Why do macroscopic objects, such as a baseball, not exhibit observable wave interference effects?

Answer

The associated de Broglie wavelength is incredibly small due to large momentum.

Although duality applies universally, for macroscopic objects, the large momentum results in a de Broglie wavelength ($\lambda = h/p$) so small that interference effects are impossible to measure or detect.

Why do macroscopic objects, such as a baseball, not exhibit observable wave interference effects?

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Wave Particle Duality Explained | Perimeter Institute for Theoretical ...

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