[time-nuts] Next Generation Time/Frequency Standards May Require Provisions Preventing Vertical Displacement
jimlux at earthlink.net
Thu Sep 30 03:58:36 UTC 2010
Jeffrey Okamitsu wrote:
> More importantly, does this impose an upper limit on data transport speed over
> networks, in particular wireless networks? If and when one produces the network
> technology that would demand the accuracy and precision of these new
> standards, if one object is moving relative to the other, there could be loss of
> data as the moving clock goes out of sync with the stationary one. We know this
> was possible just from special relativity, but motion at "normal" speeds does
> not contribute appreciably at the currently achievable accuracies and
> precisions. However, with the next generation, driving in a car or certainly
> flying in a plane will limit bandwidth. And, of course there's the gravitation
> effect to contend with in the future as well, which could also limit bandwidth.
We already deal with relativistic corrections in GPS data, and also in
deep space navigation (when you're measuring millimeter range
differences in the distance to Saturn and back, everything counts)..
A few years ago, I was working with some folks who were looking at time
transfer among different spacecraft for the Constellation program (e.g.
if you have relay satellites around the Moon or Mars or somewhere, and
you want precision timing to someone on the back side of either (i.e.
they can't see Earth directly). The velocities are high enough that you
need to start contemplating relativistic effect: e.g. at 7 km/s
sqrt(1-v^2/c^2) is about 1 part in 1E10.. If you need to synchronize
events to, say, 1 millisecond out of a day, that's 1 part in 1E11
> As I am thinking about this, does this impose a limit on GPS accuracy and
> precision based on the next gen technology?
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