Every time I look at a picture that shows the amount of space junk I'm baffled. I can't for the life of me think how anything else being launch into orbit actually makes it without hitting anything else. As an example this picture https://www.nationalgeographic.com/science/article/space-junk says " The debris field shown in the image above is an artist's impression based on actual data". Actual data! Really? Am I missing something?


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    $\begingroup$ Embedded at the bottom of the image in question is the following disclaimer: "Note: Artist's Impression; size of debris exaggerated as compared to the Earth" $\endgroup$ Sep 15 at 19:14
  • $\begingroup$ I noticed that after an answer here mentioned it but that link is just an example. Several other links/pictures don't say anything. Thanks. $\endgroup$
    – Rodo
    Sep 15 at 20:16
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    $\begingroup$ If the junk is displayed to scale, you would need a computer screen several miles wide and tall, for even the ISS (the biggest thing out there) to display as a single pixel. For analogy of that orbital picture: Display a picture of NewYork city that fills your monitor, but rescale each car in it up to 1/4 inch length on the screen. It will appear...crowded, with about 5 million car showing. $\endgroup$
    – PcMan
    Sep 16 at 14:20
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    $\begingroup$ One satellite's solar arrays will not actually span the entire width of the Mediterranean Sea. That should be a big "not-to-scale" clue... $\endgroup$
    – J...
    Sep 16 at 17:51
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    $\begingroup$ Not completely related to your question, but something that helps get the scale of things in space: joshworth.com/dev/pixelspace/pixelspace_solarsystem.html $\endgroup$
    – Gimelist
    Sep 17 at 6:09

No, it's entirely unrealistic.

The Earth is very large by the standards of what you deal with in day to day life -- it's about 13 million meters in diameter.

Satellites are typically only a few meters across, and the additional debris bits can be much smaller.

The artist here is depicting satellites as being hundreds of thousands of meters in size.

There is a lot of debris, and it is a real problem, but the illustration is misleading, and contributes to a widespread misunderstanding of how big the Earth is.

(I remember as a child making a drawing of the entire world. It consisted of a circle with a 20 or 30 rectangles around the perimeter. The rectangles represented the driveways of all the houses; my understanding of the world was the houses on the street I lived on. Apparently some people's understanding doesn't progress much further than that.)

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    $\begingroup$ Pragmatically, were the 1m debris be 1 pixel in the image, the image would have to be 13 million pixels wide. Given that the biggest screens top out around 5 thousand... $\endgroup$
    – Cort Ammon
    Sep 16 at 3:58
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    $\begingroup$ +1 for the last sentence. $\endgroup$ Sep 16 at 7:01
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    $\begingroup$ Thankfully we have august institutions like the National Geographic Society to help us become more informed about the world we live in. /s $\endgroup$ Sep 16 at 12:36

The "actual data" is that for every one of their dots, there is probably a real debris fragment, the mix of satellites/rocket bodies etc is probably broadly right, and so on.

However, the picture is also labelled with "size of debris exaggerated as compared to the Earth".

If you look at those "satellites", each one is sized as though it were a few hundred kilometres across. In reality, they are a few metres - there is a massive size discrepancy. Space is much emptier than suggested here.


We cannot depict the space junk to scale.

Neither the human vision, nor modern imaging technology can have both Earth and whatever human-made orbiting object visible at the same scale, without having the small object reduced to profoundly sub-pixel size.

The space junk is not alone in this limitation. One can open e.g. FlightRadar24 with e.g. Europe on the full screen and see airplane icons almost covering densely-populated countries and stacking one over another around the major airports. In reality, at the same scale airplanes are much, much smaller than a pixel, this is why we use icons.

The space junk dots around the Earth on these impressive pictures are exactly icons. They represent the position of each object, but in no way its ability to collide with something else.

Up to now we have a history of only 2 events of unintentional collision between a man-made space objects - even if the low-orbits have ~1 hour periods.

p.s. even intended and planned space rendezvous are hard.

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    $\begingroup$ "We cannot depict the space junk to scale" I'm not sure we can depict space anything to scale. Space is big. Really big. $\endgroup$
    – Mike G
    Sep 16 at 13:10
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    $\begingroup$ @MikeG "I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." $\endgroup$
    – Barmar
    Sep 16 at 14:29

The largest human space object in space is the International Space Station, with the largest dimension at some 100 meters. Lets depict that as a 2x2 pixel on a very good display (400 Pixels Per Inch as in iPhones). The actual size - on the display - is about 0.1 by 0.1 millimeters

The ISS "flies" at some 400 km - that's 4,000 times the size of the ISS, so on your high ppi diplay the Earth (ground) would start at 40 cm or some 16 inches. As the Earth diameter is 12,800,000 meters (128,000 times larger than the ISS), its apparent size would be 12800 mm or almost 13 meters.

Lets continue with the fun. The geo-stationary satellites orbit at 36,000 km - if you want to depict their entire orbit it's 72 million meters, or 720k times ISS size, or 72 meters of iPhone displays.

Putting iPhones edge to edge (at some 70x140mm), you would need about half a million of them to create the needed surface.

And, at 50 meters per pixel, assuming you don't paint anything larger than half a pixel (25 meters), you wouldn't see almost anything else - even the mighty Saturn V (which put men on the Moon) had a second stage marginally shorter than 25 meters. Meanwhile, the Space Shuttle (entire complex) was 50+ meters long with the orbiter (the Shuttle itself) 37 meters long (sub-pixel size).

So, half a million iPhone displays just to show the Space Shuttle as a pixel somewhere.

  • $\begingroup$ I think Space Shuttle is a typo for Space Station? $\endgroup$
    – Agent_L
    Sep 18 at 20:02
  • $\begingroup$ @Agent_L The ISS (International Space Station) is thin in proportion, but almost 100x100 meters in width and length. However, the second and third mentions refer to the full American space vehicle known as the Space Shuttle (the best known ones being the Columbia and Challenger). The second one includes the propellant tank (the huge orange thing the Space Shuttle is strapped to), while the third refers only to the actual space vehicle (the one that fixed the Hubble Space Telescope). $\endgroup$ Sep 20 at 4:38

Wikipedia gives the following estimate for the total number of space debris objects:

As of January 2019, more than 128 million pieces of debris smaller than 1 cm (0.4 in), about 900,000 pieces of debris 1–10 cm, and around 34,000 of pieces larger than 10 cm (3.9 in) were estimated to be in orbit around the Earth

Lets take the upper bounds on these numbers and assume we have 1b objects sized 1 cm², 1m objects sized 100 cm² and 100k objects sized 1000cm². Plugging the numbers into WolframAlpha we get a total area of (0.1km² + 0.01km² + 0.01km² = 0.12km²) of the objects in space. Lets round this up to 1km² to be generous, assuming current estimates might be off by a single factor of magnitude.

Now... the total area of the Earth is 510,067,420 km2 (the space orbit is a little bigger in area but not by much). So the total proportion of the orbit occupied by space junk is at most 1 in 510 million. The math does get a little trickier if you have a satellite in orbit as the of hitting debris start to compound over the years but overall this rendering is highly misleading. It's comparable to illustrations of the Great Pacific garbage patch - this is what people think it looks like but reality is a far less dramatic.

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    $\begingroup$ +1, but I would also point out that this answer is even more generous in its estimates than it appears at first... because space has 3 dimensions, not just 2. Objects in flight (whether in the atmosphere or above it) can miss each other in, not just 2, but 3 dimensions. $\endgroup$
    – reirab
    Sep 17 at 2:55

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