I have very fond memories of being an Explainer, and one of my favorites is of the time we discovered anti-rainbows! Normally a rainbow is formed by a series of pure frequencies, juxtaposed in order. An anti-rainbow is made by subtracting one frequency at a time instead. They are caused by interference in soap bubbles and oil films. Today I stumbled across another awesome idea, an anti-bubble! A bubble is a film of fluid, containing and surrounded by air. So an anti-bubble is a film of air containing and surrounded by fluid. Woah! Check it out.