13 ms·

Alien life could thrive in ancient star clusters

84 points by philbo 11y ago

pklausler 11y ago
One argument against the proposition: these very old stars have low metallicity. If life requires chemistry with elements above lithium in atomic number, it might be more rare around first-generation stars.
- mercurialshark 11y ago
  I'm always surprised this isn't discussed more or at least a variable to consider among others for updating the Drake Equation.
  - lomnakkus 11y ago
    Personally, the Drake Equation has always seemed more than a little silly to me -- in that -- the plausible range of most of the parameters means that you can get pretty much any result you want. Don't get me wrong, it's a fine thing to ponder and think about all the involved variables and probabilities, but I wouldn't take it very seriously as an actual estimate of anything meaningful.
    - ethbro 11y ago
      When you don't know a lot, estimates have wide bounds. That doesn't diminish the importance of trying to logically construct a formula for establishing bounds. They might not be useful today, but you've got to start somewhere.
      - lomnakkus 11y ago
        Sure, but we might want try to at least constrain the parameters with better (verifiable!) bounds and perhaps even modify the equation occasionally when we learn more -- as we have done (learn, that is) since it was proposed. I should make clear that I wasn't disagreeing with mercurialshark, per se. As I said: It's certainly a good thing to think about these things, but... :) EDIT: Assuming it generally agrees with observed facts, a good sign for any scientific theory is how much it constrains the explanation/solution space. (Paraphrased, obviously. For the life of me I cannot remember who said this. Perhaps David Deutsch?) I don't think the Drake Equation adequately constrains the solution/explanation space.
        noselasd 11y ago
        We do constrain the Drake equation when we know more. It's just that we don't know a lot. We have come to know the number of stars around pretty well - at least in our galaxy. Thanks to Kepler and other exoplanet hunters, we know know alot more about the number of planets. These findings are used to constrain the Drake equation. The rest of the parameters we don't know much about, yet.
    - IndianAstronaut 11y ago
      Especially considering we have a sample size of one, possibly two if you count Mars as a potential place of habitability. I would hold judgement till we explore Europa. Depending on what we find there life may or may not be common in the universe.
      - danieltillett 11y ago
        All this will tell us is that life can survive the trip to Mars or Europa. We already know this to be the case ( microbes are tough) and asteroid strikes provide the means of getting Earth life to these planets/ moons. At this point I would be more surprised if we don't find microbial life in the solar system outside of Earth.
  - Wingman4l7 11y ago
    Yes; I've often wondered about the potential existence of planets with an insufficient quantity of rare earth metals, and if that renders them basically "inhospitable" to high tech civilization.
    - erikpukinskis 11y ago
      Why rare earth metals specifically?
      - Wingman4l7 11y ago
        They're used for a whole host of technologies -- doping semiconductors, magnets, lens coatings, metal alloys, etc.
    - dogma1138 11y ago
      Life also has to be on dry land and pretty similar in to us as far as sensory capabilities go to get any where. If you can't see you aren't going to develop laser, if you live under water you won't have fire, heck even hands are required for fine tool making so it's unlikely that we'll have space elephants or squids...
    - daveguy 11y ago
      Rare earth metals are a very specific set of elements. If you are talking "nothing above lithium" that means only hydrogen helium and lithium. AKA no carbon oxygen nitrogen (or silicon).
- Retric 11y ago
  Solar wind has a fairly large effect on plant formation so even relatively early stars are likely to have some rocky inner planets. Granted, not first generation stars, but large stars can go nova in as little as 3 million years making the 'first' gen stars a very short period.
- JetSetWilly 11y ago
  Centauri Dreams covered this point well: > Working with Alak Ray (Tata Institute of Fundamental Research, Mumbai), Di Stefano points out that we have found low-metallicity stars known to have planets elsewhere in the galaxy. And while we can couple the occurrence of Jupiter-class planets with stars that have higher metallicity, there seems to be no such correlation when we’re dealing with smaller, rocky worlds like the Earth. Perhaps, then, we shouldn’t dismiss planets in globular clusters. http://www.centauri-dreams.org/?p=34775 http://www.centauri-dreams.org/?p=34775
  - Udo 11y ago
    There is still a lot about the formation of galaxies and star systems that we don't know. The reason why we assume a lower probability for rocky planets in globular clusters is the general environment of the typical cluster: a small population of slow-burning early-generation stars with no appreciable interstellar dust clouds in between them. If you compare that to low-metallicity stars in the galaxy proper, there are reasons why those might have planets that are not easily afforded to star systems located in globular clusters. Our galaxy is rich in dust and gas clouds that are also inhomogeneous. For example, a metal-poor star may be born out of a low-metal gas cloud and then attract a metal-rich dust disc later. These things are expected to happen a lot less often in globular clusters.
    - iofj 11y ago
      There's the reverse problem as well. If life develops by itself when it has (chemically) the chance ... then where is it ? Our sun is a third generation star (meaning some sun went nova, recoalesced into another sun, went nova, recoalesced in our sun and ignited, and that was 3+ billion years ago). Our sun is not a particularly early third generation star. Given that it would take a civilization about a billion years to spread through the galaxy to all liveable planets ... some civilization should have done that up to 4-5 billion years ago. If life can happen in 2nd generation stars as well, it should have happened 6-8 billion years ago. Obviously this hasn't happened. I only see 3 reasonable explanations: 1) Drake equation is too optimistic. By a huge factor (2-300 million times too optimistic) 2) It's not a problem, because civilizations kill themselves before doing interstellar travel and while we are on the way to doing that but not quite there yet. 3) There's something we don't know
jtwaleson 11y ago
"The question is not -where- are the life forms capable of interstellar communication, but -when- are they." That is the central point of the argument in the article, yet somehow it's never really mentioned.
sawwit 11y ago
What about gamma ray bursts? I've read that our position more at the outer rim of the galaxy is beneficial because there are fewer gamma ray bursts compared to more dense regions.
- pavel_lishin 11y ago
  Aren't most GRBs extra-galactic in origin? If anything, being on the outskirts means there's less matter protecting us from them.
  - Udo 11y ago
    They're only dangerous if they happen within the same galaxy and your planet happens to be right on the axis of the narrow burst cone. In that case there might still be a statistical advantage to being nearer to the core of the galaxy due to more matter density, but it might be offset by the increased chance of getting hit with a GRB there in the first place. Also, we're not actually within the outer rim of the galaxy: http://www.nasa.gov/mission_pages/sunearth/news/gallery/galaxy-location.html http://www.nasa.gov/mission_pages/sunearth/news/gallery/gala...
- stargazer-3 11y ago
  Gamma ray bursts are produced by stars that are very massive and short-lived. So one can argue that after few tens of millions of years a cluster wouldn't produce that them. On the other hand you are of course right - in a galaxy that is still undergoing intense star formation it is still dangerous to live in a dense region where a nearby young cluster can still render your home planet sterile through a GRB. However, our own Galaxy doesn't seem to be forming stars that actively anymore, and the chance of a new GRB pointing directly at a given star cluster is negligible.
Grishnakh 11y ago
The thing these speculations about alien life and communicating with them miss is: what if the aliens don't want to talk to us? That's probably why you don't hear so much about UFOs these days like we did a few decades ago: they came, they checked us out, and then they launched some beacons just outside our solar system warning everyone to stay away, along with a Galactic General Order that if we ever develop enough to send manned missions outside our system, we have to be destroyed for the good of the galaxy.
- Udo 11y ago
  There are two propositions here: One, that some UFO sightings are due to the activities of extraterrestrial intelligences. This seems very unlikely at this point. Second, that the Fermi Paradox exists at least partly due to aliens avoiding us specifically, what is commonly referred to as the "zoo hypothesis". As far as speculative explanations go, it's not an unreasonable contender. However, it is not among the most likely or the most simple hypotheses out there. The zoo hypothesis pre-supposes the ready availability of FTL technology, which itself implies that such technology is even possible in general. It also hinges on a specific combination of psychological factors and random happenstance, namely the desire to isolate an entire star system (which is not a trivial feat), and the fact that they even discovered our existence in the first place (which is also quite the coincidence, even for a culture that can travel faster than the speed of light). These reasons don't rule out the zoo hypothesis. However, if I were to bet on one scenario, it would be the practical consequences of the fact that expected distances between civilizations are enormous in both time and space, plus the weakly-shining light cone of our technologically advanced existence doesn't reach very far and isn't easy to detect - and those same factors would be preventing us from seeing an advanced civilization as well, even if they happened to be relatively close by.
  - Grishnakh 11y ago
    The problem with conjecture about aliens is that, by definition, they're alien, and since we haven't even met one yet (aside from some unsubstantiated claims by some people), we can't even begin to guess at their capabilities, motivations, etc. Remember, we're a primitive race that hasn't even left its own planet, except for a brief excursion to its nearby moon, and some primitive robotic probes to nearby bodies. We really don't know if there's some branch of physics that allows FTL travel, or if it's possible for intelligent beings to exist in multiple or parallel dimensions, etc. Everything we discuss along these lines is nothing more than wild-ass speculation. One problem I have with your assertion about the ready availability of FTL technology is that I think that assumption relies on the assumption that ETs have similar lifespans as us, which is probably a faulty assumption. A race advanced enough for interstellar travel could very well have totally different biology that doesn't age, or they might have technologically defeated aging, which is something we're already working on ourselves even though we've only sent a handful of people beyond our Van Allen belts. A species that doesn't age, or has lifespans of millennia, might not think it's that big a deal to send a ship to a nearby star system on a journey that'll take a dozen or so years (in ship-time due to relativistic dilation; centuries in planet-time). By the time they get back, their friends might be a bit older, but it'd be like us taking a trip and coming back 5 years later. And don't forget the possibility of "suspended animation". With sufficiently powerful engines able to achieve a sufficiently high fraction of c, a trip of a dozen or so light-years won't take that long in ship-time. It'll even be something we'll want to do with our lifespans. Discovering our existence shouldn't be that hard. There's hundreds of stars within a few dozen lightyears or so, so an advanced civilization should be able to build a powerful robotic ship to tour them all and gather data. A few millennia or so later, it'll return and they can analyze it, and our existence will be pretty obvious just by scanning the EM range (assuming they came within the last century), or by detecting atmospheric oxygen and photosynthesis. Of course this assumes they're looking for that kind of life, just like we're doing now with our exoplanet searches. Honestly, it shouldn't be that hard to detect other civilizations from a reasonable distance; we're already detecting various exoplanets, and as I said, we don't even have any serious spaceflight capability; we're doing it all with ground-based and some orbital telescopes. We're having problems seeing planets the size of our own, but better technology should change that eventually. If we had the ability to send a ship to tour the nearby stars and send data back, advanced civilizations should be fairly obvious to a ship inside their system, just by orbiting the likely-looking planets (inside the "habitable zone") and taking pictures, scanning EM frequencies, etc. It would take a while to get data back though since the ship would take decades or centuries to get there.
cousin_it 11y ago
An advanced alien civilization will probably have very low radiation signature. To afford the maximum amount of computation, it should completely encase the star (maximum energy) and radiate all waste heat toward a black hole (maximum cooling).
- Udo 11y ago
  > and radiate all waste heat toward a black hole (maximum cooling). It's comparatively inefficient to radiate heat into a narrow cone, and there is little advantage to radiating it into a black hole. On the contrary, matter falling into the black hole will form an accretion disk that radiates heat back to you. In order to maximize dissipation, they would simply radiate it away into all directions uniformly. However, there might be other considerations to take into account here besides physics. It might be important to such an isolated civilization to avoid detection. In that case they would gladly take the hit on efficiency and radiate their heat in narrow cones into the gaps where no nearby stars are located. > An advanced alien civilization will probably have very low radiation signature. To afford the maximum amount of computation Maybe. We can't say what the goals are of any advanced civilization. The reason why we like to talk about this specific type of civilization is that they are the type that we can actually look for right now. But as I said above, if you're an isolationist population of computer brains, it makes sense to go through the effort of avoiding other people showing up on your doorstep. Such a culture might deem it acceptable to invest most of their energy budget into avoiding detection, as opposed to computation only.
  - pavel_lishin 11y ago
    To bring it back to the parent comment, wouldn't it make sense for such a culture to live near a black hole? All of their waste emissions would be shadowed pretty well by the accretion disk, and other species might avoid the neighborhood in general given that it's not a safe or nice place to be.
    - Udo 11y ago
      > wouldn't it make sense for such a culture to live near a black hole? Technically the black hole doesn't offer anything beyond what a sun of comparable output would offer. > and other species might avoid the neighborhood in general given that it's not a safe or nice place to be True, but the reasons for avoiding close contact with it are also the reasons why building a habitat there is potentially risky. All things being equal, a Mercury-like planet would make a better base for a civilization having those goals: it offers a lot of solar energy, affords some protection from detection by being too close to the star to resolve it as a non-natural heat source, and as opposed to the black hole it's also in a stable environment.
madaxe_again 11y ago
Nightfall, as mentioned at the end of the piece, is a great little early Asimov story - a culture to whom candles are alien and the idea of artificial light is bizarre. Thoroughly recommend. In fact, here it is: https://www.uni.edu/morgans/astro/course/nightfall.pdf https://www.uni.edu/morgans/astro/course/nightfall.pdf
- Outdoorsman 11y ago
  Thanks for the link...
- jon_richards 11y ago
  Funny, in the book artificial light is extremely commonplace. A theme park actually builds a pitch black tunnel as a ride.
- 4ad 11y ago
  The End of Eternity and Nightfall (the novel with Robert Silverberg, not the short story) are Asimov's greatest novels.
cnp 11y ago
One thing that always surprises me about the search for ET is how often the purely psychological / consciousness aspect is disregarded. As anyone who has worked with DMT or Ayahuasca can tell you, you don't need to travel far to reach the outer limits of space or even have contact experiences, and this is very easy to test should the anti-scientific legal mechanisms preventing such a study be overcome. Its like, Fermi's Paradox is almost completely irrelevant if you come from the position that any sufficiently advanced civilization is aware of the possible non-local properties of consciousness.
- ElysianEagle 11y ago
  Not sure why you've been downvoted, but I think this is very much on point.
  - cnp 11y ago
    I was curious of this as well, but not surprised. For the skeptics, all I ask is that you self experiment. Its easy and cheap, requiring only a simple extraction performed on the Arcacia Confusa plant, which you can order online.
    - pavel_lishin 11y ago
      But a sample size of one is worthless, especially when the person running the experiment is high :) On a more serious note, I have no idea how you'd actually test this. How would you prove or disprove that someone experimenting with hallucinogens is actually communicating with something else? The only thing I can think of is having two people under the influence being able to communicate with each other, with absolutely no other way of doing so. Subjects A and B have never met, and don't have any way of passing messages during their experience. Subject A is told to pass some randomly generated string to subject B, either directly or via some alien intermediary. If Subject B can guess Subject A's string, then that might be evidence of something interesting and objectively external happening.
      - 11y ago

84 points by philbo 11y ago

One argument against the proposition: these very old stars have low metallicity. If life requires chemistry with elements above lithium in atomic number, it might be more rare around first-generation stars.

mercurialshark 11y ago
I'm always surprised this isn't discussed more or at least a variable to consider among others for updating the Drake Equation.
- lomnakkus 11y ago
  Personally, the Drake Equation has always seemed more than a little silly to me -- in that -- the plausible range of most of the parameters means that you can get pretty much any result you want. Don't get me wrong, it's a fine thing to ponder and think about all the involved variables and probabilities, but I wouldn't take it very seriously as an actual estimate of anything meaningful.
  - ethbro 11y ago
    When you don't know a lot, estimates have wide bounds. That doesn't diminish the importance of trying to logically construct a formula for establishing bounds. They might not be useful today, but you've got to start somewhere.
    - lomnakkus 11y ago
      Sure, but we might want try to at least constrain the parameters with better (verifiable!) bounds and perhaps even modify the equation occasionally when we learn more -- as we have done (learn, that is) since it was proposed. I should make clear that I wasn't disagreeing with mercurialshark, per se. As I said: It's certainly a good thing to think about these things, but... :) EDIT: Assuming it generally agrees with observed facts, a good sign for any scientific theory is how much it constrains the explanation/solution space. (Paraphrased, obviously. For the life of me I cannot remember who said this. Perhaps David Deutsch?) I don't think the Drake Equation adequately constrains the solution/explanation space.
      - noselasd 11y ago
        We do constrain the Drake equation when we know more. It's just that we don't know a lot. We have come to know the number of stars around pretty well - at least in our galaxy. Thanks to Kepler and other exoplanet hunters, we know know alot more about the number of planets. These findings are used to constrain the Drake equation. The rest of the parameters we don't know much about, yet.
  - IndianAstronaut 11y ago
    Especially considering we have a sample size of one, possibly two if you count Mars as a potential place of habitability. I would hold judgement till we explore Europa. Depending on what we find there life may or may not be common in the universe.
    - danieltillett 11y ago
      All this will tell us is that life can survive the trip to Mars or Europa. We already know this to be the case ( microbes are tough) and asteroid strikes provide the means of getting Earth life to these planets/ moons. At this point I would be more surprised if we don't find microbial life in the solar system outside of Earth.
- Wingman4l7 11y ago
  Yes; I've often wondered about the potential existence of planets with an insufficient quantity of rare earth metals, and if that renders them basically "inhospitable" to high tech civilization.
  - erikpukinskis 11y ago
    Why rare earth metals specifically?
    - Wingman4l7 11y ago
      They're used for a whole host of technologies -- doping semiconductors, magnets, lens coatings, metal alloys, etc.
  - dogma1138 11y ago
    Life also has to be on dry land and pretty similar in to us as far as sensory capabilities go to get any where. If you can't see you aren't going to develop laser, if you live under water you won't have fire, heck even hands are required for fine tool making so it's unlikely that we'll have space elephants or squids...
  - daveguy 11y ago
    Rare earth metals are a very specific set of elements. If you are talking "nothing above lithium" that means only hydrogen helium and lithium. AKA no carbon oxygen nitrogen (or silicon).
Retric 11y ago
Solar wind has a fairly large effect on plant formation so even relatively early stars are likely to have some rocky inner planets. Granted, not first generation stars, but large stars can go nova in as little as 3 million years making the 'first' gen stars a very short period.
JetSetWilly 11y ago
Centauri Dreams covered this point well: > Working with Alak Ray (Tata Institute of Fundamental Research, Mumbai), Di Stefano points out that we have found low-metallicity stars known to have planets elsewhere in the galaxy. And while we can couple the occurrence of Jupiter-class planets with stars that have higher metallicity, there seems to be no such correlation when we’re dealing with smaller, rocky worlds like the Earth. Perhaps, then, we shouldn’t dismiss planets in globular clusters. http://www.centauri-dreams.org/?p=34775 http://www.centauri-dreams.org/?p=34775
- Udo 11y ago
  There is still a lot about the formation of galaxies and star systems that we don't know. The reason why we assume a lower probability for rocky planets in globular clusters is the general environment of the typical cluster: a small population of slow-burning early-generation stars with no appreciable interstellar dust clouds in between them. If you compare that to low-metallicity stars in the galaxy proper, there are reasons why those might have planets that are not easily afforded to star systems located in globular clusters. Our galaxy is rich in dust and gas clouds that are also inhomogeneous. For example, a metal-poor star may be born out of a low-metal gas cloud and then attract a metal-rich dust disc later. These things are expected to happen a lot less often in globular clusters.
  - iofj 11y ago
    There's the reverse problem as well. If life develops by itself when it has (chemically) the chance ... then where is it ? Our sun is a third generation star (meaning some sun went nova, recoalesced into another sun, went nova, recoalesced in our sun and ignited, and that was 3+ billion years ago). Our sun is not a particularly early third generation star. Given that it would take a civilization about a billion years to spread through the galaxy to all liveable planets ... some civilization should have done that up to 4-5 billion years ago. If life can happen in 2nd generation stars as well, it should have happened 6-8 billion years ago. Obviously this hasn't happened. I only see 3 reasonable explanations: 1) Drake equation is too optimistic. By a huge factor (2-300 million times too optimistic) 2) It's not a problem, because civilizations kill themselves before doing interstellar travel and while we are on the way to doing that but not quite there yet. 3) There's something we don't know

jtwaleson 11y ago

"The question is not -where- are the life forms capable of interstellar communication, but -when- are they." That is the central point of the argument in the article, yet somehow it's never really mentioned.

sawwit 11y ago

What about gamma ray bursts? I've read that our position more at the outer rim of the galaxy is beneficial because there are fewer gamma ray bursts compared to more dense regions.

pavel_lishin 11y ago
Aren't most GRBs extra-galactic in origin? If anything, being on the outskirts means there's less matter protecting us from them.
- Udo 11y ago
  They're only dangerous if they happen within the same galaxy and your planet happens to be right on the axis of the narrow burst cone. In that case there might still be a statistical advantage to being nearer to the core of the galaxy due to more matter density, but it might be offset by the increased chance of getting hit with a GRB there in the first place. Also, we're not actually within the outer rim of the galaxy: http://www.nasa.gov/mission_pages/sunearth/news/gallery/galaxy-location.html http://www.nasa.gov/mission_pages/sunearth/news/gallery/gala...
stargazer-3 11y ago
Gamma ray bursts are produced by stars that are very massive and short-lived. So one can argue that after few tens of millions of years a cluster wouldn't produce that them. On the other hand you are of course right - in a galaxy that is still undergoing intense star formation it is still dangerous to live in a dense region where a nearby young cluster can still render your home planet sterile through a GRB. However, our own Galaxy doesn't seem to be forming stars that actively anymore, and the chance of a new GRB pointing directly at a given star cluster is negligible.

Grishnakh 11y ago

The thing these speculations about alien life and communicating with them miss is: what if the aliens don't want to talk to us? That's probably why you don't hear so much about UFOs these days like we did a few decades ago: they came, they checked us out, and then they launched some beacons just outside our solar system warning everyone to stay away, along with a Galactic General Order that if we ever develop enough to send manned missions outside our system, we have to be destroyed for the good of the galaxy.

Udo 11y ago
There are two propositions here: One, that some UFO sightings are due to the activities of extraterrestrial intelligences. This seems very unlikely at this point. Second, that the Fermi Paradox exists at least partly due to aliens avoiding us specifically, what is commonly referred to as the "zoo hypothesis". As far as speculative explanations go, it's not an unreasonable contender. However, it is not among the most likely or the most simple hypotheses out there. The zoo hypothesis pre-supposes the ready availability of FTL technology, which itself implies that such technology is even possible in general. It also hinges on a specific combination of psychological factors and random happenstance, namely the desire to isolate an entire star system (which is not a trivial feat), and the fact that they even discovered our existence in the first place (which is also quite the coincidence, even for a culture that can travel faster than the speed of light). These reasons don't rule out the zoo hypothesis. However, if I were to bet on one scenario, it would be the practical consequences of the fact that expected distances between civilizations are enormous in both time and space, plus the weakly-shining light cone of our technologically advanced existence doesn't reach very far and isn't easy to detect - and those same factors would be preventing us from seeing an advanced civilization as well, even if they happened to be relatively close by.
- Grishnakh 11y ago
  The problem with conjecture about aliens is that, by definition, they're alien, and since we haven't even met one yet (aside from some unsubstantiated claims by some people), we can't even begin to guess at their capabilities, motivations, etc. Remember, we're a primitive race that hasn't even left its own planet, except for a brief excursion to its nearby moon, and some primitive robotic probes to nearby bodies. We really don't know if there's some branch of physics that allows FTL travel, or if it's possible for intelligent beings to exist in multiple or parallel dimensions, etc. Everything we discuss along these lines is nothing more than wild-ass speculation. One problem I have with your assertion about the ready availability of FTL technology is that I think that assumption relies on the assumption that ETs have similar lifespans as us, which is probably a faulty assumption. A race advanced enough for interstellar travel could very well have totally different biology that doesn't age, or they might have technologically defeated aging, which is something we're already working on ourselves even though we've only sent a handful of people beyond our Van Allen belts. A species that doesn't age, or has lifespans of millennia, might not think it's that big a deal to send a ship to a nearby star system on a journey that'll take a dozen or so years (in ship-time due to relativistic dilation; centuries in planet-time). By the time they get back, their friends might be a bit older, but it'd be like us taking a trip and coming back 5 years later. And don't forget the possibility of "suspended animation". With sufficiently powerful engines able to achieve a sufficiently high fraction of c, a trip of a dozen or so light-years won't take that long in ship-time. It'll even be something we'll want to do with our lifespans. Discovering our existence shouldn't be that hard. There's hundreds of stars within a few dozen lightyears or so, so an advanced civilization should be able to build a powerful robotic ship to tour them all and gather data. A few millennia or so later, it'll return and they can analyze it, and our existence will be pretty obvious just by scanning the EM range (assuming they came within the last century), or by detecting atmospheric oxygen and photosynthesis. Of course this assumes they're looking for that kind of life, just like we're doing now with our exoplanet searches. Honestly, it shouldn't be that hard to detect other civilizations from a reasonable distance; we're already detecting various exoplanets, and as I said, we don't even have any serious spaceflight capability; we're doing it all with ground-based and some orbital telescopes. We're having problems seeing planets the size of our own, but better technology should change that eventually. If we had the ability to send a ship to tour the nearby stars and send data back, advanced civilizations should be fairly obvious to a ship inside their system, just by orbiting the likely-looking planets (inside the "habitable zone") and taking pictures, scanning EM frequencies, etc. It would take a while to get data back though since the ship would take decades or centuries to get there.

cousin_it 11y ago

An advanced alien civilization will probably have very low radiation signature. To afford the maximum amount of computation, it should completely encase the star (maximum energy) and radiate all waste heat toward a black hole (maximum cooling).

Udo 11y ago
> and radiate all waste heat toward a black hole (maximum cooling). It's comparatively inefficient to radiate heat into a narrow cone, and there is little advantage to radiating it into a black hole. On the contrary, matter falling into the black hole will form an accretion disk that radiates heat back to you. In order to maximize dissipation, they would simply radiate it away into all directions uniformly. However, there might be other considerations to take into account here besides physics. It might be important to such an isolated civilization to avoid detection. In that case they would gladly take the hit on efficiency and radiate their heat in narrow cones into the gaps where no nearby stars are located. > An advanced alien civilization will probably have very low radiation signature. To afford the maximum amount of computation Maybe. We can't say what the goals are of any advanced civilization. The reason why we like to talk about this specific type of civilization is that they are the type that we can actually look for right now. But as I said above, if you're an isolationist population of computer brains, it makes sense to go through the effort of avoiding other people showing up on your doorstep. Such a culture might deem it acceptable to invest most of their energy budget into avoiding detection, as opposed to computation only.
- pavel_lishin 11y ago
  To bring it back to the parent comment, wouldn't it make sense for such a culture to live near a black hole? All of their waste emissions would be shadowed pretty well by the accretion disk, and other species might avoid the neighborhood in general given that it's not a safe or nice place to be.
  - Udo 11y ago
    > wouldn't it make sense for such a culture to live near a black hole? Technically the black hole doesn't offer anything beyond what a sun of comparable output would offer. > and other species might avoid the neighborhood in general given that it's not a safe or nice place to be True, but the reasons for avoiding close contact with it are also the reasons why building a habitat there is potentially risky. All things being equal, a Mercury-like planet would make a better base for a civilization having those goals: it offers a lot of solar energy, affords some protection from detection by being too close to the star to resolve it as a non-natural heat source, and as opposed to the black hole it's also in a stable environment.

madaxe_again 11y ago

Nightfall, as mentioned at the end of the piece, is a great little early Asimov story - a culture to whom candles are alien and the idea of artificial light is bizarre. Thoroughly recommend. In fact, here it is: https://www.uni.edu/morgans/astro/course/nightfall.pdf https://www.uni.edu/morgans/astro/course/nightfall.pdf

Outdoorsman 11y ago
Thanks for the link...
jon_richards 11y ago
Funny, in the book artificial light is extremely commonplace. A theme park actually builds a pitch black tunnel as a ride.
4ad 11y ago
The End of Eternity and Nightfall (the novel with Robert Silverberg, not the short story) are Asimov's greatest novels.

cnp 11y ago

One thing that always surprises me about the search for ET is how often the purely psychological / consciousness aspect is disregarded. As anyone who has worked with DMT or Ayahuasca can tell you, you don't need to travel far to reach the outer limits of space or even have contact experiences, and this is very easy to test should the anti-scientific legal mechanisms preventing such a study be overcome. Its like, Fermi's Paradox is almost completely irrelevant if you come from the position that any sufficiently advanced civilization is aware of the possible non-local properties of consciousness.

ElysianEagle 11y ago
Not sure why you've been downvoted, but I think this is very much on point.
- cnp 11y ago
  I was curious of this as well, but not surprised. For the skeptics, all I ask is that you self experiment. Its easy and cheap, requiring only a simple extraction performed on the Arcacia Confusa plant, which you can order online.
  - pavel_lishin 11y ago
    But a sample size of one is worthless, especially when the person running the experiment is high :) On a more serious note, I have no idea how you'd actually test this. How would you prove or disprove that someone experimenting with hallucinogens is actually communicating with something else? The only thing I can think of is having two people under the influence being able to communicate with each other, with absolutely no other way of doing so. Subjects A and B have never met, and don't have any way of passing messages during their experience. Subject A is told to pass some randomly generated string to subject B, either directly or via some alien intermediary. If Subject B can guess Subject A's string, then that might be evidence of something interesting and objectively external happening.
    - 11y ago