This is something I wrote some time ago that describes why I use the analogy of resonance to explain what I feel in my faith when I am aware of God. 

Part 1: Physics
In physics the term resonance refers to the phenomenon where a free body will vibrate in response to an external frequency. It is what causes a hanging bell to start to ring if you sing its note – and it’s what causes a wine glass to crack to a soprano’s singing. The resonance of atoms in a laser gets light to be emitted in sync, in phase – so the laser beam is amplified and coherent. A swinging pendulum in resonance with a vibration will start to swing every larger swings.
In all these examples the body in resonance simply responds. And when it is in full resonance it has energy far bigger than it had in isolation – the pendulum swing grows, the grass cracks, the bell rings loudly.
A body can be in partial resonance too – when its frequency (note) doesn’t quite match the forcing tune. If the body is free it can come into resonance – the pendulum swing will change to match.

A body can’t be in resonance if it is touching others – glasses pushed against each other will hit each other and sound “clashing” rather than ringing a note. Atoms in a lightbulb filament emit white light (mixed “clashing” frequencies) rather than the pure colour of a laser beam.
Part 2: Explaining the analogy

An analogy that means a lot to me is the analogy that “walking in the Light” means a heart, mind and soul in resonance with God. When we are in full resonance, we respond to God. We are “in tune” with God, we are in sync with God.

In this state our response is natural, we actually can’t help obeying God – God’s Will becomes our only option. The things we struggle with when we are out of resonance: “how do I be still?” “How do I find God?” “How do I know what is God’s Will and what are my own notions?” These questions – once so urgent – become irrelevant as the answer is obvious.

“How do I resist temptation?” is no longer a question of will power, because there is no will power. We simply respond the only way a body in resonance can – we sing God’s tune.
We don’t fall immediately into resonance – we approach it, our swing gets closer to God’s. As we approach resonance we start to feel it, to sense ourselves going into the flow of Life Abundant. Our sense of strength, our ability to act, our ability to love grows – and the more we let go into resonance, the stronger the power of God acts through us – we feel that power, that energy, that overwhelming outpouring of Love. 

It is not the frenetic energy of our own adrenalin rush, it is a calm energy – an energy where time, our physical health or our limited skills don’t matter because it is not us who is acting, but God acting through us. God directs us, draws us closer.

In full resonance we cannot easily be knocked by the outside world. Our hearing of God’s tune is so much stronger than what the world throws at us.

We can, however, lose resonance. And the physics analogy works here too – we lose resonance if we become stiff (or too floppy) – if we don’t let go into the song, (or lose our integrity and wholeness). If we resist God’s tune, the resonance is dampened and we do feel that dampening – we lose the energy we had, we lose the sense of easy connection, we start to ask the questions again: how do I find God? How do I know what is of God and what is of me? How do I hear God’s Will? 

Sometimes the loss of resonance is internal – our own stiffening; sometimes it is external. Like the glasses pushed together, we can no longer sing our tune with God because we are jostled, hit into by other people’s agendas, constrained by worldly commitments. We may be knocked out of resonance by an external blow or simply slip away because we let our attention drift away.

To get back into resonance we simply need to hear the Song. We need to let go and be vulnerable and weak so we are free to move in response, not stiff from our own notions. We need to separate ourselves – slightly – from the people who stop us responding, a separation that also leaves them to respond themselves. In physics, “loosely coupled oscillators” get into sync with each other and the main beat naturally – we need some connection with other people, but not so much that we are dependent on them.

Finally, we can consider a gathered Friends’ Meeting for Worship as one in which everyone has reached resonance with God, the driving force. That resonance naturally means that we also reach resonance with one another and that energy (here – Love) flows between the different people so that we remain individual, but respond together. 

I feel spiritual resonance with God physically and in a gathered Meeting for Worship I can feel the flow of Love between people.