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by T-A 3 days ago
> How long to dissolve carved stone sculptures (in sizes ranging from 1cm to 100m?)

A quick search on "rock weathering depth per century" suggests a "typical range" of 0.05 mm to 6 mm, depending on rock type and environmental factors. At 0.05 mm, a stone object with radius 0.5 cm would crumble in 10000 years. With radius 50 m, it would take 100 million years.

I would expect them to be unrecognizable long before that though.

> And how long does it take to dissolve skin? Footprints? Because we have those from hundreds of millions of years ago.

What do those findings tell you about the cognitive abilities and social organization of the creatures who left them behind?

1 comments

> A quick search on "rock weathering depth per century"

That's a great illustration of what I meant. Of course an exposed rock consumes away in the space of a few millennia- this is exactly where the "Silurian theory" comes from. Yet it's also obvious that we have plenty of perfectly conserved rocks that are intact after hundreds of millions of years- i.e. fossils. Any small sculpture buried in clay can survive for an eternity.

> What do those findings tell you about the cognitive abilities and social organization

Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots? Drawings "I LOVE YOU" in the sand? The shape of a coca-cola bottle buried in solidified clay? Come on...

> Any small sculpture buried in clay can survive for an eternity.

If it's made of granite, maybe. But how many granite sculptures have you seen? Sculptors tend to prefer prettier and more easily shaped materials, like marble and limestone. Those happen to be mostly calcium carbonate, just like bones and teeth, so section 1.2 in [1] (chemical dissolution in acidic environments) applies, along with section 1.3 and [2] (mechanical fracturing and dispersion during wetting-drying cycles).

Even if your sculpture was buried in a maximally favorable environment, it would not have stayed that way over tens of millions of years. 50 million years ago, the Himalayas were just starting to rise as India crashed into Eurasia, Australia was waving goodbye to a forest-covered Antarctica while the Americas, North and South, had yet to link up. At a rate of one ice age every 100k years, 500 ice ages separate us from those days. One is enough to raze half a continent and turn a muddy seabed into granite.

> Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots?

This is extremely anthropocentric. A hypothetical "Silurian" civilization would obviously not have been human, and may have had no need for such things. Would bears endowed with human-level intelligence want to wear clothes and boots?

> Drawings "I LOVE YOU" in the sand?

Have any such preserved drawings in the sand been found from the ~200k years humans have been around?

> The shape of a coca-cola bottle buried in solidified clay?

See section 1.3 in [1], and remember that the time scale discussed in that kind of paper is a few thousand years, not tens of millions.

[1] https://www.sciencedirect.com/science/article/pii/S004896971...

[2] https://www.tandfonline.com/doi/abs/10.1179/0197136978063731...

> how many granite sculptures have you seen?

We use enormous amounts of it in construction, cut to precise shapes.

> just like bones and teeth

Of which we have ample amounts of fossils. Even included in marble, which is itself hundreds of millions of years old.

> it would not have stayed that way over tens of millions of years.

So we don't have fossils from hundreds of millions of years ago?

> Would bears endowed with human-level intelligence want to wear clothes and boots?

Absolutely if they had a civilisation capable of producing climate change. We're talking about at least a billion individuals living in all environments on Earth, from the tropics to the arctic, and doing all things an advanced civilization does: farming, mining, building, transporting, exploring etc. At least elements of technical clothing are needed in many of these activities.

> See section 1.3 in [1]

You keep repeating an argument that disproves the possibility of all fossils. Really you can't understand that it's contradicted by facts?

> We use enormous amounts of it in construction, cut to precise shapes.

The question, which you did not answer, was about granite sculptures.

We use enormous amounts of granite in construction, crushed and mixed with cement, sand, and water to make concrete. Larger irregular pieces are also used for roads (under the asphalt and mixed with it) and railways. Some regularly shaped objects made of granite are used in construction, which is not generally undertaken on the kind of waterlogged terrain needed for clay to sink in, and will be subject to weathering at the previously discussed rates, to the extent that they are not broken or recycled when buildings are torn down.

>> just like bones and teeth

> Of which we have ample amounts of fossils.

A few million, counting all fossils of all species which have existed over the past three billion years or so.

Humans are one out of the billion or so species which have lived on Earth [1], the ~200k years we've been around are less than a millionth of that time span, the vast majority of humans never make sculptures, and the vast majority of sculptures are destroyed within a few centuries. But here you are, complaining that we have no sculptures from tens of millions of years ago.

>> Would bears endowed with human-level intelligence want to wear clothes and boots?

> Absolutely if they had a civilisation capable of producing climate change.

Ah yes, I can totally see a bear going "OMG it's getting so hot, I totally need to wear some artificial fur over my own!"

> You keep repeating an argument that disproves the possibility of all fossils.

No. You keep ignoring the time scale, the dynamics and the odds.

[1] https://www.livescience.com/animals/how-many-animals-have-ev...