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Given the age of the Milky Way, a civilization using even slow sub light travel with generation ships or autonomous probes could have colonized the entire galax

Given the age of the Milky Way, a civilization using even slow sub light travel with generation ships or autonomous probes could have colonized the entire galaxy many times over. Why has no one done that? Hence the paradox.

eloff 6y ago
I don't know why this got down-voted. The milky way is 100K light years across. It's 13.5 billion years old. It's entirely possible to blanket the whole galaxy with probes, without even getting into self replicating probes.
- e12e 6y ago
  You have to make an assumption about speed - it certainly won't be more than a tiny fraction light speed. Eg voyager appear to travel now at less than 0.00006 c (16 km/s). Than turns 100k light years into ballpark 150 M year journey (no it doesn't its 1.8 bn years as mentioned in reply) . Still possible to cross 10.000 times - but that would be a straight line. I suspect the distances will grow somewhat fractally if you want to swing by any stars? (ed: so, not really very likely at all)
  - Baeocystin 6y ago
    To traverse 100k light-years at 16km/s would take approximately 1.8 billion years. FWIW.
    - e12e 6y ago
      Thanks, not sure how I got to just 150 mill years.
  - mistersquid 6y ago
    > Than turns 100k light years into ballpark 150 year journey. Forgive my confusion. If 100K light years is 100K years at c, how can > 0.00006 c yield 0.00150K (150) years?
    - e12e 6y ago
      It can't (unless you mistype into your plain android calculator app). Ed: Fwiw there was a typo there, too - it was supposed to say 150 million - but it's more like 1.5 billion.
  - sliken 6y ago
    There's current projects on earth seriously working on getting probes up to 1% of the speed of light. Just a small/light weight probe, a solar sail, and a large (but feasible) array of lasers.
  - eloff 6y ago
    To imagine that voyager technology will define the maximum velocity of interstellar travel, a thousand years from now, ten thousand, a million, etc is short sighted. Maybe we never can exceed light speed, but we could get up to a reasonable percentage of it.
    - e12e 6y ago
      Sure, but it puts things into perspective. If we assume 1% of c is feasible - it's still a 10 Million year journey to cross 100k light years. That's much better - it gives 1 000 chances in 10 bn years.
deeeeplearning 6y ago
Not sure why it was downvoted. Many people have looked into this. https://gtocx.jpl.nasa.gov/gtocx/competition/ https://gtocx.jpl.nasa.gov/gtocx/competition/ Even entire competitions to find optimal colonization methods. Could take 90M years with measly future human tech. Age of Milky Way is 13.5 Billion so even conservatively you could indeed colonize the galaxy many many times over in that time.
- Retric 6y ago
  The Milky Way lacked rocky planets early on, making that 12.5 Billion year age largely meaningless. Which is just one of many bad assumptions in how people do these calculations. At a minimum you don’t get a straight path from A to B. Assuming any kind of limitation in distance traveled and your at the mercy of the distribution of whatever resource you need. Aka need rocky planets with liquid water, that’s likely going to be an very indirect path. Even just non binary star systems is significant. Further, assuming every trip is successful is again unlikely. How long you need to wait before the next trip is again a major qualifier. For example, what happens if they first send a probe to verify habitability? Suddenly travel times more than double. I have seen plenty of optimistic calculations that still add up to over a billion years before total colonization and sometimes much much higher than that. And that’s a billion years where expansion is a major priority at the frontier. Look at successful colonizations that don’t expand rapidly and again things keep slowing down.
  - mylons 6y ago
    If you used the Von Neumann machine approach wouldn’t it not really matter if the planet was habitable or not?
    - Retric 6y ago
      Let’s assume your sending a Von Neumann probe to prep the way for your ship. Now it shows up and does whatever it needs to and then sends an everything is ready signal before you send your generation ship. I mean sure you could in theory send out an endlessly replicating probe that keeps going to other star systems, but that’s even more risky.
bena 6y ago
Yes, I know the paradox. It's simple. It's too simple. It has huge assumptions. Namely the assumption that the current problems to colonization can be solved in a cost-effective manner. The longest continuous length of time spent in what limited space flight we have is just under 440 days. Not to mention, all of it was spent in low Earth orbit. Once we go beyond that, we lose all protection from the Earth's magnetosphere. Then there's also the loss of bone density due to lack of gravity. 1% per month is nothing to sneeze at. We are not built for space travel. We are built to inhabit this planet. We have evolved to the conditions here. And before you say that the generation ships will just fake gravity and have appropriate shielding. Where do you get that assumption? We can't fake gravity. We have a space station where they take 10 times the radiation as here on Earth because we can't even realistically shield that. And then we get to "autonomous probes", the great handwave of people who think they can cleverly sidestep the "humans aren't built for space" issue. Who builds them? For what purpose? What's our expected return? How can you justify the investment in time and resources to shoot into space, with absolutely no hope of even knowing there's a chance for a return on that investment until generations later, a probe that can at best return data. And then there's the issue of it being an autonomous probe. Two words that hide a lot of other problems. A lot of other assumptions. One being that we'll have created an intelligence capable of running this thing. In other words, the Fermi Paradox just assumes that all of these incredibly hard problems can and will be solved and that the solutions are logistically viable. What if they're not?
- deeeeplearning 6y ago
  You talk like this is all expected to be done by 21st century humans when in reality if there were civilizations out there capable of doing this colonization they would likely be millions of years our elders and its incredibly foolish to try to guess their intentions or the capabilities of their technology. Your view is painfully anthropocentric. Just to add, there are plenty of valid criticisms or plausible solutions to the Fermi paradox but I think you've failed to identify a single one.
  - bena 6y ago
    You talk like this is all a forgone conclusion. Technology is not magic. Time is not a salve that solves all issues. You say that my view is "painfully anthropocentric", but how? It seems your only response is "but aliens". That is not good enough. You want to say that it is foolish of me to try and guess their intentions and capabilities, but that's what the paradox does as well. It assumes their intentions are to colonize and their capabilities allow it. With no proof. The only life we have to base anything off of is right here. And if you think I haven't identified a single valid criticism of the Fermi paradox, then I'm just going to assume you aren't aware of the criticisms. I've basically touched on this one https://en.wikipedia.org/wiki/Fermi_paradox#Economic_explanations https://en.wikipedia.org/wiki/Fermi_paradox#Economic_explana... So no, I'm not saying that just because it can't be done now, it can't be done ever. I'm saying the Fermi Paradox is basically saying "Once you solve these incredibly hard problems, this becomes easy." I think the Fermi Paradox is phrased wrong. It should state that if it were possible to colonize the galaxy, it would have been done by now.
tsimionescu 6y ago
There are problems of resiliency and energy storage that could be more or less fundamental problems. It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel, and civilizations may tend to collapse for various reasons before reaching such technological peaks. It's also entirely possible that we are the first, or one of the first, technological civilizations in the galaxy. Given how little we understand about the appearance of life, the emergence of multicellular life from single cell life, and the emergence of intelligence from multicellular life, there's not way to put an estimate on these probabilities. Think about the fact that in 3.5 billion years there hasn't been any new abiogenesis on the only planet in the universe we know for sure can sustain life, and in this billion years a single life form has ever evolved from a single-cell to multi-cellular life, aren't the priors pretty decent that life is an extremely rare phenomenon? Given the fact that the Milky Way is somewhere around 13 billion years old, how often can we expect a once in 3.5 billion years event have happened?
- Baeocystin 6y ago
  >Think about the fact that in 3.5 billion years there hasn't been any new abiogenesis on the only planet in the universe we know for sure can sustain life, and in this billion years a single life form has ever evolved from a single-cell to multi-cellular life, aren't the priors pretty decent that life is an extremely rare phenomenon? Any freshly-evolved life would have to compete with organisms that have already been honing their survival strategies for literal billions of years. There's no reason to think such a thing is possible, and the lack of it doesn't speak one way or another to the difficulty of it happening in a virgin environment.
- tzs 6y ago
  > It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel. For a generation ship, are you referring to all the machinery that can maintain a balanced ecosystem of plants and animals and humans in order to provide food for the people during the trip to the new planet, and to make all the things needed to keep those people healthy during the trip such as medicine and drugs? If so, there may be a way around that. Send all your colonists as frozen embryos or frozen sperm and eggs. Your ship only needs life support then to keep alive the people who run the ship. For food, don't grow it. Take it with you. At first taking your food with you seems absurd, but if you had a food with the same caloric density as rice, enough of it to provide 2000 calories/day to one human for 100k years would fit in a sphere with a radius of 24.4 meters. So once your technological civilization figures out a way to preserve food such that they can make a rice ball equivalent with a 100k year storage life, a generation ship with a small crew becomes a whole lot more feasible. For replacement crew throughout the journey, you can do a mix of using whatever kids the crew produces the old fashioned way and using kids produced from some of the frozen embryos/eggs/sperm. I think technological civilizations will reach the point of being able to do this well before they are millions of years old. We aren't too far from being able to do it ourselves. We are probably farther out on the propulsion for the ship itself.
jcims 6y ago
I'm fairly confident we'll eventually find that our form of life is the result of intentional or unintentional colonization of Earth. If you look at how quickly life began after the oceans settled out, then look at precisely how complex even the most primitive forms of life are (in terms of likelihood of stochastic construction to the point of sophistication to support evolutionary mechanisms) it seems incredibly unlikely that we originated here.
- Osiris 6y ago
  This is an interesting idea. Look at how religion explains the origin of life: A lifeform not from this planet, far more advanced than us, gave "the breath of life", and calls us their "children". The vastness of this universe leads me to believe that it's impossible to dismiss the idea that there is an intelligence/lifeform sufficiently advanced as to appear to be a God to us.
  - jcims 6y ago
    Totally agree. Joscha Bach laid out a few interesting ideas around this at the end of a podcast. If you have a few minutes start here for a broader context (starts of wholly unrelated but with some great concepts): https://youtu.be/P-2P3MSZrBM?t=10084 https://youtu.be/P-2P3MSZrBM?t=10084 If not, he drills into it here: https://youtu.be/P-2P3MSZrBM?t=10400 https://youtu.be/P-2P3MSZrBM?t=10400
  - psychoslave 6y ago
    That doesn't explain where the said intelligence /lifeform would come from itself, so what the point of such a theory?
  - sliken 6y ago
    I read a short story that explained the explosion of life on earth during a very short period on some alien that didn't follow protocol and dumped some poop.
- marta_morena_28 6y ago
  Possible, but far reaching. There are other explanations: * We are a computer simulation (hence there is no colonization, we are in an experiment) * There are like 1,000,000,000,000,000,000 habitable planets in the universe. Just because something is "extremely unlikely" doesn't mean that it didn't happen to us. I.e. whomever this happened to, would ask himself that question. We may just be the ones it happened to. Also: Why would they settle species from millions of years in their own past. If they wanted to colonize, they could start with their own life-forms. Could be several things as well: * We are a genesis project and they will simply come back later and settle in what we left behind (i.e. they let the ecosystem build for a few million years before trying out this settlement) * They don't want to create competitors * We are a population bomb, i.e. they just sent out billions of probes trying to populate any given habitable planet, and they couldn't just spawn themselves there and instead had to start from somewhere where a sustainable ecosystem would derive from
tzs 6y ago
It could be that none of them have seen any point in doing so. Generally on Earth colonization has happened in order to provide a tangible economic benefit to those supporting the colonization effort. With someplace that you can only travel to and from by slow generation ship its hard to find any such economic benefit in having a colony there.

eloff 6y ago

I don't know why this got down-voted. The milky way is 100K light years across. It's 13.5 billion years old. It's entirely possible to blanket the whole galaxy with probes, without even getting into self replicating probes.

e12e 6y ago
You have to make an assumption about speed - it certainly won't be more than a tiny fraction light speed. Eg voyager appear to travel now at less than 0.00006 c (16 km/s). Than turns 100k light years into ballpark 150 M year journey (no it doesn't its 1.8 bn years as mentioned in reply) . Still possible to cross 10.000 times - but that would be a straight line. I suspect the distances will grow somewhat fractally if you want to swing by any stars? (ed: so, not really very likely at all)
- Baeocystin 6y ago
  To traverse 100k light-years at 16km/s would take approximately 1.8 billion years. FWIW.
  - e12e 6y ago
    Thanks, not sure how I got to just 150 mill years.
- mistersquid 6y ago
  > Than turns 100k light years into ballpark 150 year journey. Forgive my confusion. If 100K light years is 100K years at c, how can > 0.00006 c yield 0.00150K (150) years?
  - e12e 6y ago
    It can't (unless you mistype into your plain android calculator app). Ed: Fwiw there was a typo there, too - it was supposed to say 150 million - but it's more like 1.5 billion.
- sliken 6y ago
  There's current projects on earth seriously working on getting probes up to 1% of the speed of light. Just a small/light weight probe, a solar sail, and a large (but feasible) array of lasers.
- eloff 6y ago
  To imagine that voyager technology will define the maximum velocity of interstellar travel, a thousand years from now, ten thousand, a million, etc is short sighted. Maybe we never can exceed light speed, but we could get up to a reasonable percentage of it.
  - e12e 6y ago
    Sure, but it puts things into perspective. If we assume 1% of c is feasible - it's still a 10 Million year journey to cross 100k light years. That's much better - it gives 1 000 chances in 10 bn years.

deeeeplearning 6y ago

Not sure why it was downvoted. Many people have looked into this. https://gtocx.jpl.nasa.gov/gtocx/competition/ https://gtocx.jpl.nasa.gov/gtocx/competition/ Even entire competitions to find optimal colonization methods. Could take 90M years with measly future human tech. Age of Milky Way is 13.5 Billion so even conservatively you could indeed colonize the galaxy many many times over in that time.

Retric 6y ago
The Milky Way lacked rocky planets early on, making that 12.5 Billion year age largely meaningless. Which is just one of many bad assumptions in how people do these calculations. At a minimum you don’t get a straight path from A to B. Assuming any kind of limitation in distance traveled and your at the mercy of the distribution of whatever resource you need. Aka need rocky planets with liquid water, that’s likely going to be an very indirect path. Even just non binary star systems is significant. Further, assuming every trip is successful is again unlikely. How long you need to wait before the next trip is again a major qualifier. For example, what happens if they first send a probe to verify habitability? Suddenly travel times more than double. I have seen plenty of optimistic calculations that still add up to over a billion years before total colonization and sometimes much much higher than that. And that’s a billion years where expansion is a major priority at the frontier. Look at successful colonizations that don’t expand rapidly and again things keep slowing down.
- mylons 6y ago
  If you used the Von Neumann machine approach wouldn’t it not really matter if the planet was habitable or not?
  - Retric 6y ago
    Let’s assume your sending a Von Neumann probe to prep the way for your ship. Now it shows up and does whatever it needs to and then sends an everything is ready signal before you send your generation ship. I mean sure you could in theory send out an endlessly replicating probe that keeps going to other star systems, but that’s even more risky.

bena 6y ago

Yes, I know the paradox. It's simple. It's too simple. It has huge assumptions. Namely the assumption that the current problems to colonization can be solved in a cost-effective manner. The longest continuous length of time spent in what limited space flight we have is just under 440 days. Not to mention, all of it was spent in low Earth orbit. Once we go beyond that, we lose all protection from the Earth's magnetosphere. Then there's also the loss of bone density due to lack of gravity. 1% per month is nothing to sneeze at. We are not built for space travel. We are built to inhabit this planet. We have evolved to the conditions here. And before you say that the generation ships will just fake gravity and have appropriate shielding. Where do you get that assumption? We can't fake gravity. We have a space station where they take 10 times the radiation as here on Earth because we can't even realistically shield that. And then we get to "autonomous probes", the great handwave of people who think they can cleverly sidestep the "humans aren't built for space" issue. Who builds them? For what purpose? What's our expected return? How can you justify the investment in time and resources to shoot into space, with absolutely no hope of even knowing there's a chance for a return on that investment until generations later, a probe that can at best return data. And then there's the issue of it being an autonomous probe. Two words that hide a lot of other problems. A lot of other assumptions. One being that we'll have created an intelligence capable of running this thing. In other words, the Fermi Paradox just assumes that all of these incredibly hard problems can and will be solved and that the solutions are logistically viable. What if they're not?

deeeeplearning 6y ago
You talk like this is all expected to be done by 21st century humans when in reality if there were civilizations out there capable of doing this colonization they would likely be millions of years our elders and its incredibly foolish to try to guess their intentions or the capabilities of their technology. Your view is painfully anthropocentric. Just to add, there are plenty of valid criticisms or plausible solutions to the Fermi paradox but I think you've failed to identify a single one.
- bena 6y ago
  You talk like this is all a forgone conclusion. Technology is not magic. Time is not a salve that solves all issues. You say that my view is "painfully anthropocentric", but how? It seems your only response is "but aliens". That is not good enough. You want to say that it is foolish of me to try and guess their intentions and capabilities, but that's what the paradox does as well. It assumes their intentions are to colonize and their capabilities allow it. With no proof. The only life we have to base anything off of is right here. And if you think I haven't identified a single valid criticism of the Fermi paradox, then I'm just going to assume you aren't aware of the criticisms. I've basically touched on this one https://en.wikipedia.org/wiki/Fermi_paradox#Economic_explanations https://en.wikipedia.org/wiki/Fermi_paradox#Economic_explana... So no, I'm not saying that just because it can't be done now, it can't be done ever. I'm saying the Fermi Paradox is basically saying "Once you solve these incredibly hard problems, this becomes easy." I think the Fermi Paradox is phrased wrong. It should state that if it were possible to colonize the galaxy, it would have been done by now.

tsimionescu 6y ago

There are problems of resiliency and energy storage that could be more or less fundamental problems. It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel, and civilizations may tend to collapse for various reasons before reaching such technological peaks. It's also entirely possible that we are the first, or one of the first, technological civilizations in the galaxy. Given how little we understand about the appearance of life, the emergence of multicellular life from single cell life, and the emergence of intelligence from multicellular life, there's not way to put an estimate on these probabilities. Think about the fact that in 3.5 billion years there hasn't been any new abiogenesis on the only planet in the universe we know for sure can sustain life, and in this billion years a single life form has ever evolved from a single-cell to multi-cellular life, aren't the priors pretty decent that life is an extremely rare phenomenon? Given the fact that the Milky Way is somewhere around 13 billion years old, how often can we expect a once in 3.5 billion years event have happened?

Baeocystin 6y ago
>Think about the fact that in 3.5 billion years there hasn't been any new abiogenesis on the only planet in the universe we know for sure can sustain life, and in this billion years a single life form has ever evolved from a single-cell to multi-cellular life, aren't the priors pretty decent that life is an extremely rare phenomenon? Any freshly-evolved life would have to compete with organisms that have already been honing their survival strategies for literal billions of years. There's no reason to think such a thing is possible, and the lack of it doesn't speak one way or another to the difficulty of it happening in a virgin environment.
tzs 6y ago
> It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel. For a generation ship, are you referring to all the machinery that can maintain a balanced ecosystem of plants and animals and humans in order to provide food for the people during the trip to the new planet, and to make all the things needed to keep those people healthy during the trip such as medicine and drugs? If so, there may be a way around that. Send all your colonists as frozen embryos or frozen sperm and eggs. Your ship only needs life support then to keep alive the people who run the ship. For food, don't grow it. Take it with you. At first taking your food with you seems absurd, but if you had a food with the same caloric density as rice, enough of it to provide 2000 calories/day to one human for 100k years would fit in a sphere with a radius of 24.4 meters. So once your technological civilization figures out a way to preserve food such that they can make a rice ball equivalent with a 100k year storage life, a generation ship with a small crew becomes a whole lot more feasible. For replacement crew throughout the journey, you can do a mix of using whatever kids the crew produces the old fashioned way and using kids produced from some of the frozen embryos/eggs/sperm. I think technological civilizations will reach the point of being able to do this well before they are millions of years old. We aren't too far from being able to do it ourselves. We are probably farther out on the propulsion for the ship itself.

jcims 6y ago

I'm fairly confident we'll eventually find that our form of life is the result of intentional or unintentional colonization of Earth. If you look at how quickly life began after the oceans settled out, then look at precisely how complex even the most primitive forms of life are (in terms of likelihood of stochastic construction to the point of sophistication to support evolutionary mechanisms) it seems incredibly unlikely that we originated here.

Osiris 6y ago
This is an interesting idea. Look at how religion explains the origin of life: A lifeform not from this planet, far more advanced than us, gave "the breath of life", and calls us their "children". The vastness of this universe leads me to believe that it's impossible to dismiss the idea that there is an intelligence/lifeform sufficiently advanced as to appear to be a God to us.
- jcims 6y ago
  Totally agree. Joscha Bach laid out a few interesting ideas around this at the end of a podcast. If you have a few minutes start here for a broader context (starts of wholly unrelated but with some great concepts): https://youtu.be/P-2P3MSZrBM?t=10084 https://youtu.be/P-2P3MSZrBM?t=10084 If not, he drills into it here: https://youtu.be/P-2P3MSZrBM?t=10400 https://youtu.be/P-2P3MSZrBM?t=10400
- psychoslave 6y ago
  That doesn't explain where the said intelligence /lifeform would come from itself, so what the point of such a theory?
- sliken 6y ago
  I read a short story that explained the explosion of life on earth during a very short period on some alien that didn't follow protocol and dumped some poop.
marta_morena_28 6y ago
Possible, but far reaching. There are other explanations: * We are a computer simulation (hence there is no colonization, we are in an experiment) * There are like 1,000,000,000,000,000,000 habitable planets in the universe. Just because something is "extremely unlikely" doesn't mean that it didn't happen to us. I.e. whomever this happened to, would ask himself that question. We may just be the ones it happened to. Also: Why would they settle species from millions of years in their own past. If they wanted to colonize, they could start with their own life-forms. Could be several things as well: * We are a genesis project and they will simply come back later and settle in what we left behind (i.e. they let the ecosystem build for a few million years before trying out this settlement) * They don't want to create competitors * We are a population bomb, i.e. they just sent out billions of probes trying to populate any given habitable planet, and they couldn't just spawn themselves there and instead had to start from somewhere where a sustainable ecosystem would derive from

tzs 6y ago

It could be that none of them have seen any point in doing so. Generally on Earth colonization has happened in order to provide a tangible economic benefit to those supporting the colonization effort. With someplace that you can only travel to and from by slow generation ship its hard to find any such economic benefit in having a colony there.