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The Silurian Hypothesis (2020)

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Re: The Silurian Hypothesis (2020)

#121

Post by 2III7 »

andrewflnr wrote: post #96
jerf wrote: post #89

Earlier quoted context omitted.

I'm not to stuck on the complete, 100% impossibility of things to be found. But one counterargument that can be made is that fossilization requires very specific circumstances, and the legacy of the dinosaurs is from millions of years of opportunities. A blip of a 500 year civilization might not leave much behind. No, I wouldn't expect a big pile of iron to leave anything interesting behind. It would rust, and rust h…

I think concrete is one of the biggest signs of humanity that will be detectable in millions of years. It's very durable and we make a lot of it in big concentrations, like the foundations of buildings in a big city. It's not an especially advanced technology either, compared to say titanium or plastic. The Romans already had it.

The concrete the Romans made actually hardened over time because they used volcanic ash and quicklime which fills micro cracks by itself. Modern concrete lasts structurally only a couple of hundred years. There will be no detectable modern concrete in millions of years. It'll be decomposed to minerals in a couple of thousand years.

Re: The Silurian Hypothesis (2020)

#122

Post by andrewflnr »

2III7 wrote: post #121
andrewflnr wrote: post #96

Earlier quoted context omitted.

I think concrete is one of the biggest signs of humanity that will be detectable in millions of years. It's very durable and we make a lot of it in big concentrations, like the foundations of buildings in a big city. It's not an especially advanced technology either, compared to say titanium or plastic. The Romans already had it.

The concrete the Romans made actually hardened over time because they used volcanic ash and quicklime which fills micro cracks by itself. Modern concrete lasts structurally only a couple of hundred years. There will be no detectable modern concrete in millions of years. It'll be decomposed to minerals in a couple of thousand years.

Decomposed to... what, though? Minerals indistinguishable from natural accumulations? Doubt it. Even if it turns to powder with rust stains where the reinforcement was, that'll be sufficient clue. (At least if it gets buried, which I'll admit is a key assumption that won't be true for all cities.)

Re: The Silurian Hypothesis (2020)

#123

Post by saidnooneever »

gtowey wrote: post #104
GolfPopper wrote: post #71

From author and druid John Michael Greer's essay, "The Next Ten Billion Years"[1], "One hundred million years from now: The universe has a surprise in store for the corvins, though. Their first moon landing included among its goals the investigation of some odd surface features, too small to be seen clearly by Earth-based equipment. That first lander thus set down on a flat lunar plain that, a very long time ago, was…

Funny, as I was reading the original article, I was thinking that anything left on the moon would survive being recycled by plate tectonics. It seems like reaching the moon isn't such a stretch for any technological civilization, so the lack of preexisting artifacts counts as pretty definitive for me.

point at a spot on the moon which was not hit by an object, its not easy. very big things have hit it too.

additionally radiation is much more so decay is accelerated a lot? (might be wrong but i think so?)

Re: The Silurian Hypothesis (2020)

#124

Post by saidnooneever »

dash2 wrote: post #20

I can't speak to dinosaur people, but the population genetics of our own DNA reveals that there were never many humans on the planet till recently, so that rules out any very large human civilization. (Unless they genetically altered themselves to hide the evidence! Ahaaa...)

they could be distinctly different dna, wiped out and evolved again from scratch.

Re: The Silurian Hypothesis (2020)

#125

Post by saidnooneever »

sgt101 wrote: post #75
graemep wrote: post #28

Earlier quoted context omitted.

If whole populations were wiped out and the world was repopulated by a small remnant would that not account for it? Or if an extinct human species had an advanced civilisation?

My thoughts: Civilisation implies large scale agriculture. Large scale agriculture implies specific pollen signatures. We don't see any of these signatures in the pollen records dredged up from lakes and seas. There was no previous civilisation in the last 1.4m years (this is the depth of the pollen records we have I think).

it could essentially be much longer ago, but you are right and imho this is strongest evidence. civilizations dont need to evolve to high technology to be a relatively advanced civilization and say, build pyramids. but they do need plenty of food structurally available in any larger numbers than 'big tribe'

Re: The Silurian Hypothesis (2020)

#126

Post by saidnooneever »

Diogenesian wrote: post #76
jerf wrote: post #25

Earlier quoted context omitted.

Yes. We'd find mines, where the richest veins were mined out and what's left is spread in a pattern that clearly appears to be "a rich deposit but with the best stuff taken already". The mine itself would have long collapsed but would also leave interesting evidence, a pattern of mismatched geological layers that rather than looking like an earthquake or a tectonic upheaval would be something that is relatively clear…

The exception that proves the rule is a nuclear reactor from Gabon that dates to 1.7bn years ago... and which was clearly natural, a uranium-rich cave got flooded and went supercritical: https://en.wikipedia.org/wiki/Oklo Of course we haven't discovered everything. But it seems very likely that if there were a civilization's worth of slag from 500m years ago, we would have discovered it. A more interesting question i…

there are many of these examples. in africa mines have been found by mining etc. its very interesting and none of it fits any current ideas. it does not prove anything definitvively but i do think if you look at billion year timescales a lot more is possible 'without any trace' than say million year timescales.

earth is very old and has had life on it for very very long, that is what we know. how exactly it looked like we're still finding out and some things we might never get a clear picture of.

Re: The Silurian Hypothesis (2020)

#127

Post by gtowey »

saidnooneever wrote: post #123
gtowey wrote: post #104

Earlier quoted context omitted.

Funny, as I was reading the original article, I was thinking that anything left on the moon would survive being recycled by plate tectonics. It seems like reaching the moon isn't such a stretch for any technological civilization, so the lack of preexisting artifacts counts as pretty definitive for me.

point at a spot on the moon which was not hit by an object, its not easy. very big things have hit it too. additionally radiation is much more so decay is accelerated a lot? (might be wrong but i think so?)

Are you saying that things on the moon are less likely to survive because of meteor impacts and radiation?

If so I think you misunderstood a few things. The earth is hit by far more meteors than the moon because of its stronger gravity well. You see the moon covered in craters not because it's hot more often, but because there is no erosion or plate tectonics to erase them. You see basically all the craters over a billion years on display.

Also, radiation doesn't just randomly destroy things. It's harmful to biology for sure, but a chunk of metal on the moon isn't going to be much affected by the level of radiation present. Like the craters, we would expect it to remain for a very long time. Radiation can make metals brittle, but without atmosphere it's unlikely to turn to dust unless someone were to go touch it.

Re: The Silurian Hypothesis (2020)

#128

Post by randomImmigrant »

throw310822 wrote: post #50
randomImmigrant wrote: post #29

Earlier quoted context omitted.

Actually correct. We have very very few fossils compared to the millions of species that have evolved and gone extinct over 4 billion years. The fossils we do have are of highly successful species in that geography. It’s a matter of chance, leaving behind a fossil, after all. And unlike biological matter that can fossilize, industrial structures etc do not. All our manufactured stuff has very short life once it reach…

> It’s more showing you the limits of scientific inquiry into the deep history of Earth. I think this is it: the point of this argument is to inspire some awe in the listener, making them realise how vast Earth's time is compared to our horizons. But in practice, the argument is wrong. A dead animal's skin is expected to lasts weeks to months- and yet we have fossilised specimens. A footprint typically lasts hours, a…

No the argument isn’t wrong. It isn’t proof of a particular civilization, but it’s not wrong about the detection threshold for such things.

You can’t compare fossilization, which is very dependent on certain properties of biological tissue, and extrapolate from that to all matter.

Re: The Silurian Hypothesis (2020)

#129

Post by saidnooneever »

gtowey wrote: post #127
saidnooneever wrote: post #123

Earlier quoted context omitted.

point at a spot on the moon which was not hit by an object, its not easy. very big things have hit it too. additionally radiation is much more so decay is accelerated a lot? (might be wrong but i think so?)

Are you saying that things on the moon are less likely to survive because of meteor impacts and radiation? If so I think you misunderstood a few things. The earth is hit by far more meteors than the moon because of its stronger gravity well. You see the moon covered in craters not because it's hot more often, but because there is no erosion or plate tectonics to erase them. You see basically all the craters over a bi…

thanks :D clearly not astronomer. doesnt the atmosphere kinda make a lot of stuff that hits the earth burn up though? i -imagine- the moon get hits also by small rocks really hard where those burn up in our atmosphere

Re: The Silurian Hypothesis (2020)

#130

Post by sgt101 »

saidnooneever wrote: post #125
sgt101 wrote: post #75

Earlier quoted context omitted.

My thoughts: Civilisation implies large scale agriculture. Large scale agriculture implies specific pollen signatures. We don't see any of these signatures in the pollen records dredged up from lakes and seas. There was no previous civilisation in the last 1.4m years (this is the depth of the pollen records we have I think).

it could essentially be much longer ago, but you are right and imho this is strongest evidence. civilizations dont need to evolve to high technology to be a relatively advanced civilization and say, build pyramids. but they do need plenty of food structurally available in any larger numbers than 'big tribe'

Agree - although I think the records we have rule out a previous *Human* "civilisation", not to say that Humans with thousands and thousands of years of culture along with ideas we have no inkling of and would find fascinating have come and gone and bloomed and faded many many times.
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