I think that Finance is indeed the obvious candidate. In neutrino experiments we've gotten pretty good at synchronized clocks with nanosecond resolution. Alth

I think that Finance is indeed the obvious candidate. In neutrino experiments we've gotten pretty good at synchronized clocks with nanosecond resolution. Although (to be fair) we cheat and get some very useful information out of the beam itself, and neutrinos luckily don't travel on optical fibers. I'd be interested to research what it would actually take to provide nanosecond synchronization of clocks in at least a dozen data centers globally, distributed to millions of servers.