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Best way to sneak up on Earth?

  1. Aug 3, 2016 #1
    Imagine a race with very little knowledge of Earthlings' capacity for violence, but they're aware that anyone could be violent if provoked. They're sending a scout ahead of their main ship. The scout wants to come as close to Earth as possible without be detected. The time frame is not "now", it's "when", this will matter in a moment.

    Currently I'm thinking they slip behind a NEO and then peel off from it when they're at PCA. The craft with be stealthy to radar but not invisible.

    So, in the next 100-200 years, are there any large NEOs that would come inside the Moon's orbit but not hit Earth?

    Better ideas are always welcome, I know my limitations.
  2. jcsd
  3. Aug 3, 2016 #2


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    With the kind of technology they would have to have, just send some kind of small drone that would never be noticed even if it were not stealthy. It would just mix in with other space junk in orbit. Silly to bring a large spacecraft into range when it just would not be necessary. A directional communications device (laser maybe) might be necessary but that's trivial.
  4. Aug 3, 2016 #3
    Well, drones are short on protagonists. I planned on having them meet humans in orbit to have a nice chat.
  5. Aug 3, 2016 #4


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    You asked how to sneak up, not how to meet them. Why be stealthy in the first place if your plan is to meet up? Reconnaissance? Use a drone for that THEN go meet the humans.
  6. Aug 3, 2016 #5

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    If they want to be sneaky, the logical thing to do is to a) stay far away and b) toss a bunch of CubeSats into orbit. If you don't want them to do this, you need a reason for them not to act logically.
  7. Aug 3, 2016 #6
    I guess there would be quite a large number of NEO due to pass nearby without actually colliding with Earth over a couple of centuries.
    Given though that your aliens already have technologies way beyond the present level of humans, I would not think stealth is much of a priority.
  8. Aug 4, 2016 #7

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    A good spot to be sneaky is between the earth and the sun - provided your aliens can keep station.
  9. Aug 4, 2016 #8
    They would have been watching our media. No need for a drone to do that.
  10. Aug 4, 2016 #9
    Scouting isn't the issue, contact is. They're afraid of us but they're planning to stay in the neighborhood.

    As for the technology, they're ahead of us enough to get a ship across the gap between stars, but they're not Buck Rogers league yet. (And the home planet won't be following them because they don't know where the ship went, but they'll know in a few decades if they're following Earth's broadcasts.)
  11. Aug 4, 2016 #10
    They left their world a long time ago, in cryosleep, and didn't know there was an intelligent race here. (And humans, too.) They have to meet the humans to decide if they're going to stay here or move on to their next objective.
  12. Aug 4, 2016 #11
    BTW, the point of this story will be how astronauts would advise another, refugee/fugitive, race in regard to staying in the system or moving on. I just need to build a plausible framework for that material to be presented.
  13. Aug 15, 2016 #12
    http://neo.jpl.nasa.gov/news/news192.html [Broken]
    This is news of a asteroid in a exotic orbit around earth between 40-100 meters in size and has an orbit around earth that goes from 38 times the distance of the moon up to a 100. It was discovered in June this year, the point being that there is no problem for your story to just invent the NEO you need. Just the remember that the size of the solar system simply makes it hard to survey and the other problem being that bodies that don't radiate energy by them self has to be illuminated by the sun this makes i very hard to see small objects in space. Even in hundred years at best we can only make like a weather prediction over when NEOs come and it will be more accurate the closer in time you make the prediction but there is a theoretical upper limit to how far in the future you can make such a predictions. The weather system on earth has an upper such limit of about teen days, after that the information you get from the predictions are more or less pointless and this is a limit in information theory and not a technological barrier. So unless you have some sort of quantum computing revolution in you world a small NEO within teen years is impossible to predict. What you are asking for will also only give you very large objects and sending a minor death star as a scouting ship feels a bit wrong. So just invent something or take the asteroid in the article, it has a interesting orbit that given some time could have been thrown there by some tricky aliens, it is only in orbit around earth for a few hundred years before it will leave us again.
    Last edited by a moderator: May 8, 2017
  14. Aug 16, 2016 #13
    Thanks. I have a suggestion that I set the story on or about 28 July 2061. The old "make them look where you ain't" gambit.
  15. Aug 16, 2016 #14
    Ah so they take a hike on the old Halley's. That comet is perhaps not great for observation since it has a lot of ionized gases around it making visibility from the surface to any distant object very hard. On top of that the place is a mess, even if aliens might be enable to dig in it is hard to think of any reasons for humans to try to land and survive there. But what about if they hid there spacecraft in the comets tail but they had to come out at some intervals to actually see anything and that's when the humans get let's say a single picture showing the alien spacecraft in an undeniable way.
  16. Aug 17, 2016 #15
    I'd just put it on the other side of the tail. And I want them to get to Earth orbit without being detected.
  17. Sep 1, 2016 #16


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    Well there are a couple of ways you could go here:

    If the aliens are crossing a gap of several lights years in a relatively short period of time then it means they are moving at a very large fraction of the speed of light. that kind of energy utilisation speaks of a civilisation far removed from us, Technologically they would be very hard for us to understand. putting them at that level of technology makes sneaking in easy because why wouldn't they have the means to cloak their emissions? If they can cloak their emissions then from Earth's point of view, the scout ship is just another space rock, one of hundreds of thousands zipping around Near Earth Orbit, many of which are not catalogued so the ship would be ignored.

    On the other hand if the Aliens are not significantly more advanced, if they could only more at a very small fraction of the speed of light and their journey took centuries (generational ship?) then it stands to reason that there would be little they could do to hind their approach because moving even at 1% of the speed of light means they would be kicking off enough waste heat that we would see them coming for quite some time. Consider that voyager is almost 12 billion miles away and yet we can detect the 20w signal it puts off. its very hard to hide things in space without the handwavium of my example in the first paragraph.
  18. Sep 1, 2016 #17
    Selective hand-waving will be needed. ;)
  19. Sep 1, 2016 #18
    Why not simply station your observer probe on the moon? It's always facing Earth. We'd never detect unless it's broadcasting something. It would look like any of the meteors that run into the moon all the time.
  20. Sep 1, 2016 #19
    The mission is face-to-face with humans.
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