back to article For all we know, aliens could be as careless with space junk as us

A physicist at the Instituto de Astrofisica de Canarias in the Canary Islands has proposed a way by which planet hunters might detect advanced alien technology. Simply look for their junk in orbit. Thousands of exoplanets have been discovered in recent years, and huge observatories such as NASA's James Webb Space Telescope ( …

  1. chivo243 Silver badge

    Simply look for their junk in orbit

    Now that's down to earth thinking! Get this man a beer!

  2. Spudley

    It's an interesting theory. The problem with it, of course, is that it means looking for a civilisation that is at *exactly* the same stage of development as we are. Any earlier (even a couple of decades) and there won't be anything significant in orbit; any later (even just a few decades), and they'll either have triggered Kessler syndrome or they'll have worked out how to clean things up.

    1. Zippy's Sausage Factory

      Plus, of course, we'll be detecting how they were several year, decades, or even millennia ago...

  3. lglethal Silver badge

    just a little rant...

    "Socas-Navarro calculates that at the current rate of exponential growth..."

    sigh... No product continues on an exponential growth curve continuously. It might grow exponentially at the start, but it will eventually slow down as saturation is reached. To assume something will continue on an exponential growth curve, especially something like satellite launches, is utter bollocks...

    It's the sort of thinking that comes from the same people who predicted that smart phone growth would continue to grow at 200% per year forever and failed to take into account the realities of product saturation and the reduction in improvements per lifecycle over time... in other words, bullsh%t artists and muppets...

    1. Chris G

      Re: just a little rant...

      Anybody up to calculating. The probable mass of an opaque satellite belt around the Earth?

      It may be quite a significant number.

      1. Grikath

        Re: just a little rant...

        Anybody up to calculating. The probable mass of an opaque satellite belt around the Earth?

        napkin time...

        Geosynchronous circumference is about 226000 km.

        Say we've gotten *good* at parking and maintaining orbit you may get as far as one satellite per 10 km. Anything closer strikes me as ..not enough elbow room.. But I may be wrong there.

        That gives us 22600 satellites in a ring.

        However geo is not a single line, but a zone where you can park several rings adjacent to each other and still do the equator-zoomy bit. Ignoring the toroïd , (, signal blocking and other Stuff, I'd guess you can get about 10 rings in either side from the center before moving out of true geo territory. That makes for 20 feasible orbits ( 200 km orbit definition), containing roughly 450.000 satellites.

        now comes the question: how much does the average geosat weigh? The thing there is that while still the heaviest birds around, their mass has been declining over the years, ( Now there's only so much you can strip, and you need some serious tech in space, so they can't drop *that* far in weight. So let's assume a 3.500kg standard mass to allow for future tech.

        The Napkin says that amounts to a total mass of 1.6*10^9 kg.

        Which, for comparison, would be 2.15*10 ^ -14 the mass of the moon.

        Worse.. the mass would be evenly distributed around the equator, so there'd be no wobble to detect. Albedo? You'd have to know what it would have been before the whole ring got up. Spectrography? Possibly a bit more metal, but that would be a hell of an assumption. Radiation? At that density you'd need *very* tight beams out, and the satellites themselves beam down.... Visual? at the right angle... That would mean whoever is looking at us can achieve a resolution high enough that they can also see our continents/major cloud patterns. Who cares about satellites at that point?

        ok. It's no XKCD , but I've done my best. Thank the damn Flu and the resulting Boredom.

    2. Naselus

      Re: just a little rant...

      "in other words, bullsh%t artists and muppets..."


      1. lglethal Silver badge
        Thumb Up

        Re: just a little rant...

        ""in other words, bullsh%t artists and muppets..."


        They did come to mind, yes...

  4. Sgt_Oddball

    totally new take on..

    One mans trash is another mans treasure.

    On a related note has any of the discovered exo planets acctually disappeared from observations? I'd be interested to note if any Dyson sphered themselves whilst we were perving watching them?

    1. DropBear

      Re: totally new take on..

      That would be stars disappearing from observations, not planets, considering how Dyson spheres are supposed to work. So they should be ridiculously easy to detect even if we aren't aware of exoplanets in orbit. That said, I only remember a single instance of this being investigated recently (star going through odd luminosity changes) with the conclusion being that it's much more likely to be caused by another phenomenon, not the building of a sphere.

      1. Fr. Ted Crilly Silver badge

        Re: totally new take on..

        The fools! they have forgotten what the Bussard ramjets are for...

        1. Sgt_Oddball

          Re: totally new take on..

          Wasn't that what Red Dwarf was powered by?

          1. JassMan

            Re: totally new take on..

            @ Sgt_Oddballs first post

            Maybe not a Dyson sphere but if they are dense enough to make an opaque ring they could tie them all together and create the beginnings of a Niven Ring as described in RingWorld.

            1. Anonymous Coward
              Anonymous Coward

              Re: totally new take on..

              Even for an advanced civilization it would take many many years to enclose a star in a Dyson sphere, so we aren't going to observe it on the scale of our recent ability to image extrasolar planets. We might want to look for unexplained IR radiators...

  5. Lee D Silver badge

    "Let's look for people as stupid and careless as us!"

    Sounds like a plan.

    1. Jason Bloomberg Silver badge

      We can also keep a look out for those screeching "Yeeha!" as they crash rockets and satellites into their own moons and passing rocks just to watch the dust settle, or recklessly launching things out of their own galaxy with no idea of where they'll end up.

      1. 404

        It's 'Yeehaw'.

        Anyway, perhaps we should also be watching for a Zesla flyby with a copy of 'A Slaver's Guide to the Galaxy'* in the sock compartment from an analog Earth...

        *Panic All You Want, It Won't Matter.

  6. Daggerchild Silver badge

    Assumption detected

    Nobody has shown that a species that leaves junk all over its planet survives for very long.

    I wonder how many silent planets out there had a flash of life before choking on seas full of plastic and agricultural chemicals.

    Why don't we look for planets that have too little pollutant in the atmosphere. They may be stewarded by species that actually survive

    1. Bob Wheeler

      Re: Assumption detected

      like wise "Nobody has shown that a species that leaves junk all over its planet has not survived."

      1. MiguelC Silver badge

        Re: Assumption detected

        And one species' pollutant may be another's breathing mix

        In finding alien life, the problem might just be that we're always looking for some other kind of humans or, at the very least, for other species that evolved like the ones we see around us

        1. Daggerchild Silver badge

          Re: Assumption detected

          I have an annoying suspicion that most life will look the same as us.

          Life is very good at finding the optimal balances - oxygen stores a delightful amount of energy and is easily transportable and reasonably stable. Atmospheric processing will be the best medium for the common energy cycle. Taking is more efficient than making. i.e. Omnivores rool. Omnivore consumption/excretion strategies are pretty much all the same. Binocular sensors planted close to the processing core just works (unless you're a crayfish, 12 colour polarisation-detecting, sheesh). Bipedal locomotion is an excellent <pun>balance</pun>.

          The only thing we're really missing is chlorophyll skin.

          If some other life found a different photon-combining energy trapper than chlorophyll, things might be very very different.

          1. Teiwaz

            Re: Assumption detected

            Bipedal locomotion is an excellent

            Hmm, quadrupeds seem to outnumber bipeds on earth I think for complex organisms anyway (not including birds, insects and others).

            Intelligent life, maybe. I you might need an extra set of appendages not otherwise needed for locomotion for development of technology.

          2. Anonymous Coward
            Anonymous Coward

            Re: Assumption detected

            >The only thing we're really missing is chlorophyll skin.

            Then again we do use skin to generate vitamin D.

        2. Alan Brown Silver badge

          Re: Assumption detected

          "And one species' pollutant may be another's breathing mix"

          The indicator of life in a planetary atmosphere is likely to be an unexplainable oxidising agent - on the basis that these can generally only exist if something is maintaining production.

          Oxygen is the logical one but there are other candidate gases and even if the life isn't air-breathing it's likely that such gasses will build up anyway. (eg, diffusing from oceans into the air, as probably happened on Earth)

          The oxygenation of our atmosphere was definitely a case of the statement above, being a byproduct of plant activity and highly toxic to just about everything that existed at the time (causing the first great extinction).

          I'd be happy if we picked up possible life signatures. Even assuming a CEB would be visible around any exoplanets, the odds of a spacefaring civilisation being within the range that we've seen exoplanets so far seems pretty unlikely. We can (so far) only detect exoplanets out to about 600 light years and the galaxy is over 100,000 light years across, so searches are par with being in a large dark room with a feeble flashlight only able to illuminate things a couple of feet away, looking for a black cat.

      2. Daggerchild Silver badge

        Re: Assumption detected

        Yeah, I don't doubt some of those dead planets still have climate-denial pamphlets blowing around...

        1. Anonymous Coward
          Anonymous Coward

          Re: Assumption detected

          Those planets whose inhabitants took ACC (alien climate change) seriously have been dead longer, but have nothing blowing in the wind. They made everything biodegradable.

    2. Chemical Bob

      Re: Assumption detected

      Civilized aliens would keep their junk in their trunks...

  7. Vinyl-Junkie

    Oh look....

    ....I've found an exo-moon!

    Wait, that's no moon....

  8. Anonymous Coward
    Anonymous Coward

    Low cost disposal....

    >>That kind of cosmic clutter would create its own problems, of course...

    Just copy the Chinese model, wait until you lose control then let it fall down to the planet.... :-)

    1. chivo243 Silver badge

      Re: Low cost disposal....

      Calling Quark!

      The show was set on a United Galaxy Sanitation Patrol Cruiser, an interstellar garbage scow operating out of United Galaxies Space Station Perma One in the year 2226. Adam Quark, the main character, works to clean up trash in space by collecting "space baggies" with his trusted and highly unusual crew.

      1. Claptrap314 Silver badge

        Re: Low cost disposal....

        Been too long for me to remember the full intro. "Where ever I go, I leave space a cleaner place." Followed by an interruption that theirs was the most polluting style of starship... :D

    2. AceRimmer1980

      Re: Low cost disposal....

      Hello, we're from the Council.

      We've warned you before about putting dilithium in the carbonite-only recycling bin.

      Next time, it's Resyk for you!

    3. dnicholas

      Re: Low cost disposal....

      **ahem** "de-orbit"

  9. Clive Galway

    Space Elevator in a crowded environment

    Please forgive my ignorance, but is the feasibility of a space elevator not inversely proportional to the amount of junk you have in orbit?

    Would a space elevator not basically mean that a certain point above the surface of the earth is always occupied, and so nothing else lower than or equal to geosynchonous (ie pretty much everything) can ever pass through that column?

  10. This post has been deleted by its author

  11. Anonymous Coward
    Anonymous Coward

    The detritus civilisations leave behind

    Given quite plausible trajectories of civilisations then their end points are perhaps quite often full-scale nuclear wars. I suspect there aren't that many ways of putting together fission or fusion weapons given their physics (this might be made more complicated if they set off salted bombs as their might be more kinds of those).

    So I wonder if the aftermaths of those are detectible, characteristic enough, and long-lived enough to be worth looking for on exoplanets? It would be kind of a depressing search but if we found them it would answer several interesting questions: in particular it might help with the Fermi paradox.

    1. Alan Brown Silver badge

      Re: The detritus civilisations leave behind

      "This might be made more complicated if they set off salted bombs "

      Salted bombs are more-or-less a way of ensuring that an area is uninhabitable for decades/centuries.

      I suspect that they're more of a science fiction plot device playing on unreasonable fear of radiation than an effective one. Little Boy had around 40kg of uranium. Only 0.7g was actually converted. The rest was vaporised and dispersed on the wind, which is what would happen to anything like cobalt unless you used several tens of tons of it and that's kind of hard to mount on the end of a missile or carry in a bomber.

      1. Anonymous Coward
        Anonymous Coward

        Re: The detritus civilisations leave behind

        My worry was that salted bombs might hugely expand the range of possible decay pathways (baded on the choice of salting) & hence the make the results harder to distinguish by looking at spectra fro far away.

  12. doublelayer Silver badge

    Collecting the reasons this could fail

    Here are some plausible reasons for this approach not to work.

    Let's say we have planet X, with intelligent life on it. Let's list some ways they might not show up on this scan.

    1. People on planet X haven't gotten things to space yet.

    2. People on planet X got things to space, and they cleaned up so now you can't see a giant cloud of junk.

    3. Planet X is small, so satellites that orbit about are less useful for communications than ground-based radio equipment. The same for navigation satellites. Much less stuff to be in orbit and thus visible.

    4. Planet X has a nearby moon or moons, and equipment lasts longer when they go and put it there. Depending on the location of the moon, this might work much better than on earth. At least their space stations won't be crashing back down if they were safe on the lunar surface.

    5. People on planet X have focused on travel rather than tech without travel. They live on a few planets and it is easier to communicate between planets X, Y, and Z with devices placed in orbital paths of the star instead of around a planet in particular. Good luck determining whether those are communication satellites or tiny asteroids.

    6. People on planet X have technology that doesn't produce opaque junk belts. Not that I'm suggesting transparent or gaseous tech (although that'd be cool), but how about tech that contains light-transmission tech so that they don't have a lot of satellite junk blocking energy from their planet (maybe they have the opposite climate change problem).

    7. Access to space on planet X is limited by some control system. Satellites that are of use can go up, but they have to be brought back at some point. Even if they aren't, people can't deliberately send perfectly useful cars up just because they feel like wasting them.

    8. Satellites on Planet X that are useful are expensive. In order to avoid breaking them, junk in orbit is brought down automatically if telemetry remains, or shocked out of orbit using ground-based devices to affect their paths. Failing that, ground-based or satellite-based lasers would make a nice light show if they did it at night.

    9. Planet X has an extreme orbital path. Satellites must be brought down to avoid damaging them (E.G. by bringing them too close to the sun without atmospheric protection).

    Come on, add yours.

    1. Not also known as SC

      Re: Collecting the reasons this could fail

      Don't forget that most exo-planets are only detected via indirect observation, for example, how much the exo-planet makes the light of its star drop off as the planet passes between us and the star (transit method). Transit drop offs are in the magnitude of a hundreth of a percent (IIRC correctly - but very small any way) and this is only good for certain combinations of stars and planets. The chances of actually being able to tell that you have an opaque shell of space junk as opposed to just a physical planet is going to be incredibly small if not impossible because the drop off in brightness just tells you something is there, not what is there.

      1. annodomini2

        Re: Collecting the reasons this could fail

        Detecting Exo-moons is currently a problem, so detecting small bits of debris is going to be an even bigger challenge.

  13. Claptrap314 Silver badge

    To be fair...

    As dubious as I consider this proposal, I'm quite certain that it is being proposed as _a_ way to detect alien life--not _the_ way.

    The point that I feel needs to be made in support of this is that convergent (intelligent) evolution suggests that there is a good chance that aliens will put up a lot of satellites, and that these satellites will tend to be composed of a lot of highly refined metals with sharp edges. But unless these structures are large enough to cause detectable interference patterns, I'm having a hard time seeing how you can detect this.

    But yeah, if they transition to a ringworld, we might just detect that...

  14. ThatOne Silver badge

    There are simpler ways

    The chances such a belt of cupboard-sized appliances will become dense enough to be visible at those distances is rather small I guess.

    If we have instruments that good it would be easier to detect the illumination of night side of the planet (absence of infrared would allow to eliminate volcano activity), wouldn't it?

  15. Anonymous Coward
    Anonymous Coward

    Or we could just

    Try my suggestion, look for high-frequency gravitational wave pulses along a flight path. Such as the ones produced by a warp drive with a slight imbalance. Normally if they are tuned correctly the fields line up, but mess around with it or suddenly change direction and you'd see all sorts of strange distortions.

    Gravitational lensing caused by a warp field might also explain certain kinds of short duration radio anomalies, the good thing is that it can be tested experimentally.

    1. Anonymous Coward
      Anonymous Coward

      Re: Or we could just

      Looking for the signals from technologies we suspect can't exist and which we don't understand if they can is pefhaos not the best aporoach, although finding things which are unexpected is historically very importan, of course.

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