> For a few decades (assuming fixed rate), until the population doubles and we'll be overpopulating two planets.

By the time mankind would be able to populate Mars, we would've probably have no effort to just build cities in space.

The amount of steel, and aluminum you can make just from moon, and earth is enough for billions of space cities.

Astronauts on the ISS have proven that living in space even for a few months is extremely unhealthy. Seems like that might be a harder problem to solve than building the space cities.

How much of that is just because it’s not spinning/ no gravity? That plus better shielding should help right?

High energy cosmic rays are tough to shield against. On Earth there’s 60 miles of atmosphere, in space you would have to reproduce that with several meters of dense material.

What if you were orbiting a planet always on the opposite side of where the Sun is?

Cosmic rays aren't caused by the sun. If anything the heliosphere shields us from some of them.

The view would suck.

You'd have to pack nuclear reactors to provide power (though that's a given for any kind of serious activity in space anyway), and your scientific and operational capabilities would be limited/made difficult by the lack of sunlight.

what about food? wouldnt that be the limiting factor?

If you can lift exatons of steel into space, you can probably already afford to solve the problem of direct synthesis of all, and every fertilizer, and probably nearly every other chemistry process just by throwing more energy at it.

Raw materials will be cheap in space, once we crack orbital manufacturing.

Plants convert light to food, you don't even need anything from science fiction.

You still need carbon; plants just extract it from the air using light.

Reuse CO2 and human waste. You need some income, as reuse can't be perfect, but I think it's manageable.

Population growth is predicted to effectively stop by 2100.

https://www.pewresearch.org/fact-tank/2019/06/17/worlds-popu...

Resource consumption is the relevant metric.

> We need to either slow down on the exponent - not just population

We did this. Population growth is slowing rapidly.

Sure. But you even quoted me saying not just population, which is the key point. Stabilizing population doesn't buy us much if the market - and thus resource exploitation - is still growing exponentially.

Economic growth doesn’t imply increased resource use. Actually it’s more likely to be the opposite - growth is more likely to be in services and moving to electricity, which is renewable. Our use of many nonrenewable resources has peaked and gone down as population has gone up.

> Our use of many nonrenewable resources has peaked and gone down as population has gone up.

Our use, or the growth rate of use? It's good when the latter goes down, but we're not out of the woods as long as it stays > 1.

> Actually it’s more likely to be the opposite - growth is more likely to be in services and moving to electricity, which is renewable.

Most services have consumables, and electrification of everything is very production-intensive. And while digital services may be growing faster than manufacturing these days, manufacturing is still growing.

Yes, in theory, we can have economic growth without commensurate manufacturing growth, but I think we're still couple abstraction layers short in our economy before we could think about running it completely on imaginary things.