>>10901726It's not a dumb question. Yes if a baseball were a very massive abstract point particle you could make the wavelength as small as you wish, and since the diffraction pattern only depends on the wavelength not the frequency (which stays very high), in principle you should get diffraction.
But a baseball is a macroscopic object and to see a diffraction pattern you need a "coherent" superposition of a baseball wave going through both slits (it also needs to fit, but I'll ignore that!). Even in ordinary optics you need a coherent light wave to see diffraction. That's why if you've ever seen a diffraction pattern in a physics class they no doubt used a laser and not ordinary light from a lightbulb. But macroscopic objects don't like to stay in coherent superpositions. Tiny interactions with the environment or their own microscopic degrees of freedom spoil the effect.
