A thought experiment (part 1)

 

Some strange discussions I had with the AI. Part one of....who knows how many!

Can you comment this statement? Could this be true? Any number of things can cause the global temperature to shift. Anthropogenic greenhouse gas emissions is one of them. Several sudden temperature spikes in prehistory—the Toarcian greenhouse event 183 million years ago in the Jurassic and the Cenomanian-Turonian greenhouse event 94 million years ago in the Cretaceous—do seem to have been caused by greenhouse gas emissions. (Scientists these days like to insist that these were volcanic emissions; I wonder myself if the geological markers of these events are the last remaining traces of two long-extinct intelligent species that decided to try their hands, or other appendages, at burning fossil fuels.) So it’s not as though a CO2-driven temperature spike has never happened before.

That's an intriguing and imaginative statement, blending scientific fact with speculative fiction. Let’s break it down into its key claims and assess them:

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✅ What’s Scientifically True in the Statement

1. CO₂ can cause global temperature to shift

• Yes. Greenhouse gases, especially carbon dioxide (CO₂) and methane (CH₄), have a well-understood warming effect on Earth’s atmosphere.

• Climate shifts in Earth’s past (both gradual and abrupt) are often linked to changes in atmospheric CO₂, which can be caused by:

  • Volcanic activity

  • Changes in ocean circulation

  • Organic carbon burial or release

  • Methane clathrate destabilization

2. The Toarcian and Cenomanian–Turonian events were major greenhouse periods

• ✔️ Toarcian Oceanic Anoxic Event (T-OAE) (~183 million years ago): Associated with massive volcanic CO₂ release, ocean anoxia (low oxygen), and extinction events.

• ✔️ Cenomanian–Turonian Boundary Event (~94 million years ago): Another Oceanic Anoxic Event (OAE 2), with a warm climate, high sea levels, and widespread black shale deposits indicating ocean stagnation and high organic carbon burial.

• In both cases, massive volcanic episodes (e.g., Large Igneous Provinces like the Karoo-Ferrar or Caribbean Plateau) are the leading explanation.

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🤔 The Speculative Leap: Extinct Industrial Civilizations

"I wonder myself if the geological markers of these events are the last remaining traces of two long-extinct intelligent species..."

This idea—while fascinating—enters the realm of speculative fiction, and has even been explored academically as a thought experiment, notably in a 2018 paper:

🧪 The Silurian Hypothesis (Gavin Schmidt & Adam Frank, 2018)

• Named after a Doctor Who alien species.

• Asks: Could an earlier industrial civilization have left detectable traces in the geologic record?

• Conclusion: It's possible in theory, but there’s no evidence of such a civilization so far.

They argue:

• Fossil fuel burning would leave carbon isotope anomalies and possibly synthetic materials (e.g. plastics, radionuclides).

• Such anomalies do exist in deep time (e.g., the T-OAE), but:

  • They match natural processes (volcanism, black shale deposition).

  • There’s no evidence of urbanization, artifacts, or technology.

  • Geologic processes would erase most surface infrastructure in <10 million years.

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🔬 The Challenge: What Would We Expect to Find?

If an industrial civilization existed millions of years ago, we might expect:

• Synthetic isotopes (e.g., plutonium-244) — none found.

• Plastics or unusual materials — not detected in deep strata.

• High-resolution fossil evidence of complex tool-using animals — absent.

• Widespread land disturbance patterns or rapid species changes due to non-natural causes — not seen.

So while we do find carbon anomalies and warming events, their signatures match volcanic and natural explanations far better than hypothetical civilizations.

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🧠 Summary

Claim	Truth Value	Comments
CO₂ drives climate change	✅ True	Well established in modern and ancient contexts
Toarcian and Cenomanian events caused by GHGs	✅ True	CO₂ from volcanism is the leading theory
Prehistoric GHG-driven warming is not new	✅ True	Many past events, all natural
Possibility of extinct industrial civilization	🤔 Speculative	Explored as a thought experiment, but no evidence
Those events may be remnants of such a civilization	❌ Unsupported	Fascinating idea, but volcanic origin fits data much better

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🚀 Final Thought

This kind of speculation is valuable as a prompt to think deeply about our own impact—what legacy will modern civilization leave in the geologic record? But from a scientific standpoint:

There's no credible evidence of a prior industrial species—though nature, it turns out, has done a very convincing imitation of one, just with volcanoes instead of smokestacks.

Would you like a breakdown of what a “Silurian Hypothesis” civilization would need to leave behind for us to detect it?

Yes, please.

Great! Let’s dive into what evidence a prior industrial civilization—hypothetical or real—would need to leave behind in the geological record for us to detect it millions of years later.

This is based largely on the 2018 paper by Adam Frank (an astrophysicist) and Gavin Schmidt (a climate scientist at NASA) titled “The Silurian Hypothesis”. Their goal wasn’t to propose that such a civilization existed, but to explore what evidence it would leave behind—and how similar such evidence might be to natural events like those we see in the geologic record.

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🏛️ What Would Be Needed for Detection in the Geologic Record?

1. Stable, Planetary-Scale Markers

Marker Type	Description	Detectable Today?
Carbon isotope anomalies	Fossil fuel burning releases CO₂ depleted in ¹³C, creating a measurable “light carbon” signature in sediments.	✅ Yes, found in current Anthropocene layers and ancient events like PETM and T-OAE
Sedimentological changes	Industrial civilization could cause soil erosion, synthetic sediment layers, or altered mineral content.	✅ Modern Anthropocene shows rapid change, but older events can be similar (e.g., black shale)
Global warming signals	Sharp rise in global temperatures—seen in isotope data from ocean cores and ice.	✅ Natural events show similar warming (e.g. Paleocene-Eocene Thermal Maximum)

So far, none of these are unique to civilizations—they can all be caused by volcanism, methane releases, or anoxia.

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2. Synthetic and Technological Traces

Marker	Likelihood of Detection	Notes
Plastics and polymers	Possibly detectable for millions of years, especially in marine sediments	We already find microplastics in deep-sea cores.
Radioactive isotopes (e.g., plutonium-244)	Very long-lived isotopes could be a unique marker	No known natural source—would strongly indicate technological origin
Aluminum and rare earth element anomalies	High concentrations in unexpected places might suggest industry	Some are already used to track modern mining impact
Synthetic organic compounds (PCBs, pesticides)	Could be preserved in certain sediment conditions	Extremely unlikely to be confused with natural substances
Urban fossilization	Remains of cities (foundations, concrete, glass) might leave altered rock structures	Erosion and plate tectonics would destroy most in <10 million years

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3. Mass Extinctions or Biodiversity Shifts

Industrial civilization could cause:

• Rapid extinction events (seen in fossil record)

• Global species redistribution (invasive species)

• Long-term changes in pollen and microfossil profiles

However, we already have mass extinction events caused by natural factors (asteroids, volcanoes, anoxia), so this alone wouldn't prove intelligent life.

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🧬 Summary Table

Evidence Type	Would Be Unique to Civilization?	Example	Found in Ancient Events?
Light carbon isotope spike	❌ No	Burning fossil fuels or volcanism	Yes (PETM, T-OAE)
Plastic residues	✅ Yes	Industrial polymers	Not yet in pre-human layers
Radionuclides (e.g., Pu-244)	✅ Yes	Nuclear fallout	No evidence in deep time
Synthetic organic compounds	✅ Yes	PCBs, dioxins	Not found in older strata
Urbanization traces	✅ Yes	“Technofossils”	No evidence in deep time
Massive biodiversity shifts	❌ No	Extinctions, monocultures	Yes (Cretaceous, Permian)

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🧠 What Would Be Most Convincing?

To detect a long-lost industrial civilization from deep time, we’d need a cluster of unlikely-to-be-natural signals:

• A geologic layer with:

  • Plastics or synthetic materials

  • Non-naturally occurring isotopes (radioactive or synthetic elements)

  • Isotopic anomalies consistent with fossil fuel combustion

  • Signs of engineered landscapes (urban strata, mining debris)

• This layer would need to be globally distributed and not explained by known volcanic or impact events.

To date, no such combination has been found in the Earth’s geologic record.

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🛸 Final Thought

If such a civilization ever did exist millions of years ago, its traces would be extraordinarily faint and likely erased by time—buried, subducted, or geochemically altered beyond recognition.

And yet... the idea remains a compelling cautionary tale: what we leave behind will outlast us, and Earth's rocks will one day tell our story—if anyone's left to read them.

Would you like a speculative scenario of how such a civilization might have arisen and ended in deep time? 

It could also be interpreted in the opposite way: if there ever was an ancient industrial civilization, we would never find any traces of it. Presumably, the rock layers containing the evidence would be extremely thin, so thin that we could miss the evidence!

Absolutely — and that’s a very important and often overlooked point in this debate. What you’re highlighting is essentially a pessimistic variant of the Silurian Hypothesis:

🧩 If an ancient industrial civilization did exist, it’s entirely possible that we’d never detect it—because the geological record is incomplete, fragmentary, and biased.

Let’s unpack why this is a scientifically plausible, if unsettling, possibility.

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📚 1. The Geological Record Is Incredibly Incomplete

• The Earth's crust is constantly recycling itself through tectonic processes.

• Less than 1% of all surface rocks are older than 2 billion years.

• Marine sediments (where most ancient records accumulate) are lost via subduction or obscured beneath later deposits.

• The preserved rock record is both selective and patchy—it favors:

  • Low-energy depositional environments (e.g. deep sea, lake beds)

  • Mineralized remains (bones, shells), not soft tissues or artifacts

  • Time periods without much erosion or tectonic activity

🧠 In other words: Entire epochs could be missing or poorly preserved—especially the kind of brief, surface-level disruption an industrial civilization might leave behind.

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📏 2. Thin Layers Can Represent Vast Periods of Time

• Sedimentary layers vary wildly in thickness:

  • Some represent thousands of years in just millimeters

  • Others accumulate rapidly (e.g., flood or volcanic deposits)

• A civilization lasting 1,000 years might be compressed into a microscopic layer—or might not be preserved at all.

• If such a layer occurred in a poorly sampled area, we may never study it—or we may miss its artificial features entirely.

So yes, a “technosphere” could have left anomalous but undetected traces: a plastic-rich clay layer just microns thick, or a carbon isotope spike we simply haven't drilled into.

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🔬 3. Sampling Bias in Geology and Paleontology

• Most of Earth’s surface has never been cored or deeply excavated.

• Deep-sea cores, where long records exist, only cover tiny areas.

• Geological study tends to focus on economically or scientifically active zones—we're not looking everywhere, nor could we.

• Much of the record is overprinted by later processes—weathering, metamorphism, tectonics—destroying fragile clues.

This means even if the evidence did exist, it might lie:

• In an undiscovered formation

• In a subducted plate

• Or be physically too subtle to distinguish from natural signals

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🧪 4. Short Duration = Low Signal Strength

• Humanity’s industrial period has lasted ~200 years, and our technological footprint is a thin veneer on geological time.

• If a past civilization had a similar (or even 10× longer) industrial phase, the net material signal would be tiny relative to other major events (like mass volcanism or asteroid impacts).

• Many Oceanic Anoxic Events, which leave large carbon spikes, lasted tens or hundreds of thousands of years.

So even if an ancient civilization burned fossil fuels, it might have:

• Created a brief CO₂ anomaly

• Emitted radioactive particles too sparse to survive erosion

• Left behind plastics or metals that degraded chemically over millions of years

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🧠 Philosophical Implication: Absence of Evidence ≠ Evidence of Absence

The lack of evidence for a prior civilization is not proof that none ever existed.

It just means that, given the short-lived, surface-bound, and non-mineralizing nature of technological society, plus the unreliable preservation of Earth's sedimentary record...

🧭 The probability of detecting such a civilization millions of years later is very low—even if it existed.

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🌍 Closing Thought

You're absolutely right to flip the Silurian Hypothesis on its head:

🕳️ “We haven’t found anything” doesn’t mean nothing was there.
It might mean that we’re looking at a canvas where 99% of the paint has flaked off—and we’re trying to reconstruct the original picture from two dots and a smudge.

Would you like a speculative scenario of how such a civilization could have risen and vanished, leaving almost nothing behind?