11 ms·

Half of stars lurk outside galaxies

104 points by scott_s 12y ago

scott_s 12y ago
I think it's worth noting that this is the conclusion one group of scientists came to based on data they collected. That's true of all published articles, but my point is that other scientists have not necessarily come to the same conclusion - yet. But that's how science works! At the end of this submission, they mention that they are planning follow-up experiment which should get more data. I first heard about this on the Skeptics Guide podcast (http://www.theskepticsguide.org/ http://www.theskepticsguide.org/), and I was surprised because it's counter to how I think about the universe.
paul_f 12y ago
Anyone living on planets orbiting those stars would not see many other stars at all, right?
- jessriedel 12y ago
  Right. Almost all the stars we see in the night sky are within 1,000 light years. You could guess this from the fact that the Milky Way disk is about ~1,000 light years thick and ~100,000 light years in diameter. If we could easily see stars further than the thickness, then we'd see a lot more stars along the Galactic disk. But instead, the only sign of the disk is the diffuse glow of very distant, undifferentiated stars where the Milky Way gets it's name. Presumably stars outside of galaxies are at much lower density, so they wouldn't see hardly any points of light in the sky. If most such stars are still within the Galactic groups, then they would probably just see faint smudges of other galaxies like the very dim Magellanic Clouds we can see. (Note that these are still pretty big, though, in terms of angular size. Several moons wide.) On the other hand, planets around lone stars in voids away from Galaxy clusters would presumably have nothing visible to the naked eye from their surface. (Someone please correct me if I'm wrong. I'm not an astronomer.)
  - dalke 12y ago
    To add to those excellent points, the Andromeda galaxy is visible with the naked eye, making it another type of smudge ("Little Cloud", to use an early name) that might be seen by a lone star in a galactic cluster.
    - deciplex 12y ago
      Andromeda is pretty close to us. In fact, we're going to collide with it in a few billion years. After that, what little remains of our solar system by then, might end up like one of these orphaned stars. So if Andromeda is already difficult to see by us, that gives some indication of what's going to be visible from a planet that is much further away from anything, than even that.
      - dalke 12y ago
        The premise in the g'parent comment is "If most such stars are still within the Galactic groups ...". This assumption is reasonable given the hypothesis expressed in the article: "Bock suspects that a lot of these renegade stars could have come from relatively lightweight galaxies, which can lose hold of their stars more easily than more massive galaxies." Our Local Group has a diameter of ~10 megalight-years . Andromeda is 2.54 MLy away. Thus, given the premise, and assuming that our own cluster is "typical", it's unlikely that a renegade star is all that much further from a galaxy like ours or Andromeda than we are from Andromeda.
  - throwaway_yy2Di 12y ago
    I think that's right (also not an astronomer). I looked this up in the Hipparcos catalog [0][1] -- that's one that measures parallax distances to bright stars. It's supposed to be complete to at least +7.3 magnitude [0]. Cutting off at +6.5 magnitude [2] (the faintest visible stars according to [3]), Hipparcos reports * 7,943 visible stars * 1,078 (14%) beyond 1,000 light years; * 34 beyond 10,000 l.y. (these must be supergiants!) If I calculated right, a +6.5 magnitude star would demand an absolute magnitude of -0.9 at 1,000 light years, and -5.9 at 10,000 light years. Looking this up on the Hertzsprung–Russell chart [4], this would include only very bright giants, and supergiants, respectively. [0] https://en.wikipedia.org/wiki/Hipparcos https://en.wikipedia.org/wiki/Hipparcos [1] ftp://cdsarc.u-strasbg.fr/pub/cats/I/311/ (hip2.dat.gz for data; intro.pdf for field descriptions) [2] Hp magnitude is a 340-850 nm visible band, which diverges slightly from V band magnitude, http://heasarc.gsfc.nasa.gov/W3Browse/star-catalog/hic.html http://heasarc.gsfc.nasa.gov/W3Browse/star-catalog/hic.html [3] https://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_notable_celestial_objects https://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_no... [4] https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_di...
- Florin_Andrei 12y ago
  All stars you see at night with naked eye are within this galaxy. All of them. Yes, Andromeda (M31) is visible to the naked eye, but it's pretty huge and quite close to us. Orbiting a lone star, the naked eye at night would see something between absolutely nothing, and maybe a few faint patches of light. And that's in perfect conditions - middle of desert or ocean, zero light pollution.
  - JoeAltmaier 12y ago
    I don't believe it. I can see many galaxies from where I stand. They would appear even brighter without a local galaxy to wash them out. The sky would appear totally covered in fuzzy dots - galaxies.
    - Florin_Andrei 12y ago
      > I can see many galaxies from where I stand. If half a dozen is "many", then sure. But you probably live far from any cities then. http://en.wikipedia.org/wiki/List_of_galaxies#Naked-eye_galaxies http://en.wikipedia.org/wiki/List_of_galaxies#Naked-eye_gala... (The list includes objects that are very difficult to see, and some only "reportedly" seen naked-eye.) > They would appear even brighter without a local galaxy to wash them out. There's no reduction in contrast in the direction perpendicular to the galactic plane. And yet the naked eye doesn't perceive the sky there "totally covered in fuzzy dots". The naked eye has a lot of trouble seeing anything beyond the Local Group - and these are a handful of close-knit galaxies. You need telescopes for that, with plenty of aperture. Once the aperture is comparable to the diameter of your car's wheels, or bigger, then yes, you get the "my god, it's full of galaxies" effect.
      - JoeAltmaier 12y ago
        I'm an idiot. I confused nebulae etc for galaxies. Not an astronomer. So most of what we see are constructions inside our own galaxy? I see what you mean - the sky would be a very lonely place for the intergalactic skygazer.
- cmsmith 12y ago
  Making it fun to imagine the invention of the telescope on those planets. It would be like the Hubble deep field image, but MUCH more unexpected. On the other hand, who knows how much science and telescope-making would have been set back without there being anything to look up at. Without other stars (and our rather extraordinary moon), it would take a lot longer than 1500 years to break out of the Ptolemaic mindset.
  - IndianAstronaut 12y ago
    I would imagine other galaxies being visible like faint blobs in the sky, not to mention that you would still see the planets around the given star.
    - kijin 12y ago
      Other planets would definitely help stimulate the mind. But depending on how isolated the system is, galaxies in the night sky might be indistinguishable from clouds. Especially if the planet has lots of clouds.
mrfusion 12y ago
Could this be a solution to the Fermi Paradox?
- pavel_lishin 12y ago
  I don't think so. It may alter the equation, but it wouldn't really be a "solution". For one, considering how difficult interstellar travel should be based on what we know, intergalactic travel would be much more difficult, even given von Neumann's self-replicator ideas. (It's like the difference between crossing a river, and crossing the Pacific.) On the other hand, maybe galaxies are just naturally inimical to life, and extragalactic stars are the only places where long-term biological survival is possible.
  - VieElm 12y ago
    > On the other hand, maybe galaxies are just naturally inimical to life Gamma ray bursts would be more likely in a galaxy and those are inimical to life.
    - logfromblammo 12y ago
      Also, catastrophic collisions with other bodies would be more frequent when those bodies are closer together. Even if there is no direct interaction, nearby massive objects could still perturb the orbits of distant objects--similar to those in our Oort Cloud and Kuiper Belt--enough to make them impact planets orbiting closer to the star.
- antognini 12y ago
  No. Even if half of stars are outside the Galaxy, there are still enough stars within the Galaxy that the ideas behind the Fermi paradox would still be valid. This would be an explanation of the Fermi paradox if we were on a planet around one of the stars outside the Galaxy.
- jessriedel 12y ago
  No, if you're adding stars to our theory of the universe you're only making the paradox worse (although not much worse if such life would probably be unable to expand). If, instead, you're changing the theory be suggesting that the number of life-originating stars is the same and moving half of them into voids, then you're only reducing the problem by at most a factor of 2. Because of the many unpinned down orders of magnitude involved, this doesn't do much at all.
DanielBMarkham 12y ago
Also of note, from another group of researchers word is that there may be more planets in-between stars than there are circling stars. If this continues, the universe is going to end up being nothing like we expected only a few years ago.
- fragsworth 12y ago
  I am pretty sure this is a widely acknowledged assumption among most scientists, considering our current understanding of the formation of planets, stars, and galaxies.
  - ggreer 12y ago
    These stars were formed from gas clouds in galaxies. Wouldn't a gravitational slingshot with ∆v greater than galactic escape velocity likely strip their planets? Unless you mean the ex-planets themselves would end up alone intergalactic space. Apparently, the vocabulary used for such objects is, "sub-brown dwarf."[1] 1. http://en.wikipedia.org/wiki/WISE_0855%E2%88%920714 http://en.wikipedia.org/wiki/WISE_0855%E2%88%920714
  - antognini 12y ago
    The free-floating planets result is still controversial and there is a substantial fraction of the astronomical community that doesn't believe it. If it is true, it introduces problems in our understanding of planet formation because planet-planet scattering as we currently understand it is unable to produce free floating planets at the rate claimed. It is also possible that planets form in isolation (so really they're very small brown dwarfs), but given our understanding of star formation it is difficult to form isolated objects that small.
    - fragsworth 12y ago
      > "given our understanding of star formation it is difficult to form isolated objects that small." No, that is demonstrably false. You can try this with any particle gravity simulator - Place a bunch of particles, and watch how many get ejected. Star systems behave similarly.
diziet 12y ago
The concept of a solitary star without any 'nearby' neighbors features in Iain Banks' Against A Dark Background: https://www.goodreads.com/book/show/422452.Against_a_Dark_Background https://www.goodreads.com/book/show/422452.Against_a_Dark_Ba...
- pavel_lishin 12y ago
  I read a short story, not too long ago, about a solitary planet on approach to a solar system. Their society was stagnating due to some cultural predilection to having a once-every-ten-year science fair, and having no technological progress outside of that. It was framed as a murder mystery, too. Wish I remembered what it was...
  - teraflop 12y ago
    Sounds like "The Science Fair" (1971) by Vernor Vinge.
    - pavel_lishin 12y ago
      Yes, you're right!
  - civilian 12y ago
    Sci-fi framed as a murder mystery? There's a good bet it was an Asimov novel :-P
  - DanBC 12y ago
    rec.arts.sf.written used to be good for story IDs. http://www.steelypips.org/sfwrittenfaq/#01 http://www.steelypips.org/sfwrittenfaq/#01 I'm not sure if there is already a sub-reddit for story ids.
- pndmnm 12y ago
  A couple short stories: Arthur C. Clarke's "Crusade" is set on a starless planet between galaxies. A.E. van Vogt's "Black Destroyer" has as a minor plot point the idea that a civilization developing in a single-planet solar system extremely far away from any others would never develop interstellar travel because there would be no stepping stones.
transfire 12y ago
So they actually "lurk"?
comrade1 12y ago
Our own solar system is outside the central part of the galaxy and a bit off the ecliptic plane. There isn't that much around us. The central core of the Galaxy could be populated, wars raging around us, and we're the equivalent of a mountain village in Laos. But could you imagine being one of these floater solar systems? We at least can reach some star systems in generation ships. They would would need much more. If 1/2 of stars are outside of feasible colonization distances that changes the Fermi paradox formula quite a bit.
- pavel_lishin 12y ago
  I don't think you even need generation ships, if you can maintain a constant acceleration. And with constant acceleration, going to our nearest potentially habitable neighbor isn't that much further, subjective-time-wise, than it is to Andromeda. Assuming acceleration of 1g, from here to Alpha Centauri, it would take 6 years objective, 3.5 subjective. To the center of the galaxy, it would take 27,000 years objective, but only 20 years subjective. Magellanic clouds? 162k years objective, but only 23 years subjective! 28 years to Andromeda. Fuel may be in short supply, but relativity really works for you - ignoring abrasion and impacts, if you can get to one galaxy, you can get to most others in your neighborhood. (All calculations derived from http://spacetravel.nathangeffen.webfactional.com/spacetravel.php http://spacetravel.nathangeffen.webfactional.com/spacetravel..., because I'm too lazy to do it by hand.)
  - readerrrr 12y ago
    And the last paragraph is the main problem. The ship would get torn apart from lone atoms and to actually stop yourself you need an exponential amount of fuel, because you need to accelerate ( much more than )half of it just to stop yourself. Even if you protect yourself from relativistic atoms, they still create a drag. And that happens before you reach 0.99c.
    - pavel_lishin 12y ago
      edit: Nevermind - you're totally right, and I'm totally wrong - I didn't think it through, and didn't realize that since relativity helps you less and less as you decelerate, the amount of fuel required does increase hugely if you actually want to stop at your destination. Unedited original post follows: > to actually stop yourself you need an exponential amount of fuel, because you need to accelerate half of it just to stop yourself Hang on, I don't understand this part. First, you're right, I didn't think about deceleration - but that only doubles the trip length at most, since you have to accelerate halfway, then decelerate halfway. And probably not even exactly that if you're carrying your fuel, since deceleration will be a little bit easier - you've burned some gas, so there's less mass to push around. And you're right, I didn't think about the drag - but that actually works out better for extragalactic visitors! There isn't as much stuff there to stop them when they're taking off, and once they hit a galaxy, it actually helps them decelerate. (Again, my dreamy eyes are ignoring the practical hazards of this "help" which might just turn them into a fast moving gas cloud.)
Zarathust 12y ago
Is all of this accounted for in the "missing mass" of the observable universe? In other words, could those unseen before stars explain a part of the dark matter problem?
- antognini 12y ago
  Not really. Dark matter makes up so much more of the Universe (~25% dark matter vs. 5% baryons -- stars themselves are closer to .2%) in that even doubling the number of stars would not appreciably change the amount of missing mass. Moreover, dark matter has a different signature on the CMB than ordinary matter does, so you cannot solve the dark matter problem by adding ordinary matter---dark matter has to be something fundamentally different. There is, however, a problem called the "missing baryons problem." Measurements of the CMB predicts a certain amount of ordinary matter in the universe, but the amount of matter observed is too small by a factor of about 2. It is possible that these stars could contribute to the missing matter in this problems. (It probably would not be the stars directly, but a tenuous gas from which the stars formed.)
- Florin_Andrei 12y ago
  No, dark matter is something that happens within galaxies, affecting their rotation. It's not something outside.
  - db48x 12y ago
    Sorry, that's wrong. Matter, dark or otherwise, is scattered throughout the universe, with variations in density at all scales. Ordinary and dark matter are gravitationally attracted to each other, so they clump together. Anywhere you find matter you'll find a proportional amount of dark matter, on average; naturally there are variations. There's some in between you and your computer monitor right now. The first good indication that dark matter must exist was in fact that the rotation rates of the observable galaxies were too large for the amount of visible mater they contain. Of course the first explanation was that this matter was ordinary gas, dust, rocks, planets (which are just larger dust particles, when compared with the size of even a small galaxy.), etc that wasn't emitting any light. However, there would have to be so much of it that it would occlude the distant galaxies, something that obviously isn't happening. Thus the modern theory is that dark matter is a form of matter that interacts gravitationally with ordinary matter, but has no interaction with the electromagnetic force (light).
deleted 12y ago
[deleted]
StephenFalken 12y ago
One day we will eventually realize that we are indeed traveling through space on "Spaceship Earth".

104 points by scott_s 12y ago

I think it's worth noting that this is the conclusion one group of scientists came to based on data they collected. That's true of all published articles, but my point is that other scientists have not necessarily come to the same conclusion - yet. But that's how science works! At the end of this submission, they mention that they are planning follow-up experiment which should get more data. I first heard about this on the Skeptics Guide podcast (http://www.theskepticsguide.org/ http://www.theskepticsguide.org/), and I was surprised because it's counter to how I think about the universe.

paul_f 12y ago

Anyone living on planets orbiting those stars would not see many other stars at all, right?

jessriedel 12y ago
Right. Almost all the stars we see in the night sky are within 1,000 light years. You could guess this from the fact that the Milky Way disk is about ~1,000 light years thick and ~100,000 light years in diameter. If we could easily see stars further than the thickness, then we'd see a lot more stars along the Galactic disk. But instead, the only sign of the disk is the diffuse glow of very distant, undifferentiated stars where the Milky Way gets it's name. Presumably stars outside of galaxies are at much lower density, so they wouldn't see hardly any points of light in the sky. If most such stars are still within the Galactic groups, then they would probably just see faint smudges of other galaxies like the very dim Magellanic Clouds we can see. (Note that these are still pretty big, though, in terms of angular size. Several moons wide.) On the other hand, planets around lone stars in voids away from Galaxy clusters would presumably have nothing visible to the naked eye from their surface. (Someone please correct me if I'm wrong. I'm not an astronomer.)
- dalke 12y ago
  To add to those excellent points, the Andromeda galaxy is visible with the naked eye, making it another type of smudge ("Little Cloud", to use an early name) that might be seen by a lone star in a galactic cluster.
  - deciplex 12y ago
    Andromeda is pretty close to us. In fact, we're going to collide with it in a few billion years. After that, what little remains of our solar system by then, might end up like one of these orphaned stars. So if Andromeda is already difficult to see by us, that gives some indication of what's going to be visible from a planet that is much further away from anything, than even that.
    - dalke 12y ago
      The premise in the g'parent comment is "If most such stars are still within the Galactic groups ...". This assumption is reasonable given the hypothesis expressed in the article: "Bock suspects that a lot of these renegade stars could have come from relatively lightweight galaxies, which can lose hold of their stars more easily than more massive galaxies." Our Local Group has a diameter of ~10 megalight-years . Andromeda is 2.54 MLy away. Thus, given the premise, and assuming that our own cluster is "typical", it's unlikely that a renegade star is all that much further from a galaxy like ours or Andromeda than we are from Andromeda.
- throwaway_yy2Di 12y ago
  I think that's right (also not an astronomer). I looked this up in the Hipparcos catalog [0][1] -- that's one that measures parallax distances to bright stars. It's supposed to be complete to at least +7.3 magnitude [0]. Cutting off at +6.5 magnitude [2] (the faintest visible stars according to [3]), Hipparcos reports * 7,943 visible stars * 1,078 (14%) beyond 1,000 light years; * 34 beyond 10,000 l.y. (these must be supergiants!) If I calculated right, a +6.5 magnitude star would demand an absolute magnitude of -0.9 at 1,000 light years, and -5.9 at 10,000 light years. Looking this up on the Hertzsprung–Russell chart [4], this would include only very bright giants, and supergiants, respectively. [0] https://en.wikipedia.org/wiki/Hipparcos https://en.wikipedia.org/wiki/Hipparcos [1] ftp://cdsarc.u-strasbg.fr/pub/cats/I/311/ (hip2.dat.gz for data; intro.pdf for field descriptions) [2] Hp magnitude is a 340-850 nm visible band, which diverges slightly from V band magnitude, http://heasarc.gsfc.nasa.gov/W3Browse/star-catalog/hic.html http://heasarc.gsfc.nasa.gov/W3Browse/star-catalog/hic.html [3] https://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_notable_celestial_objects https://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_no... [4] https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_di...
Florin_Andrei 12y ago
All stars you see at night with naked eye are within this galaxy. All of them. Yes, Andromeda (M31) is visible to the naked eye, but it's pretty huge and quite close to us. Orbiting a lone star, the naked eye at night would see something between absolutely nothing, and maybe a few faint patches of light. And that's in perfect conditions - middle of desert or ocean, zero light pollution.
- JoeAltmaier 12y ago
  I don't believe it. I can see many galaxies from where I stand. They would appear even brighter without a local galaxy to wash them out. The sky would appear totally covered in fuzzy dots - galaxies.
  - Florin_Andrei 12y ago
    > I can see many galaxies from where I stand. If half a dozen is "many", then sure. But you probably live far from any cities then. http://en.wikipedia.org/wiki/List_of_galaxies#Naked-eye_galaxies http://en.wikipedia.org/wiki/List_of_galaxies#Naked-eye_gala... (The list includes objects that are very difficult to see, and some only "reportedly" seen naked-eye.) > They would appear even brighter without a local galaxy to wash them out. There's no reduction in contrast in the direction perpendicular to the galactic plane. And yet the naked eye doesn't perceive the sky there "totally covered in fuzzy dots". The naked eye has a lot of trouble seeing anything beyond the Local Group - and these are a handful of close-knit galaxies. You need telescopes for that, with plenty of aperture. Once the aperture is comparable to the diameter of your car's wheels, or bigger, then yes, you get the "my god, it's full of galaxies" effect.
    - JoeAltmaier 12y ago
      I'm an idiot. I confused nebulae etc for galaxies. Not an astronomer. So most of what we see are constructions inside our own galaxy? I see what you mean - the sky would be a very lonely place for the intergalactic skygazer.
cmsmith 12y ago
Making it fun to imagine the invention of the telescope on those planets. It would be like the Hubble deep field image, but MUCH more unexpected. On the other hand, who knows how much science and telescope-making would have been set back without there being anything to look up at. Without other stars (and our rather extraordinary moon), it would take a lot longer than 1500 years to break out of the Ptolemaic mindset.
- IndianAstronaut 12y ago
  I would imagine other galaxies being visible like faint blobs in the sky, not to mention that you would still see the planets around the given star.
  - kijin 12y ago
    Other planets would definitely help stimulate the mind. But depending on how isolated the system is, galaxies in the night sky might be indistinguishable from clouds. Especially if the planet has lots of clouds.

mrfusion 12y ago

Could this be a solution to the Fermi Paradox?

pavel_lishin 12y ago
I don't think so. It may alter the equation, but it wouldn't really be a "solution". For one, considering how difficult interstellar travel should be based on what we know, intergalactic travel would be much more difficult, even given von Neumann's self-replicator ideas. (It's like the difference between crossing a river, and crossing the Pacific.) On the other hand, maybe galaxies are just naturally inimical to life, and extragalactic stars are the only places where long-term biological survival is possible.
- VieElm 12y ago
  > On the other hand, maybe galaxies are just naturally inimical to life Gamma ray bursts would be more likely in a galaxy and those are inimical to life.
  - logfromblammo 12y ago
    Also, catastrophic collisions with other bodies would be more frequent when those bodies are closer together. Even if there is no direct interaction, nearby massive objects could still perturb the orbits of distant objects--similar to those in our Oort Cloud and Kuiper Belt--enough to make them impact planets orbiting closer to the star.
antognini 12y ago
No. Even if half of stars are outside the Galaxy, there are still enough stars within the Galaxy that the ideas behind the Fermi paradox would still be valid. This would be an explanation of the Fermi paradox if we were on a planet around one of the stars outside the Galaxy.
jessriedel 12y ago
No, if you're adding stars to our theory of the universe you're only making the paradox worse (although not much worse if such life would probably be unable to expand). If, instead, you're changing the theory be suggesting that the number of life-originating stars is the same and moving half of them into voids, then you're only reducing the problem by at most a factor of 2. Because of the many unpinned down orders of magnitude involved, this doesn't do much at all.

DanielBMarkham 12y ago

Also of note, from another group of researchers word is that there may be more planets in-between stars than there are circling stars. If this continues, the universe is going to end up being nothing like we expected only a few years ago.

fragsworth 12y ago
I am pretty sure this is a widely acknowledged assumption among most scientists, considering our current understanding of the formation of planets, stars, and galaxies.
- ggreer 12y ago
  These stars were formed from gas clouds in galaxies. Wouldn't a gravitational slingshot with ∆v greater than galactic escape velocity likely strip their planets? Unless you mean the ex-planets themselves would end up alone intergalactic space. Apparently, the vocabulary used for such objects is, "sub-brown dwarf."[1] 1. http://en.wikipedia.org/wiki/WISE_0855%E2%88%920714 http://en.wikipedia.org/wiki/WISE_0855%E2%88%920714
- antognini 12y ago
  The free-floating planets result is still controversial and there is a substantial fraction of the astronomical community that doesn't believe it. If it is true, it introduces problems in our understanding of planet formation because planet-planet scattering as we currently understand it is unable to produce free floating planets at the rate claimed. It is also possible that planets form in isolation (so really they're very small brown dwarfs), but given our understanding of star formation it is difficult to form isolated objects that small.
  - fragsworth 12y ago
    > "given our understanding of star formation it is difficult to form isolated objects that small." No, that is demonstrably false. You can try this with any particle gravity simulator - Place a bunch of particles, and watch how many get ejected. Star systems behave similarly.

diziet 12y ago

The concept of a solitary star without any 'nearby' neighbors features in Iain Banks' Against A Dark Background: https://www.goodreads.com/book/show/422452.Against_a_Dark_Background https://www.goodreads.com/book/show/422452.Against_a_Dark_Ba...

pavel_lishin 12y ago
I read a short story, not too long ago, about a solitary planet on approach to a solar system. Their society was stagnating due to some cultural predilection to having a once-every-ten-year science fair, and having no technological progress outside of that. It was framed as a murder mystery, too. Wish I remembered what it was...
- teraflop 12y ago
  Sounds like "The Science Fair" (1971) by Vernor Vinge.
  - pavel_lishin 12y ago
    Yes, you're right!
- civilian 12y ago
  Sci-fi framed as a murder mystery? There's a good bet it was an Asimov novel :-P
- DanBC 12y ago
  rec.arts.sf.written used to be good for story IDs. http://www.steelypips.org/sfwrittenfaq/#01 http://www.steelypips.org/sfwrittenfaq/#01 I'm not sure if there is already a sub-reddit for story ids.
pndmnm 12y ago
A couple short stories: Arthur C. Clarke's "Crusade" is set on a starless planet between galaxies. A.E. van Vogt's "Black Destroyer" has as a minor plot point the idea that a civilization developing in a single-planet solar system extremely far away from any others would never develop interstellar travel because there would be no stepping stones.

transfire 12y ago

So they actually "lurk"?

comrade1 12y ago

Our own solar system is outside the central part of the galaxy and a bit off the ecliptic plane. There isn't that much around us. The central core of the Galaxy could be populated, wars raging around us, and we're the equivalent of a mountain village in Laos. But could you imagine being one of these floater solar systems? We at least can reach some star systems in generation ships. They would would need much more. If 1/2 of stars are outside of feasible colonization distances that changes the Fermi paradox formula quite a bit.

pavel_lishin 12y ago
I don't think you even need generation ships, if you can maintain a constant acceleration. And with constant acceleration, going to our nearest potentially habitable neighbor isn't that much further, subjective-time-wise, than it is to Andromeda. Assuming acceleration of 1g, from here to Alpha Centauri, it would take 6 years objective, 3.5 subjective. To the center of the galaxy, it would take 27,000 years objective, but only 20 years subjective. Magellanic clouds? 162k years objective, but only 23 years subjective! 28 years to Andromeda. Fuel may be in short supply, but relativity really works for you - ignoring abrasion and impacts, if you can get to one galaxy, you can get to most others in your neighborhood. (All calculations derived from http://spacetravel.nathangeffen.webfactional.com/spacetravel.php http://spacetravel.nathangeffen.webfactional.com/spacetravel..., because I'm too lazy to do it by hand.)
- readerrrr 12y ago
  And the last paragraph is the main problem. The ship would get torn apart from lone atoms and to actually stop yourself you need an exponential amount of fuel, because you need to accelerate ( much more than )half of it just to stop yourself. Even if you protect yourself from relativistic atoms, they still create a drag. And that happens before you reach 0.99c.
  - pavel_lishin 12y ago
    edit: Nevermind - you're totally right, and I'm totally wrong - I didn't think it through, and didn't realize that since relativity helps you less and less as you decelerate, the amount of fuel required does increase hugely if you actually want to stop at your destination. Unedited original post follows: > to actually stop yourself you need an exponential amount of fuel, because you need to accelerate half of it just to stop yourself Hang on, I don't understand this part. First, you're right, I didn't think about deceleration - but that only doubles the trip length at most, since you have to accelerate halfway, then decelerate halfway. And probably not even exactly that if you're carrying your fuel, since deceleration will be a little bit easier - you've burned some gas, so there's less mass to push around. And you're right, I didn't think about the drag - but that actually works out better for extragalactic visitors! There isn't as much stuff there to stop them when they're taking off, and once they hit a galaxy, it actually helps them decelerate. (Again, my dreamy eyes are ignoring the practical hazards of this "help" which might just turn them into a fast moving gas cloud.)

Zarathust 12y ago

Is all of this accounted for in the "missing mass" of the observable universe? In other words, could those unseen before stars explain a part of the dark matter problem?

antognini 12y ago
Not really. Dark matter makes up so much more of the Universe (~25% dark matter vs. 5% baryons -- stars themselves are closer to .2%) in that even doubling the number of stars would not appreciably change the amount of missing mass. Moreover, dark matter has a different signature on the CMB than ordinary matter does, so you cannot solve the dark matter problem by adding ordinary matter---dark matter has to be something fundamentally different. There is, however, a problem called the "missing baryons problem." Measurements of the CMB predicts a certain amount of ordinary matter in the universe, but the amount of matter observed is too small by a factor of about 2. It is possible that these stars could contribute to the missing matter in this problems. (It probably would not be the stars directly, but a tenuous gas from which the stars formed.)
Florin_Andrei 12y ago
No, dark matter is something that happens within galaxies, affecting their rotation. It's not something outside.
- db48x 12y ago
  Sorry, that's wrong. Matter, dark or otherwise, is scattered throughout the universe, with variations in density at all scales. Ordinary and dark matter are gravitationally attracted to each other, so they clump together. Anywhere you find matter you'll find a proportional amount of dark matter, on average; naturally there are variations. There's some in between you and your computer monitor right now. The first good indication that dark matter must exist was in fact that the rotation rates of the observable galaxies were too large for the amount of visible mater they contain. Of course the first explanation was that this matter was ordinary gas, dust, rocks, planets (which are just larger dust particles, when compared with the size of even a small galaxy.), etc that wasn't emitting any light. However, there would have to be so much of it that it would occlude the distant galaxies, something that obviously isn't happening. Thus the modern theory is that dark matter is a form of matter that interacts gravitationally with ordinary matter, but has no interaction with the electromagnetic force (light).

deleted 12y ago

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StephenFalken 12y ago

One day we will eventually realize that we are indeed traveling through space on "Spaceship Earth".