Optics principles. For example, the Ames room, Hering, Müller-Lyer, Orbison, Ponzo, Sander, and Wundt illusions all rely on the suggestion of the appearance of distance by using converging and diverging lines, in the same way that parallel light rays (or indeed any set of parallel lines) appear to converge at a vanishing point at infinity in two-dimensionally rendered images with artistic perspective. This suggestion is also responsible for the famous moon illusion where the moon, despite having essentially the same angular size, appears much larger near the horizon than it does at zenith. This illusion so confounded Ptolemy that he incorrectly
No Line on the Horizon to the halfway point. "Moment of Surrender" closed every show. U2 made minor changes to the setlists for the second leg of the tour. "No Line on the Horizon" was performed later in the concerts, while "Unknown Caller" was dropped for several weeks before being revived towards the end of the leg. The band did not play "Stand Up Comedy", "Fez – Being Born", "White as Snow", or "Cedars of Lebanon" at any point in 2009. The 25 October 2009 concert at the Rose Bowl in Pasadena, California, U2's penultimate concert of 2009, was filmed and streamed live over YouTube.