[ntp:questions] Accuracy of NTP - Advice Needed

Danny Mayer mayer at ntp.org
Wed Dec 28 04:36:22 UTC 2011


On 12/27/2011 10:39 PM, Greg Hennessy wrote:
>>> The bottom line is that the only thing that is relevant is how easy it is
>>> to get to a GPS antenna with an open view of the sky.
>>>
>>> Everything else is bloviation.
>>
>> GPS is not used for this kind of thing, they are too inaccurate, so it
>> doesn't matter. They use atomic clocks.
> 
> GPS is indeed used for the measurement of the time of flight in the
> CERN and Fermilab experiments. You should read the papers. They use
> GPS to get time to the order of nanosecond accuracy.
> 

You can read some of this here:
http://www.wired.com/wiredscience/2011/09/scientists-question-neutrinos/

It's not too technical but describes the basic setup. Yes they did use
GPS to get accurate locations of the equipment but it's a rather complex
and hard to get right. They then used Cesium atomic clocks for timing
the events. The calculations you have to do for all this is
mind-boggling and there is a lot of work that has to go into ensuring
that they are accurate and nothing got missed. That's the principle
reason that it's hard to be sure that an FTL result was obtained. There
are lots of scientists pouring over calculations (there were something
like 150 authors listed on the paper published in arXiv. Hords of other
scientists are also analyzing the data.

Danny


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