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Lasers Could Hide Us From Evil Aliens (washingtonpost.com) 218

An anonymous reader quotes a report from Washington Post: Most of the time when we talk about silly scientific papers related to alien life, we're talking about crazy ideas for how to find aliens. But a new study in the Monthly Notices of the Royal Astronomical Society proposes a way of hiding from aliens. Humans are so fickle. A lot of our search for Earth-like planets (and, by extension, for life as we know it) hinges on transiting planets. These are planets that pass in front of their host star in such a way that the transit is visible from our perspective. The movement of the planet in front of the host star makes the light from that star dim or flicker, and we can use that to determine all sorts of things about distant worlds -- including how suitable they may be for life. Professor David Kipping and graduate student Alex Teachey, both of Columbia University, determined how much laser light it would take to mask the dimming caused by our planet transiting the sun, or cloak the atmospheric signatures associated with biological activity, [such as oxygen, which is achievable with a peak laser power of just 160 kW per transit]. From the report: "According to their math, it would take 10 continuous hours of shining a 30 MW laser once a year to eliminate the transit signal in visible light. Actually replicating every wavelength of light emitted by the sun would take about 250 MW of power."
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Lasers Could Hide Us From Evil Aliens

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  • by pollarda ( 632730 ) on Sunday April 03, 2016 @01:51PM (#51833099)
    Use lasers to cut the aliens planet in half. Shoot first, ask questions later. Send space archeologists to figure out if they were naughty or nice. Better safe than sorry.
    • by lesincompetent ( 2836253 ) on Sunday April 03, 2016 @02:18PM (#51833279)
      I call it the Kissinger approach to foreign relations.
      • So you're saying Kissinger was a shoot first, ask questions later kind of guy? Really, what are you basing that on? I'm no historian but just a little bit of research seems to totally refute that notion.

    • Actually what they've just inadvertently suggested is a way of detecting intelligent life on other planets. If the spectral mix of a smaller planet differs from the normal spectral mix of the star during a transit I guess we just found someone who implemented this technique.
    • Use lasers to cut the aliens planet in half. Shoot first, ask questions later. Send space archeologists to figure out if they were naughty or nice. Better safe than sorry.

      The Alan Parson's Project laser would probably work just fine..

    • Nah, I have a better, cheaper idea: Tinfoil hats are really inexpensive and easy to make, and it'll make anyone worrying about 'evil space aliens' feel at least as much better than expensive lasers.
  • it is all relative (Score:4, Insightful)

    by frovingslosh ( 582462 ) on Sunday April 03, 2016 @01:56PM (#51833131)
    Yes, this might work, as long as you know exactly where the aliens are observing your transit from. If you didn't know their location then they could be anywhere in the sky and the transit would be at different times, so you wouldn't know just when to hide the transit or where to point the highly directional laser beam. I take this as another admission that we know about the aliens and this time we know where they are watching from. However, they likely have already visited us (or we wouldn't know about them) and so they know we are here and are not going to be fooled by our laser trick.
    • by Burdell ( 228580 )

      Yeah, but if you put your laser at the L2 Lagrange point, with suitable station keeping (since L2 isn't stable), and can run it continuously, you are covered.

      • Wouldn't work. Fully masking out shadow with lasers to anyone watching would take as much energy as we receive from the sun (for obvious reasons). It's much easier to eliminate the shadow we emit to a specific known star, because we only need to emit enough energy to make up for a tiny part of our shadow.

        It's the difference between having enough lamps on the ceiling of a large hangar to simulate DAYLIGHT in the hangar... and just shining a very bright flashlight at a single 1" sensor.

        • We could just cloak the planet, let all the sunlight pass around us and continue on... would be kinda hard on the photosynthesis thing, tho....

    • Yes, this might work, as long as you know exactly where the aliens are observing your transit from. If you didn't know their location then they could be anywhere in the sky and the transit would be at different times, so you wouldn't know just when to hide the transit or where to point the highly directional laser beam. I take this as another admission that we know about the aliens and this time we know where they are watching from. However, they likely have already visited us (or we wouldn't know about them) and so they know we are here and are not going to be fooled by our laser trick.

      Even if they haven't visited, if they have their own data showing worlds transiting stars in fifty systems, and suddenly one of the worlds disappears...

  • by maird ( 699535 ) on Sunday April 03, 2016 @01:57PM (#51833137) Homepage
    There is never no direction from which the earth is not currently transiting the sun. April Fool.
    • by GuB-42 ( 2483988 )

      I think it only works when we know exactly where the observer is.
      Which mean the we must detect them before they detect us, which is unlikely for aliens that can threaten us from interstellar distances.

      I don't think it is an April Fool, it is more like a thought experiment.

      • I think it only works when we know exactly where the observer is.
        Which mean the we must detect them before they detect us, which is unlikely for aliens that can threaten us from interstellar distances.

        I don't think it is an April Fool, it is more like a thought experiment.

        Any alien that is a threat to us from interstellar distances is likely going to have much much better ways of detecting us than shadows. It could be a thought experiment of how an alien who wants to hide from us could hide from us but that would likely require them to already be here and understand what we are attempting and actually care that we discover their home planet light years away that we have no means to actually reach. Not to mention that if it was started now, this magical shield would take X

  • The problem is that while this may be necessary over a single day from a single identified star, there are more than 2 stars in the universe (citation needed). And we are talking about shining directed light on the opposite side of our planet near continuously at a variety of angles, exponentially increasing the power requirements to effectively hide. This also assumes casting more light directionally wouldn't also cause greater attention due to the whole 3 dimensional nature of this problem.
    • by ceoyoyo ( 59147 )

      The aliens might also notice that a bunch of the power normally spread across the spectrum suddenly got concentrated at one frequency.

      • by athmanb ( 100367 )
        That's what I was wondering, wouldn't this create a really interesting spectrum, basically guaranteeing attention from whoever detects it?
    • ...there are more than 2 stars in the universe (citation needed).

      I was walking home last night and I can assure you there is more than two stars in the Universe. I'm pretty sure I counted at least 42.

    • You could select the stars you are spoofing by distance (if they have FTL travel, we're hosed anyway), or if you see some un-natural looking activity (stars going nova in the middle of their sequence, sudden brief flare ups like planets being converted to temporary stars) that general neighborhood might be a good one to try to hide from.

      Of course, if you screw it up, you're actually signalling to them that you are there instead of hiding.

  • Given the vastness of the galaxy, it seems inevitable that the earth is transitioning the sun from some distant viewpoint on the galactic plane essentially all the time. Are we supposed to continuously fire lasers (which would probably screw up our own astronomy) in all directions at all times?

    • Given the vastness of the galaxy, it seems inevitable that the earth is transitioning the sun from some distant viewpoint on the galactic plane essentially all the time. Are we supposed to continuously fire lasers (which would probably screw up our own astronomy) in all directions at all times?

      Alpha Centauri is about 4 light years from us, so if we actually started doing this they would get 4 transits and then none.

      Stars further out would have even more transit information, and there's no way we can retroactively take back that information.

      If the transit information suddenly stopped, wouldn't this attract more alien attention than just keeping our heads down and hoping no one notices us?

    • Given the vastness of the galaxy, it seems inevitable that the earth is transitioning the sun from some distant viewpoint on the galactic plane essentially all the time. Are we supposed to continuously fire lasers (which would probably screw up our own astronomy) in all directions at all times?

      This. You would have to be shining the laser in the opposite direction from the sun continuously, unless you already know where the aliens are you're trying to hide from. But only away from the sun, since all you have to mask is a transit.

      You'd also better hope the aliens don't do spectroscopic measurements.

    • Are we supposed to continuously fire lasers [...] in all directions at all times?
      No, you only point it away from the sun ...
      From no other viewpoint the sun is "obscured" by earth. (*facepalm*)

      • Facepalm yourself there.

        When we see a planet transit in front of its star, we see it on a path from one edge of the star to the other. For the Earth, your laser that simply points "away from the sun" would only hide our planet at one point on the path of its transit. And that only if the aliens were situated at a point that is on the plane of our orbit.

        At the worst, Nova Express would simply have to explain that he meant "in all directions away from the sun at all times". Maybe he assumed readers would pick

        • by dissy ( 172727 ) on Sunday April 03, 2016 @05:43PM (#51834325)

          At the worst, Nova Express would simply have to explain that he meant "in all directions away from the sun at all times". Maybe he assumed readers would pick up on that limitation on their own.

          I think the more important limitation not mentioned here is the time scale.

          If we want to hide the fact there is oxygen production on our planet, the lasers would have had to be turned on over 3 billion years ago.

          To hide the planets existence in general, the lasers needed turned on over 4 billion years ago.

          Sorry to say but this paper was published just a tad too late to be useful for anything related to its stated purpose.

        • For the Earth, your laser that simply points "away from the sun" would only hide our planet at one point on the path of its transit.
          No it would not, it would point away from the sun for the whole transit. Where else should it point to?

          However that point is rather mood, as the gravitational "wobbling" of the sun would still be visible. So a schema like this would never work anyway.

  • They are called demons. Read about them in an old book once.
  • by alvinrod ( 889928 ) on Sunday April 03, 2016 @02:04PM (#51833195)
    I don't know if any space faring alien society would necessarily be evil. Consider that for a species to survive long enough on a planet to develop the science to get into space it has to not cause its own destruction first. It's certainly possible that in order to make space travel more possible we'll develop the kinds of technology that make far deadlier weapons than we already have. Any species that is overly xenophobic or uncooperative would probably wipe itself out before developing the kinds of technology needed to cross the vast distances of space, assuming that it's even possible.

    If aliens with that kind of capability did find earth, they'd probably leave us the hell alone simply because we haven't evolved enough as a species to avoid destroying ourselves with the kind of advanced technology that any alien species that could reach our planet would have developed. They might study us, much like we do with insects or animals, but even that assumes that doing so provides them with knowledge they don't already have which is again a pretty big assumption.
    • by Afty0r ( 263037 )

      I don't know if any space faring alien society would necessarily be evil.

      Evil is a human concept, it does not apply to aliens. Take morals out of any deals with aliens, we have no idea if they would even have such concepts, and if they did they would almost certainly be so different to ours as to make conjecture at this point useless.

      But you can consider some more basic concepts that might have a bearing on the actions that an alien species might take upon discovering the earth.

      Consider that to be a ci

    • The thing about aliens They are alien. It’s unknowable.
      The aliens could be totally hive minded with only a tiny portion of creatures controlling everything else. No individuality. No personal greed. No personal ambition. Only serving the “hive”.
      Such a species would be hyper aggressive towards any perceived threat. If they happened on Earth, what would they see? They would see a species that is very aggressive internally and hyper aggressive towards anything perceived as different from the

    • Any species that is overly xenophobic or uncooperative would probably wipe itself out before developing the kinds of technology needed to cross the vast distances of space, assuming that it's even possible.

      So far, your data set on which you draw this conclusion is null.

  • In many countries firing lasers in any format of away from the surface of earth would require co-ordination with the national aviation administration agency. Clearly flying aircraft through the beam of a 30MW visible light laser would be a lot worse than having a laserpointer aimed at them by kids. I heard this all day on April 1st on NPR and the BBC. Although the BBC news site dates it March31st I doubt the story is anything more than an April Fool joke by the original authors.
  • Seeing as we have been doing our damnedest to make ourselves known ever since we discovered wireless technology, just how will these lasers help ?

  • So the evil aliens are scanning space. They notice a planet around an insignificant star about halfway along the Orion arm of the Milky Way. It gets filed for eventual exploitation. Then at some point it disappears. Now it's INTERESTING. That's bad.

    • Then at some point it disappears. Now it's INTERESTING. That's bad.

      Uh, no. That's progress. The Galactic Hyperspace Planning Council finally built out the hyperspatial express route. Takes forever to get anything built in this galaxy. Damn bureaucrats.

  • "According to their math, it would take 10 continuous hours of shining a 30 MW laser once a year to eliminate the transit signal in visible light. "

    For a single known direction. It will not mask it for all directions, but only a tiny 2-3 degree slice of the entire 360 dransit

  • Unless you know exactly where the aliens are in the sky, you would have to broadcast in all directions. That would take more energy than we can make, to say the least.
    • Not "all" directions, but all directions from which Earth appears to be transiting the Sun -- and that's, let's see, Sun subtends 0.5 degrees from Earth, similar triangles, you'd need a beam spread of about 0.25 square degrees. I don't even have the back of an envelope handy, but it seems like that means emulating the Sun's brightness over about 2 one-millionths of its total radiant pattern. No, wait, you'd only need to emulate the part that the Earth is blocking -- in the limit, about one ten-thousandth of

      • A shell of solar panels englobing the earth would boil us since we wouldn't be radiating heat faster than we produce it. And a hot jovian so close to the sun would have to have a lot more mass. Make for a good sci-fi story where someone forgets these little details :-)
  • by ihtoit ( 3393327 ) on Sunday April 03, 2016 @02:34PM (#51833375)

    What the hell kind of alien goes out of his way to visit a planet where the most technologically advanced species still kill each other over tribal god-images and petrochemicals?

  • That "...250 MW of power." would be for each planet we want to hide from. We might need a a lot of lasers and we have no idea where to point them.

    Aliens we need to fear probably can detect us with something more sophisticated than the transit method.
  • If there's an alien civilization out there that: 1) can detect us, 2) wants to fuck with us, and 3) has the means to travel here in a reasonable time (hundreds of light years) -- then I think we have way bigger problems than trying to fool them with lasers -- assuming we even know which planet it is...
    • 2) wants to fuck with us

      Even I with my mediocre inglish understand the difference between:
      a) wants to fuck with us
      b) wants to fuck us

      Not sure if I would object against a) if they were all she's and hot, at my age you have to take what you can get!

  • Well we could set up a bunch of really big mirrors to redirect all of the sunlight that would normally hit the earth around the earth, thus masking our transit shadow and making the earth invisible to any outside observers. This would totally cloak us and make us safe from future invading aliens. The only side effect I can think of is that it would be darker and colder here on earth.
  • As most posters note, there is never a direction from which the earth isn't transiting the sun. Therefore, a single location on the surface of earth for a laser other than perhaps either pole is not a practical implementation anyway since it will be on the sun facing side of earth about half the day. It will not be able to mask the transit taking place while it is on the daytime side of earth. You couldn't fire 30MW visible light lasers into the sky from earth without the massive objection of at least aviat
  • Nothing more easy than distinguishing coherent light with one single frequency (that is what we call a laser) from "normal sunlight".

    You could as well just place a sticker on the sun: planet 3 is inhabited, 7 billion intelligent meat bags and a few billion big animals ripe to cull.

  • Am i missing something, or would those ten hours only cloak us from one vantage point? How are they deciding which single point in the sky we need to cloak against?
    • by jmv ( 93421 )

      The assumption is that the laser would point at a specific star system. Otherwise, you would not only need to operate the laser 365 days a year, but its power would need to be equal to all the power the Earth receives from the sun. Oh and hiding the Earth is only useful if you hide all the other planets too, otherwise the aliens could just assume there's life on Venus and go check it out.

  • The story falls down when you consider the ridiculous assumption it is founded on, that we can use our technology to defeat more advanced technology that we can't even imagine. So are these guys idiots or do they think we are? I say they are idiots because as far as deliberately concocted tall stories goes that is a very lame effort.
  • Minor assumption here, we have to know where the aliens are. Lasers are kind of directional and you also need to know when the Earth will transit in front of the sun relative to their perspective. If we knew so much about the aliens it's likely they would also know about us. Still, I trust to the vast interstellar distances to keep us "safe". FTL travel belongs in sci fi.
  • Depending on where the observer is located, aren't we always transiting the sun from somebody's point of view?
  • Really? 100 comments in and not one reference to 1970s sitcom Mork and Mindy?

    At least one of the plot lines revolved around Ork being such a cowardly place that they'd hide the entire planet from other aliens.

    Looks like someone is turning old sitcoms into grant applications.

  • Now to find out ways of detecting if some planet is using a similar device to hide itself. And we'll have found life. Intelligent, paranoid, life. Perhaps that's why SETI comes still empty-handed, perhaps only the paranoid survive.

  • That's assuming the aliens are so primitive that they haven't developed the instant anywhere machine yet.

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