I'm currently working on a number of artificial space megastructures. Recently, I've been trying to work out a couple of things to do with alderson disks:

  • What a person on the surface would see (ie, there would be no horizon, so what would they see?)
  • How sunsets/sunrise would like if the star was made to bob up/down.
  • How big the ring would need to be in order to support multiple extremes (like hot deserts closest to the star, and cold arctics on the outside)

In terms of technical issues, the civilization that has made it is practically a Type-3 (Kardashev), with access to some technologies that are beyond even their understanding.
As for technical specs, I haven't decided on how large the radius should be, but for thickness I think something like 500km seems doable (roughly 50km of surface material/earth, and 50km of various subterranean installations and maintenance stations, and the other 400km would mostly be structural. So far, I think I will make the disk only one-sided.

EDIT: Summary Question: What would the world look like from the point of someone on the disk; what would the horizon be like, and how they would experience sunset/sunrise?

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    $\begingroup$ Welcome to WorldBuilding Amon! If you have a moment please take the tour and visit the help center to learn more about the site. Currently I don't see a question here, just a statement that you are working on three different problems. Could you please edit your question to make it clear at which point you have a problem in your creational process that you need help with? And please note that you should ask one question at a time. If you want to ask multiple questions about your scenario you should try to ask one at a time, wait a few days and write the next one. Have fun! $\endgroup$
    – Secespitus
    Commented Jun 19, 2017 at 7:54
  • $\begingroup$ I think what you are calling "width" is actually its thickness. If so, you can edit your question to fix this. $\endgroup$
    – a4android
    Commented Jun 19, 2017 at 12:42

1 Answer 1


What would the person on the surface see

According to this article one would see kind of an horizon due to the light bending (similar to gravity lensing)

How sunrise/sunset would be like

The sun would never rise far above the horizon nor would it sink far below. It would resemble a cycle of twilight/night. If you increase the amplitude of your bobbing star you'd get a better defined day/night cycle though still the sun wouldn't rise very high unless you decide to go for a very strong star bobbing.

How big the ring needs to be to support multiple extremes.

This is where your proposed concept of 500km radius will prove problematic. According to wikipedia, the anderson disk's climate is dictated by distance away from the sun. So to get the extremes you desire you'll have to make the thing huge.

I hope this gives you the information you desire.

  • $\begingroup$ I meant the width as in the thickness of the ring, as in the ground's thickness. My bad... $\endgroup$
    – Amon
    Commented Jun 19, 2017 at 8:23
  • $\begingroup$ @amon You're working with meta-materials. To calculate the mechanical stress the thing has to endure is a massive task but the thickness of the thing can be anywhere from a millimeter to several kilometers. It's entirely up to you whether the material you want to use for the ring can endure the forces it has to deal with, with the structure you have in mind. My recommendation is to not get too technical for story purposes. $\endgroup$
    – Hyfnae
    Commented Jun 19, 2017 at 8:59
  • $\begingroup$ My thoughts exactly. I can easily just not explain it: makes the disk seem more mysterious anyway. $\endgroup$
    – Amon
    Commented Jun 19, 2017 at 9:17

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