next major advance might be a nuclear clock using 229mTh. Wiki: "229mTh has the lowest known excitation energy of any isomer,[21] measured to be 7.6 ± 0.5 eV. This is so low that when it undergoes isomeric transition, the emitted gamma radiation is in the ultraviolet range". It would be vacuum UV at 160 nm. As in https://arxiv.org/abs/1709.05325. I couldn't find an estimate of the expected line width or accuracy improvement though. Wouter. -----Original Message----- From: Eugene Salamin via math-fun Sent: Tuesday, March 06, 2018 2:10 AM To: math-fun@mailman.xmission.com Subject: [math-fun] Atomic clock at precision 2.5e-19 https://physics.aps.org/articles/v11/22?utm_campaign=weekly&utm_medium=email... Clock consists of 10,000 Sr atoms in an optical lattice cooled to 15 nK. If this clock had been started at the big bang, it would today be off by 100 ms. == Gene _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun