6 ms·

No, there is only a limit on an order of events that holds across all possible reference frames. If you define a fixed reference frame, there is no problem. Pre

No, there is only a limit on an order of events that holds across all possible reference frames. If you define a fixed reference frame, there is no problem. Presumably, they define the same reference frame as whatever UTC uses.

6nf 8y ago
The reference frame is the location of the server. Whoever is closer to the server has an advantage because someone half way around the world will take an extra 50ms or whatever to submit their order.
- perl4ever 8y ago
  Syncing clocks implies to me that you're not just executing trades in the order of arrival. You're trying to determine which trade "actually happened" first. Hence the doubt I had about the relativity of simultaneity. Incidentally, I think I was mistaken about "general" relativity being applicable. This is probably just a "special" relativity problem.
  - 6nf 8y ago
    That's not how it works. First to get their order to the server wins.
perl4ever 8y ago
I was reading something that says UTC is based on a non-rotating inertial reference frame, whereas locations of actual people are of course in reference frames co-moving with the Earth. "UTC is a valid global time for the "Earth-Centred Inertial Frame" (ECI) in which Earth spins, because inertial frames do admit a global time. UTC is not a global time for the "Earth-Centred Earth-Fixed frame" (ECEF) in which we live our daily lives, because the ECEF is a rotating frame in the non-relativistic sense of the word, and so cannot support a global time coordinate with the same meaning as the time used in an inertial frame. That is, when two events have the same UTC time, they are simultaneous for all observers at rest in the ECI, but they are not necessarily simultaneous for any observers in the ECEF, and in fact those two events can be off by as many as 30 nanoseconds in the ECEF." http://math.ucr.edu/home/baez/physics/Relativity/SR/rotatingCoordinates.html http://math.ucr.edu/home/baez/physics/Relativity/SR/rotating...

6nf 8y ago

The reference frame is the location of the server. Whoever is closer to the server has an advantage because someone half way around the world will take an extra 50ms or whatever to submit their order.

perl4ever 8y ago
Syncing clocks implies to me that you're not just executing trades in the order of arrival. You're trying to determine which trade "actually happened" first. Hence the doubt I had about the relativity of simultaneity. Incidentally, I think I was mistaken about "general" relativity being applicable. This is probably just a "special" relativity problem.
- 6nf 8y ago
  That's not how it works. First to get their order to the server wins.

perl4ever 8y ago

I was reading something that says UTC is based on a non-rotating inertial reference frame, whereas locations of actual people are of course in reference frames co-moving with the Earth. "UTC is a valid global time for the "Earth-Centred Inertial Frame" (ECI) in which Earth spins, because inertial frames do admit a global time. UTC is not a global time for the "Earth-Centred Earth-Fixed frame" (ECEF) in which we live our daily lives, because the ECEF is a rotating frame in the non-relativistic sense of the word, and so cannot support a global time coordinate with the same meaning as the time used in an inertial frame. That is, when two events have the same UTC time, they are simultaneous for all observers at rest in the ECI, but they are not necessarily simultaneous for any observers in the ECEF, and in fact those two events can be off by as many as 30 nanoseconds in the ECEF." http://math.ucr.edu/home/baez/physics/Relativity/SR/rotatingCoordinates.html http://math.ucr.edu/home/baez/physics/Relativity/SR/rotating...