| 单词 | radium clock |
| 释义 | > as lemmasradium clock radium clock n. now rare a timing device in which beta particles from a radium source charge two electroscopic leaves, which discharge at regular intervals each time they diverge sufficiently to touch two earthed metal plates. ΘΚΠ the world > matter > physics > atomic nucleus > radioactivity > beta radiation > [noun] > device utilizing radium clock1904 1904 Daily Herald (Decatur, Illinois) 31 May 2/2 A radium clock, which will keep time indefinitely, has been constructed by Harrison Martindale, of England. 1905 E. Rutherford Radio-activity (ed. 2) iv. 123 This ‘radium clock’ should work at a sensibly uniform rate for many years, but..the number of β particles emitted would decrease exponentially with the time, falling to half value in about 1200 years. 1951 I. Asimov Foundation ii. i. 42 The radium clock will open the First Vault in three months. < as lemmas |
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