For the longest time growing up with Peak Oil and other such dire predictions, I assumed humanity had just about peaked, in terms of industrial-technological might and capacity to influence its environment. So, just like most deadly diseases are self-limiting due to their virulence, so would we eventually flare out and extinguish ourselves.
Later, as I adopted more of an engineering, back-of-the envelope Fermi calculation approach to things, I began to change my view on that. I have come to think that there are enough nuclear, solar and potential fusion power sources here on Earth to last us for centuries. Out there, in space, there are truly cosmic amounts of resources lying about the solar system, just waiting to be plucked by our greedy little hands, unspoiled worlds waiting for our buldozers, and perhaps juiciest of all, the fount of energy that is the Sun, and virtually every Joule of it is wasted, when we could turn it into plastic toys and telenovelas. Like a cancer cell on a pure sugar diet, we can spread and spread and spread.
So this got me thinking. Is there an ACTUAL hard limit to growth? When would we hit the walls of the Petri dish?
From where I'm looking, you can't even see the walls. For instance, assuming 3% year-on-year growth (the high end of our past historical average), 1000 years linearly into the future, I would get a power output (or GDP, whatever you want to call it) that is 6 thousand billion times larger than today's. Sounds insanely high, right? That's about 1% of the yearly power output of our Sun. 1% of a single-star single-layer Dyson sphere... And there are a hundred billion stars, and a hundred billion galaxies. That's a lot of Agar-Agar to spread in.
So, is there a hard limit to growth, either here on Earth, or out there in Space? What is it? To make it more specific, you can if you wish restrict the scope of the question to 1000 years, but if you want to delve farther into the future, I'd love to hear it.