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On Tuesday, October 24, 2017, Antoine Pitrou <solipsis@pitrou.net> wrote:
On Tue, 24 Oct 2017 09:00:45 +0200
Victor Stinner <victor.stinner@gmail.com> 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.
From https://en.wikipedia.org/wiki/Virtual_black_hole :
> 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.
\>From https://en.wikipedia.org/wiki/Quantum\_foam :
> 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
See https://blog.cloudflare.com/how-to-achieve-low-latency/
Regards
Antoine.
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