The Great Filter

The Great Filter is an idea regarding probabilities. Basically, the human effect on the Milky Way will be decided within the next million years. Either we'll colonize it fully, or we won't. A million years is an eye-blink in geological time.

What they are doing is looking out at roughly 10^16 stars. Technically, each star has the opportunity to generate a Type 3 civilization. Even assuming that only 1/100 have planets that are 'old' enough such that their light could reach us (i.e., a star a billion light years away is also a billion years older), that still leaves 10^14 individual opportunities for any specific star to generate a Type III civ. But the skies are silent, so why?

The idea is that there are various stages of development where only a portion of the stars will progress. Generating life in the first place. Generating multi-cellular life. Generating thinking life. Developing technology. Getting to the stars. Etc.

We don't know the odds. It could be that the first stage is very unlikely. It could be that a middle stage is. It could be that a later stage is. The point is, there's a filter that's stopping pan-gal civs from forming. Is the bulk of this risk in front of us? Is it behind us?

It's safer from a logical standpoint to guess the bulk of risk is in front of us, but scarier.

Short of violating causality as we understand it, travel between stars doesn't look very enticing. I suppose we might come up with an inexpensive/efficient enough means of energy that we could attain near-light speeds, or a way to keep people in space alive in perpetuity. Cyborg-ish type setups might work too I guess; it doesn't matter if it takes 300 years to get to the next star if you can survive the radiation and live many 1000's.

Assuming there is no way to bypass the speed-of-light constraint though, that does substantially cut down on the number of stars where we ask "if there's life there, why haven't we met it".

Even in our own galaxy though, that's still a ton of stars.

I think a big misconception is that evolution is a process of "betterment", in which creatures will progress up some ladder of sophistication until they are eventually able to touch the stars. Whereas really it's merely a process of adaptation to suit the current environment which has no end goal in mind and certainly no requirement for increased complexity or sophistication. There's no real reason why a sophisticated level of intelligence should ever be expected to come out of this process, and the fact that animal life existed for about 600 million years before it happened on Earth might indicate that it actually takes some quite unlikely confluence of events to occur to provide the evolutionary pressure to make our level of intelligence significantly beneficial.

But it's all kind of a moot point given that we have pretty much zero data to go on on how widespread life is in the universe, or if it even exists anywhere else at all.

I'm not particularly convinced travel amongst the stars is prohibitively hard (thus a great filter). Our galaxy is only 100,000 light years across. If a civilization can colonize it at 1% of 1% of C it will be done in a relatively short billion years

Personally, I slightly bend toward the idea that "The Great Filter" is reaching "life intelligent enough to get technological ability to reach space". Life itself LOOKS not that improbable to happens, but the fact is, in 1600 millions years of evolution, we seem to be the ONLY species which has reached the treshold of such intelligence, so THAT looks like a very rare happenstance.

I thought this thread would be about the liver.

TheMeInTeam said:

It's safer from a logical standpoint to guess the bulk of risk is in front of us, but scarier.

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That the intelligence and self-centric drive required for developing advanced space faring negatively correlates with the wisdom to not be suicidal with that level of development?

-or-

That applicable laws of physics render advanced space faring possible, but requiring of more resources than are generally available on a habitable planet? That we've all been trapped even if we're smart enough to figure it out? Doesn't matter if everyone so far has been awesome farmers if all they have is two dozen kernels of seed corn and no other food?

El_Machinae said:

But the skies are silent, so why?

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Maybe once you reach a certain stage of technological advancement, you cease to want to communicate via such "backwards" methods such as radio waves.

I also wouldn't be surprised if successful civilization out there figured out that you keep quiet or you face the consequences. If the universe has other civilizations in it - chances are that they are far more advanced than us. Why announce our presence to them, if we can't match their technology? Maybe we have a resource they'd want - perhaps it's just best to keep quiet.

Farm Boy said:

That the intelligence and self-centric drive required for developing advanced space faring negatively correlates with the wisdom to not be suicidal with that level of development?

-or-

That applicable laws of physics render advanced space faring possible, but requiring of more resources than are generally available on a habitable planet? That we've all been trapped even if we're smart enough to figure it out? Doesn't matter if everyone so far has been awesome farmers if all they have is two dozen kernels of seed corn and no other food?

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Either of those, or something else we're not considering that will nevertheless prove an obstacle.

I'm not particularly convinced travel amongst the stars is prohibitively hard (thus a great filter). Our galaxy is only 100,000 light years across. If a civilization can colonize it at 1% of 1% of C it will be done in a relatively short billion years

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We're not capable of it right now; anything we'd attempt to send to even the nearest stars would die before it arrives and it would be problematic to fashion cold sleep or generational ships. We have a hard enough time just planning a mission to Mars without exposing astronauts to dangerous levels of radiation.

Besides, if it really does take one billion years we could conceivably have a scenario where it's ongoing in another galaxy but we won't observe evidence of that for millions of years...or much more.

Desire/incentive to colonize it is an assumption that's not good to make either. What would prompt humanity to make a true effort at colonizing other stars at this juncture, or even 1000 years from now? Novelty isn't usually enough, though you might get some explorers that way the whole "dead long before arrival" is off-putting. Eventually we'll probably try to colonize other planets in the solar system or at least come up with a low-energy method to extract resources, though who knows what kinds of territorial disputes and wars that might cause.

On some level, it seems arrogant to believe we're the only species to be potentially capable of it, and yet at the same time we have no evidence to the contrary thus far despite looking for it (and in many cases desiring to find it).

I also wouldn't be surprised if successful civilization out there figured out that you keep quiet or you face the consequences. If the universe has other civilizations in it - chances are that they are far more advanced than us. Why announce our presence to them, if we can't match their technology? Maybe we have a resource they'd want - perhaps it's just best to keep quiet.

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I suppose there's always the possibility that intelligent life eventually evolves to a state where it's not recognizable to us, and since we're not there ourselves won't know until/if we get there.

If I were to hazard a guess at a great filter it would be oxygen metabolizing animals. Hydrocarbons in an oxygen rich atmosphere allows for incredible energy density and swift and sophisticated mobile organisms.

Here's a good collection of ideas related to the Filter: http://lesswrong.com/lw/lls/astronomy_space_exploration_and_the_great_filter/

El_Machinae said:

The Great Filter is an idea regarding probabilities. Basically, the human effect on the Milky Way will be decided within the next million years. Either we'll colonize it fully, or we won't. A million years is an eye-blink in geological time.

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Actually, the next century, or even 50 years will be even more of a decider. We have to get away from this dumbed-down science, obsession with war, and willful ignorance before we'll make any significant progress.

Akka said:

Personally, I slightly bend toward the idea that "The Great Filter" is reaching "life intelligent enough to get technological ability to reach space". Life itself LOOKS not that improbable to happens, but the fact is, in 1600 millions years of evolution, we seem to be the ONLY species which has reached the treshold of such intelligence, so THAT looks like a very rare happenstance.

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But how can we know for sure that another intelligent civilization hasn't arisen and declined on Earth already? How much evidence might one have left behind for us to find after, say 50 or 100 million years?

Perfection said:

If I were to hazard a guess at a great filter it would be oxygen metabolizing animals. Hydrocarbons in an oxygen rich atmosphere allows for incredible energy density and swift and sophisticated mobile organisms.

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TheMeInTeam said:

We're not capable of it right now; anything we'd attempt to send to even the nearest stars would die before it arrives and it would be problematic to fashion cold sleep or generational ships. We have a hard enough time just planning a mission to Mars without exposing astronauts to dangerous levels of radiation.

Besides, if it really does take one billion years we could conceivably have a scenario where it's ongoing in another galaxy but we won't observe evidence of that for millions of years...or much more.

Desire/incentive to colonize it is an assumption that's not good to make either. What would prompt humanity to make a true effort at colonizing other stars at this juncture, or even 1000 years from now? Novelty isn't usually enough, though you might get some explorers that way the whole "dead long before arrival" is off-putting. Eventually we'll probably try to colonize other planets in the solar system or at least come up with a low-energy method to extract resources, though who knows what kinds of territorial disputes and wars that might cause.

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Interstellar travel is, of course, rediculously hard, but of course. But we're talking about having geological time periods to pull it off. To that end I would place the balance on the incredible amount of time and energy we could put into it. I find the objections you raised to be tackleable by reasonably forseeable technologies.

The desire I think is sufficient to divert a small fraction of the economy to the endeavour.

It's a fair question though about detection of alien civilizations. It strikes me that any sufficiently advanced civilization would want to harness as much energy from stars as possible. And if they can pull off at least a significant fraction, that should be detectable.

Farm Boy said:

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How repulsive

I don't think alternate biochemisties are implausible (whether carbon based or not), but they're probably going to be slower then the explosive combination of hydrocarbons and oxygen due to lower energy density. This means evolution is likely to produce more conservative designs, and slowed reproduction will delay the rate of complexity increase.

That looks like a Silicoid from Master of Orion.

That's because it is.

Maybe our concept of a what constitutes a galactic civilization is off?

Perfection said:

Interstellar travel is, of course, rediculously hard, but of course. But we're talking about having geological time periods to pull it off. To that end I would place the balance on the incredible amount of time and energy we could put into it. I find the objections you raised to be tackleable by reasonably forseeable technologies.

The desire I think is sufficient to divert a small fraction of the economy to the endeavour.

It's a fair question though about detection of alien civilizations. It strikes me that any sufficiently advanced civilization would want to harness as much energy from stars as possible. And if they can pull off at least a significant fraction, that should be detectable.

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Why do you think the desire to colonize space is sufficient to divert enough of the economy to it to matter? As it is, we haven't even invested the resources to send humans back to the Moon for 43 years and counting, let alone Mars, to say nothing of taking any concrete steps toward interstellar travel. Space exploration seems to be considered a luxury not worth spending much on by most of the population and most political leaders.

I hope this changes, but as it is we will be quite lucky to see a manned Mars mission in our lifetimes even though it's technically feasible. It can't be ruled out that people in the distant future will try something like a generation ship, nuclear pulse propulsion, etc, but I don't see any evidence based on current human behavior that this is likely to occur.

I suspect that this is the correct solution to Fermi's paradox:

Farm Boy said:

That applicable laws of physics render advanced space faring possible, but requiring of more resources than are generally available on a habitable planet?

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