Define relative dating
An absolute age is one determined usually by mass-spectrometry where an isotope is measured and then an age can be calculated (a very very basic explanation).So in the end you can say this fossil is 50 thousand years old (always with an associated uncertainty)." virtually all sedimentary systems have stratigraphic disorder at come scale is probably a common feature of the fossil record " Fossils out of Sequences Cutler Palaios June 1990 on The conclusion of some scientists is that the Law of Superposition just doesn't work Shindewolf Comments on Some Stratigraphic Terms American Journal of Science June 1957 " Historical geology relies chiefly on paleontology the study of fossil organisms. The Law of Superposition makes logical sense but in practice it is the nature of the fossils found in the sedimentary layers that determine the relative ages of the rocks.
Relative dating is a less advanced technique as compared to absolute dating.We can absolute date materials but it will always have an uncertainty range, we can never know the age with infinite precision.Relative dating is like looking at a multi-layered cake.The law of superposition is based on the common sense argument that the bottom layer had to laid down first.The bottom layer because it logically had to be laid down first must be older.