I’ve always felt that the greatest and most beautiful stories in the history of humanity were not sung by wandering bards or written by playwrights a… - Liu Cixin

But more commonly, the technique is used to construct the equivalents of pits and city walls. Some reduced-lightspeed belts are large enough to traverse an entire arm of a galaxy. In places where the stars are dense, many reduced-lightspeed black holes can be connected together into chains that stretch for tens of millions of light-years. That’s a Great Wall at the scale of the universe. Even the most powerful fleets, once trapped, would not be able to escape. Those barriers are very difficult to cross.

The stern of the ship faced the Solar System, where the sun was by now no more than a yellow star just a bit brighter than the rest. The peripheral spiral arm of the Milky Way lay in this direction, its stars sparse. The depth and expanse of deep space exhibited an arrogance that left no support for the mind or the eyes. “Dark. It’s so fucking dark,” the captain murmured, and then shot himself.

Earth’s suitability for human life was no coincidence, much less an effect of the anthropic principle, but rather was an outcome of the long-term interaction between the biosphere and the natural environment,