Order of Kilopi
I trust you've read David Brin's paper on the Fermi Paradox,
http://adsabs.harvard.edu/abs/1983QJRAS..24..283B
and Milan Cirkovic's more recent one
http://arxiv.org/abs/0907.3432
it seems too simplistic to boil this great question down to two alternatives, when people think of new possible answers all the time.
Order of Kilopi
If full Dyson spheres/swarms are so easy to distinguish, how do you explain the fact that our scientific attempts to search for Dyson spheres have concentrated on searching for partial Dyson spheres?Originally Posted by kzb
The range at which WISE would be able to detect a brown dwarf (which is also about the same size as Jupiter) would depend on its temperature. A cold brown dwarf could be within 4.2LY and slip through the cracks.Also WISE is designed to detect something with the heat output of Jupiter (a planet) at 1 LY.
I know. As you know, I don't share this feeling.Where we differ boils down to whether we think it should be obvious there is an advanced galactic civilisation out there, or whether it would be reasonable to think its existence could be missed.
My feeling is it should be obvious.
I agree up to the last sentence or two. My personal belief is that a technological species that makes it as far as space colonization will eventually spread throughout the galaxy--and beyond. However, my definition of "spread throughout the galaxy" is different from yours--I think they will tend to expand to star systems they find desirable rather than all star systems.This is based on the time aspect. Statistically it'd be a highly improbable fluke if all intelligent races in the MW happened to be within a few centuries of our technological level. No, if ET civs arise almost inevitably (as some seem to argue), there should be races millions of years in advance. They would've spread throughout the MW. The MW effectively would be one big city.
I also think the time frame for expansion may be such that they have NOT necessarily spread across the galaxy by this time. What's the big rush? Expansion at relativistic speeds is possible (in my judgement--backed up by practical possible methods and calculations)--but expensive. An alternative method of galactic expansion is to simply wait for desirable star systems to pass nearby. This is much less expensive, but slower. Depending on the percentage of desirable systems, and how close they should come, it could take on the order of billions of years to expand throughout the galaxy. This takes enough time that a civilization could still be in the process of expanding.
Also, there's the question of how long it takes to exploit a particular star system. It takes on the order of a million years to perform a minimum energy deflection of an Oort cloud body into the inner system for exploitation. Each of these could provide mass and energy for more deflection missions (using, for example, the retrograde colony cluster strategy). Depending on the specifics, it could take hundreds of millions of years to exploit a star system before moving on to further interstellar expansion--the reason being that aspiring colonists get more bang for their buck by investing in Oort cloud deflection rather than moving away.
Given delay factors on the order of hundreds of millions of years, it could easily take many billions of years to expand across the galaxy.
Honestly, I expect galactic level expansion to be driven by more centralized efforts. While most (or all?) star systems would be content to only embark on interstellar expansion efforts for a short time, or when another star system conveniently passes nearby, there may be SOME star systems which go all out for galactic expansion. These "expanders" could spend millions of years sending out fleet after fleet, decade after decade, on long range missions to destinations many thousands of light years away. By the time they exhaust their star system, they could have sent missions to millions of star systems. In contrast, a star system which only expands when another desirable star system conveniently passes nearby might only send missions to one or two systems during that time. So even if these "expander" systems are rare, they could easily be the main drivers of overall expansion.
Still, these superhumanly dedicated "expanders" would pick and choose which destinations to go to. The galaxy is a big place, with a stupendous number of stars.
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I've seen the Brin paper before, but I will re-read it because it was years ago when I first saw it. I'll read the new paper also, it looks interesting.
When I started off on this thread, I new full well there are all kinds of possible explanations of the Fermi Paradox (or Great Silence), and that we have been through them many times over on here. I thought, why not cut all that out, and start off with the simplest and most direct explanation, that is, there is no-one there.
Start off with that as a given fact and see where it takes us. That was the idea anyhow.
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IsaacKuo wrote:
The range at which WISE would be able to detect a brown dwarf (which is also about the same size as Jupiter) would depend on its temperature. A cold brown dwarf could be within 4.2LY and slip through the cracks.
But why would a Dyson sphere surrounding a star have so little IR luminosity? I can see that its apparent surface temperature would be low, but it's total luminosity must be the same as the star at its centre ?
Honestly, I expect galactic level expansion to be driven by more centralized efforts. While most (or all?) star systems would be content to only embark on interstellar expansion efforts for a short time, or when another star system conveniently passes nearby, there may be SOME star systems which go all out for galactic expansion. These "expanders" could spend millions of years sending out fleet after fleet, decade after decade, on long range missions to destinations many thousands of light years away. By the time they exhaust their star system, they could have sent missions to millions of star systems.
Have you not supported MY argument with this paragraph? I mean you are right, it takes all sorts to make a galaxy, and it's reasonable to think some races would expand much faster than others. Given this distribution, and intelligent races being common, at least some races will have colonised the MW long before we came on the scene.
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From the perspective of those looking for colonization, it matters not whether we are talking about 1 civ. colonizing the entire galaxy, or 20,000 coloninzing their seperate pieces of the galaxy. THe end result would be a colonized galaxy.
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If you are a race building Dyson spheres, "hurrying" would seem incongruous anyway.
Order of Kilopi
In theory a Dyson sphere could be built quite quickly- the lowest mass version (the Dyson Bubble) only requires the mass of a large asteroid to construct. How much utility could be extracted from such a low-mass construct is another matter- but it could be used to power the construction of a larger mass alternative.
Order of Kilopi
Isaac Kuo gave one answer to this question earlier, when I asked it; he suggested that a small construct around a white dwarf would have a luminosity similar to that of a brown dwarf. An intriguing, and inspiring idea- but it does limit the number of constructs to the number of white dwarfs in the galaxy.But why would a Dyson sphere surrounding a star have so little IR luminosity?
Order of Kilopi
That would depend on the star in the center. An older white dwarf would have a total luminosity similar to a cold brown dwarf.
We don't know if there would be any of these "expander" systems at all, and even if we assume there are some "expander" systems, we may still only be looking at millions of target systems. There are hundreds of billions of stars in the galaxy. So maybe only 0.001% of the star systems were colonized.Honestly, I expect galactic level expansion to be driven by more centralized efforts. While most (or all?) star systems would be content to only embark on interstellar expansion efforts for a short time, or when another star system conveniently passes nearby, there may be SOME star systems which go all out for galactic expansion. These "expanders" could spend millions of years sending out fleet after fleet, decade after decade, on long range missions to destinations many thousands of light years away. By the time they exhaust their star system, they could have sent missions to millions of star systems.
Have you not supported MY argument with this paragraph? I mean you are right, it takes all sorts to make a galaxy, and it's reasonable to think some races would expand much faster than others. Given this distribution, and intelligent races being common, at least some races will have colonised the MW long before we came on the scene.
By my definition, even 0.001% of star systems counts as spreading "across the galaxy" if those star systems are indeed spread across the galaxy. Even if they don't start off spread across the galaxy, the natural orbital motion of them would do a lot of spreading.
Order of Kilopi
I like to start off with that as a working assumption and see where it takes us. That doesn't mean it's a fact. It just means that it's a working assumption, from which you can look at various consequences and build various theories. It is a possibility which leads to interesting scientific questions, like "Why do we exist, if life has never evolved anywhere else in the universe? In all of the billions of trillions of star systems in the observable universe alone, why are we the only ones?" (Well, billions of trillions are just in the observable universe. The universe is perhaps many many orders of magnitudes larger than that.)
Another working assumption is to assume that alien life may exist. That also leads to interesting scientific questions.
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Not to disagree, but merely to note how consistently refreshing it is to see proper qualification and conditioning of one's considerations. Not sarcasm,...applause!
Now back to the flip-side of bipolar existence!
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This seems a rather obvious consideration that I, personally, have never given much consideration.
Thank-you!
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I've read these papers now. IsaacKuo, if you've not already read these I can highly recommend them. There are a few things we ought to remind ourselves of, such as the median age of Earth-like planets in the Galaxy is calculated to be 1.6bn years older than Earth. A conservative spread-through the galaxy time scale is 60 million years, so there is a clear mis-match for us to explain.
The author of the 2009 paper says that Fermi's Paradox (FP) is actually becoming disturbing. If we assume that evolution of intelligent races is commonplace, the simplest explanation of the FP is that their lifetime is severely limited. This means, by the principle of mediocrity, that our future outlook is bleak. So we should actually hope and pray that the explanation of FP is that evolution of intelligent races is extremely rare.
Order of Kilopi
I don't see a troublesome mis-match. Like I have said, there would be nothing strange about an alien civilization being spread across the galaxy. There are plenty of plausible reasons why they might not exploit our star system.
Anyway, 60 million years might be fast. There are reasonable expansion behaviors which could take billions of years to spread across the galaxy.
The author bases this on his invalid belief that alien civilizations should have been easy for us to have already detected them. This invalid belief is justified with references to papers on the detectability of astroengineering projects. But if you actually look at the content of such papers, you get a completely different picture. What you really get is an amazing appreciation of how blind we are--both literally in terms of the sensitivity of our instruments and figuratively in terms of both our ignorance and limited creativity.
Our attempts to try and spot astroengineering projects have been severely hampered by our need to make speculative assumptions about what they might be like and to also have them be distinguishable from (presumed) natural objects. So, we end up searching for partial dyson spheres with particular characteristics that would make them distinguishable, rather than sorts that may be more sensible. And we're of course limited to what our imaginations think of. We don't know about megastructure designs and concepts that we haven't conceived of yet.
Given our relative blindness, there could indeed be millions of billion+ year old civilizations out there in our galaxy without us having yet seen evidence of them.
As I have previously stated, I would LOVE for us to be all alone in the universe. Because it opens up opportunities for the more grand scale ideas I like to come up with (like methods of intergalactic colonization).If we assume that evolution of intelligent races is commonplace, the simplest explanation of the FP is that their lifetime is severely limited. This means, by the principle of mediocrity, that our future outlook is bleak. So we should actually hope and pray that the explanation of FP is that evolution of intelligent races is extremely rare.
But I don't let this desire get in the way of my assessment of the truth. The truth is that there are far too many possibilities which fit our incredibly limited evidence.
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Intelligent life vs. life that colonize other star systems.
Neanderthal was intelligent life.
Homo Sapiens are very special. Earth is a planet that has been "near perfect" as a host spawning "intelligent life", yet the "homo" branch is the only one that has evolved into a technological species. I do not see any plausible scenario in which homo sapiens will make it out of our solar system and thus we will have colonized "nothing". That at least is the baseline. So as the FP asks, "where is everyone?". They stay at home and then they die.
I am not an astrobiologist but I read the papers, books like "Rare Earth" and threads on BA all the time. I think that it is likely that microscopic life is plentiful in the Milky Way. Animal life, rare but it exists. Intelligent life, still rarer. Homo Sapiens likely in the 99.9% percentile in that regard. The few at or above us, likely never make it out of their own star system.
Managing a planet as a dominant species is extremely complex and challenging. As long as Earth is expected to "host" 7 to 9 billion homo sapiens, the vast amount of resource allocation to really "explore the stars" (manned missions) will likely never occur, domestic priorities will always trump astro-biological projects that have "paybacks" measured in time intervals longer than the present history of Western Civilization. Sorry but it will never happen, but it sure is a lot of fun to dream and speculate.
So lets build bigger telescopes, observe, measure, extrapolate. Over time (unfortunately beyond the lifetime of all of us on this board) explore most of our solar system. That will likely increase our success quotient to that of the 99.999% percentile. Quite an accomplishment.
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We have no idea if Earth is "near perfect" for spawning intelligent life. After all, it took 4+ billion years.
It is the best for humans, but that is only because we are evolutionarily adapted to Earth.
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And you know that this isn't extraordinarily rapid for an intelligent, technological species to arise, how?
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You talking short bus and helmet "special," or is there some other reason for all the quotation marks? What evidence leads you to these considerations?
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I don't. My post started with "we have no idea..."
We don't know if this is extraordinarily rapid. We don't even really know if, in just another million years, our descendents will consider ourselves at this stage to be "intelligent" and "technological".
But I guess, if pressed, I would look at our planet's formation history. Why do we think that a 1 Earth mass planet with a paper-thin atmosphere, 23% axial tilt, orbiting a Type G star with a 24-hour rotation period, is ideal? I believe that this is just hubris. It seems ideal only because we are specifically adapted to it.
Look at it this way. In another billion years, our planet will become too hot to support liquid water. So this means the life has, on our supposedly ideal planet, a 5.6 billion year window to become intelligent and technological. If 4.6 billion years is "extraordinarily rapid", then it seems to me that planets with a longer window would be better choices.
The premise that we live in the "best of all possible worlds" has been skewered since the days of Voltaire. I see no reason to believe otherwise.
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The following factors:
1. Right level of metallicity needed to give rise to both magnetic field (reduces harmful radiation, important for Animal Life) and plate tectonics (important for the transition from microscopic to animal life).
2. Right location within galaxy. Too close to center, environment way too volatile. Further out low level of essential metals
3. Right distance from G star. Earth at +/- even a couple of % would likely never have supported Animal Life.
4. Right type of star. Smaller stars likely tidal lock planets. Bigger stars, shorter lives.
5. Many planet systems have gas giant planets too close to the sun.
6. Despite Earth having produced an amazing diversity of Animal Life over its history, only 1 such species has had the intelligence/technical skills to even consider space travel (and in my opinion won't make it out of its local star system).
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I would like to point out that this kind of list used to be a lot longer but lots of "exactly right" requirements have been found to be not as important as previously thought. For example, the rarity of a large moon (for tides) or the need for an asteroid-deflecting Jupiter.
#1 and #2 are already not that restrictive and #4 & #5 are rapidly approaching that threshold as well.
Kepler may put the kibosh on #6 as well.
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Granted, but it then goes on to treat the subject as though it were a reasonable and well-supported consideration.
Best, if left right there.We don't know if this is extraordinarily rapid.
relevence?We don't even really know if, in just another million years, our descendents will consider ourselves at this stage to be "intelligent" and "technological".
Perhaps, because the only evidence we possess supports that these are the only known conditions that result in life.But I guess, if pressed, I would look at our planet's formation history. Why do we think that a 1 Earth mass planet with a paper-thin atmosphere, 23% axial tilt, orbiting a Type G star with a 24-hour rotation period, is ideal?
(24-hour rotation may not be an exact requirement, rotation was much higher when life first developed, which, itself, may be a requirement for the abiogenesis process)
(quote)
I believe that this is just hubris. It seems ideal only because we are specifically adapted to it.
(/quote)
Really? Hubris is the only rationalization you can come up for the consideration? Other than a history of conditions exactly like those the Earth has experienced, what set of conditions is evidenced to have produced life?
And? The conditions are what they are, any considerations that I, you, or anyone else, has about what could or should be, are irrelevent to these results unless we can demonstrate evidence to support our considerations.Look at it this way. In another billion years, our planet will become too hot to support liquid water. So this means the life has, on our supposedly ideal planet, a 5.6 billion year window to become intelligent and technological.
Really? What is the known and demonstrably viable range of choices for which we can demonstrate evidence?If 4.6 billion years is "extraordinarily rapid", then it seems to me that planets with a longer window would be better choices.
I don't see anyone saying "best of all possible worlds." But there is an argument for the only possible world that could produce us, at least to the best of current understandings and evidences.The premise that we live in the "best of all possible worlds" has been skewered since the days of Voltaire. I see no reason to believe otherwise.
Order of Kilopi
Douglas Adams coined the term "puddle thinking" for this hubris. He gave a humorous example of a puddle impressed by how perfectly the hole fits him.
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Before getting into your factors, let's review what was stated and asked:
You talking short bus and helmet "special," or is there some other reason for all the quotation marks? What evidence leads you to these considerations?...Homo Sapiens are very special. Earth is a planet that has been "near perfect" as a host spawning "intelligent life", yet the "homo" branch is the only one that has evolved into a technological species...
So humanity is special because of where we arose?
Technology, seems to be directly connected to intelligence, or at the least humanity's assessment of intelligence. Many species use technology appropriate to their needs and capacities, most apes, many monkies, elephants, ravens, etc.. We have raised this to a high degree, but scrape off the accumulations of a few tens of millenia and we are left with a few shaped rocks and some sticks in our kit that aren't at first glance too far removed in shape and function from those one might find a Chimpanzee or Crow making use of.
While I'd definitely agree that the conditions you list would help distinguish the Earth from other planets in our (and some other) stellar system(s), it is more the combination and mix that seems more unique and "special."
and the metallicity of the planet is strongly correlated to the metallicity of the Star which it formed about.1. Right level of metallicity needed to give rise to both magnetic field (reduces harmful radiation, important for Animal Life) and plate tectonics (important for the transition from microscopic to animal life).
This is the least precise limitor mentioned, based upon generalities and averages that allow for many exceptions and situational loopholes.2. Right location within galaxy. Too close to center, environment way too volatile. Further out low level of essential metals
are you sure about this? Are you saying that our orbit has remained unchanged over the last 4 billion years?3. Right distance from G star. Earth at +/- even a couple of % would likely never have supported Animal Life.
Relevence?4. Right type of star. Smaller stars likely tidal lock planets. Bigger stars, shorter lives.
proximity probably isn't as important as how the gas giants came to be so close. Gas giants can't form in close in orbits.5. Many planet systems have gas giant planets too close to the sun.
evidence and relevence?6. Despite Earth having produced an amazing diversity of Animal Life over its history, only 1 such species has had the intelligence/technical skills to even consider space travel (and in my opinion won't make it out of its local star system).
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IsaacKuo, your argument is classed as a soliptimist argument in the Cirkovic 2009 article. I think it's also fair to say that arguments based on difficulty of detection of alien civs are given short shrift in both the Cirkovic and Brin (1983) papers. I'm not saying this is necessarily wrong or right in this post, I am just reporting what these two authors say.
The main reason is connected with the deep time issue. It's not just that we don't detect alien civs remotely, it's also the fact that they are not here now, and there is no reputable evidence they have been here before either. (BTW, there was a typo in my post #193: the median age of Earth-like planets in the Galaxy is 1.9 billion years older than Earth, and not 1.6 billion years as I stated).
Question: what does soliptimist mean in this context?
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A proper and complete listing would still likely be much, much longer.
I'm not sure what leads you to believe that these requirements are "not as important as previously thought" as of the two examples you list, one has always been rather shaky (*comet* deflecting Jupiter) and the other ("rarity of a large moon") is still very much in play as a major element (tides are merely one aspect of a large moon)....but lots of "exactly right" requirements have been found to be not as important as previously thought. For example, the rarity of a large moon (for tides) or the need for an asteroid-deflecting Jupiter...
Can you support these claims? (no need for specific cites, a simple explanation of why you feel the way you do about each of these aspects would suffice and be much appreciated.)#1 and #2 are already not that restrictive and #4 & #5 are rapidly approaching that threshold as well.
Kepler may put the kibosh on #6 as well.
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KABOOM wrote:
Managing a planet as a dominant species is extremely complex and challenging. As long as Earth is expected to "host" 7 to 9 billion homo sapiens, the vast amount of resource allocation to really "explore the stars" (manned missions) will likely never occur, domestic priorities will always trump astro-biological projects that have "paybacks" measured in time intervals longer than the present history of Western Civilization. Sorry but it will never happen, but it sure is a lot of fun to dream and speculate.
This is a bleak future explanation according to the Cirkovic paper. Bleak future explanations say that civilisations either never last long, or that they fall into long-term totalitarianism. This means that one of these fates await our race also; to say otherwise would be a non-Copernician viewpoint.
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I think you have a spelling error or perhaps Brin is coining a term.
Solipsism (solipsist) - Latin - solus (alone) and ipse (self), generally refers to the philosophy that anything outside one's own mind is impossible to definitively prove, or the perspective that nothing outside of one's own considerations is actually real.
I'd have to research it in a bit more depth before laying out a serious argument, but, my initial reaction would be that Brin offers this explanation in reference to the fact that like solipsism, such an argument (hubris of a perfect fit) is unfalsifiable and currently untestable.
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And you feel this is inappropriate how/why?
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I'm questioning the validity of one of the premises. That makes it relevant.
And how many non-Earthlike habitats have we checked for life? Two (Mars & the Moon), and one of those is still inconclusive.Perhaps, because the only evidence we possess supports that these are the only known conditions that result in life.
I did not say it was the only possible rationalization. I believe that it is the most common.Really? Hubris is the only rationalization you can come up for the consideration? Other than a history of conditions exactly like those the Earth has experienced, what set of conditions is evidenced to have produced life?
In absence of evidence to support it, I question the notion that intelligent life arose extraordinarily rapidly on Earth.And? The conditions are what they are, any considerations that I, you, or anyone else, has about what could or should be, are irrelevent to these results unless we can demonstrate evidence to support our considerations.
Here's a thought experiment: Consider two very similar scenarios:Really? What is the known and demonstrably viable range of choices for which we can demonstrate evidence?
Scenario 1) the Sun is fractionally less massive and the Earth's orbit slightly tighter to compensate for the very slight drop in solar radiation.
A) Does the possibility of intelligent life arising suddenly plummet from a non-zero value to zero?
B) Does the amount of time before the Sun overheats the Earth's atmosphere increase (more time to evolve) or decrease?
Scenario 2) same as #1 except the Sun is fractionally more massive and the Earth is fractionally further away
Questions: same as before.
Now you are left with two options...
A) In at least one of those scenarios, intelligent life has more time to evolve and grow, thus improving its chances
B) Neither of those scenarios improves the chances for technological life, so therefore the Earth is literally balancing on a threshold of perfection. Considering all of the other possibilities, is this plausible?
The post I responded to called Earth "near perfect". This is substantively no different than the "best of all possible worlds" argument that has been bandied about for centuries.I don't see anyone saying "best of all possible worlds." But there is an argument for the only possible world that could produce us, at least to the best of current understandings and evidences.
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