system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it impossible for objects weighing less than 0.02 milligrams to form a black hole?

Whats so special about that mass that you cant form a black hole below it?
gpt
A black hole of mass less than around .02 milligrams or so would have a Schwarzschild radius of around a Planck length or less.  At this scale, general relativity cannot be trusted; we need a theory that incorporates general relativity and quantum field theory.  Thus, at the very least, we can say that such a black hole could not be described by general relativity.  

But we can go further.  Quantum mechanics tells us that an object with such a mass would have a Compton wavelength greater than its Schwarzschild radius, which would make it not possible to constrain this mass to be in a small enough region to form a black hole.  It is reasonable to expect this to hold even in the eventual quantum theory that incorporates gravity, and if so, that would preclude the formation of a black hole with such a mass.