While reading Death's End, I realised that there seems to be a big problem with the concept of a domain.

My understanding of the concept of escape velocity is that it is the minimal necessary speed for an object to escape a gravity well with no further push. Doesn't this mean that: there is nothing preventing a ship with a constant push from its engine from leaving the Black Domain? Especially when distortion drive ships appear to be getting constant push in order to move at lightspeed.

Am I wrong when saying this? Did I misunderstand the protection that a black domain gives?

  • It is also interesting in terms of that "3D to 2D " weapon - how can anyone protect against such a thing (as I understand - it will eventually consume whole galaxy?) Commented Feb 27, 2023 at 17:42
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    Ee... we generally don't allow real-world physics questions, even about fictional works. You can ask about how it works in the work itself.
    – FuzzyBoots
    Commented Feb 27, 2023 at 17:42
  • @FuzzyBoots In this case, I assume Physics.stackexchange would be the place to ask about this? I know double posting is usually frowned upon. Is that a case where I should close and ask there?
    – 3C273
    Commented Feb 27, 2023 at 17:44
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    @FuzzyBoots I think question is just in terms of that book. And I think there are lots of points, where it is better not to talk about phisics ))) Commented Feb 27, 2023 at 17:45
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    This answer was closed because you were asking about the real world implications of an entirely fictional concept. I've edited it so that the question can be answered inside that same fictional universe.
    – Valorum
    Commented Feb 27, 2023 at 18:16

1 Answer 1


You can certainly escape from a black domain, but to do so would take an inordinate amount of time. A ship moving at lightspeed would cross from Earth to its moon (approx 384400000m) in about 32033333 seconds, or roughly a year. Traveling from a habitable planet like Earth in the centre of a solar system to its outskirts would take millions of years.

But if they’re disturbed, they’ll spread very rapidly. A death line of this size can expand to cover a region the size of a solar system. Scientists call this phenomenon a death line rupture.” “Does a rupture make the speed of light zero in the entire region?” “No, no. After rupture, it turns into a regular trail. The speed of light inside goes up as the trail dissipates over a wider region, but it will never be much more than a dozen meters per second. After these death lines expand, this entire system might turn into a reduced-lightspeed black hole, or a black domain.… Let’s go.” Cheng Xin and Guan Yifan turned toward the shuttle and began to run and leap.

  • Thank you for the edit to the question and for the answer. Now that you mention it, I think I remember a line about escaping a domain being physically possible, but impractical. I've upvoted because it at least helps me.
    – 3C273
    Commented Feb 27, 2023 at 18:32

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