They'd probably be stale, which changes the taste and texture of the cake. However, it holds pretty well, the deeper we go into the Earth, more and more towards the core, the older the rock gets. In fact, as we go deeper, the qualities of the rock change to reflect this age.Sedimentary rock, rock formed by layers of sediment being squeezed together, becomes more and more compact.
Therefore, we can tell within a range how many half-life cycles that a rock has been through and adjust its age accordingly.
These datings put the age of the Earth anywhere from around 7,000 to trillions of years old.
However, in the past few hundred years many people have been more inclined to use the scientific method to date the Earth.
For example, if the unknown layer is above the layer with all the isotopes, we know it is newer than the age revealed from radioactive dating. Simple - eventually we found that there was a ceiling for how big the ages got.
We stopped finding half-lives that were much older than four and five billion years ago.