A trio of researchers in Denmark has calculated the relative ages of the surface of the Earth versus its core and has found that the core is 2.5 years younger than the crust. In a paper published in the European Journal of Physics,U I Uggerhøj and R E Mikkelsen with Aarhus University and J Faye with the University of Copenhagen, portray the math involved in their effort and their results.
Source: phys.org