In the prologue in The City and the Stars by Arthur C. Clarke, it reads

Since the city was built, the oceans of Earth had passed away and the desert had encompassed all the globe. The last mountains had been ground to dust by the winds and the rain, and the world was too weary to bring forth more. The city did not care; Earth itself could crumble and Diaspar would still protect the children of its makers, bearing them and their treasures safely down the stream of time.

They had lived in the same city, had walked the same miraculously unchanging streets, while more than a billion years had worn away.

Now, with Lys being still alive, and all the things that Alvin and Hilvar see, the planet is not in as dire a state as the prologue says, but what would happen to Diaspar if it was? If the Earth, over time, did crumble away into dust, would Diaspar be all that was left? Would it just be a floating bubble in the universe? It's built on Earth, so does Diaspar actually need Earth to survive?

In universe answers, if possible, please. I refuse to believe anyone who says that Arthur C. Clarke didn't think it through and that it's a hole in the story.

  • I'm not going to answer this directly, but you might want to include something about the effects of the loss of gravity on Lys if Earth were destroyed - I don't know whether that belongs in the question or the answer, though.
    – Tango
    Commented Dec 16, 2011 at 19:35
  • @TangoOversway IIRC it was well established that before humanity had dwindled away to Diaspar and Lys, we had fairly well tackled artificial gravity, inertial control, etc. And the fact that the city stood without decay for a billion years seems to imply an atomic-level control of matter - either some form of "stasis-field" to preserve things or nanite-style maintenance equipment. I suspect Diaspar would survive without Earth, but I need to skim the book a bit before committing this to an answer.
    – Saiboogu
    Commented Dec 16, 2011 at 20:16
  • @Saiboogu: I would agree with you, for the most part, but even with the atom-level control of matter they had, gravity could still be an issue if structures were built to withstand stress and "push" upward, like, say, an arch. They might have known and understood artificial gravity, but that doesn't mean they built it into the city and, at the start, obviously, the residents would have no idea how to do it. There was also the opening Alvin went through that may not have automatically sealed itself.
    – Tango
    Commented Dec 16, 2011 at 21:47
  • 1
    @TangoOversway All fair points and part of why I only commented so far.
    – Saiboogu
    Commented Dec 16, 2011 at 22:05

3 Answers 3


The city was equipped with Eternity Circuits, which maintained almost every structure in it as it had been originally designed and built. Since

the early humans who left Earth had mastered space travel, we can assume that the technology exists to generate gravity and anything else that the Earth may provide (the Master's ship definitely had artificial gravity).

I believe if the Earth were to disappear, Diaspar would simply become a space station. It clearly has an infinite power source. The opening through which Alvin exited the city would seal (it's hard to imagine a lack of such fail-safes for a city built to last a billion years).


Diaspar is maintained by eternity circuits designed to prevent the city from eroding and decaying over the millions of years. As I understand it, eternity circuits are actually systems based on incredibly advanced nanotechnology paired with a super AI, simply called the Central Computer in the novel. With a limitless source of energy (no details about this in the book if I remember correctly), Diaspar would continue to exist and protect its inhabitants even in outer space.

A few relevant quotes:

"Diaspar might be held in a perpetual stasis by its eternity circuits, frozen forever according to the pattern in the memory cells, but that pattern could itself be altered, and the city would then change with it... "


"... Like Diaspar itself, like this robot - like everything that the builders of the past considered really important - it was preserved by its own eternity circuits. As long as it (the Master's ship) had a source of power, it could never went out or be destroyed; the image carried in its memory cells would never fade, and that image controlled its physical structure."

For those who don't know, this book was written in 1956 but the tech level as depicted by Clarke is way beyond what we can achieve at the moment. I really recommend SF fans to read this wonderful book!


Eventually the sun will get Diaspar. The planet will be engulfed by the sun. If Diaspar were going to relocate, it seems like the city inteligence would have done so a few million years ago.


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