Who	How	When	Value	precision	-log10(precision)
Einstein	speculation	1909	1/140(5)	36 ppk	1.4
Sommerfeld	H th./exp.	1916	1/136(2)	15 ppk	1.8
Spedding/Shane/Grace	H	1935	1/137.4(2)	1.5 ppk	2.8
Cleland/Lamb	µ-/D	1964/53	1/137.038 8(8)	6 ppm	5.2
Taylor	ac Josephson	1969	1/137.036 02(21)	1.5 ppm	5.8
CODATA		1973	1/137.036 04(11)	820 ppb	6.1
Sapirstein	µ- theory	1983	1/137.035 988(20)	146 ppb	6.8
CODATA	e- g-2	1986	1/137.035 989 5(61)	45 ppb	7.4
CODATA	e- g-2	1998	1/137.035 999 76(50)	3.6 ppb	8.4
CODATA	N/A	2002	1/137.035 999 11(46)	3.3 ppb	8.5
CODATA	Cs?	2004/6	1/137.035 999 ???(68)	0.5 ppb	9.3

CODATA=Committee on Data for Science and Technology

prev toc next talk

"The mythical Zanzibar unit is illustrated by a story which [E. Richard] Cohen et al (1957) attribute to Harrison of MIT (see figure below). Apparently there was a retired sea captain who lived on a remote part of the island of Zanzibar and, as captains are wont to do, he had introduced a ceremonial raising and lowering of the flag each day, and also fired a cannon at noon. A visiting friend enquired how the captain knew the exact time, to which he replied that he reset his chronometer according to the time displayed by the clocks in the window of the jeweller in the local town. After he had left the captain, the friend was in the town and thought that he would pursue the matter further and enquired how the jeweller 'set his clocks. `Oh, that is simple' he replied, 'there is a retired sea captain on the other side of the island who always fires a cannon at noon and I use it to set my clocks.'

From The Fundamental Physical Constants and the Frontier of Measurement, B. W. Petley, National Physical Laboratory, Adam Hilger Ltd, 1985, pg. 8-9.

1998 CODATA value of 137.035 999 76(50) is very close to weighted average of these: 137.035 999 72(50)!

Also, in 1998 CODATA, after Rydberg was adjusted and set, alpha with Planck's constant were checked for robustness.