I think one would likely need to rewind all the way to talking about Plato's *Parable* *of* *the* *Cave* to begin to answer that question, and then work our way up to adbuctive reasoning, and then get deeper into the philosophy of science itself.

But the TLDR of the response is: we don't have to do that. We can see the externalized effects of these things. The Planck scale is where quantum mechanics and general relativity come into conflict with each other. This is referred to as the domain of quantum gravity. That's what it is. It does not refer to a fixed minimum granularity of time progression in the universe. This is a seriously bad understanding of what it is, that shows up in popular understandings of quantum physics. And it's just wrong.