The causal set theory is an approach to quantum gravity. But don't understand what it claims spacetime to be made of. What is a causal set? Is it a physical object or just a spacetime event? I read the wiki page and watched a few videos on it, but I still just don't understand it.

  • $\begingroup$ To improve your chance of an answer, you should include research you have done yourself, or cite books you have read. $\endgroup$
    – user146020
    Mar 23, 2017 at 22:48
  • $\begingroup$ @JohnForkosh So, according to the Causal Sets spacetime emerges by a set of events? $\endgroup$
    – 2117
    Mar 24, 2017 at 0:32
  • $\begingroup$ Yeah, as I understand it, which isn't much. It's the causet structure (poset ordering) that's axiomatically fundamental, and everything else emerges (is constructed) from that. But, to repeat, I know next-to-nothing about it (and that's approaching zero from the negative side:) I'd started reading arxiv.org/abs/gr-qc/0106024 mostly just for its first two chapters as an intro to causets. Or you might try arxiv.org/abs/gr-qc/9909075 for an even briefer intro. Personally I found Dou's better. The introductory parts of theses often seem to have meaty-yet-accessible discussions. $\endgroup$
    – user89220
    Mar 24, 2017 at 5:00

1 Answer 1


A causal set builds a universe from just two things: particles and actions. This means that spacetime is made up of particles and each particle has a family history of causes from which it emerged.

Light traveling through space is a set of causally linked particles even though we think of space as empty. Of course, quantum space is actually chock full of vacuum oscillators and so space is already a causal set. All matter comes from other matter and so matter is also a causal set.

The real issue is what exactly does a causal set do for explaining reality. Quantum charge is already a causal set and so making quantum gravity a causal set seems to set the stage for unification of charge and gravity. However, that has not yet been the case.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.