Could we reboot a modern civilization without fossil fuels? (2016)

There are masonry techniques that are considered lost arts is probably what he's referring to, including types of load bearing cobblestone construction.

An example that comes to mind is a brick townhouse nearby that was struck by a car and part of a structural brick rounded wall collapsed. It remained that way for many years because the owner simply couldn't find a mason that knew how to rebuild it.

Where will you go?

Even if Earth is exhausted of all its resources, the two things that Earth will continue to have, is (1) gravity at 9.8 m/s^2, and (2) a magnetic field.

It’s possible the magnetic field can be eliminated, if the planet’s core turns solid, in which case, we all need to go underground. But the planet will continue to get sunlight, and it will continue to have gravity.

These 2 key things, are found nowhere else in this universe. Except for Venus, which has a similar gravity, but it’s so hot, the surface can melt lead.

And we still don’t yet have a high probability of the closest extra-solar planet, that can sustain life with earth-like gravity and a magnetic field.

Even an asteroid that eliminated the dinosaurs was still not able to eliminate life on Earth. Why? Because of this water world, its gravity, and its magnetic field.

So the best solution to having a backup for humanity, is to probably (1) dig a hole deep in the ground, and establish a deep mine colony there. Or (2) build a deep ocean habitat, and establish a deep marine colony there.

That way, if an asteroid hits land, then the deep ocean colony can survive. Or if the asteroid hits the ocean, then the deep mine colony can survive.

I agree with this, which is why the idea of fusion energy is both exciting and terrifying (and why governments may even be hesitant to disclose breakthroughs). In the theoretical ideal, fusion energy would provide such a surplus of energy that it could rewrite borders and trade deals overnight.

From working at all, sure, but how big would those rockets have to be?

Rocketry doesn’t exist just because some idealists wanted to go to space. It exists because governments wanted to invent new ways to bomb their enemies. A V-2 allows you to bomb England from continental Europe (and wasn’t even a cost-effective solution for that); nobody was going to build a Saturn V-sized rocket for that use case, and even if they wanted to, it’s not clear that they could get it to work without lots of testing with smaller prototypes.[1] Compounding this issue is that, on this hypothetically larger planet, whatever enemies you’d want to bomb in the first place could also be much farther away! Whereas on Earth it’s not hard to reach any other point on the planet; a little over a decade from the V-2 we had ICBM’s.

[1] By way of analogy, Lofstrom loops are theoretically much more efficient than rockets, but to find out for sure we’d have to build a full scale example, and that would be extremely expensive even if we didn’t run into any unforeseen cost overruns or delays—which we inevitably would because this would be the first time we built anything like this. It would be like ITER except at least ITER has a practical application if it works.

> often convey a deep sense of hubris

I meant what I said as a reply to parent's assertion about resource consumption and unsustainability, so I don't know, maybe it is hubris.

But I feel like it's safe to assume that the vast majority of people don't really think about how their behaviours in respect to consumption impacts the world as a whole. I'm probably not educated enough in this respect either, but I am pretty sure that following a philosophy where owning less things is better than owning more things is preferable.

Yes, I know that in the big picture of the environmental issues the planet has it is not individual contributions that have the largest impact. However the companies that do, are the ones that hold the same "uneducated" people in decision making positions.

So, that's why I concluded that better environmental education as a whole would mean less need for humans to flee to other planets. If I'm wrong and that's not the case, then it means the Wachowkis were right, humanity really is a virus.

Coming to your other point:

> I think they mean it in the 'species' sense:

If parent meant it like you're suggesting, it's not by saving the whole species as it is now (ie, 7+ billions of people) but as descendants of the lucky few that get to leave Earth. That in my opinion is definitely not the same as saving the species.