50 YEARS AGO

“A cæsium resonator” — A frequency standard based on the natural resonant frequency of the cæsium atom has been constructed at the National Physical Laboratory and used for calibrating the quartz clock standards with an accuracy of ±1 part in 109 (0.0001 sec. per day)... The resonance observed is that due to transitions between the hyperfine structure energy-levels caused by the interaction between the nuclear and electron spins... all the allowed transitions have been observed, and from measurements made under a variety of conditions the frequency of the central line and zero field was found to be 9 192 631 830 ± 10 c./s... The results reported here appear to be the first examples of the use of an atomic frequency standard with an accuracy greater than that obtained by using a unit of astronomical time. They also represent the highest accuracy ever achieved in the measurement of any physical quantity in terms of a definitive standard.

L. Essen & J. V. L. Parry

From Nature 13 August 1955.

100 YEARS AGO

“A Modern Utopia.” By H. G. Wells. — It is instructive to watch the growth, both in power and in hopefulness, of Mr. Wells's criticism of life. In the “Time Machine” his forecast of the future of humanity was frankly appalling; in “When the Sleeper Wakes,” more lurid (albeit far more probable) than the worst imaginings of “reforming” socialists... “Mankind in the Making” contained much vigorous criticism and many sensible and practical suggestions. In the present book Mr. Wells has become still more moderate and practicable and hopeful, without in the least derogating from his ingenuity and originality. We sincerely hope, therefore, he will not, as he threatens, stick henceforth to his “art or trade of imaginative writing,” but will continue from time to time to regale and stimulate us with sociological speculations.

From Nature 10 August 1905.