It is probably a multi-factorial process of intrinsic aging and extrinsic aging.
If time is relative then measuring distance covered with time as a factorial to calculate speed or acceleration is misleading.
The list of factorial and binomial topics contains a large number of related links.
British Dictionary definitions for factorial
the product of all the positive integers from one up to and including a given integer. Factorial zero is assigned the value of one: factorial four is 1 × 2 × 3 × 4. Symbol: n!, where n is the given integer
(fāk-tôr'ē-əl) The product of all of the positive integers from 1 to a given positive integer. It is written as the given integer followed by an exclamation point. For example, the factorial of 4 (written 4!) is 1 × 2 × 3 × 4, or 24.
mathematics The mathematical function that takes a natural number, N, and returns the product of N and all smaller positive integers. This is written N! = N * (N-1) * (N-2) * ... * 1. The factorial of zero is one because it is an empty product. Factorial can be defined recursively as 0! = 1 N! = N * (N-1)! , N > 0 The gamma function is the equivalent for real numbers. (2005-01-07)