[BoppreH]

If your signal is "transparent" enough go through so much rock and iron without being absorbed (like neutrinos), you'll have a hard time capturing it on the receiver side.

[dcminter]

Well, OPERA was 700ish km, but had Cern at one end. If one has this as the sole goal and wanted to do it real-time over 12,000km is it "engineering-possible" vs "theoretically-possible" ? My guess is that it depends how much money stands to be made ;)

https://en.wikipedia.org/wiki/OPERA_experiment

[estimator7292]

Basically just aim you accelerator at any neutron detector.

Problem is you'd drop more packets than IP over pigeons.

[dcminter]

I think you're confusing neutrons and neutrinos. Firing neutrons at the floor will definitely give you a very radioactive floor.

[Hikikomori]

Does carrier pigeons have that high packet loss?