A friend just asked if there's tech that could let a musician in Hawaii play in realtime w/ someone in NYC. Need <10ms latency for rhythm to feel ok. Quick back of the envelope calculation: NYC-HI is 8000km. Speed of light is 300,000km/s. →Takes light 26ms just to go HI - NYC!

And this would be in a ideal scenario where we could communicate with Hawaii in a straight line, with no switches and routers in between. In real life, communications take many steps to go that route. Plus computers take some time to process the data at each end.

Conclusion: it will *never* happen, by sheer laws of physics. There's absolutely no way anyone on Hawaii, or even much closer than that, will ever be able to play a duet in real time with someone in NY, with the rhythm feeling decent. Sad, but true.

(I should note that nothing can ever go faster than the speed of light. Central tenet of physics. Occasionally there are claims to the contrary but they are quickly disproved.)

Also, obviously there are many tricks one can use to play duets over the internet. The simplest is to have the musician who is accompanying — the pianist, say, in a duet with a singer — keep playing in time while ignoring the other person. That works, but it's not super fun...