-TA similar method is used in atomic clocks, except it is the electrons orbiting the nucleus that make the energy jump. The most accurate atomic clocks drift by an amount equivalent to just 4 seconds since the big bang. In principle, a nuclear clock could smash that. Ambient electric and magnetic fields affect electrons in atomic clocks, causing errors, but they would influence the tightly bound particles in the nucleus much less.
Now Corey Campbell at the Georgia Institute of Technology in Atlanta and colleagues have devised a scheme that uses lasers to carefully control the spatial orientation of the electron orbits in atoms. A thorium clock controlled in this way would drift by just 1 second in 200 billion years, the team claims - that is more than 14 times the age of the universe (arxiv.org/abs/1110.2490).