Quote

"An advanced civilization pushing its ecological limits would, almost by definition, not waste both matter and energy. Yet we see such waste in all directions, as far as we can see spiral galaxies: their spiral arms hold dust clouds made of wasted matter, backlit by wasted starlight... The idea that humanity is alone in the visible universe is consistent with what we see in the sky... Thus for now, and perhaps forever, we can make plans for our future without concern for limits imposed by other civilizations."

~ ERIC DREXLER