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I have a universe where space travel is common. A large group of settlers veered off course and crashed on a desert planet and have not yet been rescued for 50+ years and had to fight amongst themselves to survive.

I'm looking for a way to explain why nobody noticed people were living there. I'm thinking some element in the atmosphere prevents scans, and potentially even throws off sensors which is why they (and the main character) crashed there because the planet was effectively invisible and they didn't notice they were going into the atmosphere of the planet until it was too late.

Does anyone know of something that could cause this?

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    $\begingroup$ Welcome Azya. Unless you can provide exact specifications of all your sensors to enable us to establish the constraints of the question, this would be a "fishing for ideas" question which is off-topic here. Please take our tour and refer to the help center for our guidelines, paying particular attention to the How to Ask section. $\endgroup$ Oct 23 at 22:28

4 Answers 4

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Needle in a haystack

Angry Muppet is right: unless you tell us how a "scan" works, we can't speculate about sources of interference.

However, the body of your post says that what you want to do is:

explain why nobody noticed people were living there

So, let's not make this an XY problem by getting wrapped around the axle of Star Trek's "scanner" nonsense.

Here is why nobody has found these settlers: there are countless billions of planets in space. Depending on how your space travel works, there could easily be tens of thousands of planets within "reasonable" travel range of your main civilization. Given this, it is vanishingly unlikely that anybody else would be looking at this one planet.

This situation is compounded by the fact that your travelers went off course and crashed on an undesirable planet. Nobody else is going to scan a desert planet because it's a frikkin' desert.

If there's anybody looking for your travelers, they will be looking on the destination planet, and that search could take months or even years depending on its size and terrain. The search will probably expand outward from there, along the travel route.

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    $\begingroup$ Thank you! I agree that's a good explanation. Agreed on the XY problem, that's why I included my goal :) I had considered that as well, but I was thinking that depending on the circumstances it's possible they would know the path the travelers took and around where they lost signal / communication if they were expected. I think I need to consider more about who these people are and where they were traveling to and from in order to determine if that's something I even need to worry about. Maybe there are countless voyages and they're just one of many unsolved disappearances in space. $\endgroup$
    – Ayza 3D
    Oct 23 at 23:48
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    $\begingroup$ @Ayza3D depending on how your interstellar travel works (I assume FTL), "going off course" could mean they end up in a huge area, most likely not on any planet so the search might be called off as soon as they re not found on the target planet $\endgroup$
    – Hobbamok
    Oct 24 at 8:54
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    $\begingroup$ @Ayza3D There are real world examples of contact being lost with planes and them never being seen again. Take the one that disappeared around the Indian Ocean. Even though we know where the last contact was, the plane was never found (until parts of the plane washed up on Africa (IIRC)). That's "just" a single ocean. Even if you knew they planet they ended up on, how are you going to find a couple of people on an entire planet (let alone the vastness of space if you don't know where they ended up)? $\endgroup$
    – Dnomyar96
    Oct 26 at 14:27
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Being in another solar system

Read this and see how much we know about the nearest planets.

Before 2016, observations with instruments[a] at the European Southern Observatory in Chile had identified anomalies in Proxima Centauri[12] which could not be satisfactorily explained by flares[b] or chromospheric[c] activity of the star.

Without a very powerful telescope in a nearby system you're not gonna get much better than that, knowledge that based on tiny colour fluctuations that maybe there's something earth sized there which isn't just the star.

A spaceship is much smaller. It's gonna be almost impossible to detect that from lightyears away.

In system, nothing could conceal a planet. Basic newtonian calculations about the movement of planets and the star would quickly reveal every major source of gravity in system.

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Question provides too few details on the universe it's trying to describe, making it difficult to answer.

Currently we, as a spacefaring species would face two distinct, yet connected, challenges: travelling and/or communicating through the space-time continuum. In other words, we are limited to slower-than-light speeds. In addition, the distances aren't making it any easier. Consider radio transmitter - it can be used to communicate over vast distances on Earth, using (relatively) weak signal, because it's bouncing off the various layers of the atmosphere (typically ionosphere) or Moon (but that's atypical). Normally we use satellite network (sending signals from one point to another by passing it between the satellites if distances are great). There is no ionosphere in space, and there are a lot of other factors that actually dampen signals a great deal in interplanetary and/or interstellar space - for example frame-dragging effect of a sun, number and movement of gas giants (if any) or other celestial bodies, type of a star and it's emissions...

So, in order for our castaways to be able to send emergency signals they need one or more of the items off the list:

  1. FTL mode of interstellar communication or
  2. Be "close" to the interstellar route and FTL travel is not preventing receiving STL communications
  3. Powerful transmitter
  4. Know their location in terms of galaxy
  5. Know the location of the target of their transmission

If our castaways veered off course and crashed on an uninhabited planet in a binary star system, on the wrong half of the planet and in the process losing ship's power plant they may have to first relocate to a spot from which their signal will reach the part of the galaxy they need, restore their power-generation capabilities... Then their signal may be sub-light only and takes 50 years to reach the travel lanes and they have to have just a tiny window where they and the spot they send signal to have unobscured (by other planets, for example) Line-Of-Sight - yes, some sort of anti-conjunction of planets... Their star needs to go into the calm period of it's cycle, emitting much less solar wind or other radiation...

There are ways, but you need to decide what your conditions are.

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No need to be undetectable

They could simply be too far. The SOS signal after all will travel at light speed and after it is picked up it takes time to organise a rescue mission. Furthermore if the transmitter is not properly pointed a man made signal easily fades away in few light years.

A navigational error made at the beginning could send your settlers many light years away from the intended destination, in a sector of the galaxy that is unexplored and in the middle of nowhere.

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