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I've heard (though I can't find the source) that sufficiently large interstellar space debris has the potential to destroy spacecraft, and that there is considerable uncertainty about how much of a risk it is. Is it plausible that the frequency of this debris, or perhaps the frequency of it outside the local bubble, is much higher than currently thought? Is it plausible that this space debris is the Great Filter?

I know that this is partially opinion-based, but I hope it can be factually answered at least to some extent.

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  • $\begingroup$ The larger issue is that not much can be said about it. Unexpected things have to be expected when dealing with subjects where we have little knowledge. Have a look at Dark Matter and Big Sky Theory. $\endgroup$
    – kim holder
    Mar 29, 2015 at 23:33
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    $\begingroup$ This shouldn't have been closed. It is asking about the possibility of travel through interstellar medium, proliferation of life through it, and it has an unequivocal answer. If you're going to read one thing about it, then I'd suggest David Brin's The "Great Silence" (PDF) that deals with this so-called factor v to Fermi paradox solutions on pages 15-16. Also see Ian Crawford's Starship Destinations presentation made for the 2013 Starship Century Symposium. $\endgroup$
    – TildalWave
    Apr 3, 2015 at 1:16
  • $\begingroup$ Remotely related: space.stackexchange.com/questions/5387/… just to mention there's some stuff in space that might help instead of obstruct $\endgroup$
    – Everyday Astronaut
    Nov 12, 2018 at 19:38

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I don't see how it could possibly be the cause--it would make interstellar travel harder, it wouldn't make it impossible and it wouldn't destroy the species--once they found out about it they could beef up the defenses of their starships.

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  • $\begingroup$ Could defenses be strong enough to protect the ship when travelling at near-light speeds? $\endgroup$
    – Kelmikra
    Mar 28, 2015 at 22:18
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    $\begingroup$ @Kyth'Py1k We are talking about the degree of threat, not the kind of threat. $\endgroup$
    – Loren Pechtel
    Mar 28, 2015 at 22:21
  • $\begingroup$ @Kyth'Py1k That would require that species would be destroyed by the loss of a single ship or fleet, and that the ship(s) could not detect the threat in time to avoid it $\endgroup$
    – raptortech97
    Mar 30, 2015 at 0:14
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    $\begingroup$ @Kyth'Py1k I don't think you can have debris so thick you can't get through it. Projecting dust ahead of your starship will go a long ways towards punching through whatever's out there. More debris, carry more dust along. $\endgroup$
    – Loren Pechtel
    Mar 31, 2015 at 0:03
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    $\begingroup$ Interstellar debris wouldn't prevent interstellar communication. We know that electromagnetic signals can travel freely across interstellar distances (we can see the stars, and radio telescopes work). It could conceivably prevent a civilization from physically spreading across the galaxy, but species confined to their own solar systems would still be able to talk to each other. $\endgroup$
    – Keith Thompson
    Apr 21, 2015 at 18:28
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Interstellar travel isn't the issue — stars are close together and even at 10%c the Milky Way could be traversed safely in 10M years. 10M years isn't a factor. Even if it's 100x slower at 0.1%c, 1bn years to colonize an 11 or 12bn year old galaxy with 6-10bn year old metallic stars (thought to be required for life) isn't a strong filter.

If a filter parameter is the rarity of spacefaring civilization frequency, then even only one per galaxy or per 1000 galaxies isn't a limitation unless intergalactic (IG) dust density is high. (This still leaves 2bn civilizations in our visible universe.)

Need to hit 50%c to be able to send probes to a meaningful fraction of the visible universe before expansion takes them out of range. At a certain density level the redundancy factor (how many probes to send to ensure one arrives due to destruction in collisions with IG dust) becomes untenable and filters out IG travel or perhaps limits it to the local group due to Hubble constant increase.

Sharpening the Fermi paradox - intergalactic spreading has a discussion of the limiting factors due to IG dust density at specific masses/sizes and suggests another filter: IG policing of paperclip-maximizer accidents.

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  • $\begingroup$ If it is possible to have successful, self sufficient colonies on (in) deep space objects then direct travel star to star or at relativistic speeds is not required; just starting new colonies further along in the direction of another star could eventually see a space capable species reach another star. I actually think this would be a more likely means of interstellar colonisation than all-at-once type missions. $\endgroup$
    – Ken Fabian
    Nov 12, 2018 at 23:34
  • $\begingroup$ It is but it will necessarily result in a non-homogenous 'civilization' - when one end of the colonies cant ever talk to the other end ever again - and in fact to a decreasing # of colonies ongoing until they are limited (likely, depending on Hubble constant's derivatives) to the local super cluster, cluster or group (ie the biggest structures still sufficiently gravitationally bound to resist whatever the Hubble flow is in the distant future). $\endgroup$
    – math
    Nov 13, 2018 at 20:21
  • $\begingroup$ at a larger scale wouldn't the same stretching of civilisation "problem" still arise? I'm not sure I would rate it as a serious problem; the essential knowledge base and technologies would be reproduced and shared. The same life requirements will have a homogenising effect. Having thousands of occupied Deep Space Objects between one star and another could see enough 'pollution' that direct line of sight and communications are lost over larger distances. But of all problems with interstellar colonisation I suspect civilisation stretching to breaking is not high on the list. $\endgroup$
    – Ken Fabian
    Nov 13, 2018 at 20:58
  • $\begingroup$ The paper above indicates it is far more expensive to keep slowing down to drop off colonists or probes. Once you get to .5c+ you wanna keep going. The furthest colonies will likely be established not long after the 1atst, from an original launch of all colonizers. We have cultures that diverge on earth (ie in similar environmental conditions (living between -30 and +40C generally, 0.6 to 1.05 atmospheres, etc) in very short times, what happens after 100ky or 10My? Non-homogenization may lead to war as that eternal pesky filter. $\endgroup$
    – math
    Nov 14, 2018 at 16:30
  • $\begingroup$ It is all conjecture and thought experiment. Strung out colonisation between the stars wouldn't be trying for 0.5C velocities so would not have a big investment in staying at those speeds. The 'later ships will overtake the earlier ones' presumes a lot, not only about physical and economic limits to technology growth but about the launching economy having the wealth to spare to keep doing large projects that have no sound economic basis. As for distance inducing differing values to evolve - they will occur at vast distances, so it isn't going to result in material conflict. $\endgroup$
    – Ken Fabian
    Nov 14, 2018 at 22:45

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