system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: Why is a Planck length the smallest possible unit of measurement?
gpt
It is a *theoretical* limit because at sizes smaller than Planck length, our current models of physics begin to break down and produce nonsensical answers. It is not known if it represents a *physical* limit.

Basically, you have a rule with 1/16" markings. That makes 1/16th of an inch a theoretical limit to your ability to measure things because below that you can't measure reliably. But that isn't a physical limitation: you can get a measuring stick with finer increments.