Two harps stand side by side. When a string on the first harp is plucked, the corresponding string on the second harp also vibrates, albeit more faintly. The principle is as follows: The vibrations of the first string, at a specific frequency, travel through the air as sound waves to the second harp, agitating all its strings. However, only the string with the same frequency can accumulate the energy transmitted by the sound waves, resulting in noticeable vibration. Though the sound waves also act upon the other strings, because their frequencies differ, the continuous waves merely interfere with the strings' motion, making it difficult for energy to build up.
This phenomenon is like pushing a swing. If you push the swing forward in sync with its natural frequency, the swing will go higher and higher. Conversely, if your pushing frequency is out of tune with the swing’s motion — or even counter to it — the swing will only sway weakly at a low height or may not move at all.
Every living being can be seen as a unique harp in this world, with flesh and blood as its resonance chamber and mind as its countless strings, playing its own melody in the long corridor of time. Some play stirring marches, others hum sorrowful nocturnes, but most are lonely chords heard by no one. Two harps placed close to each other can only resonate when they share many common frequencies.
When a swing reaches you and is about to move away, pushing it at that moment is called being "in phase," causing the swing to rise higher. This is like meeting a soulmate or a kindred spirit — the two harps not only share many matching frequencies but also resonate in phase, creating a powerful and enduring harmony. The so-called "love at first sight" or "soulmate connection" arises precisely because of the abundance of matching frequencies, creating an instant multi-frequency resonance that stirs the deepest vibrations within each other.
Even if two frequencies match, if you push the swing as it comes toward you — disrupting its rhythm — and fail to push it in time when it moves away, and instead pull it back, you interfere even more, this is called being "out of phase." Not only does this fail to enhance resonance, but it also produces a weakening effect. When the phases are completely opposite, the result is absolute cancellation — in worldly terms, this is like encountering a toxic relationship or a karmic debtor coming to collect.Finally, and most importantly, two intangible waves cannot directly resonate with each other. For example, two beams of light or two sound waves, even if they intersect, will simply pass through one another. For resonance to occur, there must be a shared medium — typically a tangible entity or cavity capable of absorbing or capturing the energy of intangible waves. For intangible spiritual waves, this physical vessel world and our bodies serve as the common medium.