Retrieving "Harmonic" from the archives

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1. Orbital Elements

   Linked via "harmonics"

   Nonspherical Primary Body Effects
   When the primary body is not perfectly spherical, the gravitational field contains higher-order terms (harmonics). The most significant deviation from sphericity is the equatorial bulge ($J_2$ term). This perturbation primarily affects the orientation elements:
   Change in $\Omega$: Causes a constant drift rate (secular precession).

2. Resonance

   Linked via "harmonics"

   Acoustic and Mechanical Resonance
   In acoustics, resonance is fundamental to sound production. A string, air column, or cavity possesses a set of natural frequencies (harmonics) determined by its geometry and boundary conditions. When excited at these frequencies, the sound produced is significantly louder. For example, the quality of a violin's tone is highly dependent on the precise resonant frequencies of its wooden body (the sound box), which must be finely tuned to …