Comment by crystal_revenge | Hacker News Reader

Comment by crystal_revenge | Hacker News Reader

crystal_revenge

Surprised the article didn't mention the Paleocene–Eocene Thermal Maximum (PETM) [0] and it's interesting relation to "a species different from ours had achieved high intelligence and technological civilization on this planet."

For those unaware, the PETM was a rapid increasing in global temperature (and CO2 concentrations) around between 60-50 million years ago. This lead to a minor (on a geological time scale, major for those creatures living through it) climate crisis.

The cause for the rapid increase in temperatures at this time is still the subject of deep debate and largely unknown. However how very "out there" hypothesis, not even mentioned on the wikipedia page, is that this could have been when a civilization such as our experience an event more-or-less identical to our own current climate crisis caused by the rapid use of hydro-carbons.

Of course, the biggest challenge with this hypothesis is, as pointed out in the article, a civilization like this would not leave a trace on the geological record. So there's really no reasonable way to have much evidence in favor of this possible explanation.

But since here about this I've been fascinated by the problem of sending messages to the future. Suppose we come to realize that rapid use of hydrocarbons does most certainly lead to the destruction of any civilization foolish enough to tread this path. The most reasonable focus of scientific effort that would be to figure a way to warn the next advanced civilization on this planet in hopes they might not meet the same fate. But presuming that civilization is 50 million years in the future, how could this be done?

0. https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therm...

Some ideas for sending messages to the next civilization.

1. Genetically modify as many wild plants and animals as we can to have a message encoded in their DNA, and release them back into the wild.

2. In areas that we expect to be geologically not much changed over the next 50 million years arrange concentrations of long lived radioactive materials in patterns that are obviously not natural. Encode a message in those patterns.

3. We could probably do something on the moon with nuclear weapons that could make a long fairly straight trench or series of parallel trenches that would be visible in telescopes and either be obviously non-natural or at least interesting enough to get them to go take a look.

Leave millions of metal spheres, cubes, tetrahedrons, octahedrons, dodecahedrons, and icosahedrons there which contain messages inside.

Google is telling me that any given spot on the moon gets hit be a meteoroid of ping pong ball size or greater about every 1000 years, so many of the messages will likely be destroyed over 50 million years, but maybe enough will make it.

BTW, is meteoroid the correct term? That's what Google's summary used and according to the dictionary definition as a small body that would become a meteor if it entered the Earth's atmosphere it would be correct but when we are talking about impacts on other planets or moons I'm not sure we should restrict meteor and meteorite to just meteoroids that are in or have hit after passing through Earth's atmosphere, respectively.

> Leave millions of metal spheres, cubes, tetrahedrons, octahedrons, dodecahedrons, and icosahedrons there which contain messages inside.

Anyone deciding to write scifi based on this, try to involve Romans somehow: https://en.wikipedia.org/wiki/Roman_dodecahedron

> a rapid increasing in global temperature (and CO2 concentrations) around between 60-50 million years ago

> a civilization like this would not leave a trace on the geological record

Am curious: if dinosaurs can be found with intact skin [1], after 110 million years, why not remains of the civilization's "people" (bones etc.) after 60-50 million years?

1. https://en.wikipedia.org/wiki/Borealopelta

They might have just been much better than dinosaurs at not drowning in bogs and other rare fossil-promoting circumstances.

And number of dinosaurs found compared to number of individual dinosaurs that ever lived is staggeringly low.

Not a biologist, but OTOH they might have had a very different body structure that doesn't conserve well, e.g. like molluscs.

Or maybe we _did__ find their remains and just have no idea they were part of an intelligent civilization. I mean, that's not a question any respectable researcher would be inclined to raise in the paper about the discovery...

I think the point is that the 'people'/their remains might be findable, but trace or proof of their civilization would not?

If PETM was due to large scale use of hydrocarbons, there should be evidence of depletion in the strata, right? For example, currently not all sources are uniformly exploited -- some coal seams and oilfields are all but depleted, others are currently being extracted, and others are yet to be found/exploited.

We should have seen signs of similar non-uniform usage in the strata from before that time period. I wonder if any research has been done on this.

> If PETM was due to large scale use of hydrocarbons, there should be evidence of depletion in the strata, right?

And all the byproducts of this use. We are leaving abundant traces of our existence basically everywhere. We can see it in the ground, in the seas, in the ice caps. Our existence will be very obvious to anything caring to just dig for quite a long time.

Just because traces are widespread doesn't mean they'll last for 60 million years.

For example, we don't have any ice core data older than ~5 million years. (Much lower, if you limit it to continuous spans.)

The content of the atmosphere gets washed out by rainfall and does end up in the sedimentary record. Similarly, we can follow the oceans’ acidity from sediments. Large chemical changes would also show up in isotope ratios.

We’re talking about 50 million years. Literal continents move in that amount of time.

We get bones and feathers from animals living 10 million years before that. We can find the traces from the Chicxulub impact across the whole world. Same for large volcanic eruptions. Burning enough stuff to cause this kind of global warming would leave plenty of chemical traces. It’s just not serious.

The ice caps are only about 30 million years old, and the land and oceans are similarly transformed over long time scales. The only techno signature I'm aware of that would be clearly detectable 50 million years after our civilization is gone is reinforced concrete, which should produce a worldwide layer of a limestone-like mineral with iron inclusions that would be both unique in the geologic record and difficult to explain by any natural process. If a civilization did not use reinforced concrete nor some other such material that would leave a similar signature, it would be quite difficult to detect at that timescale.

I'm not sure if that's a safe assumption. Do we know what the sources we are exploiting right now are going to look like in tens of millions of years? Our models of the evolution of hydrocarbon reserves are based on those we've found, and we simply assume the differences between different deposits are natural in origin. It's easily possible that places where we didn't find hydrocarbons did in fact have them at a previous point in time, or that there was more in a given reserve in the past.

Has someone done the math on what Hydrocarbons (coil, oil) would have been available 60 million years ago?

Would they have been using the same deposits we are suing, or would new deposits have formed over the last 60 million years?

Or could they have depleted their own, but what was un-usable 60 million years ago, have become usable today. Like something that was marsh land 60 million years ago, be coal today?

Good thought but our coal is peat from 300-350 M year ago. Much of it would have probably been "ready" 60 M years ago already.

https://en.wikipedia.org/wiki/Carboniferous

I think the only option is to leave several copies of the message on the moon, and hope they stumble upon a copy.

Send it to space. To multiple places. Next guys should be able to find it sooner or later.

If only there was some way to mark a planet with a special marker.. that could be seen from anywhere in the solar system from any angle.

Maybe some rings?

> current climate crisis caused by the rapid use of hydro-carbons.

The problem I see is they either had to use sustainable hydrocarbons (so, carbon-neutral) or they would have used up the fossil fuels we're currently using.

> a civilization like this would not leave a trace on the geological record.

At all? Like nothing that would be observable 50M years later?

Nothing built with "usual" materials we have, mostly because of the constant movements and subduction of tectonic plates, as well as volcanism and erosion.

Think about something you believe would last 50 million years. I am sure someone will be able to point out how and why that would just disappear after such ridiculous amount of time.

Aren't the oldest fossils we know of assumed to be something like 500 million years old?

Or you could try leaving particular "signatures" of radioactive elements. Not ones with a short half-life, obviously, but xenon-124 lasts pretty long, tellurium-128 will survive anything except the heat death of the universe, and there's a few others like that.

Sure, how many >300 million year old fossils have we found related to how many animals lived at that time, over that span of time? The problem is many methods might work -- literally you accidentally falling on a trip to Florida might work -- but the probability can be very low.

Put up a plaque reading "This is not a place of honor ..." ?

You’re being downvoted but the reference is this https://en.wikipedia.org/wiki/Long-term_nuclear_waste_warnin...

Wrong timescale though. 10000 years vs. 50 million. Millions of years is a very very very long time, our intuition is often wrong about timescales like that. For example a lot of modern land was still molten rock underground and vice versa.

Good point about the timescale.

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