[pureliquidhw]

I agree century timescales are tough, I'm not convinced 4 of 5 of your listed things have been solved.

Rubber has been replaced with oil.

Fertilizer has been replaced with Natural Gas that comes from the same place as oil.

Coal usage has been replaced/displaced primarily by natural gas, see above.

Wood, or deforestation, was a real problem in the 1920's, but many uses were replaced by plastics (oil) and natural gas. Sustainable forestry helped a ton here too once it hit the paper industry's bottom line.

Oil is certainly not solved, so we solved 4 out of 5 with the 5th.

[achierius]

Exactly -- that means that any analysis based on the current (as of 1926) 'reserves' or 'production capacity' for rubber/fertilizer/coal/wood would have been invalidated as soon as we switched to using oil instead. Imagine if instead of harvesting helium directly we find an economic way to split nitrogen (somehow, who knows). At that point, what you'd have to have forecasted would be the 'reserves' of nitrogen, which are functionally infinite.

[vlovich123]

That still amounts to magical thinking. And the point of the post that you’re replying to is that we didn’t actually make things better. We actually accelerated our exploitation of other resources to make up for the shortage of the others which had serious other negative side effects.

Since we’re dealing in magical hypotheticals, what if this new economical way to split nitrogen generated so much pollution that it poisoned natural water supplies? Also the “economic way” is misleading. If prices shoot up enough, then crazy things become economical like missions to other planets to retrieve it. But that’s an insane cost that has to be borne out by all humanity. Historically that worked because you increased how many people were on earth so it spread the cost out. However, it’s pretty clear the Earth is at carrying capacity for humans with our current technology which is why the population growth has slowed drastically. So increasing costs threaten to become a weight the next generation can’t lift resulting in societal collapse.

[don_esteban]

> Imagine if instead of harvesting helium directly we find an economic way to split nitrogen (somehow, who knows).

This is nonsense, from the physics point of view.

The reason why rubber/fertilizer were replaced by oil/gas products is that oil/gas has the energy needed for the (relatively simple) chemical transformations needed to obtain rubber/fertilizer from the feedstocks.

Splitting nitrogen into helium is a nuclear reaction that requires copious amounts of energy.

At least using fusion or collecting helium from Moon/Jupiter are physically sane, if economically insane.