The laws of optics may be well known, but this video does a really concise job of clarifying the complexity of what we see and why we can’t always trust our eyes. This lesson helps us understand the work of an artist who plays with our perceptions at every turn — like James Turrell. I think the disappointment many people felt seeing Turrell’s “Iltar” (1976) at the current Guggenheim show comes from our inability to discern when our perceptions are being warped or skewed. One of his Space Division Constructions, “Iltar” creates the impression that the opening in the wall is a solid plane of color. Without an accompanying text, the viewer would never “see” that reality. Our eyes want to believe one thing, while our mind tells us that we are being deceived.