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OT- Was There a Civilization On Earth Before Humans?
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a425couple
2018-04-21 22:39:28 UTC
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Was There a Civilization On Earth Before Humans?
A look at the available evidence

(as done in "Boundary" & "Inherit the Stars")

Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters

ADAM FRANK APR 13, 2018 SCIENCE

Like ​The Atlantic? Subscribe to ​The Atlantic Daily​, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.

Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.

Just as I was revving up my pitch, Gavin stopped me in my tracks.

“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”

It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”

We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.

We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.

When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.

And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.

So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.

Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.

Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.

And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.

The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.

When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?

Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).

Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.

But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.

It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.

RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.

In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.

By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.

ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.

https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
D B Davis
2018-04-22 00:19:42 UTC
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Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa's Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I'd begun researching global warming from an "astrobiological
perspective." That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That's how I
ended up in Gavin's office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
"Wait a second," he said. "How do you know we're the only time there's
been a civilization on our own planet?"
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin's office prepared for eye rolls at the mention of
"exo-civilizations." But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth's
past, but also onto our own future.
<snip>

How do you know that humanity's mechanized flight only starts with the
Wright brothers?

Flying Machines in Ancient India? The Vedic Vimanas
https://ashtronort.wordpress.com/2013/11/22/flying-machines-in-indias-ancient-past/

Thank you,

--
Don
J. Clarke
2018-04-22 03:53:16 UTC
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Post by D B Davis
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa's Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I'd begun researching global warming from an "astrobiological
perspective." That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That's how I
ended up in Gavin's office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
"Wait a second," he said. "How do you know we're the only time there's
been a civilization on our own planet?"
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin's office prepared for eye rolls at the mention of
"exo-civilizations." But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth's
past, but also onto our own future.
<snip>
How do you know that humanity's mechanized flight only starts with the
Wright brothers?
Flying Machines in Ancient India? The Vedic Vimanas
https://ashtronort.wordpress.com/2013/11/22/flying-machines-in-indias-ancient-past/
Yeah, yeah, and the world really was saved by Hobbits.
Quadibloc
2018-04-22 17:07:00 UTC
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Post by J. Clarke
Post by D B Davis
How do you know that humanity's mechanized flight only starts with the
Wright brothers?
Flying Machines in Ancient India? The Vedic Vimanas
https://ashtronort.wordpress.com/2013/11/22/flying-machines-in-indias-ancient-past/
Yeah, yeah, and the world really was saved by Hobbits.
While I agree that Vimanas are not to be taken seriously, Samuel Pierpoint
Langley is accepted by some as the real originator, prior to the Wright
Brothers, of heavier-than-air flight.

John Savard
J. Clarke
2018-04-22 19:37:41 UTC
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On Sun, 22 Apr 2018 10:07:00 -0700 (PDT), Quadibloc
Post by Quadibloc
Post by J. Clarke
Post by D B Davis
How do you know that humanity's mechanized flight only starts with the
Wright brothers?
Flying Machines in Ancient India? The Vedic Vimanas
https://ashtronort.wordpress.com/2013/11/22/flying-machines-in-indias-ancient-past/
Yeah, yeah, and the world really was saved by Hobbits.
While I agree that Vimanas are not to be taken seriously, Samuel Pierpoint
Langley is accepted by some as the real originator, prior to the Wright
Brothers, of heavier-than-air flight.
Not by any serious researcher. Langley tried but like many before him
he never succeeded in doing more than getting high enough to crash. A
major flaw in his designs was the lack of an effective control system.
There is a stronger claim for Gustave Whitehead, reports of whose
flight appeared in newspapers in 1901, however his work had little
influence on later development.
Post by Quadibloc
John Savard
Kevrob
2018-04-22 19:43:19 UTC
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Post by Quadibloc
Post by J. Clarke
Post by D B Davis
How do you know that humanity's mechanized flight only starts with the
Wright brothers?
Flying Machines in Ancient India? The Vedic Vimanas
https://ashtronort.wordpress.com/2013/11/22/flying-machines-in-indias-ancient-past/
Yeah, yeah, and the world really was saved by Hobbits.
While I agree that Vimanas are not to be taken seriously, Samuel Pierpoint
Langley is accepted by some as the real originator, prior to the Wright
Brothers, of heavier-than-air flight.
...and some plump for Gustave Whitehead, or for others.

https://www.nytimes.com/2015/04/18/nyregion/where-was-modern-flight-invented-connecticut-believes-it-holds-the-answer.html

The Wrights beat Langley on getting a heavier-than-air craft that
carried a pilot aloft, though SPL did get unpiloted models in the
air for limited distance/duration. He was well behind the Wrights
in controlling his vehicle's flight.

Kevin R
J. Clarke
2018-04-22 03:57:05 UTC
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On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
Like ?The Atlantic? Subscribe to ?The Atlantic Daily?, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.
And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?
Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).
Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.
But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.
It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.
RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.
In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.
By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.
ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Robert Carnegie
2018-04-22 14:22:17 UTC
Reply
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Post by J. Clarke
On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
Like ?The Atlantic? Subscribe to ?The Atlantic Daily?, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.
And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?
Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).
Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.
But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.
It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.
RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.
In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.
By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.
ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Maybe it used diamonds. There's hardly any left.
J. Clarke
2018-04-22 14:43:57 UTC
Reply
Permalink
Raw Message
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Post by J. Clarke
On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
Like ?The Atlantic? Subscribe to ?The Atlantic Daily?, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.
And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?
Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).
Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.
But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.
It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.
RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.
In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.
By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.
ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?

And why would they use diamonds instead of coal?
Robert Carnegie
2018-04-22 18:26:24 UTC
Reply
Permalink
Raw Message
Post by J. Clarke
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Post by J. Clarke
On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
Like ?The Atlantic? Subscribe to ?The Atlantic Daily?, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.
And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?
Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).
Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.
But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.
It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.
RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.
In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.
By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.
ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?
There were national parks?
Post by J. Clarke
And why would they use diamonds instead of coal?
I assume diamonds are low-sulphur? And cleaner generally.
J. Clarke
2018-04-22 19:39:03 UTC
Reply
Permalink
Raw Message
On Sun, 22 Apr 2018 11:26:24 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Post by J. Clarke
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Post by J. Clarke
On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
Like ?The Atlantic? Subscribe to ?The Atlantic Daily?, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.
And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?
Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).
Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.
But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.
It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.
RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.
In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.
By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.
ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?
There were national parks?
Post by J. Clarke
And why would they use diamonds instead of coal?
I assume diamonds are low-sulphur? And cleaner generally.
And you have to chip them one at a time out of a hard mineral, which
likely consumes considerably more energy than you would get by burning
the diamonds.
Default User
2018-04-22 18:28:54 UTC
Reply
Permalink
Raw Message
Post by J. Clarke
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?
And why would they use diamonds instead of coal?
Is there a reason why you two felt the need to quote the entire damn
article for your little responses?


Brian
Joe Pfeiffer
2018-04-22 18:38:16 UTC
Reply
Permalink
Raw Message
Post by Default User
Post by J. Clarke
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?
And why would they use diamonds instead of coal?
Is there a reason why you two felt the need to quote the entire damn
article for your little responses?
I'm guessing it was to make it easy for us to go back and verify that
yes, the article does talk about plastics.
Robert Carnegie
2018-04-22 18:53:13 UTC
Reply
Permalink
Raw Message
Post by Joe Pfeiffer
Post by Default User
Post by J. Clarke
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?
And why would they use diamonds instead of coal?
Is there a reason why you two felt the need to quote the entire damn
article for your little responses?
I'm guessing it was to make it easy for us to go back and verify that
yes, the article does talk about plastics.
And about " The Silurians" in _Doctor Who_, the ancient reptile
civilisation which... is hibernating.

They probably were plastic - the masks anyway. I've got some
extremely thorough "how Doctor Who get made" books, and the licensed
fan magazine has a "do it to yourself" feature series.
Robert Carnegie
2018-04-22 18:44:19 UTC
Reply
Permalink
Raw Message
Post by Default User
Post by J. Clarke
On Sun, 22 Apr 2018 07:22:17 -0700 (PDT), Robert Carnegie
Post by Robert Carnegie
Maybe it used diamonds. There's hardly any left.
But why are there any Kimberlite pipes left then?
And why would they use diamonds instead of coal?
Is there a reason why you two felt the need to quote the entire damn
article for your little responses?
Twice? Sorry.

I'm using Google Groups on a touch screen, so, long quote trimming
only happens when I make s real effort - both to do it and to notice
it's called for; I'm reading articles with quoted text tidied away,
and I reply in a 12 lines scrollable box. But still - not cool.
h***@gmail.com
2018-04-22 14:35:31 UTC
Reply
Permalink
Raw Message
Post by J. Clarke
On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
Partial skeleton remains from an ancient burial site
Regis Duvignau / Reuters
ADAM FRANK APR 13, 2018 SCIENCE
Like ?The Atlantic? Subscribe to ?The Atlantic Daily?, our free weekday
email newsletter.
Email
It only took five minutes for Gavin Schmidt to out-speculate me.
Schmidt is the director of nasa’s Goddard Institute for Space Studies
(a.k.a. GISS) a world-class climate-science facility. One day last year,
I came to GISS with a far-out proposal. In my work as an astrophysicist,
I’d begun researching global warming from an “astrobiological
perspective.” That meant asking whether any industrial civilization that
rises on any planet will, through their own activity, trigger their own
version of a climate shift. I was visiting GISS that day hoping to gain
some climate science insights and, perhaps, collaborators. That’s how I
ended up in Gavin’s office.
Just as I was revving up my pitch, Gavin stopped me in my tracks.
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a
new study we’ve recently published in the International Journal of
Astrobiology. Though neither of us could see it at that moment, Gavin’s
penetrating question opened a window not just onto Earth’s past, but
also onto our own future.
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built
a relatively short-lived industrial civilization long before our own?
Perhaps, for example, some early mammal rose briefly to civilization
building during the Paleocene epoch about 60 million years ago. There
are fossils, of course. But the fraction of life that gets fossilized is
always minuscule and varies a lot depending on time and habitat. It
would be easy, therefore, to miss an industrial civilization that only
lasted 100,000 years—which would be 500 times longer than our industrial
civilization has made it so far.
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. The extensive
use of fertilizer, for example, keeps 7 billion people fed, but it also
means we’re redirecting the planet’s flows of nitrogen into food
production. Future researchers should see this in characteristics of
nitrogen showing up in sediments from our era. Likewise our relentless
hunger for the rare-Earth elements used in electronic gizmos. Far more
of these atoms are now wandering around the planet’s surface because of
us than would otherwise be the case. They might also show up in future
sediments, too. Even our creation, and use, of synthetic steroids has
now become so pervasive that it too may be detectable in geologic strata
10 million years from now.
And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales.
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
When we burn fossil fuels, we’re releasing carbon back into the
atmosphere that was once part of living tissues. This ancient carbon is
depleted in one of that element’s three naturally occurring varieties,
or isotopes. The more fossil fuels we burn, the more the balance of
these carbon isotopes shifts. Atmospheric scientists call this shift the
Suess effect, and the change in isotopic ratios of carbon due to
fossil-fuel use is easy to see over the last century. Increases in
temperature also leave isotopic signals. These shifts should be apparent
to any future scientist who chemically analyzes exposed layers of rock
from our era. Along with these spikes, this Anthropocene layer might
also hold brief peaks in nitrogen, plastic nanoparticles, and even
synthetic steroids. So if these are traces our civilization is bound to
leave to the future, might the same “signals” exist right now in rocks
just waiting to tell us of civilizations long gone?
Fifty-six million years ago, Earth passed through the Paleocene-Eocene
Thermal Maximum (PETM). During the PETM, the planet’s average
temperature climbed as high as 15 degrees Fahrenheit above what we
experience today. It was a world almost without ice, as typical summer
temperatures at the poles reached close to a balmy 70 degrees
Fahrenheit. Looking at the isotopic record from the PETM, scientists see
both carbon and oxygen isotope ratios spiking in exactly the way we
expect to see in the Anthropocene record. There are also other events
like the PETM in the Earth’s history that show traces like our
hypothetical Anthropocene signal. These include an event a few million
years after the PETM dubbed the Eocene Layers of Mysterious Origin, and
massive events in the Cretaceous that left the ocean without oxygen for
many millennia (or even longer).
Are these events indications of previous nonhuman industrial
civilizations? Almost certainly not. While there is evidence that the
PETM may have been driven by a massive release of buried fossil carbon
into the air, it’s the timescale of these changes that matter. The
PETM’s isotope spikes rise and fall over a few hundred thousand years.
But what makes the Anthropocene so remarkable in terms of Earth’s
history is the speed at which we’re dumping fossil carbon into the
atmosphere. There have been geological periods where Earth’s CO2 has
been as high or higher than today, but never before in the planet’s
multibillion-year history has so much buried carbon been dumped back
into the atmosphere so quickly. So the isotopic spikes we do see in the
geologic record may not be spiky enough to fit the Silurian hypothesis’s
bill.
But there is a conundrum here. If an earlier species’s industrial
activity is short-lived, we might not be able to easily see it. The
PETM’s spikes mostly show us the Earth’s timescales for responding to
whatever caused it, not necessarily the timescale of the cause. So it
might take both dedicated and novel detection methods to find evidence
of a truly short-lived event in ancient sediments. In other words, if
you’re not explicitly looking for it, you might not see it. That
recognition was, perhaps, the most concrete conclusion of our study.
It’s not often that you write a paper proposing a hypothesis that you
don’t support. Gavin and I don’t believe the Earth once hosted a
50-million-year-old Paleocene civilization. But by asking if we could
“see” truly ancient industrial civilizations, we were forced to ask
about the generic kinds of impacts any civilization might have on a
planet. That’s exactly what the astrobiological perspective on climate
change is all about. Civilization building means harvesting energy from
the planet to do work (i.e., the work of civilization building). Once
the civilization reaches truly planetary scales, there has to be some
feedback on the coupled planetary systems that gave it birth (air,
water, rock). This will be particularly true for young civilizations
like ours still climbing up the ladder of technological capacity. There
is, in other words, no free lunch. While some energy sources will have
lower impact—say solar vs. fossil fuels—you can’t power a global
civilization without some degree of impact on the planet.
RELATED STORIES
A person holds a globe against a background of Earths hit by meteors,
crumbling, and colliding with rockets.
Why Earth's History Appears So Miraculous
A Foreboding Similarity in Today’s Oceans and a 94-Million-Year-Old
Catastrophe
Once you realize, through climate change, the need to find lower-impact
energy sources, the less impact you will leave. So the more sustainable
your civilization becomes, the smaller the signal you’ll leave for
future generations.
In addition, our work also opened up the speculative possibility that
some planets might have fossil-fuel-driven cycles of civilization
building and collapse. If a civilization uses fossil fuels, the climate
change they trigger can lead to a large decrease in ocean oxygen levels.
These low oxygen levels (called ocean anoxia) help trigger the
conditions needed for making fossil fuels like oil and coal in the first
place. In this way, a civilization and its demise might sow the seed for
new civilizations in the future.
By asking about civilizations lost in deep time, we’re also asking about
the possibility for universal rules guiding the evolution of all
biospheres in all their creative potential, including the emergence of
civilizations. Even without pickup-driving Paleocenians, we’re only now
learning to see how rich that potential might be.
ABOUT THE AUTHOR
ADAM FRANK is a professor of astrophysics at the University of
Rochester. His work has appeared in Scientific American, The New York
Times, and NPR. He is the author of Light of the Stars: Alien Worlds and
the Fate of the Earth.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics,
Yeah, they completely missed plastic
"And then there’s all that plastic. Studies have shown increasing amounts
of plastic “marine litter” are being deposited on the seafloor
everywhere from coastal areas to deep basins and even in the Arctic.
Wind, sun, and waves grind down large-scale plastic artifacts, leaving
the seas full of microscopic plastic particles that will eventually rain
down on the ocean floor, creating a layer that could persist for
geological timescales. "

so either (a) there would be plastics in the environment or
Post by J. Clarke
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such).
Not sure whether they're evolving or whether we're discovering them now but they've been around for a long time.
However it's quite likely that if things did evolve to eat plastics in the deep past they either died out or had to change again after eating plastics
Post by J. Clarke
Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
or died out before using it all
Paul Colquhoun
2018-04-23 07:44:19 UTC
Reply
Permalink
Raw Message
On Sun, 22 Apr 2018 07:35:31 -0700 (PDT), ***@gmail.com <***@gmail.com> wrote:
| On Sunday, April 22, 2018 at 1:57:09 PM UTC+10, J. Clarke wrote:
|> On Sat, 21 Apr 2018 15:39:28 -0700, a425couple
|> <***@hotmail.com> wrote:

|> >https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
|>
|> He misses a few points. Like if there had been an advanced (i.e. went
|> through our level) civilization in the past, they would have produced
|> plastics,
|
| Yeah, they completely missed plastic
| "And then there’s all that plastic. Studies have shown increasing amounts
| of plastic “marine litter” are being deposited on the seafloor
| everywhere from coastal areas to deep basins and even in the Arctic.
| Wind, sun, and waves grind down large-scale plastic artifacts, leaving
| the seas full of microscopic plastic particles that will eventually rain
| down on the ocean floor, creating a layer that could persist for
| geological timescales. "
|
| so either (a) there would be plastics in the environment or
|> (b) there would be critters around now that can digest plastics (such
|> critters do seem to be evolving so after us there will be such).
|
| Not sure whether they're evolving or whether we're discovering them now but
| they've been around for a long time. However it's quite likely that if things
| did evolve to eat plastics in the deep past they either died out or had to
| change again after eating plastics
|
|> Then
|> there's the matter of what that civilization used for fuel since it
|> did not burn up the coal and petrochemicals.
|
| or died out before using it all


Or, their plastic layer became our oil reserve after millennia of high
pressures and temperatures.
--
Reverend Paul Colquhoun, ULC. http://andor.dropbear.id.au/
Asking for technical help in newsgroups? Read this first:
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Greg Goss
2018-04-22 15:47:28 UTC
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Post by J. Clarke
Post by a425couple
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Oil migrates. Over time, small amounts left in untappable pools will
re-collect into the domes and fault corners that are easier to tap. I
don't think the presence of oil negates the hypothesis.

Coal, sure.

Unless they learned very early how to tap zero-point energy.
--
We are geeks. Resistance is voltage over current.
David DeLaney
2018-04-23 20:52:37 UTC
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Post by Greg Goss
Post by J. Clarke
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Oil migrates. Over time, small amounts left in untappable pools will
re-collect into the domes and fault corners that are easier to tap. I
don't think the presence of oil negates the hypothesis.
Coal, sure.
Unless they learned very early how to tap zero-point energy.
Thus the diamonds; they were necessary psionic catalysts in the process, and
could be used in situ, but the previous civilization drained all the psi energy
out of them (and emeralds for healing, etc.) and now we're left with none. Oh
the embarrassment!

Dave
--
\/David DeLaney posting thru EarthLink - "It's not the pot that grows the flower
It's not the clock that slows the hour The definition's plain for anyone to see
Love is all it takes to make a family" - R&P. VISUALIZE HAPPYNET VRbeable<BLINK>
my gatekeeper archives are no longer accessible :( / I WUV you in all CAPS! --K.
Peter Trei
2018-04-24 14:57:48 UTC
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Post by David DeLaney
Post by Greg Goss
Post by J. Clarke
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Oil migrates. Over time, small amounts left in untappable pools will
re-collect into the domes and fault corners that are easier to tap. I
don't think the presence of oil negates the hypothesis.
Coal, sure.
Unless they learned very early how to tap zero-point energy.
Thus the diamonds; they were necessary psionic catalysts in the process, and
could be used in situ, but the previous civilization drained all the psi energy
out of them (and emeralds for healing, etc.) and now we're left with none. Oh
the embarrassment!
You mean The Magic Went Away?

pt
Robert Carnegie
2018-04-24 20:27:47 UTC
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Post by Peter Trei
Post by David DeLaney
Post by Greg Goss
Post by J. Clarke
He misses a few points. Like if there had been an advanced (i.e. went
through our level) civilization in the past, they would have produced
plastics, so either (a) there would be plastics in the environment or
(b) there would be critters around now that can digest plastics (such
critters do seem to be evolving so after us there will be such). Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
Oil migrates. Over time, small amounts left in untappable pools will
re-collect into the domes and fault corners that are easier to tap. I
don't think the presence of oil negates the hypothesis.
Coal, sure.
Unless they learned very early how to tap zero-point energy.
Thus the diamonds; they were necessary psionic catalysts in the process, and
could be used in situ, but the previous civilization drained all the psi energy
out of them (and emeralds for healing, etc.) and now we're left with none. Oh
the embarrassment!
You mean The Magic Went Away?
pt
Or, _The Diamond Age_ :-)
Quadibloc
2018-04-24 18:36:51 UTC
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Post by David DeLaney
Thus the diamonds; they were necessary psionic catalysts in the process, and
could be used in situ, but the previous civilization drained all the psi energy
out of them (and emeralds for healing, etc.) and now we're left with none. Oh
the embarrassment!
Hey, that explains why our miners never dig up any dilithium crystals too!

John Savard
Quadibloc
2018-04-22 17:09:40 UTC
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Post by J. Clarke
Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
But our oil dates from the time of the dinosaurs!

So ancient lizardmen who lived during the time of the dinosaurs could well have
used up all the oil and coal that was *even older* than the oil and coal we use
now, which had enough time to be formed by geological processes *after* their
civilization died out!

The paper referenced, though, doesn't seriously suggest that there was a pre-
human civilization on Earth, it merely notes that it might by *hard to tell* if
there was one. That's valid science.

John Savard
Greg Goss
2018-04-22 19:02:22 UTC
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Post by Quadibloc
Post by J. Clarke
Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
But our oil dates from the time of the dinosaurs!
So ancient lizardmen who lived during the time of the dinosaurs could well have
used up all the oil and coal that was *even older* than the oil and coal we use
now, which had enough time to be formed by geological processes *after* their
civilization died out!
It's hard to date oil. (Just ask Bluto.) So the old Sinclair logo may
well be fantasy.

Coal appears to have originated after trees invented structures that
allowed extreme height but before bacteria evolved mechanisms to
digest those trees. So the deadwood piled up before getting buried
and converted to coal. I'm not so sure that any significant coal has
deveoped after that period.

The carboniferous period was before the Permian Triassic "great
dying", long before the dinosaurs ever arrived.
--
We are geeks. Resistance is voltage over current.
Thomas Koenig
2018-04-22 21:55:37 UTC
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Post by Greg Goss
Post by Quadibloc
Post by J. Clarke
Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
But our oil dates from the time of the dinosaurs!
So ancient lizardmen who lived during the time of the dinosaurs could well have
used up all the oil and coal that was *even older* than the oil and coal we use
now, which had enough time to be formed by geological processes *after* their
civilization died out!
It's hard to date oil. (Just ask Bluto.) So the old Sinclair logo may
well be fantasy.
Coal appears to have originated after trees invented structures that
allowed extreme height but before bacteria evolved mechanisms to
digest those trees. So the deadwood piled up before getting buried
and converted to coal. I'm not so sure that any significant coal has
deveoped after that period.
When was that supposed to be? Ligtnie was formed much earlier than
you indicate in
Post by Greg Goss
The carboniferous period was before the Permian Triassic "great
dying", long before the dinosaurs ever arrived.
German deposits of lignite were formed 65 to 2 million years ago.
J. Clarke
2018-04-22 19:45:28 UTC
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On Sun, 22 Apr 2018 10:09:40 -0700 (PDT), Quadibloc
Post by Quadibloc
Post by J. Clarke
Then
there's the matter of what that civilization used for fuel since it
did not burn up the coal and petrochemicals.
But our oil dates from the time of the dinosaurs!
So ancient lizardmen who lived during the time of the dinosaurs could well have
used up all the oil and coal that was *even older* than the oil and coal we use
now, which had enough time to be formed by geological processes *after* their
civilization died out!
How about the coal?.
Post by Quadibloc
The paper referenced, though, doesn't seriously suggest that there was a pre-
human civilization on Earth, it merely notes that it might by *hard to tell* if
there was one. That's valid science.
However as I said, it seems to ignore some of the evidence.
Post by Quadibloc
John Savard
a425couple
2018-04-22 22:33:31 UTC
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Post by a425couple
Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
It only took five minutes for Gavin Schmidt to out-speculate me.
----
“Wait a second,” he said. “How do you know we’re the only time there’s
been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. I had certainly
come into Gavin’s office prepared for eye rolls at the mention of
“exo-civilizations.” But the civilizations he was asking about would
have existed many millions of years ago. Sitting there, seeing Earth’s
vast evolutionary past telescope before my mind’s eye, I felt a kind of
temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an
industrial civilization that deep in time?” ------
We’re used to imagining extinct civilizations in terms of the sunken
statues and subterranean ruins. These kinds of artifacts of previous
societies are fine if you’re only interested in timescales of a few
thousands of years. But once you roll the clock back to tens of millions
or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things
like cities, factories, and roads—the geologic record doesn’t go back
past what’s called the Quaternary period 2.6 million years ago. For
example, the oldest large-scale stretch of ancient surface lies in the
Negev Desert. It’s “just” 1.8 million years old—older surfaces are
mostly visible in cross section via something like a cliff face or rock
cuts. Go back much farther than the Quaternary and everything has been
turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human
civilizations anymore. Homo sapiens didn’t make their appearance on the
planet until just 300,000 years or so ago. That means the question
shifts to other species, which is why Gavin called the idea the Silurian
hypothesis, after an old Dr. Who episode with intelligent reptiles.---
Given that all direct evidence would be long gone after many millions of
years, what kinds of evidence might then still exist? The best way to
answer this question is to figure out what evidence we’d leave behind if
human civilization collapsed at its current stage of development.
Now that our industrial civilization has truly gone global, humanity’s
collective activity is laying down a variety of traces that will be
detectable by scientists 100 million years in the future. ----
The big question is how long any of these traces of our civilization
will last. In our study, we found each had the possibility of making it
into future sediments. Ironically, however, the most promising marker of
humanity’s presence as an advanced civilization is a by-product of one
activity that may threaten it most.
https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/
I was reminded of a TV show about 10 years ago.
I searched for:
Earth 100 years after humans
There are lots of interesting readings (or viewings).

EARTH - 100 years later (Documentary) - YouTube
Video for Earth 100 years after humans▶ 24:11

Mar 31, 2017 - Uploaded by BeeShocK
EARTH - 100 years later from now - documentary

How Earth Will Look Like Millions of Years After Humans - ATTN:
https://www.attn.com/stories/.../what-earth-will-look-like-millions-of-years-after-huma...
Jun 1, 2016 - What would Earth look like if humans disappeared?

Life After People - Wikipedia
https://en.wikipedia.org/wiki/Life_After_People
Life After People is a television series on which scientists, structural
engineers, and other experts speculate about what might become of Earth
should humanity instantly disappear. The featured experts also talk
about the impact of human absence on the environment and the vestiges of
civilization thus left behind.
‎Format · ‎Episodes · ‎Season 1 (2009) · ‎Season 2 (2010)

Timeline of collapses | Life After People Wiki | FANDOM powered by ...
lifeafterpeople.wikia.com/wiki/Timeline_of_collapses
600 Years after People: The main collapse of the US Bank Tower (Los
Angeles), National Congress of Brazil, Chapel of the Holy Cross, Luxor
Hotel Pyramid, Diamond tower ...

Timeline | Life After People Wiki | FANDOM powered by Wikia
lifeafterpeople.wikia.com/wiki/Timeline
This timeline includes events depicted in the original Life After People
special that aired on January 21, 2008, Life After People: The Series
which aired from April 21, 2009 to March 16, ... On Ross Island in
Antarctica, the expedition hut of Robert Falcon Scott and Ernest
Shackleton remains preserved as it has for 100 years.

How Earth Will Look Like 300 Million Years After Humans Disappear
https://nextshark.com/earth-will-look-like-300-million-years-humans-disappear/
Jun 2, 2016 - How Earth Will Look Like 300 Million Years After Humans
Disappear ... channel #Mind Warehouse produced one of the most
fascinating looks into a future without humans from just a few hours to
hundreds of millions of years. ... 100 Million Years. – Plastic bottles
and glass will have finally broken down.

Earth After Humans | Owlcation
https://owlcation.com › Miscellaneous
May 6, 2016 - Have you ever wondered about what would happen to the
earth if humans were to suddenly vanish? ..... Sixty years after the
extinction of humans, and virtually all domestic dog breeds are gone, as
natural selection morphs our once faithful companions into something
more like their wild ancestors, wolves.

Life After People Full Episodes, Video & More | HISTORY
www.history.com/shows/life-after-people
What if every human being on earth disappeared? This isn't the story of
how we might vanish–it is the story of what happens to the world we
leave behind. In this episode, we'll see what happens to some of the
bodies left behind. Most embalmed and buried, some mummified, others
cryogenically frozen. Will any of them ...

Earth Without People | DiscoverMagazine.com
discovermagazine.com/2005/feb/earth-without-people
Feb 6, 2005 - “The wild carnivores would make short work of livestock,”
he says. “Few domestic animals would remain after a couple of hundred
years. Dogs would go feral, but they wouldn't last long: They'd never be
able to compete.” If people were no longer present anywhere on Earth, a
worldwide shakeout would ...

Life After People - Top Documentary Films
https://topdocumentaryfilms.com › Environment
Rating: 8.1/10 - ‎268 votes
Based on an odd, slightly morbid but deliriously intriguing premise, the
feature-length premiere episode of the History Channel series Life after
People supposes what would become of the planet's infrastructure,
natural environment and animal population if its human inhabitants were
to suddenly disappear. A world without ...

How would earth look like after humans disappear for 50 years? - Quora
https://www.quora.com/How-would-earth-look-like-after-humans-disappear-for-50-y...
Dec 16, 2016 - A documentary actually covered this topic, it's called
Aftermath: Population Zero If you don't know the documentary, here is
how it goes. Humans suddenly disappear while everything else is in
motion, so cars will crash, planes will crash, pretty m...
How would life be on Earth 100 years from now (2017)? Jul 27, 2017
What would happen to the Earth 100 million years later? Jul 1, 2016
What do you think the future on Earth will look like in 100 or 200 ...
Mar 17, 2015
If humans suddenly disappeared, what would happen to our planet? Mar 16,
2015
More results from www.quora.com

Terrifying video shows the Earth once all humans have been wiped ...
https://www.express.co.uk › News › Science
Jun 2, 2016 - THE terrifying reality of what would happen to the Earth
if all humans were to vanish overnight is demonstrated in this powerful
video. ... Estimates suggest that after 10,000 years, the only evidence
humans ever existed would be ancient monuments made with stone such as
the pyramids in Egypt, the Great ...

What would happen to Earth if humans disappeared? - Daily Mail
www.dailymail.co.uk/.../What-happen-Earth-humans-disappeared-Watch-terrifying-se...
Jun 2, 2016 - 'If we fired a 100 km [62 mile] wide asteroid on an
elliptical orbit that passed close to the Earth every 5,000 years, we
could slowly gravitationally nudge the planet's orbit ... One year after
the disappearance of humans, satellites around Earth would start to fall
from their orbit, creating strange 'stars' in the sky.

What will the Earth look like in 500 years? | HowStuffWorks
https://science.howstuffworks.com › ... › Earth Science › Geology ›
Geologic Processes
Learn about the Earth in 500 years. ... Theoretical physicist and
futurist Michio Kaku predicts that in a mere 100 years, humanity will
make the leap from a type zero civilization to a type I civilization on
the ... Technology has improved exponentially since the 1500s, and this
pace will likely continue in the centuries to come.

Stephen Hawking says humans must flee Earth within century | Fox ...
www.foxnews.com/.../stephen-hawking-says-humans-must-flee-earth-within-century.ht...
May 4, 2017 - Stephen Hawking is giving humanity a tall order: Colonize
Mars in the next century or watch as life on Earth fizzles out. After
last year claiming that humans have 1,000 years left on Earth, Hawking
says in a new documentary that we instead have about 100 years until
we'll need to jump ship as Earth is ...

Stephen Hawking: Humans must leave Earth within 100 years to survive
https://inhabitat.com › News
May 8, 2017 - In an article published on Forbes, Mack expressed that a
reality check is needed for anyone who believes Mars, the moon, or other
nearby planets are more hospital than Earth after countless disasters.
“Just cleaning up our own mess and starting over by rising from the
rubble seems more practical” and ...

Humanity has 100 years left on Earth, according to Stephen Hawking ...
https://www.weforum.org/.../stephen-hawking-thinks-humanity-only-has-100-years-le...
May 9, 2017 - Stephen Hawking adjusted his doomsday timer for Earth,
slashing 900 years from his initial 1000-year estimate.

Other Searches related to Earth 100 years after humans
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earth without humans timeline
a425couple
2018-04-23 15:01:26 UTC
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Was There a Civilization On Earth Before Humans?
A look at the available evidence
(as done in "Boundary" & "Inherit the Stars")
ADAM FRANK  APR 13, 2018   SCIENCE
---- “Wait a second,” he said. “How do you know we’re the only
time there’s been a civilization on our own planet?”
A similar, related story

Could an Industrial Prehuman Civilization Have Existed on Earth
Before Ours?
A provocative new paper suggests some ways to find out

By Steven Ashley on April 23, 2018
Could an Industrial Prehuman Civilization Have Existed on Earth Before Ours?
How could we really know if industrial civilizations existed on Earth
long before human beings appeared? That is the question posed in a
scientific thought experiment by climate scientist Gavin Schmidt and
astrophysicist Adam Frank. Credit: Michael Osadciw University of Rochester
One of the creepier conclusions drawn by scientists studying the
Anthropocene—the proposed epoch of Earth’s geologic history in which
humankind’s activities dominate the globe—is how closely today’s
industrially induced climate change resembles conditions seen in past
periods of rapid temperature rise.

“These ‘hyperthermals,’ the thermal-maximum events of prehistory, are
the genesis of this research,” says Gavin Schmidt, climate modeler and
director of the NASA Goddard Institute for Space Studies. “Whether the
warming was caused by humans or by natural forces, the fingerprints—the
chemical signals and tracers that give evidence of what happened
then—look very similar.”

The canonical example of a hyperthermal is the Paleocene–Eocene Thermal
Maximum (PETM), a 200,000-year period that occurred some 55.5 million
years ago when global average temperatures rose by 5 to 8 degrees
Celsius (about 9 to 14 degrees Fahrenheit). Schmidt has pondered the
PETM for his entire career, and it was on his mind one day in his office
last year when the University of Rochester astrophysicist Adam Frank
paid him a visit.

Frank was there to discuss the idea of studying global warming from an
“astrobiological perspective”—that is, investigating whether the rise of
an alien industrial civilization on an exoplanet might necessarily
trigger climate changes similar to those we see during Earth’s own
Anthropocene. But almost before Frank could describe how one might
search for the climatic effects of industrial “exocivilizations” on
newly discovered planets, Schmidt caught him up short with a surprising
question: “How do you know we’re the only time there’s been a
civilization on our own planet?”

Frank considered a moment before responding with a question of his own:
“Could we even tell if there had been an industrial civilization [long
before this one]?”

Their subsequent attempt to address both questions has yielded a
provocative paper on the possibility Earth might have spawned more than
one technological society during its 4.5-billion-year history. And if
indeed some such culture arose on Earth in the murky depths of geologic
time, how might scientists today discern signs of that incredible
development? Or, as the paper put it: “If an industrial civilization had
existed on Earth many millions of years prior to our own era, what
traces would it have left and would they be detectable today?”

Schmidt and Frank began by forecasting the geologic fingerprints the
Anthropocene will likely leave behind—such as hints of soaring
temperatures and rising seas laid down in beds of sedimentary rock.
These features, they noted, are very similar to the geologic leftovers
of the PETM and other hyperthermal events. They then considered what
tests could plausibly distinguish an industrial cause from otherwise
naturally occurring climate changes. “These issues have never really
been addressed to any great extent,” Schmidt notes. And that goes not
only for scientists, but evidently for science fiction writers as well,
he adds: “I looked back into the science fiction literature to try to
find the earliest example of a story featuring a nonhuman industrial
civilization on Earth. The earliest I could find was in a Doctor Who
episode.”

That 1970 episode of the classic TV series involves the present-day
discovery of “Silurians”—an ancient race of technologically advanced,
reptilian humanoids who predated the arrival of humans by hundreds of
millions of years. According to the plot, these highly civilized
saurians flourished for centuries until Earth’s atmosphere entered a
period of cataclysmic upheaval that forced Homo reptilia to go into
hibernation underground to wait out the danger. Schmidt and Frank paid
tribute to the episode in the title of their paper: “The Silurian
Hypothesis.”

LOST IN STRATA
Any plausibility for the Silurian hypothesis stems chiefly from the vast
incompleteness of the geologic record, which only gets sparser the
farther back in time you go.

Today, less than 1 percent of Earth’s surface is urbanized, and the
chance that any of our great cities would remain over tens of millions
of years is vanishingly low, says Jan Zalasiewicz, a geologist at the
University of Leicester in England. A metropolis’s ultimate fate, he
notes, mostly depends on whether the surrounding surface is subsiding
(to be locked in rock) or rising (to be eroded away by rain and wind).
“New Orleans is sinking; San Francisco is rising,” he says. The French
Quarter, it seems, has much better chances of entering the geologic
record than Haight–Ashbury.

“To estimate the odds of finding artifacts,” Schmidt says, “The
back-of-the-envelope calculation for dinosaur fossils says that one
fossil emerges every 10,000 years.” Dinosaur footprints are rarer still.

“After a couple of million years,” Frank says, “the chances are that any
physical reminder of your civilization has vanished, so you have to
search for things like sedimentary anomalies or isotopic ratios that
look off.” The shadows of many prehuman civilizations could, in
principle, lurk hidden in such subtleties.

But exactly what we would look for depends to some degree on how an
Earthly-but-alien technological culture would choose to behave. Schmidt
and Frank decided the safest assumption to make would be that any
industrial civilization now or hundreds of millions of years ago should
be hungry for energy. Which means any ancient industrial society would
develop the capacity to widely exploit fossil fuels as well as other
power sources, just as we have today. “We’d be looking for globalized
effects that would leave a worldwide trace”—planetary-scale
physical-chemical tracers of energy-intensive industrial processes and
their wastes, Schmidt says.


ADVERTISEMENT
Next comes the issue of longevity—the longer a civilization’s
energy-intensive period persists and grows, the more obvious its
presence should become in the geologic record. Consider our own
industrial age, which has only existed for about 300 years out of a
multimillion-year history of humanity. Now compare that minuscule slice
of time with the half-billion years or so that creatures have lived on
land. Humanity’s present rapacious phase of fossil fuel use and
environmental degradation, Frank says, is unsustainable for long
periods. In time it will diminish either by human choice or by the force
of nature, making the Anthropocene less of an enduring era and more of a
blip in the geologic record. “Maybe [civilization like ours] has
happened multiple times, but if they each only last 300 years, no one
would ever see it,” Frank says.

Taking all this into consideration, what remains is a menu of diffuse
long-lived tracers including fossil fuel combustion residues (carbon,
primarily), evidence of mass extinctions, plastic pollutants, synthetic
chemical compounds not found in nature and even transuranic isotopes
from nuclear fission. In other words, what we would need to look for in
the geologic record are the same distinctive signals that humans are
laying down right now.

SIGNS OF CIVILIZATION
Finding signs of an altered carbon cycle would be one big clue to
previous industrial periods, Schmidt says. “Since the mid–18th century,
humans have released a half-trillion tons of fossil carbon at high
rates. Such changes are detectable in changes in the carbon isotope
ratio between biological and inorganic carbon—that is, between the
carbon incorporated into things like seashells and that which goes
instead into lifeless volcanic rock.”

Another tracer would be distinctive patterns of sediment deposition.
Large coastal deltas would hint at boosted levels of erosion and rivers
(or engineered canals) swollen from increased rainfall. Telltale traces
of nitrogen in the sediments could suggest the widespread use of
fertilizer, fingering industrial-scale agriculture as a possible
culprit; spikes in metal levels in the sediments might instead point to
runoff from manufacturing and other heavy industry.

More unique, specific tracers would be non-naturally occurring, stable
synthetic molecules such as steroids and many plastics, along with
well-known pollutants including PCBs—toxic polychlorinated biphenyls
from electrical devices—and CFCs—ozone-eating chlorofluorocarbons from
refrigerators and aerosol sprays.

The key strategy in distinguishing the presence of industry from nature,
Schmidt notes, is developing a multifactor signature. Absent artifacts
or convincingly clear markers, the uniqueness of an event may well be
seen in many relatively independent fingerprints as opposed to the
coherent set of changes that are seen to be associated with a single
geophysical cause.

“I find it amazing that no one had worked all this out before, and I’m
really glad that somebody has taken a closer look at it,” says
Pennsylvania State University astronomer Jason Wright, who last year
published “a fluffy little paper” exploring the counterintuitive notion
that the best place to find evidence of any of Earth’s putative prehuman
civilizations may well be off-world. If, for instance, dinosaurs built
interplanetary rockets, presumably some remnants of that activity might
remain preserved in stable orbits or on the surfaces of more
geologically inert celestial bodies such as the moon.

“Look, 200 years ago the question of whether there might be a
civilization on Mars was a legitimate one,” Wright says. “But once the
pictures came out from interplanetary probes, that was settled for good.
And that view became ingrained, so now it’s not a valid topic for
scientific inquiry; it’s considered ridiculous. But no one’s ever put
the actual scientific limits on it—on what may have happened a long time
ago.”

Wright also acknowledges the potential for this work to be
misinterpreted. “Of course, no matter what, this is going to be
interpreted as ‘Astronomers Say Silurians Might Have Existed,’ even
though the premise of this work is that there is no such evidence,” he
says. “Then again, absence of evidence is not evidence of absence.”

ABOUT THE AUTHOR(S)
Steven Ashley
Steven Ashley is a staff editor and writer.
https://www.scientificamerican.com/article/could-an-industrial-prehuman-civilization-have-existed-on-earth-before-ours/
D B Davis
2018-04-23 17:00:33 UTC
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a425couple <***@hotmail.com> wrote:

<snip>
"After a couple of million years," Frank says, "the chances are that any
physical reminder of your civilization has vanished, so you have to
search for things like sedimentary anomalies or isotopic ratios that
look off." The shadows of many prehuman civilizations could, in
principle, lurk hidden in such subtleties.
Plate tectonics tend to obliterate evidence. Plate tectonics may also be
necessary for life as we know it.
Gonzalez and Richards posit that one of the prerequisites for life
as we know it is the recycling of a planet's crust through plate
tectonics. They argue that plate tectonics are essential to the carbon
cycle, preserves continents, and, along with the hydrologic cycle, are
indispensable for concentrating mineral ores.

Thank you,

--
Don
a425couple
2018-04-25 16:10:37 UTC
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Post by D B Davis
<snip>
"After a couple of million years," Frank says, "the chances are that any
physical reminder of your civilization has vanished, so you have to
search for things like sedimentary anomalies or isotopic ratios that
look off." The shadows of many prehuman civilizations could, in
principle, lurk hidden in such subtleties.
Plate tectonics tend to obliterate evidence. Plate tectonics may also be
necessary for life as we know it.
Gonzalez and Richards posit that one of the prerequisites for life
as we know it is the recycling of a planet's crust through plate
tectonics. They argue that plate tectonics are essential to the carbon
cycle, preserves continents, and, along with the hydrologic cycle, are
indispensable for concentrating mineral ores.
Yes, indeed.
Also, Plate tectonics are important for the magnetic field
that protects life from cosmic rays.

One key in our search for life elsewhere, is that
on planets smaller than earth, like Mars, plate tectonics
have stopped before our 5 Billion years.
Moriarty
2018-04-26 02:22:17 UTC
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Post by a425couple
Post by D B Davis
<snip>
"After a couple of million years," Frank says, "the chances are that any
physical reminder of your civilization has vanished, so you have to
search for things like sedimentary anomalies or isotopic ratios that
look off." The shadows of many prehuman civilizations could, in
principle, lurk hidden in such subtleties.
Plate tectonics tend to obliterate evidence. Plate tectonics may also be
necessary for life as we know it.
Gonzalez and Richards posit that one of the prerequisites for life
as we know it is the recycling of a planet's crust through plate
tectonics. They argue that plate tectonics are essential to the carbon
cycle, preserves continents, and, along with the hydrologic cycle, are
indispensable for concentrating mineral ores.
Yes, indeed.
Also, Plate tectonics are important for the magnetic field
that protects life from cosmic rays.
One key in our search for life elsewhere, is that
on planets smaller than earth, like Mars, plate tectonics
have stopped before our 5 Billion years.
A few years back, Scientific American had an article on what an "ideal" Earth would be like. That is, if you designed from scratch a world best suited to create and harbour life long-term, how would you do it and what features would it have.

A key component was plate tectonics for the reasons you mention. For that reason, the ideal world was about twice as large as Earth, in order for plate tectonics to last longer.

The other key difference from what we actually have was placement in the habitable zone (we're too close to the sun). I think our land/sea ratio and atmospheric composition could be better too, but I'm hazy on the details.

We're also orbiting the wrong sort of star.

-Moriarty
Greg Goss
2018-04-26 09:15:47 UTC
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Post by a425couple
Post by D B Davis
Gonzalez and Richards posit that one of the prerequisites for life
as we know it is the recycling of a planet's crust through plate
tectonics. They argue that plate tectonics are essential to the carbon
cycle, preserves continents, and, along with the hydrologic cycle, are
indispensable for concentrating mineral ores.
Yes, indeed.
Also, Plate tectonics are important for the magnetic field
that protects life from cosmic rays.
I think that the magnetic field is MUCH deeper than anything affected
by plate movement.
--
We are geeks. Resistance is voltage over current.
D B Davis
2018-04-26 12:46:38 UTC
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Post by Greg Goss
Post by a425couple
Post by D B Davis
Gonzalez and Richards posit that one of the prerequisites for life
as we know it is the recycling of a planet's crust through plate
tectonics. They argue that plate tectonics are essential to the carbon
cycle, preserves continents, and, along with the hydrologic cycle, are
indispensable for concentrating mineral ores.
Yes, indeed.
Also, Plate tectonics are important for the magnetic field
that protects life from cosmic rays.
I think that the magnetic field is MUCH deeper than anything affected
by plate movement.
AFAIK you're correct. Although plate tectonics melt iron to cause it to
sink, it's actually a molten metallic core that creates a geomagnetic
field. That field deflects the solar wind enough to keep it from
stripping away the ozone layer that protects life on Earth from harmful
radiation.
Gonzalez and Richards regard a sufficiently sized molten metallic
core as yet another prerequisite for life as we know it. Although the
gas giants in our Solar System posses a magnetic moment greater than
Earth's, the innermost planets, including Mars, fall far short [1].

Note.

1. http://lasp.colorado.edu/~bagenal/3750/ClassNotes/Class13/Class13.html

Thank you,

--
Don
David DeLaney
2018-04-29 09:13:34 UTC
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Post by D B Davis
gas giants in our Solar System posses a magnetic moment greater than
Earth's, the innermost planets, including Mars, fall far short [1].
ObSF: James Blish, the first part of Cities in Flight, which I think is They
Shall Have Stars; they couldn't test a key proposition underlying the eventual
spindizzy on Earth, they had to build a Bridge on Jupiter to do so. Senatorial
accusations of wasted budget money and hijinx ensued.

Dave
--
\/David DeLaney posting thru EarthLink - "It's not the pot that grows the flower
It's not the clock that slows the hour The definition's plain for anyone to see
Love is all it takes to make a family" - R&P. VISUALIZE HAPPYNET VRbeable<BLINK>
my gatekeeper archives are no longer accessible :( / I WUV you in all CAPS! --K.
Daniel60
2018-04-30 09:52:52 UTC
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Post by David DeLaney
Post by D B Davis
gas giants in our Solar System posses a magnetic moment greater than
Earth's, the innermost planets, including Mars, fall far short [1].
ObSF: James Blish, the first part of Cities in Flight, which I think is They
Shall Have Stars; they couldn't test a key proposition underlying the eventual
spindizzy on Earth, they had to build a Bridge on Jupiter to do so. Senatorial
accusations of wasted budget money and hijinx ensued.
Dave
Gee Whiz!! What company was responsible for building a bridge on Jupiter??

I reckon they'd get a few construction jobs here on Earth!! ;-P
--
Daniel
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