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Old 11-15-2017, 12:23 PM   #21
Fred Brackin
 
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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Originally Posted by Anthony View Post
I was assuming a more reasonable 1% of c, but yeah, it's not likely to make a drastic difference. In any case, based on the fact that the aliens aren't here, we're forced to conclude one of two things:
  1. Interstellar colonization is functionally impossible.
  2. We're the first.
Careful with that "we" there pardner. I can conclude a not specifically limited but large number of other things.

Such as the aliens have already been here but are gone now because they found nothing of interest to them as just one example.

Then there's possibilities such as the number of alien species capable of interstellar travel being small enough that the probability of none of them being interested in colonization is not that unlikely.

There are many, many others.
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Old 11-15-2017, 01:10 PM   #22
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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This really has no valid answer.

A civilization a million years older than us is further from us than we are from the Neandertals. Unless it just so happens that we've finally learned the real rules and there's no much left to find, it's not clear that we can even say anything about what kind of magic they might 'plausibly' possess.

Just for illustration, imagine a Roman in the time of Augustus Caesar trying to figure out what a civilization even 2000 years away might 'plausibly' have. He wouldn't even be able to express or define the context.
Oh sure, it's a futile endeavor to some degree. But the point is not to predict the future, so much as set a lower bound.

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If I could definitively answer this, I would have patents worth trillions and probably the Nobel. However, aging isn't an inevitable consequence of biological systems, but rather a beneficial trait that evolved in multicellular organisms and there are organisms that are biologically immortal. I certainly can't speak about a nonspecific alien biology in anything but the broadest terms. Any solution to longevity is probably a complex one, since the causes of senescence in vertebrates are myriad, no one technology is adequate.
There's the rub. The immortal organisms we know of mostly don't even have brains. Immortal jellyfish don't have brains. Planarian flatworms only dubiously have brains. Lobsters have brains, but aren't truly immortal—maybe if you modified them to stop growing after a certain point in time, it would solve the molting issue and they'd become immortal, but we don't really know.

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In which case then they don't have a million year old civilization. That technology is extremely optimistic, much more than any of the things you are keen to dismiss.
Vilani technology is extremely optimistic? Well of course, it's superscience. To be clear, I'm not trying to make the Vilani per se. More to ask, "what things would be very surprising to see a very old civilization not have?" Dyson swarms are one, I agree.

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It doesn't, I think, require materials that violate any known properties of matter. It probably requires materials we don't have now, but if that is your restriction, they don't have a Dyson swarm either.
"Not provably impossible" is not the same as "proven possible." Lots of macroscopic behaviors of matter can't be predicted from basic physics (because we haven't solved the quantum n-body problem yet). For comparison, my understanding is that we don't really know if we can make materials with the tensile strength to build an Earth space elevator. Maybe the materials engineering issues in building a Dyson bubble are known to be more tractable than those in building an Earth space elevator, but I'd like to see a source for that if so.
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Old 11-15-2017, 01:30 PM   #23
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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There's the rub. The immortal organisms we know of mostly don't even have brains. Immortal jellyfish don't have brains. Planarian flatworms only dubiously have brains. Lobsters have brains, but aren't truly immortal—maybe if you modified them to stop growing after a certain point in time, it would solve the molting issue and they'd become immortal, but we don't really know.
There are fairly complex organisms with significant longevity, so even if senescence can't be completely eliminated in multicellular organisms, it almost certainly can be delayed quite a bit. These mechanisms evolved because the single-cell bottleneck prevents the accumulation of deleterious mutations in multicellular organisms, and because sex gives a significant evolutionary advantage to organisms that do not compete with their offspring; they aren't inevitable features of biological systems, even those with complex nervous systems.

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Vilani technology is extremely optimistic? Well of course, it's superscience. To be clear, I'm not trying to make the Vilani per se. More to ask, "what things would be very surprising to see a very old civilization not have?" Dyson swarms are one, I agree.
A million year old civilization is an optimistic technology. I know what it would take to make a Dyson swarm, but I haven't the slightest idea what sorts of institutions could make a civilization that survives this long. It certainly isn't "proven possible".
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"Not provably impossible" is not the same as "proven possible." Lots of macroscopic behaviors of matter can't be predicted from basic physics (because we haven't solved the quantum n-body problem yet). For comparison, my understanding is that we don't really know if we can make materials with the tensile strength to build an Earth space elevator. Maybe the materials engineering issues in building a Dyson bubble are known to be more tractable than those in building an Earth space elevator, but I'd like to see a source for that if so.
Solar statites do require low density materials that we do not yet know how to make into large enough structures, although we have manufactured materials, like graphene sheets, that do have low enough density.
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Old 11-15-2017, 01:44 PM   #24
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

Existence is risky for biological organisms. Even the best precautions will occasionally fail. I doubt you'd get more than a few absurdly luck and/or paranoid individuals to survive more than a thousand or so years regardless of reasonable technological projections.
Though enough of those will probably skew society to something even our most safety conscious helicopter parents could only gawk at.

We are at the cusp of gaining the ability to radically alter our very nature, something as different from us as stone age people are to pond scum.
I don't think just thinking, "wow, one million years from now is like one million years ago but in reverse." works as an analogy.
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Old 11-15-2017, 01:55 PM   #25
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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Existence is risky for biological organisms. Even the best precautions will occasionally fail. I doubt you'd get more than a few absurdly luck and/or paranoid individuals to survive more than a thousand or so years regardless of reasonable technological projections.
On a long enough timeline everyone's survival rate drops to zero. Nobody is disputing this. Living to be hundreds of years old instead of three score and ten, is definitely biologically feasible.
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Old 11-15-2017, 02:05 PM   #26
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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A million year old civilization is an optimistic technology. I know what it would take to make a Dyson swarm, but I haven't the slightest idea what sorts of institutions could make a civilization that survives this long. It certainly isn't "proven possible".
What do you mean by "civilization"? How old is Chinese civilization, by your reckoning?

I suspect we Westerners tend to over-extrapolate from the case of Rome. Rome's problem was heavy dependence on grain from Egypt, leaving it vulnerable to catastrophic collapse. That sort of collapse is actually fairly rare AFAICT.
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Old 11-15-2017, 02:16 PM   #27
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

Re: colonization speeds, can we really expect the fastest possible ships to get used for this purpose? If antimatter propulsion is possible but prohibitively expensive, it matters whether the ship's designers suck up the cost, or decide to go with a fusion design even if the fusion ship is 1/10th the specific impulse. There's also likely to be some limit on how many stages anyone would build an interstellar rocket with.
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Old 11-15-2017, 02:25 PM   #28
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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How old is Chinese civilization, by your reckoning?
Nowhere near a million years, that's for sure!!!

Last edited by NineDaysDead; 11-15-2017 at 02:28 PM.
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Old 11-15-2017, 02:32 PM   #29
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

Except... antimatter vs. fusion might not matter if laser-powered lightsails are the preferred mode of interplanetary transportation. Does anyone know of good sources for the laser-powered lightsail concept? I've heard it's complicated, and that's about all I know.
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Old 11-15-2017, 02:37 PM   #30
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Default Re: [Ultra-Tech] Conservative hard SF... but not implausibly conservative

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What do you mean by "civilization"?
In this case, I think "a set of cultural institutions that are distinct and haven't suffered a major collapse or technological discontinuity" fits the requirement.
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How old is Chinese civilization, by your reckoning?
Even if you count the PRC as the same civilization as started agriculture in Chengtoushan, it is still a 100th of the age of your proposed civilization. This is a stretch, though, the PRC today is the result of nine thousand years of emigration, unrest, war, and foreign conquest. No institutions survive from 9000 years ago, and three relativity recent discontinuities: the Mongol conquest, the Manchurian conquest, and the Communist Revolution had profound, transformative, effects on the cultures of the region.

You are proposing a civilization that is able to maintain the technological and economic infrastructure necessary for a Type II civilization with a Class B stellar engine for nearly five times as long as anatomically modern humans even existed.

What is "proven to exist" are a few rare institutions that have continuously operated for about 1500 years. Claims can be made for slightly older, but can't be substantiated, and many (the Japanese Imperial Throne, the lineage of Elizabeth Windsor) are clearly political fiction.

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