Warning: the following contains spoilers for the following works:
The Expanse, S01E01-S03E10. Abaddon’s Gate (Book 3), James S.A. Corey Three-Body Problem &The Dark Forest, Cixin Liu
If you want to try it out, read 5 books and watch almost three seasons of television.
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!!The ring gates are a Dark Forest weapons system. If this was clear to others, and I’m catching up, well, I’m slow. But, I just found out about Brin (1983).!!
Then, I got it. It’s such a well-structured Whatsit.
I feel pretty good about this realization. I’m glad that these works work so well together.
I think its supposed to be more like, the builders sent the protomolecule to terraform any planets with life. They are the filter. Earth escaped because the protomolecule unexpectedly was trapped by Phoebe. I am not sure the builders are hiding so much as paving over everyone else.