[time-nuts] Neutrino timing
ws at Yahoo
warrensjmail-one at yahoo.com
Mon Oct 24 22:22:01 UTC 2011
I see how your comments apply to the later reported test but not so much to
the US experiment IF one accepts as accurate the statements that Marvin
Marshak posted which said in part;
"This U.S. beam has been used to make a similar measurement,
but the GPS timing equipment that was used resulted in an estimated
uncertainty of about 70 ns
in the neutrino time-of-flight, too large to test the recently reported
I am one of a group of physicists working with the neutrino beam in the
Are you saying that the 70ns uncertainty statement was not due to Just the
time of flight as he stated?
Or did he mean "error" and Not "uncertainty" ?
What I also find interesting is that the US test "Uncertainty" was about
the same number as the others "reported results"
.More unbelievable to me that they have the skill and money and a 100 people
envolved for 5 years in this to shoot neutrinos and hit a target that far
away, but can not measure relitive time at two known points any better than
There's got to be something missing and more to this story than that.
On 10/24/2011 10:02 PM, Tom Van Baak wrote:
>> I have a more basic time-nut question. Why is it a problem at all?
>> How can the time uncertainty between two known and fixed locations be
>> that large?
> In principal it's simple. But the logistics of equipment and cables
> and rooms and labs is quite complicated. Read a few documents
> at http://www.ohwr.org/projects/cngs-time-transfer/wiki and you'll
> get a sense. All the numbers should add up. But it didn't.
> The stakes are really high so everyone is double checking their
> piece of the pie more carefully than a moon landing.
I think I have essentially all the equipment needed for both sides.
Double frequency receivers with antennas, counters, cesiums etc. Lacking
What I don't have is the time to build two complete sets with software
etc. Not that I am not trying, as being the time-nut that I am.
I think a few other time-nuts such as Tom would also be able to provide
the equipment. Again the time to build a pair of functional sets.
>> If they know they have a 70ns uncertainty in time, that would suggest
>> that their time measurement is known to be varying at one or both places.
>> Is this just from a spec or do they see a true variation in time
>> between something, and if so compared to what?
> It's not varying. It was a 3 year experiment and there appears to
> be a fixed discrepancy of 60 ns in time or 18 meters in distance.
> Remember it's not certain that the error is in the timing at all; it
> could just as well be in the distance. Or in the start trigger, or the
> stop signal, etc.
Just re-validating the distance, time and time-distribution would be fun
>> Is this time difference or variation between several difference timing
>> devices at each end or is it variation when compared to time of flight
>> of the supposedly same neutrinos?
> The latter.
>> I can not say anything about the accuracy of my absolute time, but the
>> difference and uncertainly comparing the phase difference between
>> different external Osc Tbolts at the same location is way way under 70ns.
> Yeah, this is true for most GPS receivers, which is why it's hard
> to imagine the problem has anything to do with their GPS timing
> set up. Their error budget is a couple of ns, stable over years,
> which is why they use atomic clocks along with dual-frequency
> carrier-phase receivers in common view, and calibration visits by
> more than one national UTC lab, etc. It would appear they really
> did their homework.
> It's unfortunate that GPS even got brought into the whole neutrino
> situation because GPS brings with it all sort of UTC and physics
> and relativity baggage. The experiment could have done relative
> timing without using GPS at all. It's not about GPS; it's about having
> synchronized clocks at two locations. There are many ways to
> achieve that. And when the stakes are high, then one must do it
> in multiple independent ways.
This is also why the preliminary PTB report is a bit unfortunate, as it
leaves bits and pieces out which the professional should need, but also
the larger picture of bias compensations intended for the
non-professional on GPS based time-transfer systems. There are many
enhancements to be done to be able to present to physics people. The
necessary backlog of articles to read is quite high.
> So that's why there's talk of direct fiber links, radio links, satellite
> links (non-GPS), traveling clocks, etc.
Indeed. PTB should have used a traveling clock alongside their GPS
>> Sure lots of BASIC things to do to make sure the two Tbolts are set
>> the same so that their oscillator's phase do they agree, such as using
>> the same type antenna and same cable and length, and getting the
>> antenna's location correct, etc, etc,
>> but basic stuff and seems like if using the same basic GPS system at
>> two different locations, what would the additional problems be except
>> to make sure both ends are syncing on the same 100ns 10MHz cycle.
>> I was under the impression that getting down to ns uncertainly
>> differences (and staying there) at theses distances is old stuff using
>> common view GPS.
>> So what are the problems that cause their large timing uncertainty?
> Yes, it is very old hat to those in the timing community. It just takes
> time for the rest of the physics community to catch up. Many of us
> amateurs have better timing at home than most physics laboratories.
Indeed. It's strange that a few private time-nuts have the capability to
do this, but it is fully possible. There is a few things like recording
RINEX data, get it post-processed alongside some other measurement stuff.
So, to come back to the original question, I agree with TvB that the way
to go would be to get the assistance from NIST. I think we are a few
time-nuts that would be "happy to assist" as a fun treat. :)
However, I think that one should combine traveling clock (traveling both
directions) with double frequency GPS receivers exercise. It would
assist in providing consistency.
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