## NiAndMe

^z 25th March 2024 at 5:15pm

Chapter V of my dissertation appeared in Physical Review as a joint paper with Wei-Tou Ni of the National Tsing Hua University, Taiwan. It was a slightly-messy theoretical exercise in exploring the "natural" coordinate system which might be used by a gravitational experimenter. In 1976, at the suggestion of Kip Thorne (my thesis advisor) I had begun studying the local coordinates of a person who was both rotating and accelerating. After a few months of ugly calculations I came up with some new, publishable equations. In the summer of 1977, when Ni visited Caltech, we discovered that we were both in the process of writing up identical results on the same subject! So we decided to publish together.

Such a coincidence isn't unusual in science; open questions are often "in the air" and several people are likely to work on solving them at once. In this case the synchronicity was even less startling. "Victor" Ni had been a grad student of Kip's a few years earlier, and his research had been in this general area. It was good luck that we met before submitting our separate papers; both of us saved time and potential embarrassment by teaming up.

The topic we addressed was a simple one: imagine trying to do an experiment on a roller-coaster. You would see all sorts of weird effects, seemingly strange forces and accelerations, just because your apparatus is being twisted and pushed about. You would have to compensate carefully for those pseudoforces in order to actually measure something independent of your motions.

Well, in real life hardly anybody works in free fall. The Earth rotates on its axis and revolves around the Sun. So do we. The ground shakes and tides tug. Our laboratory equipment is turned and shoved around relative to the "fixed stars" — and therefore experiments see pseudoforces, centrifugal/centripetal and Coriolis accelerations that wouldn't be there if we were floating in space.

Easy to say — but it's nontrivial to compute the precise effects, accurately, taking into account special and general relativity. But that degree of precision is needed in order to analyze delicate gravitational-wave detectors, where sensors are striving to pick up signals of one part in a trillion trillion or less.

Wei-Tou Ni and I hacked through the algebra and found 14 different types of pseudoforces. There's the usual inertial acceleration plus the well-known Doppler (a.k.a. "gravitational") red-shift correction. (Physical processes "overhead" run more quickly than one would expect; light gains energy and oscillates faster as it falls downhill.) Then there are special-relativistic and red-shift corrections to those terms. Next the Coriolis acceleration appears; it's the same force that makes hurricanes swirl counter-clockwise in the Northern hemisphere. The centripetal (or centrifugal) force is in there too. Beyond that, we found "electric" and "magnetic" gravitational effects, analogous to those that work on charged particles but arising from inhomogeneous gravity fields (tides, based on the Riemann curvature of spacetime).

Quite a thicket of complexity, but reasonably straightforward to measure and neutralize in an experiment — once one knows what to watch out for. Our paper appeared in the 15 March 1978 issue of Physical Review D. It was titled "Inertial and gravitational effects in the proper reference frame of an accelerated, rotating observer", by Wei-Tou Ni and Mark Zimmermann. Almost certainly, fewer people read it than have already read this ^zhurnal. Such are the laurels of science.

But more amusing, perhaps, was a mundane factor that arises in every joint publication: Whose name comes first on the paper?! Victor Ni was a bit shy about asking me, but via Kip he requested permission to be the lead author. I happily agreed. Ni was (slightly!) my elder, an established scholar but still struggling to get tenure and respect; I was already thinking about moving on to work outside of physics. It was an easy and collegial decision to appear last. (Besides, with the name "Zimmermann" I was used to it!)

In other cases, alas, name-order is far more controversial an issue. I was a minor co-author on a paper (which shall remain otherwise unidentified) where the "natural" solution, alphabetical listing of the players by their surnames, would have hidden the magnitude of contribution by one of the authors. The person who came first alphabetically deserved the lion's share of credit for the work. How to signify that fact?

I was in a dead heat for last place among the co-authors, deservedly so given the minor nature of my involvement. The Solomonic solution: move "Zimmermann" up a notch — making it obvious by the incongruity of that out-of-place "Z" that the author list was not alphabetized, but signified the proper share of glory. Silly-sounding, to be sure, but such subtle games keep blood from being shed in the groves of Academe every day. When ideas are the coin of the realm, getting proper credit is the only route to wealth.

(see KipTheDragon, RelativityPlusAstrophysics, CherishedBeliefs, PulsarWaves, SoftOutsideCrunchyCenter, and SpinningSources for other ^z thesis work)

Thursday, April 27, 2000 at 17:53:17 (EDT) = 2000-04-27

(correlates: Subway Agreement, ErdosNumberz, ToastyOvaries, ...)