The Silurian Hypothesis (2020)

+1 in general that anthropic bias is strong, but it cuts both ways, even in relatively hard nosed statistical models (@see Drake equation vs Rare Earth hypothesis). Truth is, there are a ton of factors we just can't observe (yet?) that play a big part. For example, since the rare earth hypothesis was published, we know a lot more about exoplanets, and earth-range size in the habitable zone of a stable star and galaxy appears much more common than we thought. But we don't know if plate tectonics are really required, or gas giant "vacuum cleaner" planets int he same system, or even oxygen. But we do know that the minimum value for intelligent species is at least 1, because we exist.

For me, it's carl sagan's "invisible dragon" comparison that sticks in the back of my head. If there's intelligent life out there (or in earth's ancient past) but there's no physical way to detect or know it... Then like the invisible dragon in mu garage, it's the same as not existing.

Maybe we'll develop new techniques and gather new evidence, but until we figure out how to bend spacetime for FTL anything, or find clear evidence, we should act as if it isn't/wasn't there.

So TFA says that 55M years ago there was a climate fluctuation that looks similar to the anthropocene one. Good start. But interpretation of ancient stories across cultures is practically the definition of anthropic bias. We have to wait until there is real evidence that the temperatuee bump was dragonfire and not my heating system acting up, to ascribe cause.

There’s always the hollow earth!

How can anyone say the hypothesis is true? There is absolutely no evidence for it. It’s just a thought experiment.

People get way too excited about the word "reactor". They hear "reactor" and think "oh, a natural formation of uranium was evaporating water into steam and generating electricity". They don't consciously examine that, of course, but it's clear a lot of people are letting that in unexamined.

What really happened is that some uranium got concentrated, and then it did was uranium does.

Similarly, if you want to make a very, very basic atomic bomb, you can do it by picking up two subcritical bits of uranium of the right isotopes and slamming it together in your hands. Basically the demon core but even more pure. The yield will be pathetic by military standards but you won't be around to care.

Fission isn't a process that requires intelligence, and fission causing cascading fission doesn't either.

"A more interesting question is the civilizational technology of domestication, especially since that is short-term technology coupled with long-term evolution. It does seem possible (but purely fantastical) that Earth had talking dinosaurs with sophisticated ideologies and mythologies, feeding dumber dinosaurs and curating the growth of nutritious plants, the descendants of which all died 65m years ago."

Yes, that's why I'm careful to qualify it with "technological", which is by implication the whole thing we do with metals and minerals and oil and all that stuff. A past intelligent society that lived like hippies and had all sorts of fascinating philosophical debates until they died out with no major footprint can't be completely excluded. But I am fairly confident they never went to space. Well... you know... real space, like the kind of orbit the ISS is in. What they may have gotten up to on the influence of drugs I have no comment about.

Part of the reason I couldn't exclude it is that it has basically happened. If hypothetically an asteroid blew away humanity two or three thousand years ago, that's basically what would have been left behind. They did mining then, but at a scale easy to believe could be erased by time. Quite a bit of that time period is already gone as it is, let alone across millions of years. It's really that modern industrial mining that we do today, the cumulative effect of many decades of that mining, and barring disaster, the cumulative effect of yet more decades/centuries of mining that would survive for millions of years.

1.) It's definitely a giant leap from current technology to interstellar colonization.

2.) Other civilizations even in the nearest solar system would basically be impossible to detect. Even in our own solar system, there could be millions of undetected spacecraft right now. They're simply too small to see. To be detectable, they'd either have to be massive and massively disruptive, like Dyson spheres, which are and most likely will forever remain pure fiction, or they'd have to happen to use radio for communication.

3.) There are good reasons for them not to be using radio for communication. They might have discovered a different physical phenomenon that allows them to communicate in ways we can't detect. Or they might not be as reckless as humans and don't want to broadcast their presence and activity to completely unknown and potentially hostile other species.