That's a question in geology and archaeology called the Silurian Hypothesis: Could we even detect a millions-of-years old civilization in the geological record?
An Earth-originating civilization would have left our species bereft of the natural resources to industrialize with.
Coal was only made once. Maybe if abiotic theory of petroleum is true, you get that back over immense timescales, but you don't get a second shot at coal. Without coal, you can't even do metallurgy at scale. Is there some gotcha that I'm missing?
Coal was only made once because the earth basically ran out of carbon to turn into coal. There’s 1,100,000 million tons of economically viable coal and we’re running into environmental issues by burning ~1/1,000th of it.
Most projections suggest coal use is going to plummet over the next 50 years, both because we have better options and because we have little choice.
There’s enough coal in the ground to make earths atmosphere actively lethal to humanity. At ~70,000 ppm people are rendered unconscious in minutes and there’s enough coal go well over 100,000 ppm. There’s no way for humanity to use up the worlds coal as fuel, perhaps we could ship it into space as carbon source but that seems unlikely.
> Most projections suggest coal use is going to plummet over the next 50 years, both because we have better options and because we have little choice.
Sure. Already industrialized civilizations have better options. But if you're starting from scratch, you don't get to jump immediately to photovoltaics or whatever.
> and we’re running into environmental issues by burning ~1/1,000th of it.
But which 1/1000th? We didn't dig out the deepest coal first. "Economically viable coal" by 21st century standards isn't the same "economically viable coal" by the standards at the dawn of the industrial revolution.
> But which 1/1000th? We didn't dig out the deepest coal first. "Economically viable coal" by 21st century standards isn't the same "economically viable coal" by the standards at the dawn of the industrial revolution.
Across geologic timescales what’s accessible changes. It makes a huge difference if deposits are above or below sea level for example. The Industrial Revolution kicked off in a small geological area which would have looked very different even 100k years before.
Even beyond that we’re actually more selective not less when it comes to coal mines. Unlike say copper/silver/gold/etc there’s so much coal that what would have been a perfectly viable mine 150 years ago simply isn’t today. Larger equipment means fewer workers but it also requires thicker coal seams. Similarly we’re a lot more picky about sulfur content etc.
That’s also somewhat true of stuff copper, gold, etc. The minimum concentration required to make ore viable has decreased dramatically, but only when there’s huge quantities of ore. Plenty of potential mines could be worked by hand, but can’t complete with industrial scale mines or be used as one.
PS: It’s worth remembering even if things aren’t quite as efficient they can be viable. Building canals takes more effort than rail lines but they can still transport bulk goods on the cheap using minimal technology. Similarly solar smelting can reach extreme temperatures, just not 24/7. Wood plus just about any rock can get you to steel with enough effort and know how. It might take slightly longer but our history isn’t the only way to get to transistors and spacecraft etc.
Yes, that was sort of the point. So you get 100's of millions of years during which things can rearrange themselves. Whoever - or even whatever - inherits the Earth after the next big impact will find it changed dramatically compared to how it is today. By the time they evolve intelligence (optional) have toolmaking needs (optional) and are living on land (optional) they will have plenty of time to figure out where it is going to come from, the earths crust will be rearranged enough that you can expect all kinds of stuff to have risen to the surface that is now inaccessible.
Heck even the Himalayas have formed only 50 million years ago.
DNA sequences are undergoing frequent changes if there is no evolutionary pressure on them. The message would quickly be scrambled. They would have to encode it into highly conserved gene sequences, i.e., completely reinvent life as we know it.
The moon is a harsh environment and (like most places in the solar system) exposed to significant danger from meteorites over geological timescales.
1. https://arxiv.org/abs/1804.03748