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Comment by Jedd | Hacker News Reader

It's a bit more complicated than this, but one shortcoming is that wood simply doesn't burn hot enough to smelt steel (1100 or so?). Coal was, for us, effectively an essential step.

Advances you mention in your third paragraph don't include the jumps in precision that were predicated on this capability, and indeed necessary for the next steps.

There may of course be some civilisations out there that managed what you're describing - it's a big ol' universe after all - but my gut feel is mitochondria is probably the great filter, rather than an abundance of energy-dense naturally occurring fuel.

This link pops up regularly on HN. It's a spectacularly good read, highly relevant here, in terms of the necessary set of converging prerequisites for an industrial revolution:

https://acoup.blog/2022/08/26/collections-why-no-roman-indus...

View on HN

Sorry I'm a bit late to reply here, but I still think coal isn't strictly necessary. You don't need steel to develop wind and hydropower, and you can electrify with metals that don't require such high temperatures.

Once you have sufficient electrical power, you can heat things in other ways - for example, aluminum smelting requires even higher temperatures than steel and uses electricity https://en.wikipedia.org/wiki/Aluminium_smelting.

Lewis Dartnell's 2016 story published in Aeon (and based on his 2014 book) pops up periodically - eg: https://news.ycombinator.com/item?id=25187100

The title of the piece is Could we reboot a modern civilisation without fossil fuels?, and is well worth the read.

So, sure, yeah, aluminium melts at about 650 degrees (I considered this fact when looking at aluminium pizza trays for my oven, which can, though rarely does, go beyond 450) and is smelted about 150 more than that.

But in order to smelt it you of course need receptacles that won't melt at that temperature - ie, steel (plus insulation). I was off by a couple of hundred degrees in my earlier comment - steel smelting is around 1300-1500 degrees. So we're back to the original problem.

As to wind and hydro, sure, yes, you can easily generate power from those, as we did for millennia using mostly timber constructs. Though I'm not sure if you're suggesting getting electrical power from those sources is easy, absent some sophisticated technological capabilities (wire-making, for starters).

Mitochondria are just a hack to integrate efficient oxygen metabolism into archaean cells, and I wish people wouldn't worship them so much. Mitochondria started as free living cells that had that metabolism. There's no reason life on a different world couldn't develop it directly in the same lineage as cells destined for multicellularity.

Worship?

I appreciate I only have a sample size of one - but then, so does the 'it's no big deal' crowd.

On this planet we have no alternative routes to the same outcome, and no clear evidence that alternative routes a) couldn't have come about, or b) did but were subsequently out-competed.

I suggest everyone with a Fermi-opinion is in the same camp - massively speculative and a single datapoint (unless you count the myriad (in their absence) counter-points).

The original bacteria that were engulfed to become mitochondria are the "alternative route". It's clearly possible for a cell to have oxygen metabolism on its own because that's how we got here. So the question is, is endosymbiosis the only way to integrate that with a large, complex cell? When you phrase it that way, it should be clear which way the odds lie.

But yes, "worship" is not quite the right word for whatever obsession it is that people have with mitochondria.

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