There's a famous claim along the lines of "40 dp of PI are sufficient to calculate the circumference of the Observable Universe to the width of a hydrogen atom"
I don't know the accuracy and detail of claim, but it prompted me to be curious ...
I assume that the claim (if it were true and accurately remembered) if equivalent to stating: "There are 40 orders of (decimal) magnitude difference between the diameter of the universe and the diamater of a hydrogen atom".
But that's not the biggest possible difference between interestingly measurable things, because the diameter of a hydrogen atom isn't the smallest length ... we could go smaller (protons, electrons, quarks, planck length)
I don't know astrophysics well enough to know whether there's anything that's interesting to describe bigger than the Observable Universe.
But, it seems that whilst considering length you can arrive at "The greatest possible difference in orders of magnitude".
But there are other things that can be measured. Time for example.
So question: What metric has the greatest range of orders of magnitude that are interesting to talk about? and how big is that range?