I might need a better title (It has now been updated), but here goes, anyway:
I've been considering this for a while now. Suppose we reach a point where we can live for centuries, maybe even millenia, then how do we balance? Even assuming we're as efficient as possible, there's a limit for how much resources we can have, meaning an artificial limit at the amount of people that could exist at any given moment even if we explore what we can of the galaxy and use any avaliable resource. There would have to be roughly the same rate of births and deaths in a stable population.
How would this be achieved? Somehow limiting lifespan, or children, assuming it's available to a majority? Or would this lead to a genespliced, technologically augmented and essentially immortal elite that the poor, unaugmented ones would have no chance of measuring up to? I'm sorry if this has already been considered, I'm very uneducated on the topic. If it has, could someone maybe link an analysis of the topic of lifespans and the like?
This reminds me. An interesting question is, assuming constant mass/person, how long until the speed of light becomes a limiting factor? I.e. given a fixed growth rate, at what total population would the colonization speed be approaching the speed of light just to keep the # humans per cubic parsec of space constant? It is clear that this will happen at some point, given the assumptions of constant birth rate and constant body mass, because the volume of colonized space only grows as time cubed, while the population grows exponentially.
Here is a back-of-the-envelope stab at it. I have not googled it beforehand, because it's fun to do one's own estimate.
Assume 1 habitable planet (10^10 people) per cubic light year, the total colonized number of planets ~ #years^3 after the onset of interstellar travel at near light speed. (I am not accounting for the relativistic time dilation, though the correction should be small, since only a minority of people are in-flight at any given time.) I'm ignoring the factors of the order of 1, such as 4 pi/3 for the volume of a sphere.
Assume 0.1%/year growth rate. This is about 1/20 of the current birth rate. Total number of occupied planets = 1.001^(#years).
The two numbers become comparable after about 30,000 years. This is less than one third of the size of the Milky Way galaxy (in light years). After that, the population growth will be limited by the known physical laws, long before other galaxies are explored.
Other physical angles:
If the economy continues to grow at roughly the present rate, using more energy as it does so, when will we be consuming the entire solar energy output each year? And if this energy growth happens on the surface of the earth and heat dissipation works in a naive way then how long till the surface of the earth is as hot as the sun? Answers: A bit less than 1400 years from now to be eating the sun, and a bit less than 1000 years from now till Earth's surface is equally hot, respectively. Blog post citation!
The same blogger did a foll... (read more)