With a long enough time horizon, the GP consideration ("If we continue to grow GDP (~energy consumption) at about 1%/y, we’ll boil oceans in 400 years.") will still come true even if expanding in space. A sphere expanding around earth at the speed of light grows quadratically in the outer boundary and cubically in volume, and will be overcome eventually by any exponent > 1.

I'm pretty convinced that increasing human activity so much to increase the background radiation to 373K is never going to happen, the point is more that any exponential energy growth eventually can't continue.

In a way though it's already happening, the GDP ~ energy consumption equivalence from the GP assumption does not hold (https://data.worldbank.org/indicator/EG.GDP.PUSE.KO.PP). We'll just keep inventing ways for the GDP number to keep growing exponentially in questionable ways for the system to keep going, until we can't anymore.

the dataset is interesting, thanks for linking to it. the relationship is for now linear, which I believe doesn't invalidate the point that you and I both make that exponential is not sustainable. the GDP-energy consumption decoupling must also become exponential, which I lack vision for how to achieve.

Hand-wavy predictions like this scare me - it suggests people don't understand space travel or the distances involved at all.

Sure, if you think of the Earth as a game of SimCity plus Kerbal Space Program, these discussions about exponential growth are interesting. However, they miss the part where the intervening 30-100 years become literal hell on Earth while space travel ramps up.

I started my career at NASA. I'm working on an asteroid mining startup. I'm well aware of the vastness of space :)

The GP said 400 years. That's the time since the age of exploration until now. That's a vast era of time, and exponential technology development goes both ways.