other than what would normally occur during a new Moon) and no adverse effects on the power grid or behavior of satellites. People will need to stay safe by using eye protection when viewing the eclipse as well as keeping their wits about them while continuously gazing skyward amongst what will in many places be large crowds in unfamiliar outdoor environments. That’s not to mention the expected traffic congestion during travel to and from such places. But technically the eclipse itself is not hazardous. (It has been discovered that many species of wild animals and even insects exhibit behavior changes during total eclipses though…pack some extra bug spray!)
Planning on taking pictures? Share your photos of the eclipse in the NASA Flickr group!
Want to learn more about the August 21 eclipse? Visit NationalEclipse.com, GreatAmericanEclipse.com and NASA’s eclipse activity site here. And if you’re planning on traveling to witness the event on August 21, have a safe and happy shadow hunt!