# Is there a way to create an artificial solar eclipse?

I heard this story, where they celebrated the birthday of the now defunct North Korean dictator Kim Il-sung in the 1970s and as a birthday present they created through some very complex artillery maneuvers an artificial total solar eclipse over Pyongyang. At that very moment, the dictator stepped out of his palace, in front of the crowd in a suit covered with reflecting material and had giant reflectors directed at him, so he practically 'outshone' the sun... While this seems plausible in view of the megalomania and extreme personality cult we all know about, I still wonder whether that is technically feasible. (I'm not looking for an answer whether the story is true or not.)

So my question is whether there is any possibility to have an artificial, man-made total solar eclipse and if so, how?

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There's a total eclipse of the Sun every night. – Keith Thompson May 21 '12 at 2:54
In a way, that's how a coronagraph works. – biziclop Oct 27 '14 at 23:05

It would be very hard to reduce the sense of daylight at the Earths surface as light reaching any point could have been scattered bby the atmosphere over a large angle. This rules out just covering the couple of square degrees the sun extends over.

Solar eclipses get much darker because the light is blocked before it reaches our atmosphere and can not be scattered over a large angle. Even on a cloudy day look up and see how uniform the illumination appears practically from horizon to horizon...

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I think you are confusing Kim Jong-il and Pyongyang with C. Montgomery Burns and Springfield. Apart from that, your recollection is correct.

In fact, the sun is extremely large and it would take an object the size of the moon to totally block out its light. This is what happens during a real solar eclipse.

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+1 LOOOOOOOL :D – Count Zero Jan 7 '12 at 20:07
This is a gem, but unfortunately falls short of providing an actual answer; it would be awesome if you could expand your input to provide one in order to aid this post's longevity. – Grant Thomas Jan 7 '12 at 21:38
@Mr.Disappointment: I'd love to keep it! I shared a link to this on another SE site. I was also looking for some info on the historical background of the story... But it seems it's just an invention. :) – Count Zero Jan 7 '12 at 23:13
I've added a brief, but hopefully illuminating, explanation of why this is infeasible in practice. – RoundTower Jan 8 '12 at 1:00
"it would take an object the size of the moon to totally block out its light" is not entirely true. At the distance of the moon, it would indeed take an object the moons size. At half the distance, it would take half the size object (in diameter). If the blocking object is extremely close to the earth's surface, It would need to be much smaller. A large dense cloud can often block the sun completely. However atmosphere scattering would probably not make it completely dark. – Jus12 Jan 13 '12 at 9:15

In order to get anything remotely appearing like an eclipse, it would need to be above the atmosphere, in order to darken the sky. According to the wikipedia article:

At the altitude of the International Space Station, for example, an object would need to be about 3.35 km (2.08 mi) across to blot the Sun out entirely.

And while that would technically be an eclipse, and the corona of the sun would probably be visible, it's only really going to have a small part of the effect. Essentially, the entire horizon would need to be covered. I don't have an exact number, but let's just say that 50 miles would be required. Essentially, take that 2 mile disc from the previous point, and add it all the way around. A 50 mile disc in orbit at the altitude of the ISS should provide a 1 second eclipse for someone on the ground, if they know exactly where to look for it;-)

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Yes, it could be made out of aluminum foil or something quite light. – anna v May 21 '12 at 4:07
Good try, but such an object in the space station's orbit would be moving pretty fast so the eclipse wouldn't last long. I guess you could make a retrograde orbit that would roughly stay under the sun, and it would have to have sufficient inclination to bring it up to the latitude of Pyongyang. That would be quite a project. – Mike Dunlavey May 21 '12 at 4:40
@MikeDunlavey: The point is, it could be done. It might take a huge solar sail type device, but... I'll give you, the speed would be extremely quick, so... – PearsonArtPhoto May 21 '12 at 4:44
Re At the altitude of the International Space Station, for example, an object would need to be about 3.35 km (2.08 mi) across to blot the Sun out entirely. That's wikipedia for ya'. Pile o' excrement! What does altitude have to do with it? The answer is, absolutely nothing. The ISS is the same distance from the Sun as am I on the surface of the Earth. The size of a disc needed to block the Sun depends on the size of the observer and on the distance between the disc and the observer versus the distance between the Sun and the observer. – David Hammen Oct 27 '14 at 23:15
The altitude is the distance from the observer, that's what. For an eclipse to happen, the object in orbit would have to be directly overhead, and that distance happens to be the altitude. – PearsonArtPhoto Oct 27 '14 at 23:17

It wouldn't be practical to create a big enough 'object' to occlude the Sun over any very big area.

So I would suspect either:

1) It was very localized. E.g. only positioned correctly for viewers right in front of the palace, say using a balloon.

2) Maybe they just filled sky with smoke/vapor. This wouldn't be much of an 'eclipse' in the sense intended, but the effect would be close enough for the uneducated. This might work over a somewhat bigger area.

3) The entire story is apocryphal.

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Re Idea 2: This is North Korea we're talking about, after all. – Andrew Jan 7 '12 at 17:48

It depends on how realistic solar eclipse do you want. Solar eclipses have two important characteristics:

• Naked eye visibility of the solar corona.
• Darkness.

To have darkness like the real thing you would need a shadow that's as large as the Moon's umbra during a total ecipse, that's hundreds of kilometers, that would need to be a huge object. That's isn't practical I think.

The naked eye visibility of the corona probably easier. In order to see the corona somehow we need to get rid of the forward scattered light. The moon does it by simply have a large shadow so the whole atmosphere is under the umbra so there is no forward scattered light.

I think the same idea can be done in small. Just have an umbra large enough to provide just a little view around the sun without forward scattered light, in this case we have a geometry like this:

There $\alpha$ is the angular radius of the sun, which is roughly $0.25$ degrees.

The $\beta$ is the desired angular radius of the area of dakness where we would like to observe the corona. Let's say it's $0.5$ degrees.

The $h$ is the height of the atmosphere where scattering becomes negligible so the sky is totally dark. I don't know exact numbers here. I only have an educated guess.

One is from the many pictures or videos taken from high altitude balloons that reach 30km altitude regularly an example of such view is:

But I'm not sure if it's really that dark or just the white balance.

Another guess comes from making a calculation based on twilight brightness. After sunset, higher and higher layers of the atmosphere scatter the light until there is completely dark. From wikipedia:

Evening nautical twilight is defined to begin at sunset and end when the center of the sun is 12 degrees below the horizon. In general, nautical twilight ends when navigation via the horizon at sea is no longer possible.

So we need to calculate $h$ when we put 12 degrees in into $\alpha$ at the center of Earth.

I did the math and got roughly 35km. ($\sqrt{R^2 + (R \mathrm{tan}(\alpha/2))^2} - R$)

So I think setting $h$ to 30km is reasonable.

But in order avoid the shading object itself blocking the view of the corona we need to send it even higher, so it appears smaller. The highest altitude a balloon ever reached is above 50km. So we can fix it at 50km altitude for example.

Now let's see the numbers.

At 30km a circular disk that have 0.5° apparent radius from the ground have 262m radius (30*tan(0.5°)). Considering the angular size of sun, at 50km high we would need a sphere that has 349m radius (0.262+(50-30)*tan(0.25°)) to cast 262m radius shadow at the 30km level. So a really large balloon would probably do it.

A sperical balloon with 349m radius would have 178 millions of cubic meter capacity, which is 200 times more that was used in Felix Baumgartner's jump.

It would have an umbra on the ground with a radius of 131m (0.349-50*tan(0.25°)). And a penumbra with a radius of 567m (0.349+50*tan(0.25°)).

It's apparent size would be a circle with an angular radius of 0.4°. So it would still block most of the view, but the dark patch will always extend beyond the apparent view so at near the end of the totality we may have a better view of the corona.

Although there are still some problems:

• Scattered light from the environment. The shadow tube might not be dark enough after all. When the sun sets at west the shadow of earth rises at the east. It's dark but it's not completely black even if it's a shadow going through the entire atmosphere. But it will probably be dark enough to reveal the corona.

• The balloon must be made of a very opaque or a very reflective material, so it appears truly dark for the shadow side. Or must be simply thick enough.

• My calculations are for the case when the sun is at the zenith. When it's not then we would need an even larger ballon.

So apart from the enormous ballon we would need it seems to entirely possible to make naked eye visibility of the corona from the ground with a shading object.

For scientific purposes it's much easier to bring a coronagraph satellite like SOHO into the space, or using polarizers and image processing in a ground based coronagraph.

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## protected by Qmechanic♦Oct 27 '14 at 23:06

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