OptionProbability
No decision made in 2026 conference
Second defined by a (dynamic) weighted sum of atomic transitions
Second defined by 199Hg 265nm transition
Second defined by 27Al+ 267nm transition
Second defined by 199Hg+ 282 nm transition
Second defined by 171Yb+ (E2) 436nm transition
Second defined by 171Yb+ (E3) 467nm transition
Second defined by 171Yb 578nm transition
Second defined by 88Sr+ 674nm transition
Second defined by 88Sr 698nm transition
Second defined by 87Sr 698nm transition
Second defined by 40Ca+ 729nm transition
Second defined by 87Rb 6.8GHz microwave transition
Second defined by a (fixed) weighted sum of atomic transitions
Second defined by fixing the Rydberg constant
Decision made to not redefine the second
Other
95
1
0
The cesium 133 F=3 <-> F=4 hyperfine microwave transition (no change)
Any system based on weighted averages of uncertainty or timekeeping contributions
The strontium 87 1S0 <-> 3P0 optical transition
The ytterbium 171 1S0 <-> 3P0 optical transition
Any other optical transition in ions
Any other optical transition in neutral atoms
The thorium 229 metastable nuclear optical transition (any realization)
39
22
12
8
5
2
