> And in space, there is plenty of space for everyone. Assuming that we can travel at the speed of light, humanity can expand into a spherical region of space

> And in space, there is plenty of space for everyone. Assuming that we can travel at the speed of light, humanity can expand into a spherical region of space where the radius grows at a constant rate. That is to say, under the most optimistic assumptions, expansion is limited by a cubic growth curve. That is fundamentally incompatible with exponential population growth. Of course, the constants elided in the analysis above are enormous, but it's a limitation that a galactic species would eventually butt up against.