Slightly unrelated but your comment led me to actually learning what the Planck length is, and the Wikipedia article for it has a great section on how to visualize it [1].
I am unconvinced that time is a real dimension, sure we can model movement/interactions of particles as a 4th dimension, but nothing in our understanding of physics requires it being a physical reality. IMO it's less space-time and more just space, it's just the rate of change slows with more mass.
There's at least one prominent physicist [1] who is working on showing that time is an emergent property of quantum physics rather than a fundamental one.
He's not claiming time isn't real, which the definition of "real" is difficult and troubling to define in itself.
I think he doesn't consider time to be 4th (or part of 3+1 or \R^3 \times \R ) dimension... or in heat equation language: that the domain is a not parabolic cylinder.
Check out "The Order of Time" by Carlo Rovelli! You might find it interesting. He explains (WAY more eloquently than I could) that time is most likely an interpretation of underlying physical law, rather than a fundamental part of it!
I have a hard time buying that, given the Lorentz Transform. Time is just as much a real dimension as space is. (Or are the dimensions of space also "an interpretation of underlying physical law"?)
I believe the Lorentz Transformation more than I believe eloquent arguments.
