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The Silurian Hypothesis (2020)

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Re: The Silurian Hypothesis (2020)

#101

Post by hdgvhicv »

mike_hock wrote: post #90
hdgvhicv wrote: post #34

Earlier quoted context omitted.

How can a galaxy spanning civilisation fail. If life can spread to other worlds, unless you get FTL, how could you end all life in a galaxy As such it seems impossible for life to have reached interstellar travel anywhere in the Milky Way before at most a few million years ago, otherwise we would see it. Which is weird because life surely can’t be that rare in the entirety of space time. Of course the galaxy could be…

1.) It's definitely a giant leap from current technology to interstellar colonization. 2.) Other civilizations even in the nearest solar system would basically be impossible to detect. Even in our own solar system, there could be millions of undetected spacecraft right now. They're simply too small to see. To be detectable, they'd either have to be massive and massively disruptive, like Dyson spheres, which are and m…

Not compared to the leap from something as advanced as pyramid building to today, let alone the advancement in the last 100,000 years

Any life form will expand to use all resources. We know that nothing is consuming all resources in our solar system.

Re: The Silurian Hypothesis (2020)

#102

Post by rubylimetea »

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...)

> I can't speak to dinosaur people

Dash out of context

Re: The Silurian Hypothesis (2020)

#103

Post by hdgvhicv »

DFHippie wrote: post #68
hdgvhicv wrote: post #34

Earlier quoted context omitted.

How can a galaxy spanning civilisation fail. If life can spread to other worlds, unless you get FTL, how could you end all life in a galaxy As such it seems impossible for life to have reached interstellar travel anywhere in the Milky Way before at most a few million years ago, otherwise we would see it. Which is weird because life surely can’t be that rare in the entirety of space time. Of course the galaxy could be…

Though there is likely life throughout the galaxy, it's probably difficult for one sentient spacefaring race to find another habitable planet they'd be comfortable on, i.e., one with a similar atmosphere and mass. If it's a long way from your planet to another you'd care to set foot on, you're left with lots of space stations. But who wants to live in that precarity?

The main requirement is energy. From stars. Our system has a star, and thus is a resource to be tapped.

Without FTL you don’t get a single civilisation, so even if one civilisation doesn’t rant to expand evolution will mean the ones that do will do so.

So you’re left with “they haven’t tapped our star yet” or “nothing can reach us”

Re: The Silurian Hypothesis (2020)

#104

Post by gtowey »

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.

Re: The Silurian Hypothesis (2020)

#105

Post by throw310822 »

T-A wrote: post #95
throw310822 wrote: post #55

Earlier quoted context omitted.

How long to dissolve carved stone sculptures (in sizes ranging from 1cm to 100m?) And how long does it take to dissolve skin? Footprints? Because we have those from hundreds of millions of years ago.

> How long to dissolve carved stone sculptures (in sizes ranging from 1cm to 100m?) A quick search on "rock weathering depth per century" suggests a "typical range" of 0.05 mm to 6 mm, depending on rock type and environmental factors. At 0.05 mm, a stone object with radius 0.5 cm would crumble in 10000 years. With radius 50 m, it would take 100 million years. I would expect them to be unrecognizable long before that…

> A quick search on "rock weathering depth per century"

That's a great illustration of what I meant. Of course an exposed rock consumes away in the space of a few millennia- this is exactly where the "Silurian theory" comes from. Yet it's also obvious that we have plenty of perfectly conserved rocks that are intact after hundreds of millions of years- i.e. fossils. Any small sculpture buried in clay can survive for an eternity.

> What do those findings tell you about the cognitive abilities and social organization

Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots? Drawings "I LOVE YOU" in the sand? The shape of a coca-cola bottle buried in solidified clay? Come on...

Re: The Silurian Hypothesis (2020)

#106

Post by nkrisc »

amazingamazing wrote: post #22
nkrisc wrote: post #19

Earlier quoted context omitted.

We’ll never know of the existence of most species that ever existed. Fossilization is rare.

right, so how can one easily say this hypothesis is false? "advanced civilization" seems to be strangely characterized. would something a few steps above beavers be advanced enough?

Typically the ones proposing a hypothesis have the burden of proof. Still waiting on any evidence in favor of the hypothesis.

I won’t hold my breath.

Re: The Silurian Hypothesis (2020)

#107

Post by mcswell »

jerf wrote: post #88
Diogenesian wrote: post #76

Earlier quoted context omitted.

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…

People get way too excited about the word "reactor". They hear "reactor" and think "oh, a natural formation of uranium was evaporating water into steam and generating electricity". They don't consciously examine that, of course, but it's clear a lot of people are letting that in unexamined. What really happened is that some uranium got concentrated, and then it did was uranium does. Similarly, if you want to make a v…

"talking dinosaurs": I don't know about that, but the Farside had a picture of cigarette-smoking dinosaurs, which requires at least some intelligence: https://i.pinimg.com/736x/6a/87/1a/6a871af3a7754a3ac7f1b2c11...

Re: The Silurian Hypothesis (2020)

#108

Post by T-A »

throw310822 wrote: post #105
T-A wrote: post #95

Earlier quoted context omitted.

> How long to dissolve carved stone sculptures (in sizes ranging from 1cm to 100m?) A quick search on "rock weathering depth per century" suggests a "typical range" of 0.05 mm to 6 mm, depending on rock type and environmental factors. At 0.05 mm, a stone object with radius 0.5 cm would crumble in 10000 years. With radius 50 m, it would take 100 million years. I would expect them to be unrecognizable long before that…

> A quick search on "rock weathering depth per century" That's a great illustration of what I meant. Of course an exposed rock consumes away in the space of a few millennia- this is exactly where the "Silurian theory" comes from. Yet it's also obvious that we have plenty of perfectly conserved rocks that are intact after hundreds of millions of years- i.e. fossils. Any small sculpture buried in clay can survive for a…

> Any small sculpture buried in clay can survive for an eternity.

If it's made of granite, maybe. But how many granite sculptures have you seen? Sculptors tend to prefer prettier and more easily shaped materials, like marble and limestone. Those happen to be mostly calcium carbonate, just like bones and teeth, so section 1.2 in [1] (chemical dissolution in acidic environments) applies, along with section 1.3 and [2] (mechanical fracturing and dispersion during wetting-drying cycles).

Even if your sculpture was buried in a maximally favorable environment, it would not have stayed that way over tens of millions of years. 50 million years ago, the Himalayas were just starting to rise as India crashed into Eurasia, Australia was waving goodbye to a forest-covered Antarctica while the Americas, North and South, had yet to link up. At a rate of one ice age every 100k years, 500 ice ages separate us from those days. One is enough to raze half a continent and turn a muddy seabed into granite.

> Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots?

This is extremely anthropocentric. A hypothetical "Silurian" civilization would obviously not have been human, and may have had no need for such things. Would bears endowed with human-level intelligence want to wear clothes and boots?

> Drawings "I LOVE YOU" in the sand?

Have any such preserved drawings in the sand been found from the ~200k years humans have been around?

> The shape of a coca-cola bottle buried in solidified clay?

See section 1.3 in [1], and remember that the time scale discussed in that kind of paper is a few thousand years, not tens of millions.

[1] https://www.sciencedirect.com/science/article/pii/S004896971...

[2] https://www.tandfonline.com/doi/abs/10.1179/0197136978063731...

Re: The Silurian Hypothesis (2020)

#109

Post by mcswell »

I wrote a sci-fi short story on this idea once. It took place in the present, and left the truth of the hypothesis open. Submitted it to Analog, but it was rejected. I suppose there are now places one can self-publish sci-fi stuff, but I'm not sure I can even find my original.

Edit: Did a Linux find, and...it did find the story. Unfortunately, it didn't find me a place to publish it.

Re: The Silurian Hypothesis (2020)

#110

Post by jerf »

Diogenesian wrote: post #94
jerf wrote: post #88

Earlier quoted context omitted.

People get way too excited about the word "reactor". They hear "reactor" and think "oh, a natural formation of uranium was evaporating water into steam and generating electricity". They don't consciously examine that, of course, but it's clear a lot of people are letting that in unexamined. What really happened is that some uranium got concentrated, and then it did was uranium does. Similarly, if you want to make a v…

The first part of your comment seems to be replying to a pure strawman, and missing the point of my argument. My point was even small natural reactors leave very obvious evidence, so it seems like a city's worth of metallurgy could be detected 200m years later, probably by a surprised geologist in the 1800s. The fact that we haven't seen anything is conclusive evidence that modern humans were the first metallurgists.…

Ah, sorry, I did misinterpret. My apologies.

Add our nuclear waste dumps to the list of things I mention in another reply that I can't guarantee wouldn't still leave legible evidence even millions of years later. Especially since we seek out geologically stable places to put them... not that we've actually put them there yet, but, you know, maybe over the next couple hundred years we'll get it together....

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