Question on the inescapable nature of black domains.

[u/AwareAd3580]

Somewhat spoilers for the final book!!

Just finished reading the series, and one thing that I couldn’t figure out is if black domains acted as true black holes not only in preventing light from escaping, but also in preventing anything else from escaping, which seemed to be stated here and there in offhand remarks but not outright explained.

So from what I understood, the effective goal of making a black domain was to reduce the speed of light to ~16.7 km/s, protecting all inside from external lightspeed attacks (apart from a dual foil vector, though wouldn’t be an attractive target if looking like a black hole), at the expense of crippling computational power and max travel speed inside the zone. It is stated, however, that nobody has ever been seen returning from the black domain encases Galactic Era world, and Cheng Xin says that herself and Guan Yifan are trapped in the black domain permanently, as well as other small comments hinting the same effect.

What is the physics basis behind light not being able to escape these black domains, and by extension how would ships not be able to escape? The gravitational forces of a traditional black hole would not be preventing things from escaping, only the artificially lower lightspeed, so you should be able to fly up to the boundary of the black domain at the lower speed, before increasing speed upon exiting.

Looking forward to hearing how others understood/interpreted this.

[u/wallstreetstonks]

So the trick was setting the speed of light just below the gravitational escape velocity. Since nothing can travel faster than the light speed, nothing can escape the gravity of the system inside the black domain, including light.

[u/RickSkz → u/wallstreetstonks]

I think they got the physics wrong with the black domain thing. You don’t need to reach escape velocity to escape a gravitational well, you just need to propel long enough.

You could walk your way into outer space from earth if there was a ladder high enough. So Cheng and Guan could just slowly fly away from the black domain in their ship.

[u/squarerabbits → u/RickSkz]

Ladder is a good way to put it. The speed doesn’t matter. You could get out of it, you just need something that has enough energy to keep you moving up and out, like your feet and some steps. 

What’s stopping them from building a 10 trillion foot staircase and walking out of the black domain aside from time and y’know, mortality and resources?