I thoroughly enjoyed the article “Superfluid helium interferometers,” by Yuki Sato and Richard Packard (Physics Today, October 2012, page 31), but I was surprised and a bit mystified by the closing comment: “Two decades ago no one would have expected that superfluids could find application in geodesy to probe variations in Earth’s rotation, yet the application is becoming a feasible reality today.” I admit I had to refresh my memory by referring to the proceedings of an American Geophysical Union Chapman Conference that I had organized in 1991, but sure enough, among the papers presented was one titled “The superfluid helium gyroscope: An emerging technology for Earth rotation studies.”1 

In 1991 the geodetic community was still refining the new International Earth Rotation Service (IERS), which had debuted in January 1988. As chief of the advanced technology branch of the Geosciences Laboratory at the National Oceanic and Atmospheric Administration and principal coordinator for the IERS very long baseline interferometry center, I was leading the operation of a global network of VLBI observatories to regularly determine Earth’s nutation, polar motion, and variations in rate of rotation.2 Funding constraints limited the number and length of VLBI observing sessions we could do, and I was looking for an alternative way to continuously monitor changes in Earth’s rotation rate with as high a temporal resolution as feasible—hopefully, a few hours or less. Based on information then available, both superfluid and ring-laser gyroscopes appeared potentially capable of meeting our goals. After contacting and consulting with Packard, I initiated a research grant for him to develop a superfluid gyroscope explicitly designed for monitoring Earth’s rotation.3 

Unfortunately, management changes at NOAA after Bill Clinton was elected president in 1992 soon cut off funding for the superfluid gyroscope and, just a few years later, for the NOAA VLBI program as well. I had not kept track of work on superfluid gyroscopes during the ensuing years, but apparently, more than two decades later, the superfluid gyroscope is just now “becoming a feasible reality.” Still, the world of superfluid helium and Packard’s research into it remain undeniably fascinating.

1.
J. C.
Davis
,
R. E.
Packard
, in
Proceedings of the AGU Chapman Conference on Geodetic VLBI: Monitoring Global Change
, NOAA Technical Report NOS 137 NGS 49,
US Department of Commerce
,
Rockville, MD
(
1991
), p.
325
; available at http://www.ngs.noaa.gov/PUBS_LIB/Proceedings_of_AGU_Chapman_Conference_on_Geodetic_VLBI_TM_NOS137_NGS49.pdf.
2.
W. E.
Carter
,
D. S.
Robertson
,
Sci. Am.
, November
1986
, p.
46
.
3.
W. E.
Carter
,
D. S.
Robertson
,
D. H.
Eckhardt
,
G. L.
Shaw
,
EOS Trans. Am. Geophys. Union
73
(
48
),
515
(
1992
).