Opposites interfere

In a classic physics experiment, photons (light particles), electrons, or any other quantum particles are fired, one at a time, at a sheet with two slits cut in it that sits in front of a recording plate. For photons, a photographic plate reveals an oscillating pattern (bands of light and dark) – a sign that each particle, behaving like a wave, has somehow passed through both slits simultaneously and interfered, canceling the light in some places and enhancing it in others.