What's the greatest range of orders of magnitude?

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?

Answer

Your question is pretty vague, but I will restrict it to mean: what is the physical property with the largest range of measured values. This is still probably subjective, but it's a little more manageable and fun to think about anyway.

Here's one possibility: range of measured half-lives of radioactive isotopes (see wiki list). The shortest measured half-life (that of hydrogen-7) is order $10^{-23}$ seconds, and the longest (that of tellurium-128) is order $10^{31}$ seconds, so they span an amazing 54 orders of magnitude in all.

This is kind of ridiculous. It is more than the ratio between the size of a proton and the size of the observable universe, which are separated by a mere 41 orders of magnitude (maybe this is what your quote is supposed to say?), and it is about the difference between the Planck length and a light-year (!). It's fun to think about what the experimental challenges must be making measurements on both ends of that spectrum. Both ends (particularly the long-time end) are bounded by experimental ability, so this is not too far from being a list of the range of times over which we can measure anything. Naturally, that means it is subject to change. For example, we've been looking for proton decay for a long time, but all we can say right now is that the lifetime must be more than order $10^{39}$ seconds. If we ever find it this range will shoot at least another hundred million times larger.