Carbon dating the gospels
Bruce Metzger of Princeton University, a prominent modern textual critic, describes the role of textual criticism this way: The necessity of applying textual criticism to the books of the New Testament arises from two circumstances: (a) none of the original documents is extant, and (b) the existing copies differ from one another.
As one would expect, they contain some scribal errors.
These fragments are named with a "P" followed by a number.
The vast majority of them were found in Egypt in the twentieth century, and are now kept in various museums and libraries throughout the world, including at Dublin, Ann Arbor, Cologny (Switzerland), the Vatican and Vienna.
In fact, "there is not a single copy wholly free from mistakes." That said, the variances are theologically inconsequential and the vast majority don't affect translation.
It is the task of textual criticism, therefore, to study and compare the available manuscripts in order to discern which of the variations conforms the closest to the original.