On Tuesday, October 24, 2017, Antoine Pitrou
On Tue, 24 Oct 2017 09:00:45 +0200 Victor Stinner
wrote: By the way, you mentionned that clocks are not synchronized. That's another revelant point. Even if system clocks are synchronized on a single computer, I read that you cannot reach nanosecond resolution for a NTP synchronization even in a small LAN.
For large systems or distributed systems, a "global (synchronized) clock" is not an option. You cannot synchronize clocks correctly, so your algorithms must not rely on time, or at least not too precise resolution.
I am saying that to again repeat that we are far from sub-second nanosecond resolution for system clock.
What does synchronization have to do with it? If synchronization matters, then your PEP should be rejected, because current computers using NTP can't synchronize with a better precision than 230 ns.
In the derivation of his equations, Einstein suggested that physical space-time is Riemannian, ie curved. A small domain of it is approximately flat space-time.
Based on the uncertainty principles of quantum mechanics and the general theory of relativity, there is no reason that spacetime needs to be fundamentally smooth. Instead, in a quantum theory of gravity, spacetime would consist of many small, ever-changing regions in which space and time are not definite, but fluctuate in a foam-like manner.
So, in regards to time synchronization, FWIU: - WWVB "can provide time with an accuracy of about 100 microseconds" - GPS time can synchronize down to "tens of nanoseconds" - Blockchains work around local timestamp issues by "enforcing" linearity
Regards
Antoine.
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