The Washington Post

Q&A: Have any last-minute eclipse questions for a NASA expert?

Aug 15, 2017

Washington Post reporter Joel Achenbach is online with Ryan Milligan, a solar physicist with NASA, to answer all your questions about the eclipse.

Want to read more? Catch up on our latest eclipse coverage:

- A total solar eclipse is happening Aug. 21, and here’s what you need to know

- Here’s every total solar eclipse happening in your lifetime. Is this year your best chance?

- You'll need special glasses to see the solar eclipse. Here's where to get them free.

We're about to get started here, we've already got lots of good questions lined up and we are so lucky to have a solar physicist, Dr. Ryan Milligan, here to answer all our eclipse questions. Important Rule: THERE ARE NO DUMB QUESTIONS. For example I am very curious about what the sun is, exactly, and why it doesn't burn up so quickly. I will post some of my questions as we go along.

How often do solar eclipses happen, and why are they so important to the scientific community?

They happen - on average - every 18 months. They are scientifically important as they allow us to see the lowest parts of the solar corona, where we believe the solar wind and solar storms get accelerated. Our current technology can't yet replicate what nature allows us to see during an eclipse.

Yes, I know it probably matters for a scientist, but my question is how much does it matter whether I get through the crowds to a place where the duration of totality is two minutes vs. one minute? I am trying to move the last 30 miles to Madras, OR, on the day before the eclipse.

Duration is everything. You will want this to last for as long as possible. Your heart will sink once it's over and you will wish it could have lasted just a few seconds more. Also, the closer you are to the central line, the darker and more dramatic it will be as well.

Is it worth buying special sunglasses to view the eclipse in the D.C. area (since its partial will there be anything to view)? How can we make sure of the quality? I see a wide range of pricing from $1 to $100. Do you have any recommendations?

From DC, a maximum of about 82% of the sun will be covered at around 2:30pm. You won't notice anything is happening without some kind of approved eye protection. I have been handing out pairs for free, but I wouldn't spend anymore than $1-2 on a pair if you find some. You can check the ISO number against those listed on the NASA Eclipse2017 website.

I am going to Nashville for the eclipse, but am now concerned that traffic is going to make it difficult to leave the city. How can I find out if they're making precautions to stop streetlights etc from coming on during totality?

I think traffic is going to be an issue across the country, and worse in the big cities. Be prepared to wait a few hours, or even an extra day, until traffic clears. And each town/city will be making their own arrangements on automatic street lighting. You would need to check with local officials.

I am supposed to be driving from South Dakota to Kansas on the day of the eclipse. Should I be concerned about the eclipse occurring while I'm driving in or near its path? Should I be stopping somewhere and waiting for it to pass? What should I be doing?

I suggest getting out of the car and witnessing the astronomical event of the decade. But that's just me.

You could use the 2 minutes of darkness to take a power nap.

Is there a safe, affordable way to make "eclipse glasses" at home?

No! Please don't even try. You can try to make a pinhole projector using a cereal box (instructions on NASA Eclipse 2017 website) which will do a similar job. Proper approved glasses should be free or $1 if you can find an approved distributor.

Anyplace in the DC area where I can still get (legitimate) eclipse glasses? Or, have I procrastinated long enough that I'll have to watch on TV or online?

I heard that Warby Parker stores are handing them out for free.

Is looking at the sun more dangerous during an eclipse, or is the danger the same?

It's never safe to stare at the sun. It's just that people are more inclined to do so during an eclipse to see the moon cover it up. Only use safe approved methods to view the eclipse.

DO NOT STARE AT THE SUN. Except if the sun is completely not there anymore because of aforementioned eclipse. Which lasts 2 minutes. As has been duly noted.

This whole focus on the corona is going to be a huge boost for a certain brand of beer, is my guess. Question for Ryan: Why can't modern technology create the equivalent of a moon-disk to block out the sun's light? Like, a starshade? A whatchamacall? An occulting disk. There's a word for one of those things. It's like a thumb held at arm's length to block the light. Why doesn't that work?


Yes we currently use occulting disks on some of our satellites to recreate an eclipse. The problem is the way the sunlight 'bends' around the disk, which causes aberrations and dispersion patterns in the images. New ideas have been proposed to use spherical occulters in the future, much more like the moon, to allow us to see lower in the corona.

Gonna brag all over the newsroom about getting "occulting disk" right.

Hello! Is it totally, completely, 100 percent safe to remove protective glasses during the two minute or less totality? And how do we know when the totality is complete-- should we time it on our watches? Thanks!

Completely safe! But only once the Sun has been completely covered by the moon. You will know to put your glasses back on when you see the second diamond ring at third contact.

If I am at the beach during the eclipse (I live in the Boston area, so it will only be partial for me), do I need to be worried about the reflection of the sun on the water during the eclipse if I am NOT looking directly at the sun? For example, if the sun is behind me, can I safely look out at the water (where sunlight will be reflected) without wearing special eclipse-viewing glasses?

No, that should be perfectly fine. Just like any other day at the beach. :-)

Even within the Path of Totality is there an even More Bodacious Path of Totality, like the Ultimate Path, the Central-most Amazingest Path of Mega-totality? I ask this as someone who is also going to be in Oregon covering this for the WaPo.


Anyone within the Path of Totality will be able to see the spectacular solar corona. The question is, for how long. The closer you are to the middle of the path, the longer totality will last. It will also get darker than it would if you were on the edge of the path. Although there are a breed of eclipse chasers called 'Edge Chasers' who deliberately watch from the edge as Bailey's Beads are even more pronounced.

Where will be a good location to watch eclipse from National Mall. I work near Air&Space

Air & Space is always a good place! :-) But any place in DC is as good as any other place. If you have clear skies above you, and have a safe method to view the partial eclipse, then you're all set.

Can you tell me where to buy the correct type of glasses for viewing the eclipse? I don't want to buy something off the internet which isn't safe. Thanks very much.

Warby Parker stores in DC are handing them out for free apparently.

I bought the solar eclipse glasses and plan on using them, but I seriously don't get the blindness risk. I can stare at the sun now for 2 straight minutes. It makes me squint, but it doesn't make me blind. Why is looking at the sun during an eclipse different?


We were planning on driving from Milwaukee to some no-name town off of some no-name highway in Missouri that is located in the path of totality. At the proper time, we plan to just pull off to the side, get out of our car (safely), and watch from the side of the road. Any flaws in our plan?

The flaw is that you won't be able to find that no-name town on your map. On account of it lacks a name.

NASM downtown gift shot was out of eclipse glasses at 11:30. Woman sent me to IMAX and they still had some 15 minutes ago. Free...

Thank you.

Ryan, we always hear that the corona is a million degrees, or something like that. But what IS it, exactly? The sun's atmosphere? It is gaseous or is it a plasma and remind us what a plasma is, exactly? Fourth state of matter. Discuss. And why does it get so hot? Shouldn't it be cold, being further out in space, where it's cold? Why doesn't the corona cool down? Help.

Yes, the corona is the Sun's outer atmosphere. It's where the Sun's magnetic field dominates the plasma. Plasma is just a gas that has been heated so that the electrons are no longer bound to the atoms. So what we see during an eclipse is this superhot gas tracing out the magnetic field lines from the Sun. Kind of similar to how the aurora occur here on earth. Exactly why is gets so hot is still not fully understood, and is something this eclipse may help us answer.

It is a bit difficult to envision the mechanics but is it possible that somewhere over the Pacific the sun will rise in full eclipse?

Absolutely! And it will end with a sunset eclipse somewhere over the Atlantic.

So cool! I wanna see the ring of fire setting into the ocean, and the resulting steam rising explosively.

I haven't made plans yet and only now realized I'm missing a big deal. New Jersey-based, modest income. Best ideas to still catch totality?

Bummer. NJ is not really close to eclipse this time. There's another total eclipse in South America in 2019, and then there's one in the USA in something like 2024. As I dimly recall.

I live in Atlanta where we are expecting 97% coverage. I can't get away to drive where it'll be total. What can we expect here?

At 97% you should experience some change in the light. It won't go dark, but you will definitely feel some kind of change, albeit slight. It will feel almost eerie. This only happens above around 95% coverage.

Remind us what those are. So the really cool people are Edge Chasers? Where do you watch your eclipses? Where will you be on Aug. 21? Aren't the solar physicists all meeting in Portland that week?

Bailey's Beads are the last chinks of sunlight shining through the valleys in the lunar surface. It looks almost like a string of pearls. Yes, there is a meeting in Portland that week, but I'm skipping it to go to Alliance, NE to view the eclipse. All my eclipse trips are my vacations, and this one is no different. I don't want to be distracted by "work". :-)

Oh that's genius: You actually get to enjoy the eclipse! You don't have to, for example (and this is just a hypothetical that springs to mind) spend the entire time trying to document OTHER people enjoying the eclipse and hoping you can file in a timely manner to the Live Blog.

What's the best place to find estimates of how bad traffic will be? We're driving from Portland, Ore. to Madras on Sunday and returning Monday. I'm hoping we are not stuck in traffic for three days, like the folks at Woodstock.

You should email me at the WaPo and I'll give you a traffic report. I'm told that the traffic jams will be apocalyptic, but there are always such fears in advance of big events. So we'll just have to see. You might want to go a bit earlier than planned.

I'm having a hard time picturing why the timing of the eclipse starts on the west coast and moves to the east coast when the sun moves the other direction: from east to west. Any good graphics out there to help me out?

My colleague Sarah Kaplan answered this in our last eclipse chat:

The gist of it is, the moon orbits the Earth. It's not a static thing. So, yeah, the Earth spins on its axis and the moon and sun rise in the East, but the moon has its own agenda, and is orbiting the Earth in the same direction as the Earth is turning. And then geometry happens and there you go.


I have heard that there might be "eclipse fog" that rises above a lake during totality. True?

I don't recall hearing about 'eclipse fog', but eclipses do cause a drop in temperature, which can cause clouds to form along mountain ranges. That's why I'm watching from the plains this time around.

I'll be somewhere with 97% coverage. So should I be staring at the sky for 2 hours during the entirety of the event, or just the 2 minutes when it's 97% covered?

If possible, get yourself to the 100% line! 97% doesn't get you much. The light might change slightly but it won't go dark. The 2 minutes only applies to the 100% level. And don't stare up for the whole 2 hours. Just check in with the moon's progress every 10 minutes or so.

I'm going to Kearney NE but Post was saying might be cloudy. :(( If forecast isn't good the night before, any thoughts about what to do???

It's still a bit too early to start believing weather forecasts. By the weekend I'd start paying more attention. I'll be just west in Alliance, NE, and I'm prepared to move if things look cloudy on the day.

I think that could be a big story: Millions of people surging west or east to escape the clouds.

I have a Welding Helmet, can I use that to view the eclipse? If so, what darkness setting should it be on?

Admit it, you wear the Welding Helmet around town just for style points. You are wearing it now. At Whole Foods.

I'll be on a plane leaving Washington, Dulles at around 12:30 pm and heading to Denver. Will I end up missing this, or will I be able to catch some spectacular views?

That sounds like it might pass through the shadow during totality but I would check with the airline to be sure. And get a window seat. :-)

I am sure the pilot will let people come up front into the cockpit during the key moments.

I will be in the totality zone staying intending to view from Gallatin, but I'm prepared to chase clear skies if I can. Who will have the best real-time weather reports on-line on Aug. 21?

The National Weather Service and NOAA have a dedicated eclipse weather page. I would check there. Also check the incredibly useful eclipsophile site.

So in DC we shouldn't expect to experience anything too dramatic?

Unfortunately not. :-/

Other than the usual Plague of Toads

Should I be looking at the shadow racing toward me? Looking for the Diamond Ring? Seems tough to do both.

Seeing the shadow rushing towards you is tricky. I've only ever seen it once (my first ever eclipse) when I was up a mountain in Turkey with a stunning view. On the other hand, you can't miss the Diamond Ring (both of them, one at the start, one at the end of totality).

As a solar physicist, what are you most excited to see during this eclipse? What are the physics unknowns associated with this event?

Honestly? I'm mostly excited about seeing my friend's reactions who've never seen one. But also, the star Regulus is supposed to be particularly bright during this eclipse, and I've never seen a star shine through the corona before. That will be special.

One of the better star names.

Living near Seattle and planning to go to Madras, but I see there are brush fires that might obscure the area. What news are you getting and is there a good website to check it out before I leave?

This story in the Seattle Times doesn't have me worried much -- because wildfires are a given throughout the West and if there were to be a big blaze near Madras, the inability to see the eclipse may not be everyone's biggest problem. But right now doesn't look that bad to me.

With small children (3-5 years old) I have legitimate concerns that viewing would not be safe since I can give them explicit directions but they may not listen and look at the sun anyway. Will there be some sort of televised coverage they can safely enjoy - whether by NASA or reputable sources?

Agreed. And they may not appreciate what is happening anyway. If you do have glasses available, make sure they are supervised at all times while looking through them. Yes, NASA are doing a live broadcast, but there are other fun ways of enjoying the partial phase. Try using a kitchen colander to protect tiny pinhole eclipses on the ground, or look for crescents of sunlight coming through the gaps in the leaves in the trees.

How much would people in Tampa, Florida Would be able to experience this eclipse

I think Tampa will get about an 82% partial eclipse. Same as DC.

Why sneer at the question? No. 14 welding filters (the darkest) were recognized as safe viewing tools before people started selling "eclipse viewers," and the AAS says shades 12 through 14 are safe. So tell the guy to set it (I assume it's an electronic helmet) to 13 or 14. And some foresighted welding supply shops might still have some No. 14s. They sell for a couple bucks.

There's an answer!

NASA's official eclipse info mentions removing solar filters from telescopes and binoculars during totality. I asked a telescope shop staffer about this and he said you should have someone count down during totality, using a timer, replacing filters w/in 10 seconds or so of sunlight reappearing. Sounds dangerous. What do you think? (I'll be watching near Salem, Ore. -- expecting 1 minute, 58 seconds of totality.)

Telescopes and binoculars are fairly durable. But you won't seen anything through them if you leave the filters on (a mistake I made last year). Just give them a break from direct sunlight every now and again.

Thanks so much Ryan Milligan and thanks everyone for sending in so many good questions. Onward to the Great American Eclipse of 2017! We will  have lots of coverage here at the Post, with reporters and photographers and videographers all across the country, and possibly on the moon if not actually on the surface of the sun itself. Remember: Protect your eyes!

We still have a few minutes...send them in!

You should post some links for detailed information, including safe viewing tips. Two of the best are NASA and the American Astronomical Society:


In This Chat
Joel Achenbach
Joel Achenbach writes on science and politics for the Post's national desk. He has been a staff writer for The Washington Post since 1990, started the newsroom’s first online column, "Rough Draft," in 1999, and started’s first blog, Achenblog, in 2005.
Ryan Milligan
Dr. Ryan Milligan is a solar physicist who has been studying the solar corona and solar flares for 14 years. He currently holds the position of Ernest Rutherford Research Fellow at the University of Glasgow, Scotland, and he also receives funding from NASA to collaborate with colleagues at the Goddard Space Flight Center. He has seen 7 solar eclipses to date.
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