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There's an obvious possibility that people ignore because it's not very sexy: maybe life is common, but sending messages clearly over interstellar distances is

There's an obvious possibility that people ignore because it's not very sexy: maybe life is common, but sending messages clearly over interstellar distances is pointless and extremely expensive. Maybe the energy cost of transmitting a signal that can be clearly heard over interstellar distances -- mixed with the time/distance barriers of interstellar travel and communication -- makes it kind of pointless outside of novelty. (Not to mention any communication would happen on the scale of rise and fall of civilizations -- how do you even have a coherent conversation across hundreds of years?). I mean maybe most societies that form just don't have the energy and willpower to colonize outside their solar system. They might also be like us where dominant civilisations and philosophy’s rise and fall every few years — meaning not enough stability for a 50000 year long conversation Perhaps the universe is silent simply because there's no reason to speak up.

setr 8y ago
Presumably any space-faring civilization would be interested in knowing if others exist; at a minimum, first contact (should they have any expectation of external life) would likely offer an extreme advantage in whatever competition they have locally (eg technological gifts, information exchange, prinary point of contact, etc). Furthermore, if they are spacefaring, they will require long-range transmissions regardless: it would be odd to think they’d send ships into multi-year journeys without being able to phone home, or having the tech and not utilizing it (a lost ship is likely costlier than transmission). A civilization not capable of spaceflight might be in your position, incapable of producing transmission cheap enough, and not being curious enough to cast it into the void, but otherwise, any being capable (and willing) of long-distance travel should find sufficient use for long-distance communication to utilize it, independent of a search for alternate life. That is, advanced civilization should be noisy for their own sake. (Though perhaps in a manner we can’t detect, or don’t expect).
- mcv 8y ago
  Communication within a civilisation is quite a bit different from highly speculative permanent signals to billions of starts in the hope that someone is listening. And even if someone is listening, they might not be able to answer. So this sounds rather unlikely to me. A bigger issue is: would they actually send spaceships on multi-year journeys to other solar systems? If they would, then why aren't they already here? Some of those civilisations must have a million or billion year head start on us. Plenty to colonise the galaxy, yet we see no trace of them here. So the odds of there being interstellar civilisations out there is extremely slim. I think our best bet to find alien civilisations is by detecting the signature of alien megastructures; Dyson Spheres and the like. Tabby's Star sounds to me like the most likely way we might find alien life.
  - ForHackernews 8y ago
    > If they would, then why aren't they already here? Space is really really big and there are a lot of star systems. Maybe it's just statistics. > Plenty to colonise the galaxy, I think you're seriously underestimating how big a galaxy is: https://www.reddit.com/r/theydidthemath/comments/2i6le7/request_how_many_individual_pieces_of_saltsand_is/ https://www.reddit.com/r/theydidthemath/comments/2i6le7/requ...
    - mcv 8y ago
      I know how big the galaxy is, but I also know how much a billion years is, and how fast exponential growth grows. Of course a civilisation won't be able to keep growing exponentially for ever; pretty soon only the outer rim will have anything nearby to colonise. But still, a billion years is a lot. But if colonies don't grow up to colonise other planets, you're stuck with linear growth, which is never going to be enough.
mcv 8y ago
> maybe life is common, but sending messages clearly over interstellar distances is pointless and extremely expensive It certainly is. I've heard that we wouldn't be able to detect Earth's most powerful broadcasts from a distance of half a light year. So expecting broadcasts to make it across interstellar distances is ridiculous. Tight beam signals might work, but then you've got to know somebody is listening. Nobody knows anyone here is listening, so nobody is sending anything to us. But I thought the real paradox according to Fermi is not that we don't receive signals, but that they're not already here. If interstellar travel and colonisation is even the slightest bit possible, and spacefaring civilisations are somewhat common, then some of them must have had a millions or billions of years head start on us, which should have been plenty to colonise the entire galaxy. Why did nobody discover this fertile planet somewhere during the age of the dinosaurs? The obvious solution here is of course that interstellar travel is so impractical that even in a million years, nobody will ever colonise another solar system. That, or Erich von Daniken was right.
- krapp 8y ago
  >The obvious solution here is of course that interstellar travel is so impractical that even in a million years, nobody will ever colonise another solar system. It's also entirely possible that a civilization that colonizes another solar system won't also inevitably colonize the entire galaxy. I think people assume this because the mathematical progression makes sense and because the precedent of humans colonizing other continents makes it seem intuitively plausible, as if space were just a bigger ocean. Decades of space opera and science fiction stories have turned the metaphor into an archetype. Yet if it is true that rockets and radio waves are all anyone ever gets, then every new colony is an investment of hundreds or thousands of years' effort or more, assuming there is always a stellar body nearby with a planet which is amenable to colonization, as if stars were equidistant from one another, and assuming all previous colonies continue and survive. Many people seem to assume that either the entire galaxy must be converted to computronium by Von Neumann probes or no life exists elsewhere in the universe, but to me, detecting the signs of interstellar civilization anywhere in the universe is the least likely possible scenario even if life is common.
  - 8y ago
KnightOfWords 8y ago
> There's an obvious possibility that people ignore because it's not very sexy: maybe life is common, but sending messages clearly over interstellar distances is pointless and extremely expensive. That's the simplest solution to the Fermi paradox. Perhaps interstellar communication and travel are simply too challenging and uneconomic to be feasible.
- Tepix 8y ago
  This seems unlikely. We already know about technologies that seem likely candidates to enable communications and travel between stars. Give us a couple of centuries without global disasters and we will master them.
  - shireboy 8y ago
    Do we? Our physics today suggest there are hard limits. We do have some creative theories (Alcubierre, wormholes) to work around those limits, but they could run into issues and in current forms require massive energy that could well be impossible to generate or harvest. Laser/solar sails seem most likely to me, but could be limited to small payloads and the general vicinity of our solar system. As much as I like sci-fi and real science, it seems quite likely that there are physical limits that keep intelligent life constrained to their solar system. Space is really really big.
ryanmercer 8y ago
>Perhaps the universe is silent simply because there's no reason to speak up. Perhaps the interactable bubble of our simulation end long before the next closest star. Perhaps other civilizations never even messed with radio transmissions, perhaps they got to fiberoptics before or around the same time and decided to just used wired connections for everything. Perhaps other civilizations long ago abandoned radio for some other form of transmission that we've yet to even discover, some multi-dimensional/subspace communication or some sort of quantum entanglement or maybe they communicate chemically and can transmit massive amounts of data with particles in the parts per million or billion. Or maybe their civilizations came and went time and time again spanning billions and billions of years. I once did some math ( https://www.ryanmercer.com/ryansthoughts/2014/11/30/this-just-in-you-dont-matter https://www.ryanmercer.com/ryansthoughts/2014/11/30/this-jus... ), if we assume 1 sextillion stars in a total of 100 billion galaxies in the universe (likely a quite low figure) and that 1 in 2 of those stars has a body orbiting it that hosts life and that 1 in 2 of those worlds has at least one tool-building species that gives you 250 septillion planets with tool-building life. That gives you an average of 25,000 tool-building worlds per galaxy. Now let's take our galaxy and let's assume that in the first billion years of our galaxy, there were ZERO tool building species. That leaves you with 12.21 billion years to divide 25,000 civilizations over a galaxy with 100,000-180,000 light year diameter. Let's assume 140,000 light years. That's more than 15,000,000,000 square light years. That gives us 1 tool building civilization per 600,000 square light years spread out over 12 billion years. :( Obviously this figure could be way way lower than in reality. If a species develops space technology they could easily begin to spread. Even if a civilization needed a thousand years to spread to a neighboring star in 10,000 years you could have a presence in 512 star systems, in 20,000 years 524,288 star systems.

setr 8y ago

Presumably any space-faring civilization would be interested in knowing if others exist; at a minimum, first contact (should they have any expectation of external life) would likely offer an extreme advantage in whatever competition they have locally (eg technological gifts, information exchange, prinary point of contact, etc). Furthermore, if they are spacefaring, they will require long-range transmissions regardless: it would be odd to think they’d send ships into multi-year journeys without being able to phone home, or having the tech and not utilizing it (a lost ship is likely costlier than transmission). A civilization not capable of spaceflight might be in your position, incapable of producing transmission cheap enough, and not being curious enough to cast it into the void, but otherwise, any being capable (and willing) of long-distance travel should find sufficient use for long-distance communication to utilize it, independent of a search for alternate life. That is, advanced civilization should be noisy for their own sake. (Though perhaps in a manner we can’t detect, or don’t expect).

mcv 8y ago
Communication within a civilisation is quite a bit different from highly speculative permanent signals to billions of starts in the hope that someone is listening. And even if someone is listening, they might not be able to answer. So this sounds rather unlikely to me. A bigger issue is: would they actually send spaceships on multi-year journeys to other solar systems? If they would, then why aren't they already here? Some of those civilisations must have a million or billion year head start on us. Plenty to colonise the galaxy, yet we see no trace of them here. So the odds of there being interstellar civilisations out there is extremely slim. I think our best bet to find alien civilisations is by detecting the signature of alien megastructures; Dyson Spheres and the like. Tabby's Star sounds to me like the most likely way we might find alien life.
- ForHackernews 8y ago
  > If they would, then why aren't they already here? Space is really really big and there are a lot of star systems. Maybe it's just statistics. > Plenty to colonise the galaxy, I think you're seriously underestimating how big a galaxy is: https://www.reddit.com/r/theydidthemath/comments/2i6le7/request_how_many_individual_pieces_of_saltsand_is/ https://www.reddit.com/r/theydidthemath/comments/2i6le7/requ...
  - mcv 8y ago
    I know how big the galaxy is, but I also know how much a billion years is, and how fast exponential growth grows. Of course a civilisation won't be able to keep growing exponentially for ever; pretty soon only the outer rim will have anything nearby to colonise. But still, a billion years is a lot. But if colonies don't grow up to colonise other planets, you're stuck with linear growth, which is never going to be enough.

mcv 8y ago

> maybe life is common, but sending messages clearly over interstellar distances is pointless and extremely expensive It certainly is. I've heard that we wouldn't be able to detect Earth's most powerful broadcasts from a distance of half a light year. So expecting broadcasts to make it across interstellar distances is ridiculous. Tight beam signals might work, but then you've got to know somebody is listening. Nobody knows anyone here is listening, so nobody is sending anything to us. But I thought the real paradox according to Fermi is not that we don't receive signals, but that they're not already here. If interstellar travel and colonisation is even the slightest bit possible, and spacefaring civilisations are somewhat common, then some of them must have had a millions or billions of years head start on us, which should have been plenty to colonise the entire galaxy. Why did nobody discover this fertile planet somewhere during the age of the dinosaurs? The obvious solution here is of course that interstellar travel is so impractical that even in a million years, nobody will ever colonise another solar system. That, or Erich von Daniken was right.

krapp 8y ago
>The obvious solution here is of course that interstellar travel is so impractical that even in a million years, nobody will ever colonise another solar system. It's also entirely possible that a civilization that colonizes another solar system won't also inevitably colonize the entire galaxy. I think people assume this because the mathematical progression makes sense and because the precedent of humans colonizing other continents makes it seem intuitively plausible, as if space were just a bigger ocean. Decades of space opera and science fiction stories have turned the metaphor into an archetype. Yet if it is true that rockets and radio waves are all anyone ever gets, then every new colony is an investment of hundreds or thousands of years' effort or more, assuming there is always a stellar body nearby with a planet which is amenable to colonization, as if stars were equidistant from one another, and assuming all previous colonies continue and survive. Many people seem to assume that either the entire galaxy must be converted to computronium by Von Neumann probes or no life exists elsewhere in the universe, but to me, detecting the signs of interstellar civilization anywhere in the universe is the least likely possible scenario even if life is common.
- 8y ago

KnightOfWords 8y ago

> There's an obvious possibility that people ignore because it's not very sexy: maybe life is common, but sending messages clearly over interstellar distances is pointless and extremely expensive. That's the simplest solution to the Fermi paradox. Perhaps interstellar communication and travel are simply too challenging and uneconomic to be feasible.

Tepix 8y ago
This seems unlikely. We already know about technologies that seem likely candidates to enable communications and travel between stars. Give us a couple of centuries without global disasters and we will master them.
- shireboy 8y ago
  Do we? Our physics today suggest there are hard limits. We do have some creative theories (Alcubierre, wormholes) to work around those limits, but they could run into issues and in current forms require massive energy that could well be impossible to generate or harvest. Laser/solar sails seem most likely to me, but could be limited to small payloads and the general vicinity of our solar system. As much as I like sci-fi and real science, it seems quite likely that there are physical limits that keep intelligent life constrained to their solar system. Space is really really big.

ryanmercer 8y ago

>Perhaps the universe is silent simply because there's no reason to speak up. Perhaps the interactable bubble of our simulation end long before the next closest star. Perhaps other civilizations never even messed with radio transmissions, perhaps they got to fiberoptics before or around the same time and decided to just used wired connections for everything. Perhaps other civilizations long ago abandoned radio for some other form of transmission that we've yet to even discover, some multi-dimensional/subspace communication or some sort of quantum entanglement or maybe they communicate chemically and can transmit massive amounts of data with particles in the parts per million or billion. Or maybe their civilizations came and went time and time again spanning billions and billions of years. I once did some math ( https://www.ryanmercer.com/ryansthoughts/2014/11/30/this-just-in-you-dont-matter https://www.ryanmercer.com/ryansthoughts/2014/11/30/this-jus... ), if we assume 1 sextillion stars in a total of 100 billion galaxies in the universe (likely a quite low figure) and that 1 in 2 of those stars has a body orbiting it that hosts life and that 1 in 2 of those worlds has at least one tool-building species that gives you 250 septillion planets with tool-building life. That gives you an average of 25,000 tool-building worlds per galaxy. Now let's take our galaxy and let's assume that in the first billion years of our galaxy, there were ZERO tool building species. That leaves you with 12.21 billion years to divide 25,000 civilizations over a galaxy with 100,000-180,000 light year diameter. Let's assume 140,000 light years. That's more than 15,000,000,000 square light years. That gives us 1 tool building civilization per 600,000 square light years spread out over 12 billion years. :( Obviously this figure could be way way lower than in reality. If a species develops space technology they could easily begin to spread. Even if a civilization needed a thousand years to spread to a neighboring star in 10,000 years you could have a presence in 512 star systems, in 20,000 years 524,288 star systems.