The ' Theory of simultaneity ' leading to a working ' Ansible ' has long interested me.  In 2015 I thought I might be able to create something like it through what I called ' Split-key-cosmology " - incorporate cryptography into quantum-gravity.  Quantum-mechanics is all quantum-encrypted by default anyway. Later, I found out someone had beat me to this approach. Charles K. Rhodes 2003 - Cryptographic Unification of Mass and Space https://www.worldscientific.com/doi/abs/10.1142/S0217751X03016392?journalCod... 2010 - Cryptographic Theoretical Calculation of the Fine-Structure Constant https://arxiv.org/abs/1008.4537 2012 - Direct Cryptographic Computation of the Cosmological Constant ( PDF ) https://arxiv.org/ftp/arxiv/papers/1212/1212.5941.pdf In a crypto-anarchist universe you might be able to use a primitive pair of ansibles - just placing them in position though would have to take classical timelines to establish.