A few decades ago the Third World War destroyed Earth. Space infrastructure was considered a priority target by both sides. Orbital space was in the years before the war was filled with skyhooks, power satellites, zero-gee factories, several habitats, shipyards, and so on. The mass of the entire infrastructure within 1000 km above the surface was about 10^10 kg. The timeframe I'm interested in is the first few decades after things went down. I guess the whole thing would get worse over time as more collisions happen.

Since both sides feared that a single surviving enemy space station might be able to purge the remnants of their respective faction using its launch assist system (laser arrays, tethers, electromagnetic launchers), they pursued a policy of ensuring absolute overkill against any space structure. As further-out debris won't be visible from Earth, they are irrelevant for the purpose of this question. Concerning debris sizes, the largest ones will be a few dozen meters long. I suspect that a graph depicting the relationship between the number and size of debris will show a long tail distribution.

So what effects will this have, especially visual ones? (Spacetravel is kinda low on everyone's priority list.) I imagine that shooting stars would be the new normal and that especially the night sky would be filled with bright and fast-moving debris. Would the night sky become milky due to the high number of small particles? Additionally, the infrastructure would mostly have existed around the equatorial plane, so how would an observer's position on the planet change what they see?


2 Answers 2


Permanent skyglow

If Kessler syndrome does occur, most satellites in orbit would be properly shattered, which means that few, if any, would be seen with naked eye. Significant proportion of the mass would depart low Earth orbit and fall to Earth over few decades, however, there still be more than enough in orbit to cause visible effects.

Total mass of 10^10 kg is almost 3 orders of magnitude higher than the total estimated mass of satellites today (What is the total mass sent into orbit over all history?)

According to this source, today's satellites contribute at least 1.6 E-5 cd/m2 of luminance to the dark sky.

Assuming that satellites are fractured to an average 1/100 of their size, their total luminance should increase by the factor of 100, which, for today's satellites would give us 1.6 E-3 cd/m2.

Further assuming that future's satellites would be pulverized to the same sized debris, we arrive at about 1 cd/m2 skyglow - which would be at the peak of Kessler syndrome. Next assume that 50% of debris would deorbit in the next several years, and we arrive at 0.5 cd/m2 total average skyglow.

For a night sky, 0.5 cd/m2 is a lot. This is the luminosity at civil twilight, when sun is just set (or about to rise), when sky outshines full moon by far and people can do reading and writing almost comfortably. Observations of celestial objects at this stage is almost impossible - only brightest stars, planets and the Moon are visible in twilight.

This skyglow would not be uniform - it will be brightest towards the direction of the Sun and faintest in the direction opposite to it, in Earth's full shadow, or umbra.

  • $\begingroup$ So in the tropics it would gradually get darker until midnight, and gradually get lighter after that? Midnight would probably be quite a bit below the 0.5cd/m^2 but still above good dark-sky regions today, I think. $\endgroup$ Commented Apr 16, 2022 at 5:34
  • $\begingroup$ I feel like this (and the heat added by microbolides entering the atmosphere) could have negative effects on the earth's overall temperature - though as the frame challenge below suggests, probably nothing compared to the consequences of WWIII. $\endgroup$
    – jdunlop
    Commented Apr 16, 2022 at 7:35
  • $\begingroup$ @Kevin Kostlan - sort of. Today, in twilight time, you can notice that the sky above setting/rising Sun is quite bright, while on the opposite side of the horizon the sky is very dark. This effect will be much more pronounced - even long time after sun set, you will be able to track its position well below the horizon by observing moving skyglow. And yes, midnight in tropics will be relatively dark (but still much brighter that dark sky today). $\endgroup$
    – Alexander
    Commented Apr 16, 2022 at 8:51

(frame challenge)

Q: "A few decades ago the Third World War destroyed Earth"

You won't see it coming in, through the dust of nuclear winter

First, I wonder if your "debris storm" would last for decades. When debris reaches the upper atmosphere, it could take only a few weeks or months, to be decelerated and fall. Not years.

Second, we're talking about 10 million tons of space debris. Half of that would not reach the atmosphere (go into higher orbit) and only a small part would consist of material that can reach earth. When "the earth is destroyed" as you state, that destruction cannot be a result of 4-5 million tons of space debris penetrating Earth's atmosphere, let alone the small fraction of that debris large enough to cause damage on impact.

So I have to assume, because you say "the earth is destroyed" there would have been a nuclear war on the planet surface as well, resulting from nuclear attacks on cities. Such a war would cause a nuclear winter, with lots of dust blocking sunlight for years. The sky would look grey. The falling debris from space would not be visible at all.. and surprise the survivors with sudden havoc.

  • $\begingroup$ Interesting point, though if I remember correctly even the worst simulations show the soot would only last a few years, not decades. Even if that is enough to get an ice albedo feedback loop going, that prolonged the winter, the sky would be visiting. $\endgroup$ Commented Apr 16, 2022 at 5:15

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