Physics
Phase Inversion
Quick fact
When a wave is phase-inverted and added to the original wave, the result is complete cancellation (zero amplitude) if both waves are identical. This is the principle behind active noise cancellation.
Why this is interesting
You've probably used noise-canceling headphones that magically silence background hum. That magic is phase inversion—the same trick that can turn two loudspeakers into silence or create optical illusions with light.