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Conversation with Canterbury Group
G. Hathaway
This report is a summary of the
telephone conversation between Hathaway (GDH) and members of the
Present in NZ were Prof. Phil Butler (x 6541), Clive Rowe (?), Dr. Bob Hurst (x7613), Rob Thirkettle (x6510).
Subsequent to my telephone call (left message with Phil Butler) of >1 wk ago, the NZ group (NZ) had googled Earthtech.org and were up to date on what we were attempting to do. Bob Hurst is semi-retired, Phil Butler is still on staff, and Rob Thirkettle is a technician working with UG-2 (the large RLG). I didn’t get Clive’s affiliation.
NZ started with the possibility, (“startling but unlikely”) that Martin Tajmar (MT) may have seen some effect that might be amenable to UG-2 investigation, but first they tried the simpler FOG approach (which failed). They had speculated much earlier about the possibility that UG-2 could be used to detect Lense-Thirring dragging and so had invested some time considering the “classical L-T effect”. They had some background in LHe physics but had to do some work to prepare for this type & size of LHe experiment. As they proceeded with their experimental design they recognized that MT’s experiment and theoretical underpinning was changing over time. However their approach was still based on MT’s apparent L-T frame dragging enhancement.
The FOG used in their initial FOG runs was of “marginal sensitivity” although it could detect earth’s rotation at a S/N ~1 after about 1 sec of data taking & low pass filtering. They could not immediately give model number/manufacturer data on the FOG (recall the experiment was performed over 1 yr ago). Raw data from the FOG runs still exists and can be made available if really necessary. The main problem with the FOG results were that NZ were not sure that the Pb mass was always in its superconducting state (ie ~ 7K) during rotation. This was during the period they were “getting their feet wet” in LHe experimentation at this scale. They are much more certain that the Pb was superconducting in the UG-2 experiments. Therefore the FOG data may contain systematic errors/artifact and they therefore considered it not worthy of publication. [Besides, they had the world’s most sensitive RLG so why continue with a FOG? - ed] Nonetheless, they saw no evidence of frame-dragging with the FOG.
They suggest experimenting with our FOG to see if earth’s apparent rotation direction reverses with reversing the orientation of the FOG [which, I believe, Scott has already done] plus aligning it with earth’s spin axis to maximize the reading – all to check whether it is OK.
Regarding the issue of using the relatively huge area of UG-2 versus the small size of the Pb mass, they invoke the assumption of 1/r3 fall-off of the dipole field and state that although they got the Pb as close as physically possible to an arm of UG-2, they still recognized a possible “geometric dilution” of the effect due to the area mismatch compared to using a FOG of smaller “detection” area. NZ suggest they should have gotten an effect with the FOG (assuming the Pb was <7K).
Their UG-2 experiment was hampered by the problems of getting LHe & LN down near the UG-2 and their supply of LHe was limited to an old, low capacity (~6 l/da) in-house liquefier. They used around 20 – 30 l of LHe per experiment from a 50 l storage dewar.
The raw data are available for the UG-2 runs, both during the LHe experiment as well as before the LHe was introduced.
Originally NZ changed direction of Pb rotation every 30 seconds but found this was too hard on the drive motor. Then they went to the 5 minute reversal. There was lots of microseismic noise on an approx. 30 sec time scale which also prompted them to switch to the longer time. They had to low-pass filter due to the 0.2 Hz noise.
Apparently NZ only did 1 “run” at the 5 minute reversal time scale. I did not ask what a “run” constituted.
With reference to Fig. 5 of their report (showing 2 slopes of Sagnac deviation vs rotational vel.) as far as they are concerned, the experimental slope, determined by regression, is ZERO (to within their experimental error), but appears non-zero only due to noise. All NZ agree that the results are NULL. Thus they would need a great deal of convincing and additional evidence before they would revisit the experiment. They are not motivated to consider it primarily due to their concerns that a reasonable theory has not been sufficiently established.
They are interested in following our experimental attempts and, more importantly, are quite willing to put the UG-2 at our disposal should we make a convincing case for its use!
They will review such data as they have and send us a summary for our perusal.