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I am surprised a more common argument was not mentioned: other life exists but the laws of physics limit our interaction. Maybe there is undiscovered physics li

I am surprised a more common argument was not mentioned: other life exists but the laws of physics limit our interaction. Maybe there is undiscovered physics like wormholes or time travel, or maybe there isn't and the speed of light really is a fundamental limit that cannot be surpassed. In that case, no matter how advanced another civilization becomes, they still can't violate natural law and are thus unable to reach us.

joe_the_user 12y ago
The laws of any potential biology and the messiness of the world could together effectively limit a civilization's energy usage to much lower than indicated by the easily deducible laws of physic (the explicit laws of physics might limit the output of an internal combustion engine to a certain but the effective maximum winds up less than that. Human biological systems experience serious damage by being weightless for significant periods, etc). I only recently realized that this "paradox" looking at the possibility not of "earth advanced" civilization but supposed advanced civilizations that would put out much more energy than humans put out. The whole thing seems to rest on false-extrapolations of mid 20th century hard-science fiction authors. Our Western Civilization has experienced an exponential growth of some things, has expanded it's "frontiers" quickly in a variety of ways, conquering the rest of the globe and then labeling space "the final frontier". But all this has been low-hanging fruit. We're reaching the end of population expansion, space is fundamentally hostile to human life in a way that would take tremendous progress to overcome and we're facing longer term consequences of the rapid expansions we have achieved (global warming is just one of the consequences). If humans survive this, we'll have to have somehow achieve a steady-state for energy consumption and related things. But once we do achieve that steady state, why would we want or need to suddenly start using the energy of an entire star (after the thousand years of scientific progress we'd need to under how to do that)?
- XorNot 12y ago
  The problem here is the assumption we need scientific progress to do this. We don't. We have the technology today to launch satellites into solar-orbits which would be capable of beaming power back to Earth. It would be clean, efficient and non-disasterous to the biosphere. With any amount of space-borne industry, the costs would also plummet and get cheaper with every additional satellite. Once you can harness the energy of an entire star, there's almost no reason not to achieve it.
- vorg 12y ago
  Humans can build large sealed cities on the Earth-facing side of the Moon using solar-propelled remote-controlled "drone" technology. The response time is only about 1 or 2 seconds so the human operators on Earth wouldn't need the equipment to have much of its own AI (unlike later on when humans repeat the process on Mars). Once enough such specialized machinery is on the Moon, entire "cities" the size of an apartment building could be built, funded in the same way Ordos in China was. The hard part would be experimenting with different biochemical processes afterwards in each city so one of them could provide enough oxygen, water, and food for humans who'd arrive much later on.
nhaehnle 12y ago
I often wonder this as well. The speed of light isn't really a physical limit to expansion - generation ships are theoretically possible. It may just be that the Great Filter takes the form of relatively benign[1] economic and/or sociological obstacles. At least, if you take a diff between typical beliefs at the time the Fermi Paradox was formulated vs. typical beliefs now, I would say the experience of the shutting down of Apollo and overall reduction of human space exploration is probably the most relevant new observation we have made since then. [1] In the sense of: You don't need nuclear armageddon to stop humans from spreading to other solar systems; the price tag of interstellar travel is sufficient.
- XorNot 12y ago
  If you consider the declining birth rates of modern nations as the standard of living goes up, then it stands to reason that once a civilization reaches the point where it might be able to engage in large scale space exploration, the population that can do so has become relatively stable. So you simply never (or rarely) get exponential cosmic expansion. There might be a few billions of that race roaming the stars, but their numbers do not increase.
  - dennisgorelik 12y ago
    Evolution takes care of that obstacle: whatever individuals keep replicate themselves - win, and keep pushing expansion forward.
  - rwallace 12y ago
    But declining birth rates don't lead to stable populations, they lead to shrinking populations. So if we don't manage to restore birth rates, this would be an example of 'Great Filter ahead of us'.
    - fixedd 12y ago
      Declining birth rates only lead to shrinking populations when the birth rate was stable to begin with. -- Date 1: Every two people produce four offspring. Date 2: Every two people produce three offspring. Between Date 1 and Date 2 the birthrate declined by 25%, but the total rate is still positive.
SideburnsOfDoom 12y ago
> I am surprised a more common argument was not mentioned: ... maybe the speed of light really is a fundamental limit ... they still can't violate natural law and are thus unable to reach us. One of the assumptions of the article and of most serious scientific discussion of the topic is that the speed of light really is the fundamental limit that it appears to be. It's not mentioned because it's axiomatic. The only thing in favour of the speed of light not being an absolute limit is that people don't want it to be. And wishful thinking is a very weak argument. This does not make interstellar travel impossible, just very difficult. It is not feasible for us at this time, but it does not "violate natural law".
danielweber 12y ago
Even without FTL, if civs can travel across stars, they should have already colonized the galaxy. Imagine a civ arising 50 million years ago (a majority of the other stars in the Milky Way are billions of years older than the Sun). It takes 50,000 years to become interplanetary, and then 1000 years later it's ready to launch a mission to the nearest neighbor, 8 light years away. It travels at 0.02c and then arrives 400 years later. After 2000 years it has colonized that system enough that it has local resources to repeat the process. The galaxy is 100,000 light years across, so that allows a spread from one edge to the other in 30 million years, which is long ago for us. Forming closer to the center and allowing for the mixing of star systems with galactic rotation would shrink that number. Wormholes or warp drive would actually explain the Fermi paradox for me: since the other civs are used to their stars that are older and hotter, and they only pay attention to the prime real estate. But limited to the speed of light, a civ will spread by filling each nook and cranny it can live in.
- JoeAltmaier 12y ago
  Its unlikely any race would last unchanged for 50 million years. They could likely lose interest in colonizing long before that much time had passed. So the question becomes: how much colonization can one race accomplish before burning out their will to continue? Just 2 million years ago, human ancestors were small-brained apemen. A million years is a long time.
  - danielweber 12y ago
    Even if most lose their interest in colonization, there would still be some interested in colonization, and those would do so. Unless there were some enforcement mechanism to stop potential settlers from leaving.
    - JoeAltmaier 12y ago
      I don't mean intellectually. I mean, they become a creature that can't/doesn't leave the nest. At all.

joe_the_user 12y ago

The laws of any potential biology and the messiness of the world could together effectively limit a civilization's energy usage to much lower than indicated by the easily deducible laws of physic (the explicit laws of physics might limit the output of an internal combustion engine to a certain but the effective maximum winds up less than that. Human biological systems experience serious damage by being weightless for significant periods, etc). I only recently realized that this "paradox" looking at the possibility not of "earth advanced" civilization but supposed advanced civilizations that would put out much more energy than humans put out. The whole thing seems to rest on false-extrapolations of mid 20th century hard-science fiction authors. Our Western Civilization has experienced an exponential growth of some things, has expanded it's "frontiers" quickly in a variety of ways, conquering the rest of the globe and then labeling space "the final frontier". But all this has been low-hanging fruit. We're reaching the end of population expansion, space is fundamentally hostile to human life in a way that would take tremendous progress to overcome and we're facing longer term consequences of the rapid expansions we have achieved (global warming is just one of the consequences). If humans survive this, we'll have to have somehow achieve a steady-state for energy consumption and related things. But once we do achieve that steady state, why would we want or need to suddenly start using the energy of an entire star (after the thousand years of scientific progress we'd need to under how to do that)?

XorNot 12y ago
The problem here is the assumption we need scientific progress to do this. We don't. We have the technology today to launch satellites into solar-orbits which would be capable of beaming power back to Earth. It would be clean, efficient and non-disasterous to the biosphere. With any amount of space-borne industry, the costs would also plummet and get cheaper with every additional satellite. Once you can harness the energy of an entire star, there's almost no reason not to achieve it.
vorg 12y ago
Humans can build large sealed cities on the Earth-facing side of the Moon using solar-propelled remote-controlled "drone" technology. The response time is only about 1 or 2 seconds so the human operators on Earth wouldn't need the equipment to have much of its own AI (unlike later on when humans repeat the process on Mars). Once enough such specialized machinery is on the Moon, entire "cities" the size of an apartment building could be built, funded in the same way Ordos in China was. The hard part would be experimenting with different biochemical processes afterwards in each city so one of them could provide enough oxygen, water, and food for humans who'd arrive much later on.

nhaehnle 12y ago

I often wonder this as well. The speed of light isn't really a physical limit to expansion - generation ships are theoretically possible. It may just be that the Great Filter takes the form of relatively benign[1] economic and/or sociological obstacles. At least, if you take a diff between typical beliefs at the time the Fermi Paradox was formulated vs. typical beliefs now, I would say the experience of the shutting down of Apollo and overall reduction of human space exploration is probably the most relevant new observation we have made since then. [1] In the sense of: You don't need nuclear armageddon to stop humans from spreading to other solar systems; the price tag of interstellar travel is sufficient.

XorNot 12y ago
If you consider the declining birth rates of modern nations as the standard of living goes up, then it stands to reason that once a civilization reaches the point where it might be able to engage in large scale space exploration, the population that can do so has become relatively stable. So you simply never (or rarely) get exponential cosmic expansion. There might be a few billions of that race roaming the stars, but their numbers do not increase.
- dennisgorelik 12y ago
  Evolution takes care of that obstacle: whatever individuals keep replicate themselves - win, and keep pushing expansion forward.
- rwallace 12y ago
  But declining birth rates don't lead to stable populations, they lead to shrinking populations. So if we don't manage to restore birth rates, this would be an example of 'Great Filter ahead of us'.
  - fixedd 12y ago
    Declining birth rates only lead to shrinking populations when the birth rate was stable to begin with. -- Date 1: Every two people produce four offspring. Date 2: Every two people produce three offspring. Between Date 1 and Date 2 the birthrate declined by 25%, but the total rate is still positive.

SideburnsOfDoom 12y ago

> I am surprised a more common argument was not mentioned: ... maybe the speed of light really is a fundamental limit ... they still can't violate natural law and are thus unable to reach us. One of the assumptions of the article and of most serious scientific discussion of the topic is that the speed of light really is the fundamental limit that it appears to be. It's not mentioned because it's axiomatic. The only thing in favour of the speed of light not being an absolute limit is that people don't want it to be. And wishful thinking is a very weak argument. This does not make interstellar travel impossible, just very difficult. It is not feasible for us at this time, but it does not "violate natural law".

danielweber 12y ago

Even without FTL, if civs can travel across stars, they should have already colonized the galaxy. Imagine a civ arising 50 million years ago (a majority of the other stars in the Milky Way are billions of years older than the Sun). It takes 50,000 years to become interplanetary, and then 1000 years later it's ready to launch a mission to the nearest neighbor, 8 light years away. It travels at 0.02c and then arrives 400 years later. After 2000 years it has colonized that system enough that it has local resources to repeat the process. The galaxy is 100,000 light years across, so that allows a spread from one edge to the other in 30 million years, which is long ago for us. Forming closer to the center and allowing for the mixing of star systems with galactic rotation would shrink that number. Wormholes or warp drive would actually explain the Fermi paradox for me: since the other civs are used to their stars that are older and hotter, and they only pay attention to the prime real estate. But limited to the speed of light, a civ will spread by filling each nook and cranny it can live in.

JoeAltmaier 12y ago
Its unlikely any race would last unchanged for 50 million years. They could likely lose interest in colonizing long before that much time had passed. So the question becomes: how much colonization can one race accomplish before burning out their will to continue? Just 2 million years ago, human ancestors were small-brained apemen. A million years is a long time.
- danielweber 12y ago
  Even if most lose their interest in colonization, there would still be some interested in colonization, and those would do so. Unless there were some enforcement mechanism to stop potential settlers from leaving.
  - JoeAltmaier 12y ago
    I don't mean intellectually. I mean, they become a creature that can't/doesn't leave the nest. At all.