While that's an interesting argument I don't this applies to the Fe-60 isotope. I don't think we know of an energy production process (fission or fusion) that would result in Fe-60 as a byproduct which would cater to the Silurian hypothesis.
Especially in the quantities and locations discovered. Hence I think their assumptions - of looking for natural places where the isotope is forged - in this case are valid.
A DT fusion reactor with iron in its structure would produce a small amount of Fe-60, by double neutron capture on Fe-58. The amount would be limited because the half life of Fe-59 is 44.5 days.
Because it seems pretty ridiculous on it's face. We might not have monuments of an ancient civilization, but we'd expect to see records of an equivalent anthropocene in the geologic record, similar to what we're making now, more or less. Increased bio-carbon deposits, increased sedimentation from agriculture, etc.
We might as well wonder why scientists didn't consider whether the deposits of iron 60 were put there by mischievous leprechauns.
'scientists' need not consider every crackpot theory because someone on the Internet thinks they should.
It's ridiculous because a past civilization wouldn't have spread iron-60 all over the planet the way a supernova would have.
But a fairly advanced civilization could have existed in a fairly local part of the planet that we don't much explore (think of the Sahara desert) and so haven't found the remains of, or it could be buried or under quite a bit of water (if it developed during a glacial period).
It’s not so ridiculous once you learn that most of the earths crust gets recycled within 500 million years, and more than half gets recycled within a mere 100 million years.
That’s why we don’t find fossils everywhere. And if humanity goes extinct today, it would be fairly tricky to find evidence of us in a billion years.
It’s of course a non falsifiable hypothesis, so there’s not much we can do. But plenty of people believe in another non falsifiable hypothesis——invisible man in the sky.
This isn't really accurate. There are some plates that are extremely geologically stable, location-wise. There are parts of the Canadian shield over 4 billion years old.
That is completely false. Most of Earth's continental crust is more than 2.5 billion years old, with the oldest parts being 4 billion years old. Only Earth's oceanic crust is young.
We do find fossils everywhere. Not all rock types are conducive to fossil formation, and many parts of Earth are less explored than others, but there exists no region on earth without a fossil record.
Evidence of humanity's existence would be clear in the fossil record for billions of years. Reinforced concrete, plastics, artificial ceramics, mined fertilizers, they would all be preserved over geologic timescales. On top of this, intelligence does not simply pop into existence - there would need to be many millions of years of fossil record showing the evolution of some intelligent lineage.
> On top of this, intelligence does not simply pop into existence - there would need to be many millions of years of fossil record showing the evolution of some intelligent lineage.
What is the evolutionary gradient leading to “intelligence?” Where is there evidence of .99, .98, .97.. of Human intelligence?
Could an intelligent life form not leave a fossil or any other record? Is a material culture always evident where human-level intelligence exists?
If this civilisation was advanced enough to forge fancy isotopes they were probably advanced enough for space travel. They would have visited the Moon and Mars but there's no evidence of that, which is especially suspicious on the Moon as it's geologically inactive.
It would be really weird if a Silurian civilization randomly pumped out a bunch of radioactive iron and didn't do anything else.
Any industrial civilization comparable to ours within the past few hundred million years would be very detectable today - reinforced concrete, plastics, ceramic shards, mined fertilizers, all would show up in the geologic record. Further one would expect fossil evidence of some lineage approaching intelligent levels over time. The only plausible place for a Silurian civilization to hide would be several billion years ago, so long ago that the crust they lived on has been subducted back into the mantle, taking the evidence for their existence along with it.
I agree with this comment fully but I just wanted add a little on the subduction.
It’s a lot quicker than people think.
The vast majority of rocks we can find that aren’t of extra terrestrial origin are only around 200 million years old.
>A few seams of very old rock have been discovered, such as the billions of years old Nuvvuagittuq greenstone belt in Hudson Bay, Canada, as well as similarly ancient outcrops in Australia, China, Greenland and South Africa. But even this very old rock has had a complex history. “Exposure to high temperatures during past collision can change the chemistry,” notes Boyet. “This disturbs the isotopic system we use for dating rock.”
Most continental crust is over 2.5 billion years old. Very old rocks aren't exposed at the surface very frequently, because they tend to get covered over in younger rock, but it's still there, and we can sample it with deep drilling.
Oceanic crust tends to be less than 200 million years old, though even then there are some much older examples.
> It would be really weird if a Silurian civilization randomly pumped out a bunch of radioactive iron and didn't do anything else.
We never know any data before interpreting it through theories. All observations are, as Popper put it, theory-laden, and hence fallible, as all our theories are.
Deutsch, David. The Beginning of Infinity
Probably the best evidence that Fe60 is not "Silurian" in origin is that it still arrives on Earth [0].
The Silurian Theory is sometimes an interesting way to explore ideas. I don't think that a large pre-human "civilization" need take the same form as what we think of as human civilization. Even some large human civilizations like that of the Indus River Valley or Harappan culture are less understood because they left less in the way of stuff analogous to current times: "In sharp contrast to this civilisation's contemporaries, Mesopotamia and ancient Egypt, no large monumental structures were built. There is no conclusive evidence of palaces or temples."
Some scientists will do anything but consider the Silurian hypothesis.
https://en.wikipedia.org/wiki/Silurian_hypothesis