Comment by adrian_b

The hope is that with nuclear clocks there will be no need for the very complex single-ion traps or optical lattices required for clocks that use ionic or atomic energy levels.

Even with the atoms of thorium contained in a small crystal, the frequency of their clock transitions should not be influenced by the environment.

Unfortunately, for now no other suitable nucleus has been found, because the frequency corresponding to nuclear energy levels is normally too high for the current or near future technology.

With thorium 229, the potential simplicity of the clock is counterbalanced by the great expense required for producing this artificial isotope.